ALBERT

Beschreibung: Abstract Experimental study of the effects of projected climate change on plant phenology allows us to isolate effects of warming on life history events such as leaf out. We simulated a 2°C temperature increase and 20% precipitation increase in a recently harvested temperate deciduous forest community in central Pennsylvania, USA, and observed the leaf out phenology of all species in 2009 and 2010. Over 130 plant species were monitored weekly in study plots, but due to high variability in species composition among plots, species were grouped into five functional groups: short forbs, tall forbs, shrubs, small trees, and large trees. Tall forbs and large trees, which usually emerge in the late spring, advanced leaf out 14‐18 days in response to warming. Short forbs, shrubs, and small trees emerge early in spring and did not alter their phenology in response to warming or increased precipitation treatments. Earlier leaf out of tall forbs and large trees coincided with almost three weeks of increased community‐level leaf area index (LAI), indicating greater competition and a condensed spring green‐up period. While phenology of large trees and tall forbs appears to be strongly influenced by temperature‐based growth cues, our results suggest that photoperiod and chilling cues more strongly influence the leaf out of other functional groups. Reduced freeze events and warmer temperatures from predicted climate change will interact with non‐temperature growth cues to have cascading consequences throughout the ecosystem.

Beschreibung: At least half of the world's population resides in the coastal zone and the livelihoods of billions of people are affected either directly or indirectly by the production and sustainability of nearshore fisheries. Landscape change, specifically development of tree plantations, is accelerating worldwide as developing countries integrate into global markets to sell goods, offer climate-mitigation services (carbon), and/or provide renewable energy. These changes can release excess nutrients into adjacent coastal waters causing eutrophication that alters the structure and function of coastal ecosystems. This study examined the relationship between coastal drainage basin land use/ land cover change (LCLUC), specifically development of tree plantations, patterns of chlorophyll a in nearshore coastal waters, and the biological condition of commercially important shellfish, Concholepas concholepas ( loco ) in southern Chile. Locos (N= 1,374) were sampled across 13 watersheds (35,853 km 2 ) and 42 fisheries management areas (spanning 250 km of coastline). Locos harvested from management areas influenced by tree plantations had approximately 30% more endobiont (shell-boring) phoronids, almost twice as many endobiont polychaetes and twice as many epibiont (shell-attaching) barnacles than locos from areas in close proximity to watersheds dominated by native forests (15-20% of the watershed). Phoronid infested locos from coastal waters adjacent to watersheds with tree plantations were of relatively poor biological condition (smaller and narrower in width) and of reduced market value. Our study suggests that tree plantations result in indirect ecological impacts to coastal fisheries (more nutrients and higher phytoplankton biomass, resulting in smaller, low quality locos), and costs are born by coastal fishers (lower prices for locos). Increases in tree plantations could thus potentially significantly impact coastal fisheries worldwide and such problems should be managed as an interconnected network of land use change, oceanic ecosystems, and economic systems that are considered an integrated socio-ecological system.

Beschreibung: Glacial retreat creates new habitat which is colonised and developed by plants and animals during the process of primary succession. While there has been much debate about the relative role of deterministic and stochastic processes during terrestrial succession, evidence from freshwater ecosystems remains minimal and a general consensus is lacking. Using a unique 27 year record of community assembly following glacial recession in southeast Alaska, we demonstrate significant change in the trait composition of stream invertebrate communities as catchment glacial cover decreased from 〉70% to zero. Functional diversity increased significantly as glacier cover decreased and taxonomic richness increased. Null modelling approaches led to a key finding that niche filtering processes were dominant when glacial cover was extensive, reflecting water temperature and dispersal constraints. Thereafter the community shifted towards co-occurrence of stochastic and deterministic assembly processes. A further novel discovery was that intrinsic functional redundancy developed throughout the study, particularly because new colonisers possessed similar traits to taxa already present. Rapid glacial retreat is occurring in Arctic and alpine environments worldwide and the assembly processes observed in this study provide new fundamental insights into how glacially influenced stream ecosystems will respond. These findings support tolerance as a key primary successional mechanism in this system, and have broader value for developing our understanding of how biological communities in river ecosystems assemble or restructure in response to environmental change.

Beschreibung: Major sources of greenhouse gas (GHG) emissions from agricultural crop production are nitrous oxide (N 2 O) emissions resulting from the application of mineral and organic fertiliser, and carbon dioxide (CO 2 ) emissions from soil carbon losses. Consequently, choice of fertiliser type, optimising fertiliser application rates and timing, reducing microbial denitrification and improving soil carbon management are focus areas for mitigation. We have integrated separate models derived from global data on fertiliser induced soil N 2 O emissions, soil nitrification inhibitors, and the effects of tillage and soil inputs of soil C stocks into a single model in order to determine optimal mitigation options as a function of soil type, climate, and fertilisation rates. After Monte Carlo sampling of input variables we aggregated the outputs according to climate, soil and fertiliser factors to consider the benefits of several possible emissions mitigation strategies, and identified the most beneficial option for each factor class on a per hectare basis. The optimal mitigation for each soil-climate-region was then mapped to propose geographically specific optimal GHG mitigation strategies for crops with varying N requirements. The use of empirical models reduces the requirements for validation (since they are calibrated on globally or continentally observed phenomena). However, since they are relatively simple in structure, they may not be applicable for accurate site specific prediction of GHG emissions. The value of this modelling approach is for initial screening and ranking of potential agricultural mitigation options and to explore the potential impact of regional agricultural GHG abatement policies. Given the clear association between management practice and crop productivity, it is essential to incorporate characterisation of the yield effect on a given crop before recommending any mitigation practice.

Beschreibung: Climate change may considerably impact the carbon (C) dynamics and C stocks of forest soils. To assess the combined effects of warming and reduced precipitation on soil CO 2 efflux, we conducted a two-way factorial manipulation experiment (4 °C soil warming + throughfall exclusion) in a temperate spruce forest from 2008 until 2010. Soil was warmed by heating cables throughout the growing seasons. Soil drought was simulated by throughfall exclusions with three 100 m 2 roofs during 25 days in July/August 2008 and 2009. Soil warming permanently increased the CO 2 efflux from soil whereas throughfall exclusion led to a sharp decrease in soil CO 2 efflux (45% and 50% reduction during roof installation in 2008 and 2009, respectively). In 2008, CO 2 efflux did not recover after natural rewetting and remained lowered until autumn. In 2009, CO 2 efflux recovered shortly after rewetting, but relapsed again for several weeks. Drought offset the increase in soil CO 2 efflux by warming in 2008 (growing season CO 2 efflux in t C ha −1 : control: 7.1 ± 1.0; warmed: 9.5 ± 1.7; warmed + roof: 7.4 ± 0.3; roof: 5.9 ± 0.4) and in 2009 (control: 7.6 ± 0.8; warmed + roof: 8.3 ± 1.0). Throughfall exclusion mainly affected the organic layer and the top 5 cm of the mineral soil. Radiocarbon data suggest that heterotrophic and autotrophic respiration were affected to the same extent by soil warming and drying. Microbial biomass in the mineral soil (0 - 5 cm) was not affected by the treatments. Our results suggest that warming causes significant C losses from the soil as long as precipitation patterns remain steady at our site. If summer droughts become more severe in the future, warming induced C losses will likely be offset by reduced soil CO 2 efflux during and after summer drought.

Beschreibung: Emissions of the trace gas nitrous oxide (N 2 O) play an important role for the greenhouse effect and stratospheric ozone depletion, but the impacts of climate change on N 2 O fluxes and the underlying microbial drivers remain unclear. The aim of this study was to determine effects of sustained climate change on field N 2 O fluxes and associated microbial enzymatic activities, microbial population abundance and community diversity in an extensively managed, upland grassland. We recorded N 2 O fluxes, nitrification and denitrification, microbial population size involved in these processes and community structure of nitrite reducers ( nir K) in a grassland exposed for four years to elevated atmospheric CO 2 (+ 200 ppm), elevated temperature (+ 3.5°C) and reduction of summer precipitations (-20%) as part of a long-term, multifactor climate change experiment. Our results showed that both warming and simultaneous application of warming, summer drought and elevated CO 2 had a positive effect on N 2 O fluxes, nitrification, N 2 O release by denitrification and the population size of N 2 O reducers and NH 4 oxidizers. In situ N 2 O fluxes showed a stronger correlation with microbial population size under warmed conditions compared with the control site. Specific lineages of nir K denitrifier communities responded significantly to temperature. In addition, nir K community composition showed significant changes in response to drought. Path analysis explained more than 85% of in situ N 2 O fluxes variance by soil temperature, denitrification activity and specific denitrifying lineages. Overall, our study underlines that climate-induced changes in grassland N 2 O emissions reflect climate-induced changes in microbial community structure, which in turn modify microbial processes.

Beschreibung: Understanding how species and ecosystems respond to climate change requires spatially and temporally rich data for a diverse set of species and habitats, combined with models that test and predict responses. Yet current work is hampered by the long-known problems of inadequate management of data and insufficient description of analytical procedures, especially in the field of ecology. Despite recent institutional incentives to share data and new data archiving infrastructure, many ecologists do not archive and publish their data and code. Given current rapid rates of global change, the consequences of this are extreme: because an ecological dataset collected at a certain place and time represents an irreproducible set of observations, ecologists doing local, independent research possess, in their file cabinets and spreadsheets, a wealth of information about the natural world and how it is changing. Although large-scale initiatives will increasingly enable and reward open science, we believe that change demands action and personal commitment by individuals—from students and PIs. Here, we outline the major benefits of sharing data and analytical procedures in the context of global change ecology, and provide guidelines for overcoming common obstacles and concerns. If individual scientists and labs can embrace a culture of archiving and sharing we can accelerate the pace of the scientific method and redefine how local science can most robustly scale up to globally-relevant questions.

Beschreibung: Changes in C 4 grass distribution and abundance are frequently observed in Quaternary, Holocene and future environmental-change scenarios. However, the factors driving these dynamics are not fully understood, and conflicting theories have been reported. In this paper, we present a very large dataset of modern altitudinal distribution profiles of C 3 and C 4 grasses covering the entire Neotropical Andes, which was compared with actual climate data. The results of multivariate analysis demonstrate that, in the Neotropical Andes, mean annual temperature is the main factor governing the modern altitudinal distribution of C 3 and C 4 grass species. The C 3 and C 4 grass distributions were compared with simulations based on the Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM), which allowed the present grass distribution to be estimated. Finally, the DGVM was employed to simulate past and future scenarios, using the IPCC's climate projections for 2100 and PMIP2 models for the Holocene Optimum (HO, 6000 yrs BP) and the Last Glacial Maximum (LGM, 21000 yrs BP). The results were found to be significantly different to those obtained using a simple photosynthetic model. According to LPJ forced with the PMIP2 models for the LGM, during the LGM, the C 4 grasses would not have reached higher altitudes than found in the present day.

Beschreibung: Mechanisms to mitigate global climate change by sequestering carbon (C) in different ‘sinks’ have been proposed as at least temporary measures. Of the major global C pools, terrestrial ecosystems hold the potential to capture and store substantially increased volumes of C in soil organic matter (SOM) through changes in management that are also of benefit to the multitude of ecosystem services that soils provide. This potential can only be realised by determining the amount of SOM stored in soils now, with subsequent quantification of how this is affected by management strategies intended to increase SOM concentrations, and used in soil C models for the prediction of the roles of soils in future climate change. An apparently obvious method to increase C stocks in soils is to augment the soil C pools with the longest mean residence times (MRT). Computer simulation models of soil C dynamics, e.g. RothC and Century, partition these refractory constituents into slow and passive pools with MRTs of centuries to millennia. This partitioning is assumed to reflect (i) the average biomolecular properties of SOM in the pools with reference to their source in plant litter, (ii) the accessibility of the SOM to decomposer organisms or catalytic enzymes, or (iii) constraints imposed on decomposition by environmental conditions, including soil moisture and temperature. However, contemporary analytical approaches suggest that the chemical composition of these pools is not necessarily predictable because, despite considerable progress with understanding decomposition processes and the role of decomposer organisms, along with refinements in simulation models, little progress has been made in reconciling biochemical properties with the kinetically-defined pools. In this review, we will explore how advances in quantitative analytical technologies have redefined the new understanding of SOM dynamics and how this is impacting on the development and application of new modelling approaches to soil C.

Beschreibung: It is often assumed that daytime patterns of ecosystem carbon assimilation are mostly driven by direct physiological responses to exogenous environmental cues. Under limited environmental variability, little variation in carbon assimilation should thus be expected unless endogenous plant controls on carbon assimilation, which regulate photosynthesis in time, are active. We evaluated this assumption with eddy flux data, and we selected periods when net ecosystem exchange (NEE) was decoupled from environmental variability in seven sites from highly contrasting biomes across a 74º latitudinal gradient over a total of 36 site-years. Under relatively constant conditions of light, temperature, and other environmental factors, significant diurnal NEE oscillations were observed at six sites, where daily NEE variation was between 20% and 90% of that under variable environmental conditions. These results are consistent with fluctuations driven by the circadian clock and other endogenous processes. Our results open a promising avenue of research for a more complete understanding of ecosystem fluxes that integrates from cellular to ecosystem processes.

Beschreibung: The impact of climate change on the advancement of plant phenological events has been heavily studied in the last decade. While the majority of spring plant phenological events have been trending earlier, this is not universally true. Recent work has suggested that species that are not advancing in their spring phenological behavior are responding more to lack of winter chill than increased spring heat. One way to test this hypothesis is by evaluating the behavior of a species known to have a moderate to high chilling requirement and examining how it is responding to increased warming. This study used a 60-year data set for timing of leaf-out and male flowering of walnut ( Juglans regia ) cultivar ‘Payne’ to examine this issue. The spring phenological behavior of ‘Payne’ walnut differed depending on bud type. The vegetative buds, which have a higher chilling requirement, trended towards earlier leaf-out until about 1994, when they shifted to later leaf-out. The date of male bud pollen shedding advanced over the course of the whole record. Our findings suggest that many species which have exhibited earlier bud-break are responding to warmer spring temperatures, but may shift into responding more to winter temperatures (lack of adequate chilling) as warming continues. © 2012 Blackwell Publishing Ltd

Beschreibung: Alien species are considered one of the prime threats to biodiversity, driving major changes in ecosystem structure and function. Identifying the traits associated with alien introduction has been largely restricted to comparing indigenous and alien species or comparing alien species that differ in abundance or impact. However, a more complete understanding may emerge when the entire pool of potential alien species is used as a control, information that is rarely available. In the eastern Mediterranean the marine environment is undergoing an unparalleled species composition transformation, as a flood of aliens have entered from the Red Sea following the opening of the Suez Canal in 1869. In this study, we compile data on species traits, geographical distribution and environmental affinity of the entire pool of reef-associated fish species in the Red Sea and more generally across the Indo-Pacific. We use this extensive data to identify the prime characteristics separating Red Sea species that have become alien in the Mediterranean from those that have not. We find that alien species occupy a larger range of environments in their native ranges, explaining their ability to colonize the seasonal Mediterranean. Red Sea species that naturally experience high maximum temperatures in their native range have a high probability of becoming alien. Thus, contrary to predictions of an accelerating number of aliens following increased water temperatures, hotter summers in this region may prevent the establishment of many alien species. We further find that ecological trait diversity of alien species is substantially more evenly spaced and more divergent than random samples from the pool of Red Sea species, pointing at additional processes, such as competition, promoting ecological diversity among alien species. We use these results to provide a first quantitative ranking of the potential of Red Sea species to become established in the eastern Mediterranean. © 2012 Blackwell Publishing Ltd

Beschreibung: Arctic organisms are adapted to the strong seasonality of environmental forcing. A small timing mismatch between biological processes and the environment could potentially have significant consequences for the entire food web. Climate warming causes shrinking ice coverage and earlier ice retreat in the Arctic, which is likely to change the timing of primary production. In this study, we test predictions on the interactions among sea ice phenology and production timing of ice algae and pelagic phytoplankton. We do so using 1) a synthesis of available satellite observation data; and 2) the application of a coupled ice-ocean ecosystem model. The data and model results suggest that, over a large portion of the Arctic marginal seas, the timing variability of ice retreat at a specific location has a strong impact on the timing variability of pelagic phytoplankton peaks but weak or no impact on the timing of ice-algae blooms in those regions. The model predicts latitudinal and regional differences in the timing of ice algae biomass peak (varying from April to May) and the time lags between ice algae and pelagic phytoplankton peaks (varying from 45 to 90 days). The correlation between the time lag and ice retreat is significant in areas where ice retreat has no significant impact on ice-algae peak timing, suggesting that changes in pelagic phytoplankton peak timing control the variability of time lags. Phenological variability of primary production is likely to have consequences for higher trophic levels, particularly for the zooplankton grazers, whose main food source is composed of the dually pulsed algae production of the Arctic. © 2012 Blackwell Publishing Ltd

Beschreibung: Output from an earth system model is paired with a size-based food web model to investigate the effects of climate change on the abundance of large fish over the 21 st century. The earth system model, forced by the IPCC Special Report on Emission Scenario A2, combines a coupled climate model with a biogeochemical model including major nutrients, three phytoplankton functional groups, and zooplankton grazing. The size-based food web model includes linkages between two size-structured pelagic communities: primary producers and consumers. Our investigation focuses on seven sites in the North Pacific, each highlighting a specific aspect of projected climate change, and includes top-down ecosystem depletion through fishing. We project declines in large fish abundance ranging from 0 to 75.8% in the central North Pacific and increases of up to 43.0% in the California Current region over the 21 st century in response to change in phytoplankton size structure and direct physiological effects. We find that fish abundance is especially sensitive to projected changes in large phytoplankton density and our model projects changes in the abundance of large fish being of the same order of magnitude as changes in the abundance of large phytoplankton. Thus, studies that address only climate-induced impacts to primary production without including changes to phytoplankton size structure may not adequately project ecosystem responses. © 2012 Blackwell Publishing Ltd

Beschreibung: Facing climate change (CC), species are prone to multiple modifications of their environment that can lead to extinction, migration or adaptation. Identifying the role and interplay of different potential stressors becomes a key question. Anadromous fishes will be exposed to both river and oceanic habitat changes. For Atlantic salmon, the river water temperature, river flow and oceanic growth conditions appear as three main stressing factors. They could act on population dynamics or as selective forces on life-history pathways. Using an individual-based demo-genetic model, we assessed the effects of these factors 1) to compare risks of extinction resulting from CC in river and ocean, 2) to assess CC effects on life-history pathways including the evolution of underlying genetic control of phenotypic plasticity. We focused on Atlantic salmon populations from Southern Europe for a time horizon of three decades. We showed that CC in river alone should not lead to extinction of Southern European salmon populations. In contrast, the reduced oceanic growth appeared as a significant threat for population persistence. An increase in river flow amplitude increased the risk of local extinction in synergy with the oceanic effects, but river temperature rise reduced this risk. In terms of life-history modifications, the reduced oceanic growth increased the age of return of individuals through plastic and genetic responses. The river temperature rise increased the proportion of sexually mature parr, but the genetic evolution of the maturation threshold lowered the maturation rate of male parr. This was identified as a case of environmentally driven plastic response that masked an underlying evolutionary response of plasticity going in the opposite direction. We concluded that to counteract oceanic effects, river flow management represented the sole potential force to reduce the extinction probability of Atlantic salmon populations in Southern Europe, although this might not impede changes in migration life-history. © 2012 Blackwell Publishing Ltd

Beschreibung: Evasion of gaseous carbon (C) from streams is often poorly quantified in landscape C budgets. Even though the potential importance of the capillary network of streams as C conduits across the land-water-atmosphere interfaces is sometimes mentioned, low-order streams are often left out of budget estimates due to being poorly characterized in terms of gas exchange and even areal surface coverage. We show that evasion of C is greater than all the total dissolved C (both organic and inorganic) exported downstream in the waters of a boreal landscape. In this study evasion of carbon dioxide (CO 2 ) from running waters within a 67 km 2 boreal catchment was studied. During a four year period (2006-2009) 13 streams were sampled on 104 different occasions for dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). From a locally determined model of gas exchange properties, we estimated the daily CO 2 evasion with a high-resolution (5×5 m) grid based stream evasion model comprising the entire ~100 km stream network. Despite the low areal coverage of stream surface the evasion of CO 2 from the stream network constituted 53% (5.0 (±1.8) g C m −2 yr −1 ) of the entire stream C flux (9.6 (±2.4) g C m −2 yr −1 ) (lateral as DIC, DOC and vertical as CO 2 ). In addition, 72% of the total CO 2 loss took place already in the 1 st and 2 nd order streams. This study demonstrates the importance of including CO 2 evasion from low-order boreal streams into landscape C budgets since it more than doubled the magnitude of the aquatic conduit for C from this landscape. Neglecting this term will consequently result in an overestimation of the terrestrial C sink strength in the boreal landscape. © 2012 Blackwell Publishing Ltd

Beschreibung: Climate change is expected to impact the amount and distribution of precipitation in the arid southwestern U.S. In addition, nitrogen (N) deposition is increasing in these regions due to increased urbanization. Responses of belowground plant activity to increases in soil water content and N have shown inconsistent patterns between biomes. In arid lands, plant productivity is limited by water and N availability so it is expected that changes in these factors will affect fine root dynamics. The objectives of this study were to quantify the effects of increased summer precipitation and N deposition on fine root dynamics in a Mojave Desert ecosystem during a two-year field experiment using minirhizotron measurements. Root length density, production, and mortality were measured in field plots in the Mojave Desert receiving three 25 mm summer rain events and/or 40 kg N ha -1 yr -1 . Increased summer precipitation and N additions did not have an overall significant effect on any of the measured root parameters. However, differences in winter precipitation resulting from interannual variability in rainfall appeared to affect root parameters with root production and turnover increasing following a wet winter most likely due to stimulation of annual grasses. In addition, roots were distributed more deeply in the soil following the wet winter. Root length density was initially higher under canopies compared to canopy interspaces but converged towards the end of the study. In addition, roots tended to be distributed more deeply into the soil in canopy interspace areas. Results from this study indicated that increased summer precipitation and N deposition in response to climate change and urbanization are not likely to affect fine root dynamics in these Mojave Desert ecosystems, despite studies showing aboveground plant physiological responses to these environmental perturbations. However, changes in the amount and possibly distribution of winter precipitation may affect fine root dynamics. © 2012 Blackwell Publishing Ltd

Beschreibung: In a global change context, the intensity and the frequency of drastic low flow periods or drought events will most likely increase to a substantial extent over the coming decades, leading to a modification of the abiotic characteristics of wetlands. This change in environmental parameters may induce severe shifts in plant and animal communities and the functioning of ecosystems. In this study, we experimentally estimated the effect of drought and the accumulation of ammonia (NH 3 ) on the feeding activities of three generalist macroinvertebrates (i.e., Gammarus pulex , Gammarus roeselii and Asellus aquaticus ) on three types of organic matter: leaves of Berula erecta growing in submerged conditions, leaves of the same species growing in emerged conditions, and dead leaves of Alnus glutinosa . We observed a modification of the biomechanical and stoichiometric characteristics of the plants as a result of the emersion of the aquatic plants. This shift produced a substantial decrease in organic matter recycling by invertebrates and in their associated physiological ability (i.e., the energy stores of the animals) to face conditions associated with environmental change. Moreover, the accumulation of NH 3 amplified the negative effect of emersion. This snowball effect on invertebrates may profoundly modify the functioning of ecosystems, particularly in terms of organic matter production/degradation and carbon mineralisation. © 2012 Blackwell Publishing Ltd

Beschreibung: The occurrence of summer heat waves is predicted to increase in amplitude and frequency in the near future, but the consequences of such extreme events are largely unknown, especially for belowground organisms. Soil organisms usually exhibit strong vertical stratification, resulting in more frequent exposure to extreme temperatures for surface-dwelling species than for soil-dwelling species. Therefore soil-dwelling species are expected to have poor acclimation responses to cope with temperature changes. We used five species of surface-dwelling and four species of soil-dwelling Collembola that habituate different depths in the soil. We tested for differences in tolerance to extreme temperatures after acclimation to warm and cold conditions. We also tested for differences in acclimation of the underlying physiology by looking at changes in membrane lipid composition. Chill coma recovery time, heat knockdown time, and fatty acid profiles were determined after one week of acclimation to either 5°C or 20°C. Our results showed that surface-dwelling Collembola better maintained increased heat tolerance across acclimation temperatures, but no such response was found for cold tolerance. Concordantly, four of the five surface-dwelling Collembola showed up to 4-fold changes in relative abundance of fatty acids after one week of acclimation, whereas none of the soil-dwelling species showed a significant adjustment in fatty acid composition. Strong physiological responses to temperature fluctuations may have become redundant in soil-dwelling species due to the relative thermal stability of their subterranean habitat. Based on the results of the four species studied, we expect that unless soil-dwelling species can temporarily retreat to avoid extreme temperatures, the predicted increase in heat waves under climatic change renders these soil-dwelling species more vulnerable to extinction than species with better physiological capabilities. Being able to act under a larger thermal range is probably costly and could reduce maximum performance at the optimal temperature. © 2012 Blackwell Publishing Ltd

Beschreibung: More than 50% of the word's population feeds on rice. Soils used for rice production are mostly managed under submerged conditions (paddy soils). This management, which favors carbon sequestration, potentially decouples surface from subsurface carbon cycling. The objective of this study was to elucidate the long-term rates of carbon accrual in surface and subsurface soil horizons relative to that of soils under non-paddy management. We assessed changes in total soil organic as well as of inorganic carbon stocks along a 2000-year chronosequence of soils under paddy and adjacent non-paddy management in the Yangtze delta, China. The initial organic carbon accumulation phase lasts much longer and is more intensive than previously assumed, e.g., by the Intergovernmental Panel on Climate Change (IPCC). Paddy topsoils accumulated 170–178 kg organic carbon ha –1 a –1 in the first 300 years; subsoils lost 29–84 kg organic carbon ha –1 a –1 during this period of time. Subsoil carbon losses were largest during the first 50 years after land embankment and again large beyond 700 years of cultivation, due to inorganic carbonate weathering and the lack of organic carbon replenishment. Carbon losses in subsoils may therefore offset soil carbon gains or losses in the surface soils. We strongly recommend including subsoils into global carbon accounting schemes, particularly for paddy fields. © 2012 Blackwell Publishing Ltd

Beschreibung: Understanding spring phenology changes in response to the rapid climate change at biome-level is crucial for projecting regional ecosystem carbon exchange and climate–biosphere interactions. In this study, we assessed the long–term changes and responses to changing climate of the spring phenology in six temperate biomes of China by analyzing the GIMMS NOAA/AVHRR Normalized Difference Vegetation Index (NDVI) and concurrent mean temperature and precipitation data for 1982–2006. Results show that the spring phenology trends in the six temperate biomes are not continuous throughout the 25-year period. The spring phenology in most areas of the six biomes showed obvious advancing trends (ranging from -0.09 to -0.65 day year -1 ) during the 1980s and early 1990s, but has subsequently suffered consistently delaying trends (ranging from 0.22 to 1.22 day year –1 ). Changes in spring (February–April) temperature are the dominating factor governing the pattern of spring vegetation phenology in the temperate biomes of China. The recently delayed spring phenology in these temperate biomes has been mainly triggered by the stalling or reversal of the warming trend in spring temperatures. Results in this study also reveal that precipitation during November–January can explain 16.1% ( p 〈 0.05), 20.9% ( p 〈 0.05) and 14.2% ( p 〈 0.05) of the variations in temperate deciduous forest, temperate steppe and temperate desert, respectively, highlighting the important role of winter precipitation in regulating changes in the spring vegetation phenology of water–limited biomes. © 2012 Blackwell Publishing Ltd

Beschreibung: Low spring temperatures have been found to benefit mobile herbivores by reducing the rate of spring-flush, while high rainfall increases forage availability. Cold winters prove detrimental, by increasing herbivore thermoregulatory burdens. Here we examine the effects of temperature and rainfall variability on a temperate sedentary herbivore, the Eurasian beaver, Castor fiber , in terms of inter-annual variation in mean body weight and per territory offspring production. Data pertain to 198 individuals, over 11 years, using capture-mark-recapture. We use plant growth (tree-cores) and fAPAR (a satellite-derived plant productivity index) to examine potential mechanisms through which weather conditions affect the availability and the seasonal phenology of beaver forage. Juvenile body weights were lighter after colder winters, while warmer spring temperatures were associated with lighter adult body weights, mediated by enhanced green-up phenology rates. Counter-intuitively, we observed a negative association between rainfall and body weight in juveniles and adults, and also with reproductive success. Alder, Alnus incana , (n=68) growth rings (principal beaver food in the study area) exhibited a positive relationship with rainfall for trees growing at elevations 〉2m above water level, but a negative relationship for trees growing 〈0.5m. We deduce that temperature influences beavers at the landscape scale via effects on spring green-up phenology and winter thermoregulation. Rainfall influences beavers at finer spatial scales, through topographical interactions with plant growth, where trees near water level, prone to water-logging, producing poorer forage in wetter years. Unlike most other herbivores, beavers are an obligate aquatic species that utilize a restricted ‘central-place’ foraging range, limiting their ability to take advantage of better forage growth further from water during wetter years. With respect to anthropogenic climate change, interactions between weather variables, plant phenology and topography on forage growth are instructive, and consequently warrant examination when developing conservation management strategies for populations of medium to large herbivores. © 2012 Blackwell Publishing Ltd

Beschreibung: This study explores effects of climate change and fuel management on unplanned fire activity in ecosystems representing contrasting extremes of the moisture availability spectrum (mesic and arid). Simulation modelling examined unplanned fire activity (fire incidence and area burned, and the area burned by large fires) for alternate climate scenarios and prescribed burning levels in: (i) a cool, moist temperate forest and wet moorland ecosystem in south-west Tasmania (mesic); and (ii) a spinifex and mulga ecosystem in central Australia (arid). Contemporary fire activity in these case study systems is limited respectively by fuel availability and fuel amount. For future climates, unplanned fire incidence and area burned increased in the mesic landscape, but decreased in the arid landscape in accordance with predictions based on these limiting factors. Area burned by large fires (greater than the 95 th percentile of historical, unplanned fire size) increased with future climates in the mesic landscape. Simulated prescribed burning was more effective in reducing unplanned fire activity in the mesic landscape. However, the inhibitory effects of prescribed burning are predicted to be outweighed by climate change in the mesic landscape, whereas in the arid landscape prescribed burning reinforced a predicted decline in fire under climate change. The potentially contrasting direction of future changes to fire will have fundamentally different consequences for biodiversity in these contrasting ecosystems, and these will need to be accommodated through contrasting, innovative management solutions. © 2012 Blackwell Publishing Ltd

Beschreibung: Although climate change is predicted to place mountain-top and other narrowly endemic species at severe risk of extinction, the ecological processes involved in such extinctions are still poorly resolved. In addition, much of this biodiversity loss will likely go unobserved, and therefore largely unappreciated. The Haleakalā silversword is restricted to a single volcano summit in Hawaiʻi, but is a highly charismatic giant rosette plant that is viewed by 1-2 million visitors annually. We link detailed local climate data to a lengthy demographic record, and combine both with a population-wide assessment of recent plant mortality and recruitment, to show that after decades of strong recovery following successful management, this iconic species has entered a period of substantial climate-associated decline. Mortality has been highest at the lower end of the distributional range, where most silverswords occur, and the strong association of annual population growth rates with patterns of precipitation suggests an increasing frequency of lethal water stress. Local climate data confirm trends towards warmer and drier conditions on the mountain, and signify a bleak outlook for silverswords if these trends continue. The silversword example foreshadows trouble for diversity in other biological hotspots, and illustrates how even well-protected and relatively abundant species may succumb to climate-induced stresses. © 2012 Blackwell Publishing Ltd

Beschreibung: The currently observed Arctic warming will increase permafrost degradation followed by mineralization of formerly frozen organic matter to carbon dioxide (CO 2 ) and methane (CH 4 ). Despite increasing awareness of permafrost carbon vulnerability the potential long-term formation of trace gases from thawing permafrost remains unclear. The objective of the current study is to quantify the potential long-term release of trace gases from permafrost organic matter. Therefore, Holocene and Pleistocene permafrost deposits were sampled in the Lena River Delta, Northeast Siberia. The sampled permafrost contained between 0.6 and 12.4% organic carbon. CO 2 and CH 4 production was measured for 1200 days in aerobic and anaerobic incubations at 4°C. The derived fluxes were used to estimate parameters of a two pool carbon degradation model. Total CO 2 production was similar in Holocene permafrost (1.3 ± 0.8 mg CO 2 -C gdw −1 aerobically, 0.25 ± 0.13 mg CO 2 -C gdw −1 anaerobically) as in 34,000 to 42,000 year old Pleistocene permafrost (1.6 ± 1.2 mg CO 2 -C gdw −1 aerobically, 0.26 ± 0.10 mg CO 2 -C gdw −1 anaerobically). The main predictor for carbon mineralization was the content of organic matter. Anaerobic conditions strongly reduced carbon mineralization since only 25% of aerobically mineralized carbon was released as CO 2 and CH 4 in the absence of oxygen. CH 4 production was low or absent in most of the Pleistocene permafrost and always started after a significant delay. After 1200 days on average 3.1% of initial carbon was mineralized to CO 2 under aerobic conditions while without oxygen 0.55% were released as CO 2 and 0.28% as CH 4 . The calibrated carbon degradation model predicted cumulative CO 2 production over a period of 100 years accounting for 15.1% (aerobic) and 1.8% (anaerobic) of initial organic carbon, which is significantly less than recent estimates. The multi-year time series from the incubation experiments helps to more reliably constrain projections of future trace gas fluxes from thawing permafrost landscapes. © 2012 Blackwell Publishing Ltd

Beschreibung: Meeting the projected 50% increase in global grain demand by 2030 without further environmental degradation poses a major challenge for agricultural production. Because surface ozone (O 3 ) has a significant negative impact on crop yields, one way to increase future production is to reduce O 3 -induced agricultural losses. We present two strategies whereby O 3 damage to crops may be reduced. We first examine the potential benefits of an O 3 mitigation strategy motivated by climate change goals: gradual emission reductions of methane (CH 4 ), an important greenhouse gas and tropospheric O 3 precursor that has not yet been targeted for O 3 pollution abatement. Our second strategy focuses on adapting crops to O 3 exposure by selecting cultivars with demonstrated O 3 resistance. We find that the CH 4 reductions considered would increase global production of soybean, maize and wheat by 23-102 Mt in 2030 – the equivalent of a ~2-8% increase in year 2000 production worth $3.5-15 billion worldwide (USD 2000 ), increasing the cost-effectiveness of this CH 4 mitigation policy. Choosing crop varieties with O 3 resistance (relative to median-sensitivity cultivars) could improve global agricultural production in 2030 by over 140 Mt, the equivalent of a 12% increase in 2000 production worth ~$22 billion. Benefits are dominated by improvements for wheat in South Asia, where O 3 -induced crop losses would otherwise be severe. Combining the two strategies generates benefits that are less than fully additive given the nature of O 3 effects on crops. Our results demonstrate the significant potential to sustainably improve global agricultural production by decreasing O 3 -induced reductions in crop yields. © 2012 Blackwell Publishing Ltd

Beschreibung: Land cover changes may affect climate and the energy balance of the Earth through their influence on the greenhouse gas composition of the atmosphere (biogeochemical effects) but also through shifts in the physical properties of the land surface (biophysical effects). We explored how the radiation budget changes following the replacement of temperate dry forests by crops in central semi-arid Argentina and quantified the biophysical radiative forcing of this transformation. For this purpose, we computed the albedo and surface temperature for a 7-year period (2003-2009) from MODIS imagery at 70 paired sites occupied by native forests and crops and calculated the radiation budget at the tropopause and surface levels using a columnar radiation model parameterized with satellite data. Mean annual black-sky albedo and diurnal surface temperature were 50% and 2.5ºC higher in croplands than in dry forests. These contrasts increased the outgoing shortwave energy flux at the top of the atmosphere in croplands by a quarter (58.4 vs. 45.9 W m -2 ) which, together with a slight increase in the outgoing longwave flux, yielded a net cooling of -14 W m -2 . This biophysical cooling effect would be equivalent to a reduction of atmospheric CO 2 of 22 Mg C ha -1 , which involves approximately a quarter to a half of the typical carbon emissions that accompany deforestation in these ecosystems. We showed that the replacement of dry forests by crops in central Argentina has strong biophysical effects on the energy budget which could counterbalance the biogeochemical effects of deforestation. Underestimating or ignoring these biophysical consequences of land use changes on climate will certainly curtail the effectiveness of many warming mitigation actions, particularly in semi-arid regions where high radiation load and smaller active carbon pools would increase the relative importance of biophysical forcing. © 2012 Blackwell Publishing Ltd

Beschreibung: Previous studies have shown a correspondence between the abundance of particular plant species and methane flux. Here we apply multivariate analyses, including a weighted averaging approach, to assess the suitability of vegetation composition as a predictor of methane flux. We developed a functional classification of the vegetation, in terms of a number of plant traits expected to influence methane production and transport, and compared this with a purely taxonomic classification at species-level and higher. We applied both weighted averaging and indirect and direct ordination approaches to six sites in the UK, and found good relationships between methane flux and vegetation composition (classified both taxonomically and functionally). Plant species and functional groups also showed meaningful responses to management and experimental treatments. In addition to the UK, we applied the functional group classification across different geographical regions (Canada and Netherlands) to assess the generality of the method. Again, the relationship appeared good at the site level, suggesting some general applicability of the functional classification. The method seems to have the potential for incorporation into large-scale (national) greenhouse gas accounting programmes (in relation to peatland condition/management) using vegetation mapping schemes. The results presented here strongly suggest that robust predictive models can be derived using plant species data (for use in national-scale studies). For trans-national-scale studies, where the taxonomic assemblage of vegetation differs widely between study sites, a functional classification of plant species data provide an appropriate basis for predictive models of methane flux. © 2012 Blackwell Publishing Ltd

Beschreibung: Sources of methane (CH 4 ) become highly variable for countries undergoing a heightened period of development due to both human activity and climate change. An urgent need therefore exists to budget key sources of CH 4 , such as wetlands (rice paddies and natural wetlands) and lakes (including reservoirs and ponds), which are sensitive to these changes. For this study, references in relation to CH 4 emissions from rice paddies, natural wetlands, and lakes in China were first reviewed and then re-estimated based upon the review itself. Total emissions from the three CH 4 sources were 11.25 Tg CH 4 yr −1 (ranging from 7.98 to 15.16 Tg CH 4 yr −1 ). Among the emissions, 8.11 Tg CH 4 yr −1 (ranging from 5.20 to 11.36 Tg CH 4 yr −1 ) derived from rice paddies, 2.69 Tg CH 4 yr −1 (ranging from 2.46 to 3.20 Tg CH 4 yr −1 ) from naturalwetlands, and 0.46 Tg CH 4 yr −1 (ranging from 0.33 to 0.59 Tg CH 4 yr −1 ) from lakes (including reservoirs and ponds). Plentiful water and warm conditions, as well as it large rice paddy area make rice paddies in southeastern China the greatest overall source of CH 4 , accounting for approximately 55% of total paddy emissions. Natural wetland estimates were slightly higher than the other estimates owing to the higher CH 4 emissions recorded within Qinghai-Tibetan Plateau peatlands. Total CH 4 emissions from lakes were estimated for the first time by this study, with three quarters from the littoral zone and one quarter from lake surfaces. Rice paddies, natural wetlands, and lakes are not constant sources of CH 4 but decreasing ones influenced by anthropogenic activity and climate change. A new progress-based model used in conjunction with more observations through model-data fusion approach could help obtain better estimates and insights with regard to CH 4 emissions deriving from wetlands and lakes in China. © 2012 Blackwell Publishing Ltd

Beschreibung: To predict the long-term effects of climate change—global warming and changes in precipitation—on the diameter (radial) growth of jack pine ( Pinus banksiana Lamb.) and black spruce ( Picea mariana [Mill.] B.S.P.) trees in boreal Ontario, we modified an existing diameter growth model to include climate variables. Diameter chronologies of 927 jack pine and 1,173 black spruce trees, growing in the area from 47° N to 50° N and 80° W to 92° W, were used to develop diameter growth models in a non-linear mixed-effects approach. Our results showed that the variables long-term average of mean growing season temperature, precipitation during wettest quarter, and total precipitation during growing season were significant (alpha = 0.05) in explaining variation in diameter growth of the sample trees. Model results indicated that higher temperatures during the growing season would increase the diameter growth of jack pine trees, but decrease that of black spruce trees. More precipitation during the wettest quarter would favor the diameter growth of both species. On the other hand, a wetter growing season, which may decrease radiation inputs, increase nutrient leaching, and reduce the decomposition rate, would reduce the diameter growth of both species. Moreover, our results indicated that future (2041-2070) diameter growth rate may differ from current (1971-2000) growth rates for both species, with conditions being more favorable for jack pine than black spruce trees. Expected future changes in the growth rate of boreal trees needs to be considered in forest management decisions. We recommend that knowledge of climate–growth relationships, as represented by models, be combined with learning from adaptive management to reduce the risks and uncertainties associated with forest management decisions. © 2012 Blackwell Publishing Ltd

Beschreibung: An increasing number of studies have reported on forest declines and vegetation shifts triggered by drought. In the Swiss Rhone valley (Valais), one of the driest inner-Alpine regions, the species composition in low-elevation forests is changing: The sub-boreal Scots pine ( Pinus sylvestris L.) dominating the dry forests is showing high mortality rates. Concurrently the sub-Mediterranean pubescent oak ( Quercus pubescens Willd.) has locally increased in abundance. However, it remains unclear whether this local change in species composition is part of a larger-scale vegetation shift. To study variability in mortality and regeneration in these dry forests we analyzed data from the Swiss National Forest Inventory (NFI) on a regular grid between 1983 and 2003, and combined it with annual mortality data from a monitoring site. Pine mortality was found to be highest at low elevation (below 1000 m a.s.l.). Annual variation in pine mortality was correlated with a drought index computed for the summer months prior to observed tree death. A generalized linear mixed-effects model indicated for the NFI data increased pine mortality on dryer sites with high stand competition, particularly for small-diameter trees. Pine regeneration was low in comparison to its occurrence in the overstorey, while oak regeneration was comparably abundant. While both species regenerated well at dry sites, pine regeneration was favoured at cooler sites at higher altitude and oak regeneration was more frequent at warmer sites, indicating a higher adaptation potential of oaks under future warming. Our results thus suggest that an extended shift in species composition is actually occuring in the pine forests in the Valais. The main driving factors are found to be climatic variability, particularly drought, and variability in stand structure and topography. Thus, pine forests at low elevations are developing into oak forests with unknown consequences for these ecosystems and their goods and services. © 2012 Blackwell Publishing Ltd

Beschreibung: A number of studies have demonstrated the ecological sorting of C 3 and C 4 grasses along temperature and moisture gradients. Yet previous studies of C 3 and C 4 grass biogeography have often inadvertently compared species in different and relatively unrelated lineages, which are associated with different environmental settings and distinct adaptive traits. Such confounded comparisons of C 3 and C 4 grasses may bias our understanding of ecological sorting imposed strictly by photosynthetic pathway. Here we used MaxEnt species distribution modeling in combination with satellite data to understand the functional diversity of C 3 and C 4 grasses by comparing both large clades and closely related sister taxa. Similar to previous work, we found that C 4 grasses showed a preference for regions with higher temperatures and lower precipitation compared to grasses using the C 3 pathway. However, air temperature differences were smaller (2° C vs. 4°C) and precipitation and % tree cover differences were larger (1783 mm vs. 755 mm, 21.3% vs. 7.7%, respectively) when comparing C 3 and C 4 grasses within the same clade versus comparing all C 4 and all C 3 grasses (i.e., ignoring phylogenetic structure). These results were due to important differences in the environmental preferences of C 3 BEP and PACMAD clades (the two main grass clades). Winter precipitation was found to be more important for understanding the distribution and environmental niche of C 3 PACMADs in comparison to both C 3 BEPs and C 4 taxa, for which temperature was much more important. Results comparing closely related C 3 -C 4 sister taxa supported the patterns derived from our modeling of the larger clade groupings. Our findings, which are novel in comparing the distribution and niches of clades, demonstrate that the evolutionary history of taxa is important for understanding the functional diversity of C 3 and C 4 grasses, and should have implications for how grasslands will respond to global change. © 2012 Blackwell Publishing Ltd

Beschreibung: The combination of global and local stressors is leading to a decline in coral reef health globally. In the case of eutrophication, increased concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) are largely attributed to local land use changes. From the global perspective, increased atmospheric CO 2 levels are not only contributing to global warming but also ocean acidification (OA). Both eutrophication and OA have serious implications for calcium carbonate production and dissolution among calcifying organisms. In particular, benthic foraminifera precipitate the most soluble form of mineral calcium carbonate (high-Mg calcite), potentially making them more sensitive to dissolution. In the present study a manipulative orthogonal two-factor experiment was conducted to test the effects of dissolved inorganic nutrients and OA on the growth, respiration and photophysiology of the large photosymbiont-bearing benthic foraminifer, Marginopora rossi . This study found the growth rate of M. rossi was inhibited by the interaction of eutrophication and acidification. The relationship between M. rossi and its photosymbionts became destabilised due to the photosymbiont's release from nutrient limitation in the nitrate-enriched treatment, as shown by an increase in zooxanthellae cells per host surface area. Foraminifers from the OA treatments had an increased amount of Chl a per cell, suggesting a greater potential to harvest light energy, however there was no net benefit to foraminifer growth. Overall, this study demonstrates that the impacts of OA and eutrophication are dose-dependant and interactive. This research indicates an OA threshold at pH 7.6, alone or in combination with eutrophication, will lead to a decline in M. rossi calcification. The decline in foraminifera calcification associated with pollution and OA will have broad ecological implications across their ubiquitous range and suggests that without mitigation it could have serious implications for the future of coral reefs. © 2012 Blackwell Publishing Ltd

Beschreibung: Glaciers around the globe are melting rapidly, threatening the receiving environments of the world's fresh water reservoirs with significant changes. The meltwater, carried by rivers, contains large amounts of suspended sediment particles, producing longitudinal gradients in the receiving lakes. These gradients may result in changes in the light:nutrient ratio that affect grazer performance by altering elemental food quality. Thus, glacial melting may induce a shift in the phytoplankton carbon:nutrient ratio and hence influence the dominance of herbivorous zooplankton through stoichiometric mechanisms. To test this hypothesis, we combined field and experimental data, taking advantage of a natural light intensity gradient caused by glacial clay input in a deep oligotrophic Patagonian lake. Across this gradient, we evaluated the abundances of two consumer taxa with different phosphorus requirements, the copepod Boeckella gracilipes and the cladoceran Daphnia commutata , using a six-station transect along the lake. We found significant differences in light:nutrient ratio and stoichiometric food quality of the seston, together with a switch from dominance of P-rich Daphnia in low carbon:nutrient stations to dominance of low-P copepods in high carbon:nutrient stations. The laboratory experiments confirmed that the difference in the carbon:nutrient ratio across the gradient is sufficient to impair Daphnia growth. The overall patterns are consistent with our prediction that shifts in the environmental light:nutrient ratio as a result of glacial melting would contribute to shifts in the dominance of stoichiometrically contrasting taxa in consumer guilds. © 2012 Blackwell Publishing Ltd

Beschreibung: Global climate warming is predicted to lead to global and regional changes in the distribution of organisms. One influential approach to test this prediction using temporally repeated mapping surveys of organisms was suggested in a seminal paper by Thomas & Lennon (1999, Nature). The Thomas & Lennon approach corrects observed changes in the range margin for changes in the range size, and thus potentially controls for other broad-scale environmental changes between surveys, however the approach does not necessarily account for potential biases in sampling effort. To verify whether the issue of variation in sampling effort affects empirical estimates of shifts in range margin, we re-analyzed all three published studies exploring range margin changes of breeding birds in Great Britain (GB), Finland and New York State (NY). Accounting for changes in survey effort on range margins lowered the estimated shift for breeding birds in NY, but the shift remained statistically significant. For GB and Finland, for which no direct estimate of survey effort is available, we used species richness (a strong correlate of survey effort in NY) as a proxy and found that in both cases the estimated shift in range margin was significantly reduced and became non-significant. To understand how robust the approach is to sampling biases we use a simulation model to show that the Thomas & Lennon approach is, under certain conditions, sensitive to changes in detection probability (probability to detect true occupancy) which in turn may be affected by changes in surveying effort between surveys. We thus found evidence that temporal changes in the distribution of breeding birds based on repeated mapping surveys may be inflated by changes in survey effort along range boundaries. We discuss possible approaches to deal with this issue in the analysis and design of national or regional surveys. © 2012 Blackwell Publishing Ltd

Beschreibung: Non-native, invasive grasses have been linked to altered grass-fire cycles worldwide. Although a few studies have quantified resulting changes in fire activity at local scales, and many have speculated about larger scales, regional alterations to fire regimes remain poorly documented. We assessed the influence of large-scale Bromus tectorum (hereafter cheatgrass) invasion on fire size, duration, spread rate and inter-annual variability in comparison to other prominent land cover classes across the Great Basin, USA. We compared regional land cover maps to burned area measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) for 2000-2009 and to fire extents recorded by the USGS registry of fires from 1980-2009. Cheatgrass dominates at least 6% of the 650,000 km 2 composing the central Great Basin. MODIS records show that 13% of these cheatgrass-dominated lands burned, resulting in a fire return interval of 78 years for any given location within cheatgrass. This proportion was more than double the amount burned across all other vegetation types (range: 0.5-6% burned). During the 1990s, this difference was even more extreme, with cheatgrass burning nearly four times more frequently than any native vegetation type (16% of cheatgrass burned compared to 1-5% of native vegetation). Cheatgrass was disproportionately represented in the largest fires, comprising 24% of the land area of the 50 largest fires recorded by MODIS during the 2000s. Further, multi-date fires that burned across multiple vegetation types were significantly more likely to have started in cheatgrass. Finally, cheatgrass fires showed a strong inter-annual response to wet years, a trend only weakly observed in native vegetation types. These results demonstrate that cheatgrass invasion has substantially altered the regional fire regime. While this result has been suspected by managers for decades, this study is the first to document recent cheatgrass-driven fire regimes at a regional scale. © 2012 Blackwell Publishing Ltd

Beschreibung: Abstarct To quantify the carbon (C) sink in intact tropical forests, Pan et al. (2011) multiplied “…region-specific estimates of C density or change in C density times the associated areas represented by the region-specific estimates.” A retrospective interpolation based on their numbers provides insight into the possible causes of a C sink in intact tropical forests. First, however, there are two reasons to believe their estimated sink of 1.2 Pg C yr −1 between 1990 and 2007 is too large. Published 2012. This article is a U.S. Government work and is in the public domain in the USA

Beschreibung: Urbanisation causes severe environmental degradation and continues to increase in scale and intensity around the world, but little is known about how we should design cities to minimise their ecological impact. With a sprawling style of urban development, low intensity impact is spread across a wide area and with a compact form of development intense impact is concentrated over a small area; it is unclear which of these development styles has a lower overall ecological impact. Here, we compare the consequences of compact and sprawling urban growth patterns on bird distributions across the city of Brisbane, Australia. We predicted the impact on bird populations of adding 84,642 houses to the city in either a compact or sprawling design using statistical models of bird distributions. We show that urban growth of any type reduces bird distributions overall, but compact development substantially slows these reductions at the city scale. Urban-sensitive species particularly benefited from compact development at the city scale because large green spaces were left intact, while the distributions of non-native species expanded as a result of sprawling development. As well as minimising ecological disruption, compact urban development maintains human access to public green spaces. However, backyards are smaller, which impacts opportunities for people to experience nature close to home. Our results suggest that cities built to minimise per capita ecological impact are characterised by high residential density, with large interstitial green spaces and small backyards, and that there are important trade-offs between maintaining city-wide species diversity and people's access to biodiversity in their own backyard. © 2012 Blackwell Publishing Ltd

Beschreibung: As a consequence of land use change and the burning of fossil fuels, atmospheric concentrations of CO 2 are increasing and altering the dynamics of the carbon cycle in forest ecosystems. In a number of studies using single tree species, fine root biomass has been shown to be strongly increased by elevated CO 2. However, natural forests are often intimate mixtures of a number of co-occurring species. To investigate the interaction between tree mixture and elevated CO 2, Alnus glutinosa , Betula pendula and Fagus sylvatica were planted in areas of single species and a three species polyculture in a free-air CO 2 enrichment study (BangorFACE). The trees were exposed to ambient or elevated CO 2 (580 μmol mol -1 ) for four years. Fine and coarse root biomass, together with fine root turnover and fine root morphological characteristics were measured. Fine root biomass, and morphology responded differentially to elevated CO 2 at different soil depths in the three species when grown in monocultures. In polyculture, a greater response to elevated CO 2 was observed in coarse roots to a depth of 20 cm, and fine root area index to a depth of 30 cm. Total fine root biomass was positively affected by elevated CO 2 at the end of the experiment, but not by species diversity. Our data suggest that existing biogeochemical cycling models parameterised with data from species grown in monoculture may be underestimating the belowground response to global change. © 2012 Blackwell Publishing Ltd

Beschreibung: Carbon (C) uptake by terrestrial ecosystems represents an important option for partially mitigating anthropogenic CO 2 emissions. Short-term atmospheric elevated CO 2 exposure has been shown to create major shifts in C flow routes and diversity of the active soil-borne microbial community. Long-term increases in CO 2 have been hypothesized to have subtle effects due to the potential adaptation of soil micro-organism to the increased flow of organic C. Here, we studied the effects of prolonged elevated atmospheric CO 2 exposure on microbial C flow and microbial communities in the rhizosphere. Carex arenaria (a non-mycorrhizal plant species) and Festuca rubra (a mycorrhizal plant species) were grown at defined atmospheric conditions differing in CO 2 concentration (350 and 700 ppm) for three years. During this period, C flow was assessed repeatedly (after 6 months, 1, 2 and 3 years) by 13 C pulse-chase experiments, and label was tracked through the rhizosphere bacterial, general fungal and arbuscular mycorrhizal fungal (AMF) communities. Fatty acid biomarker analyses and RNA-Stable Isotope Probing (RNA-SIP), in combination with real-time PCR and PCR-DGGE, were used to examine microbial community dynamics and abundance. Throughout the experiment the influence of elevated CO 2 was highly plant dependent, with the mycorrhizal plant exerting a greater influence on both bacterial and fungal communities. Biomarker data confirmed that rhizodeposited C was first processed by AMF and subsequently transferred to bacterial and fungal communities in the rhizosphere soil. Over the course of three years, elevated CO 2 caused a continuous increase in the 13 C enrichment retained in AMF and an increasing delay in the transfer of C to the bacterial community. These results show that, not only do elevated atmospheric CO 2 conditions induce changes in rhizosphere C flow and dynamics, but also continue to develop over multiple seasons, thereby affecting terrestrial ecosystems C utilization processes. © 2012 Blackwell Publishing Ltd

Beschreibung: A hypothesized underlying principle of the diversity-functioning relationship is that functional groups respond differently to environmental change. Over three years, we investigated how pollinator diversity contributes to the magnitude of pollination service through spatial complementarity and differential response to high winds in California almond orchards. We found honey bees preferentially visited the top sections of the tree. Where wild pollinators were present, they showed spatial complementarity to honey bees and visited the bottom tree sections more frequently. As wind speed increased, honey bees’ spatial preference shifted towards the bottom tree sections. In high winds (〉2.5 m/s), orchards with low pollinator diversity (honey bees only) received almost no flower visits. In orchards with high pollinator diversity, visitation decreased to a lesser extent as wild bee visitation was unaffected by high winds. Our results demonstrate how spatial complementarity in diverse communities can help buffer pollination services to environmental changes like wind speed. © 2012 Blackwell Publishing Ltd

Beschreibung: Increasing reactive nitrogen (N) input has been recognized as one of important factors influencing climate system through affecting the uptake and emission of greenhouse gases (GHG). However, the magnitude and spatiotemporal variations of N-induced GHG fluxes at regional and global scales remain far from certain. Here we selected China as an example, and used a coupled biogeochemical model in conjunction with spatially-explicit data sets (including climate, atmospheric CO 2 , O 3 , N deposition, land use and land cover changes, and N fertilizer application) to simulate the concurrent impacts of increasing atmospheric and fertilized N inputs on balance of three major GHGs (CO 2 , CH 4 and N 2 O). Our simulations showed that these two N enrichment sources in China decreased global warming potential (GWP) through stimulating CO 2 sink and suppressing CH 4 emission. However, direct N 2 O emission was estimated to offset 39% of N-induced carbon (C) benefit, with a net GWP of three GHGs averaging -376.3 ± 146.4 Tg CO 2 eq yr -1 (the standard deviation is interannual variability of GWP) during 2000-2008. The chemical N fertilizer uses were estimated to increase GWP by 45.6 ± 34.3 Tg CO 2 eq yr -1 in the same period, and C sink was offset by 136%. The largest C sink offset ratio due to increasing N input was found in Southeast and Central mainland of China, where rapid industrial development and intensively managed crop system located. Although exposed to the rapidly increasing N deposition, most of natural vegetation covers were still decreasing GWP. However, due to extensive overuses of N fertilizer, China's cropland was found to show the least negative GWP, or even positive GWP in recent decade. From both scientific and policy perspectives, it is essential to incorporate multiple GHGs into a coupled biogeochemical framework for fully assessing N impacts on climate changes. © 2012 Blackwell Publishing Ltd

Beschreibung: Whilst global environmental change in the Twenty First Century will undoubtedly have direct impacts on built heritage, it will also have important indirect effects through its influence on microbial, plant and animal life on heritage sites. Environmental change will affect both the structure of biotic communities and the function of such communities. Both impacts will, in turn, influence the deterioration and conservation of heritage sites. Changes in precipitation will exert a major, but as yet poorly understood, control on heritage biotas, whilst changes in atmospheric composition may also be important. Climatic changes will cause range shifts for some taxa, further influencing community composition. Whilst there are many unknowns, making prediction difficult, some scenarios can be proposed based on ecological response to stress and disturbance. This approach indicates some ‘hotspots’ at risk of experiencing dramatic shifts in biotic communities and their impacts, which may switch from biodeteriogenic to bioprotective or vice versa. Such hotspots include vulnerable sandstone and limestone heritage structures in areas of the Mediterranean, Middle East, Caribbean and Southern Africa.

Beschreibung: Biological soil crusts (biocrusts) are common and ecologically important members of dryland ecosystems worldwide, where they stabilize soil surfaces and contribute newly fixed C and N to soils. To test the impacts of predicted climate change scenarios on biocrusts in a dryland ecosystem, the effects of a 2-3 °C increase in soil temperature and an increased frequency of smaller summer precipitation events were examined in a large, replicated field study conducted in the cold desert of the Colorado Plateau, USA. Surface soil biomass (DNA concentration), photosynthetically active cyanobacterial biomass (chlorophyll a concentration), cyanobacterial abundance (quantitative PCR assay), and bacterial community composition (16S rRNA gene sequencing) were monitored seasonally over two years. Soil microbial biomass and bacterial community composition were highly stratified between the 0-2 cm depth biocrusts and 5-10 cm depth soil beneath the biocrusts. The increase in temperature did not have a detectable effect on any of the measured parameters over two years. However, after the second summer of altered summer precipitation pattern, significant declines occurred in the surface soil biomass (avg. DNA concentration declined 38%), photosynthetic cyanobacterial biomass (avg. chlorophyll a concentration declined 78%), cyanobacterial abundance (avg. gene copies/g soil declined 95%), and proportion of Cyanobacteria in the biocrust bacterial community (avg. representation in sequence libraries declined 85%). Biocrusts are important contributors to soil stability, soil C and N stores, and plant performance, and the loss or reduction of biocrusts under an altered precipitation pattern associated with climate change could contribute significantly to lower soil fertility and increased erosion and dust production in dryland ecosystems at a regional scale.

Beschreibung: Climate change is increasingly recognised as a major risk to human health, and health concerns are assuming more importance in international debates on mitigation and adaptation strategies. Health consequences of climate change will occur through direct and indirect routes, and as a result of interactions with other environmental exposures. Heatwaves will become more common and are associated with higher mortality particularly in the elderly and those with pre-existing cardiovascular and respiratory illnesses. Warmer ambient temperatures will result in more dehydration episodes and increased risks of renal disease and, through effects on pollen seasons, there may be an increase in allergic disease such as asthma and hayfever. Other adverse effects including on air quality, food safety and security and an expanding distribution of some infectious diseases, including vector-borne diseases, are postulated. A related but separate environmental exposure is that of ultraviolet radiation. Interactions between climate change and stratospheric ozone (and the causes of ozone depletion) will cause changes to levels of ambient ultraviolet radiation in the future and warmer temperatures are likely to change sun exposure behaviour. Co-occurring effects on aquatic and terrestrial ecosystems have potential consequences for food safety, quality and supply. Climate change-related exposures are likely to affect the incidence and distribution of diseases usually considered as caused by UVR exposure; and changes in UVR exposure will modulate the climate change effects on human health. For example, in some regions warmer temperatures due to climate change will encourage more outdoor behaviour, with likely consequences for increasing skin cancer incidence. While many of the health outcomes of both climate change and the interaction of climate change and UVR exposure are somewhat speculative, there are risks to over- or under-estimations of health risks if synergistic and antagonistic effects of co-occurring environmental changes are not considered.

Beschreibung: Artificial lighting is a key biodiversity threat and produces 1900 million tonnes of CO 2 emissions globally, more than three times that produced by aviation. The need to meet climate change targets has led to a global increase in energy-efficient light sources such as high-brightness light-emitting diodes (LEDs). Despite the energetic benefits of LEDs, their ecological impacts have not been tested. Using an experimental approach we show that LED street lights caused a reduction in activity of slow-flying bats ( Rhinolophus hipposideros and Myotis spp.). Both R. hipposideros and Myotis spp. activity was significantly reduced even during low light levels of 3.6 lux. There was no effect of LED lighting on the relatively fast-flying Pipistrellus pipistrellus , P. pygmaeus and Nyctalus/Eptesicus spp. We provide the first evidence of the effects of LED lights on bats. Despite having considerable energy-saving benefits, LED lights can potentially fragment commuting routes for bats with associated negative conservation consequences. Our results add to the growing evidence of negative impacts of lighting on a wide range of taxa. We highlight the complexities involved in simultaneously meeting targets for reduction of greenhouse gas emissions and biodiversity loss. New lighting strategies should integrate climate change targets with the cultural, social, and ecological impacts of emerging lighting technologies.

Beschreibung: Although climate change models predict relatively modest increases in temperature in the tropics by the end of the century, recent analyses identify tropical ectotherms as the organisms most at risk from climate warming. Because metabolic rate in ectotherms increases exponentially with temperature, even a small rise in temperature poses a physiological threat to tropical ectotherms inhabiting an already hot environment. If correct, the metabolic theory of climate warming has profound implications for global biodiversity, since tropical insects and arachnids constitute the vast majority of animal species. Predicting how climate change will translate into fitness consequences for tropical arthropods requires an understanding of the effects of temperature increase on the entire life history of the species. Here, in a comprehensive case study of the fitness consequences of the projected temperature increase for the tropics, we conducted a split-brood experiment on the neotropical pseudoscorpion, Cordylochernes scorpioides , in which 792 offspring from 33 females were randomly assigned at birth to control- and high-temperature treatments for rearing through the adult stage. The diurnally varying, control treatment temperature was determined from long-term, average daily temperature minima and maxima in the pseudoscorpion's native habitat. In the high temperature treatment, increasing temperature by the 3.5 °C predicted for the tropics significantly reduced survival and accelerated development at the cost of reduced adult size and a dramatic decrease in level of sexual dimorphism. The most striking effects, however, involved reproductive traits. Reared at high temperature, males produced 45% as many sperm as control males, and females failed to reproduce. Sequencing of the mitochondrial ND2 gene revealed two highly divergent haplogroups that differed substantially in developmental rate and survivorship but not in reproductive response to high temperature. Our findings suggest that reproduction may be the Achilles’ heel of tropical ectotherms, as climate warming subjects them to an increasingly adverse thermal environment.

Beschreibung: Uncertainties in model projections of carbon cycling in terrestrial ecosystems stem from inaccurate parameterization of incorporated processes (endogenous uncertainties) and processes or drivers that are not accounted for by the model (exogenous uncertainties). Here we assess endogenous and exogenous uncertainties using a model-data fusion framework benchmarked with an artificial neural network (ANN). We used 18 years of eddy-covariance carbon flux data from the Harvard Forest, where ecosystem carbon uptake has doubled over the measurement period, along with 15 ancillary ecological data sets relative to the carbon cycle. We test the ability of combinations of diverse data to constrain projections of a process-based carbon cycle model, both against the measured decadal trend and under future long-term climate change. The use of high-frequency eddy-covariance data alone is shown to be insufficient to constrain model projections at the annual or longer time step. Future projections of carbon cycling under climate change in particular are shown to be highly dependent on the data used to constrain the model. Endogenous uncertainties in long-term model projections of future carbon stocks and fluxes were greatly reduced by the use of aggregated flux budgets in conjunction with ancillary data sets. The data-informed model, however, poorly reproduced interannual variability in net ecosystem carbon exchange and biomass increments, and did not reproduce the long-term trend. Furthermore, we use the model-data fusion framework, and the ANN, to show that the long-term doubling of the rate of carbon uptake at Harvard forest cannot be explained by meteorological drivers, and is driven by changes during the growing season. By integrating all available data with the model-data fusion framework we show that the observed trend can only be reproduced with temporal changes in model parameters. Together, the results show that exogenous uncertainty dominates uncertainty in future projections from a data-informed process-based model.

Beschreibung: This study tested the hypothesis that the response of corals to temperature and pCO 2 is consistent between taxa. Juvenile massive Porites spp. and branches of P. rus from the back reef of Moorea were incubated for 1 month under combinations of temperature (29.3°C and 25.6°C) and pCO 2 (41.6 Pa and 81.5 Pa) at an irradiance of 599 μmol quanta m −2 s −1 . Using microcosms and CO 2 gas mixing technology, treatments were created in a partly nested design (tanks) with two between-plot factors (temperature and pCO 2 ), and one within-plot factor (taxon); calcification was used as a dependent variable. pCO 2 and temperature independently affected calcification, but the response differed between taxa. Massive Porites spp. was largely unaffected by the treatments, but P. rus grew 50% faster at 29.3°C compared to 25.6°C, and 28% slower at 81.5 Pa versus 41.6 Pa CO 2 . A compilation of studies placed the present results in a broader context and tested the hypothesis that calcification for individual coral genera is independent of pH, [HCO 3 - ] and [CO 3 2- ]. Unlike recent reviews, this analysis was restricted to studies reporting calcification in units that could be converted to nmol CaCO 3 cm −2 h −1 . The compilation revealed a high degree of variation in calcification as a function of pH, [HCO 3 - ] and [CO 3 2- ], and supported three conclusions: (1) studies of the effects of OA on corals need to pay closer attention to reducing variance in experimental outcomes to achieve stronger synthetic capacity, (2) coral genera respond in dissimilar ways to pH, [HCO 3 - ] and [CO 3 2- ], and (3) calcification of massive Porites spp. is relatively resistant to short exposures of increased pCO 2 , similar to that expected within 100 y.

Beschreibung: Soils retain large quantities of carbon, thereby slowing its return to the atmosphere. The mechanisms governing organic carbon sequestration in soil remain poorly understood, yet are integral to understanding soil-climate feedbacks. We evaluated the biochemistry of dissolved and solid organic carbon in potential source and sink horizons across a chronosequence of volcanic soils in Hawai'i. The soils are derived from similar basaltic parent material on gently sloping volcanic shield surfaces, support the same vegetation assemblage, and yet exhibit strong shifts in soil mineralogy and soil carbon content as a function of volcanic substrate age. Solid-state 13 carbon nuclear magnetic resonance spectra indicate that the most persistent mineral-bound carbon is comprised of partially oxidized aromatic compounds with strong chemical resemblance to dissolved organic matter derived from plant litter. A molecular mixing model indicates that protein, lipid, carbohydrate and char content decreased whereas oxidized lignin and carboxyl/carbonyl content increased with increasing short-range order mineral content. When solutions rich in dissolved organic matter were passed through Bw-horizon mineral cores, aromatic compounds were preferentially sorbed with the greatest retention occurring in horizons containing the greatest amount of short-range ordered minerals. These minerals are reactive metastable nanocrystals that are most common in volcanic soils, but exist in smaller amounts in nearly all major soil classes. Our results indicate that long-term carbon storage in short-range ordered minerals occurs via chemical retention with dissolved aromatic acids derived from plant litter and carried along preferential flow paths to deeper B horizons.

Beschreibung: Although it is established that there exist potential trade-offs between grain yield and grain quality in wheat exposed to elevated carbon dioxide ( CO 2 ) and ozone ( O 3 ), their underlying causes remain poorly explored. To investigate the processes affecting grain quality under altered CO 2 and O 3 , we analysed 57 experiments with CO 2 or O 3 exposure in different exposure systems. The study covered 24 cultivars studied in 112 experimental treatments from 11 countries. A significant growth dilution effect on grain protein was found: a change in grain yield of 10% by O 3 was associated with a change in grain protein yield of 8.1% (R 2 =0.96), while a change in yield effect of 10% by CO 2 was linked to a change in grain protein yield effect of 7.5% (R 2 =0.74). Superimposed on this effect, elevated CO 2 , but not O 3 , had a significant negative effect on grain protein yield also in the absence of effects on grain yield, indicating that there exists a process by which CO 2 restricts grain protein accumulation, which is absent for O 3 . Grain mass, another quality trait, was more strongly affected by O 3 than grain number, while the opposite was true for CO 2 . Harvest index was strongly and negatively influenced by O 3 , but was unaffected by CO 2 . We conclude that yield vs. protein trade-offs for wheat in response to CO 2 and O 3 are constrained by close relationships between effects on grain biomass and less than proportional effects on grain protein. An important and novel finding was that elevated CO 2 has a direct negative effect on grain protein accumulation independent of the yield effect, supporting recent evidence of CO 2 -induced impairment of nitrate uptake/assimilation. Finally, our results demonstrated that processes underlying responses of grain yield vs. quality trade-offs are very different in wheat exposed to elevated O 3 compared to elevated CO 2 .

Beschreibung: Intergovernmental Panel on Climate Change (IPCC) Tier 1 methodologies commonly underpin project-scale carbon accounting for changes in land use and management and are used in frameworks for Life Cycle Assessment and carbon footprinting of food and energy crops. These methodologies were intended for use at large spatial scales. This can introduce error in predictions at finer spatial scales. There is an urgent need for development and implementation of higher tier methodologies that can be applied at fine spatial scales (e.g. farm/project/plantation) for food and bioenergy crop greenhouse gas (GHG) accounting to facilitate decision making in the land-based sectors. Higher tier methods have been defined by IPCC and must be well evaluated and operate across a range of domains (e.g. climate region, soil type, crop type, topography), and must account for land use transitions and management changes being implemented. Furthermore, the data required to calibrate and drive the models used at higher tiers need to be available and applicable at fine spatial resolution, covering the meteorological, soil, cropping system and management domains, with quantified uncertainties. Testing the reliability of the models will require data either from sites with repeated measurements or from chronosequences. We review current global capability for estimating changes in soil carbon at fine spatial scales and present a vision for a framework capable of quantifying land use change and management impacts on soil carbon, which could be used for addressing issues such as bioenergy and biofuel sustainability, food security, forest protection, and direct/indirect impacts of land use change. The aim of this framework is to provide a globally accepted standard of carbon measurement and modelling appropriate for GHG accounting that could be applied at project to national scales (allowing outputs to be scaled up to a country level), to address the impacts of land use and land management change on soil carbon.

Beschreibung: Anticipating species movement under climate change is a major focus in conservation. Bioclimate models are one of the few predictive tools for adaptation planning, but are limited in accounting for (i) climatic tolerances in preadult life stages that are potentially more vulnerable to warming; and (ii) local-scale movement and use of climatic refugia as an alternative or complement to large-scale changes in distribution. To assess whether these shortfalls can be addressed with field demographic data, we used California valley oak ( Quercus lobata Nee), a long-lived species with juvenile life stages known to be sensitive to climate. We hypothesized that the valley oak bioclimate model, based on adults, would overpredict the species' ability to remain in the projected persisting area, due to higher climate vulnerability of young life stages; and underpredict the potential for the species to remain in the projected contracting area in local-scale refugia. We assessed the bioclimate model projections against actual demographic patterns in natural populations. We found that saplings were more constricted around surface water than adults in the projected contracting area. We also found that the climate envelope for saplings is narrower than that for adults. Saplings disappeared at a summer maximum temperature 3 °C below that associated with adults. Our findings indicate that rather than a complete shift northward and upward, as predicted by the species bioclimate model, valley oaks are more likely to experience constriction around water bodies, and eventual disappearance from areas exceeding a threshold of maximum temperature. Ours is the first study we know of to examine the importance of discrete life stage climate sensitivities in determining bioclimate modeling inputs, and to identify current climate change-related constriction of a species around microrefugia. Our findings illustrate that targeted biological fieldwork can be central to understanding climate change-related movement for long-lived, sessile species.

Beschreibung: At least half of the world's population resides in the coastal zone and the livelihoods of billions of people are affected either directly or indirectly by the production and sustainability of nearshore fisheries. Landscape change, specifically development of tree plantations, is accelerating worldwide as developing countries integrate into global markets to sell goods, offer climate-mitigation services (carbon), and/or provide renewable energy. These changes can release excess nutrients into adjacent coastal waters causing eutrophication that alters the structure and function of coastal ecosystems. This study examined the relationship between coastal drainage basin land use/land cover change (LCLUC), specifically development of tree plantations, patterns of chlorophyll- a in nearshore coastal waters, and the biological condition of commercially important shellfish, Concholepas concholepas ( loco ) in southern Chile. Locos ( N  = 1374) were sampled across 13 watersheds (35 853 km 2 ) and 42 fisheries management areas (spanning 250 km of coastline). Locos harvested from management areas influenced by tree plantations had approximately 30% more endobiont (shell-boring) phoronids, almost twice as many endobiont polychaetes and twice as many epibiont (shell-attaching) barnacles than locos from areas in close proximity to watersheds dominated by native forests (15–20% of the watershed). Phoronid infested locos from coastal waters adjacent to watersheds with tree plantations were of relatively poor biological condition (smaller and narrower in width) and of reduced market value. Our study suggests that tree plantations result in indirect ecological impacts to coastal fisheries (more nutrients and higher phytoplankton biomass, resulting in smaller, low quality locos), and costs are born by coastal fishers (lower prices for locos). Increases in tree plantations could thus potentially significantly impact coastal fisheries worldwide and such problems should be managed as an interconnected network of land use change, oceanic ecosystems, and economic systems that are considered an integrated socio-ecological system.

Beschreibung: Interannual variability in biosphere-atmosphere exchange of CO 2 is driven by a diverse range of biotic and abiotic factors. Replicating this variability thus represents the ‘acid test’ for terrestrial biosphere models. Although such models are commonly used to project responses to both normal and anomalous variability in climate, they are rarely tested explicitly against inter-annual variability in observations. Herein, using standardized data from the North American Carbon Program, we assess the performance of 16 terrestrial biosphere models and 3 remote sensing products against long-term measurements of biosphere-atmosphere CO 2 exchange made with eddy-covariance flux towers at 11 forested sites in North America. Instead of focusing on model-data agreement we take a systematic, variability-oriented approach and show that although the models tend to reproduce the mean magnitude of the observed annual flux variability, they fail to reproduce the timing. Large biases in modeled annual means are evident for all models. Observed interannual variability is found to commonly be on the order of magnitude of the mean fluxes. None of the models consistently reproduce observed interannual variability within measurement uncertainty. Underrepresentation of variability in spring phenology, soil thaw and snowpack melting, and difficulties in reproducing the lagged response to extreme climatic events are identified as systematic errors, common to all models included in this study.

Beschreibung: Aquatic biodiversity faces increasing threats from climate change, escalating exploitation of water and land use intensification. Loss of vegetation in catchments (= watersheds) has been identified as a substantial problem for many river basins, and there is an urgent need to better understand how climate change may interact with changes in catchment vegetation to influence the ecological condition of freshwater ecosystems. We used 20 years of biological monitoring data from Victoria, southeastern Australia, to explore the influences of catchment vegetation and climate on stream macroinvertebrate assemblages. Southeastern Australia experienced a severe drought from 1997 to 2009, with reductions of stream flows 〉50% in some areas. The prolonged drying substantially altered macroinvertebrate assemblages, with reduced prevalence of many flow-dependent taxa and increased prevalence of taxa that are tolerant of low-flow conditions and poor water quality. Stream condition, as assessed by several commonly used macroinvertebrate indices, was consistently better in reaches with extensive native tree cover in upstream catchments. Prolonged drought apparently caused similar absolute declines in macroinvertebrate condition indices regardless of vegetation cover, but streams with intact catchment and riparian vegetation started in better condition and remained so throughout the drought. The largest positive effects of catchment tree cover on both water quality and macroinvertebrate assemblages occurred above a threshold of ca. 60% areal tree cover in upstream catchments and in higher rainfall areas. Riparian tree cover also had positive effects on macroinvertebrate assemblages, especially in warmer catchments. Our results suggest that the benefits of extensive tree cover via improved water quality and in-channel habitat persist during drought and show the potential for vegetation management to reduce negative impacts of climatic extremes for aquatic ecosystems.

Beschreibung: We used microbial lipid analysis to analyze microbial biomass and community structure during 6 years of experimental treatment at the Jasper Ridge Global Change Experiment (JRGCE), a long-term multi-factor global change experiment in a California annual grassland. The microbial community fingerprint and specific biomarkers varied substantially from year to year, in both control and experimental treatment plots. Possible drivers of the variability included plant growth, soil moisture, and ambient temperature. Surprisingly, background variation in the microbial community was of a larger magnitude than even very significant treatment effects, and this variation appeared to constrain responses to treatment. Microbial communities were mostly not responsive or not consistently responsive to the experimental treatments. Both arbuscular mycorrhizal fungi biomarker abundance (16 : 1 ω5c) and the fungal to bacterial ratio were lower under nitrogen addition in most years. Bacterial lipid biomarker abundances (15 : 0 iso and 16 : 1 ω7c) were higher under nitrogen addition in 2002, the year of largest microbial biomass, suggesting that bacteria could respond more to nitrogen addition in years of better growth conditions. Nitrogen addition and warming led to an interactive effect on the Gram-positive bacterial biomarker and the fungal to bacterial ratio. These patterns indicate that in California grassland ecosystems, microbial communities may not respond substantially to future changes in climate and that nitrogen deposition may be a determinant of the soil response to global change. Further, year-to-year variation in microbial growth or community composition may be important determinants of ecosystem response to global change.

Beschreibung: Changes in C 4 grass distribution and abundance are frequently observed in Quaternary, Holocene and future environmental-change scenarios. However, the factors driving these dynamics are not fully understood, and conflicting theories have been reported. In this paper, we present a very large dataset of modern altitudinal distribution profiles of C 3 and C 4 grasses covering the entire Neotropical Andes, which was compared with actual climate data. The results of multivariate analysis demonstrate that, in the Neotropical Andes, mean annual temperature is the main factor governing the modern altitudinal distribution of C 3 and C 4 grass species. The C 3 and C 4 grass distributions were compared with simulations based on the Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM), which allowed the present grass distribution to be estimated. Finally, the DGVM was employed to simulate past and future scenarios, using the IPCC's climate projections for 2100 and PMIP2 models for the Holocene Optimum (HO, 6000 years  bp ) and the Last Glacial Maximum (LGM, 21 000 years  bp ). The results were found to be significantly different from those obtained using a simple photosynthetic model. According to LPJ forced with the PMIP2 models for the LGM, during the LGM, the C 4 grasses would not have reached higher altitudes than found in the present day.

Beschreibung: Recent studies have highlighted the tight coupling between geomorphic processes and soil carbon (C) turnover and suggested that eroding landscapes can stabilize more C than their non-eroding counterparts. However, large uncertainties remain and a mechanistic understanding of geomorphic effects on C storage in soils is still lacking. Here, we quantified the soil organic carbon (SOC) stock and pool distribution along geomorphic gradients and combined data derived from soil organic matter fractionation and incubation experiments. The size and composition of the SOC pools were strongly related to geomorphic position: 1.6 to 6.2 times more C was stabilized in the subsoils (25–100cm) of depositional profiles than in those of eroding profiles. Subsoil C of depositional profiles is predominantly associated with microaggregates and silt-sized particles which are associated with pools of intermediate stability. We observed a significantly higher mean residence time for the fast and intermediate turnover pools of buried C at depositional positions, relative to non-eroding and eroding positions, resulting from the physical protection of C associated with microaggregates and silt particles. Conversely, significant amounts of C were replaced at eroding positions but the lower degree of decomposition and the lack of physically protected C, resulted in higher respiration rates. By considering C cycling at non-eroding, eroding and depositional positions, we found that the eroding landscapes studied store up to 10% more C due to soil redistribution processes than non-eroding landscapes. This is the result of the stabilization of C in former subsoil at eroding positions and partial preservation of buried C in pools of intermediate turnover at depositional positions. However, the sink strength was limited by significant losses of buried C as only a small fraction of the C was associated with stable pools.

Beschreibung: Anthropogenically induced change in soil redistribution plays an important role in the soil organic carbon (SOC) budget. Uncertainty of its impact is large because of the dearth of recent soil redistribution estimates concomitant with changing land use and management practices. An Australian national survey used the artificial radionuclide caesium-137 ( 137 Cs) to estimate net (1950s–1990) soil redistribution. South-eastern Australia showed a median net soil loss of 9.7 t ha −1  yr −1 . We resurveyed the region using the same 137 Cs technique and found a median net (1990–2010) soil gain of 3.9 t ha −1  yr −1 with an interquartile range from −1.6 t ha −1  yr −1 to +10.7 t ha −1  yr −1 . Despite this variation, soil erosion across the region has declined as a likely consequence of the widespread adoption of soil conservation measures over the last ca 30 years. The implication of omitted soil redistribution dynamics in SOC accounting is to increase uncertainty and diminish its accuracy.

Beschreibung: Predicting forest responses to warming climates relies on assumptions about niche and temperature sensitivity that remain largely untested. Observational studies have related current and historical temperatures to phenological shifts, but experimental evidence is sparse, particularly for autumn responses. A 4 year field experiment exposed four deciduous forest species from contrasting climates ( Liquidambar styraciflua, Quercus rubra, Populus grandidentata, and Betula alleghaniensis ) to air temperatures 2 and 4 °C above ambient controls, using temperature-controlled open top chambers. Impacts of year-round warming on bud burst (BB), senescence, and abscission were evaluated in relation to thermal provenance. Leaves emerged earlier in all species by an average of 4–9 days at +2 °C and 6–14 days at +4 °C. Magnitude of advance varied with species and year, but was larger for the first 2 °C increment than for the second. Effect of warming increased with early BB, favoring Liquidambar , but even BB of northern species advanced, despite temperatures exceeding those of the realized niche. Treatment differences in BB were inadequately explained by temperature sums alone. In autumn, chlorophyll was retained an average of 4 and 7 days longer in +2 and +4 °C treatments, respectively, and abscission delayed by 8 and 13 days. Growing seasons in the warmer atmospheres averaged 5–18 days (E2) and 6–28 days (E4) longer, according to species, with the least impact in Quercus . Results are compared with a 16 years record of canopy onset and offset in a nearby upland deciduous forest, where BB showed similar responsiveness to spring temperatures (2–4 days °C −1 ). Offset dates in the stand tracked August–September temperatures, except when late summer drought caused premature senescence. The common garden-like experiment provides evidence that warming alone extends the growing season, at both ends, even if stand-level impacts may be complicated by variation in other environmental factors.

Beschreibung: Glacial retreat creates new habitat which is colonized and developed by plants and animals during the process of primary succession. While there has been much debate about the relative role of deterministic and stochastic processes during terrestrial succession, evidence from freshwater ecosystems remains minimal and a general consensus is lacking. Using a unique 27 years record of community assembly following glacial recession in southeast Alaska, we demonstrate significant change in the trait composition of stream invertebrate communities as catchment glacial cover decreased from ∼70% to zero. Functional diversity increased significantly as glacier cover decreased and taxonomic richness increased. Null modelling approaches led to a key finding that niche filtering processes were dominant when glacial cover was extensive, reflecting water temperature and dispersal constraints. Thereafter the community shifted towards co-occurrence of stochastic and deterministic assembly processes. A further novel discovery was that intrinsic functional redundancy developed throughout the study, particularly because new colonizers possessed similar traits to taxa already present. Rapid glacial retreat is occurring in Arctic and alpine environments worldwide and the assembly processes observed in this study provide new fundamental insights into how glacially influenced stream ecosystems will respond. The findings support tolerance as a key primary successional mechanism in this system, and have broader value for developing our understanding of how biological communities in river ecosystems assemble or restructure in response to environmental change.

Beschreibung: Anthropogenic ocean acidification is likely to have negative effects on marine calcifying organisms, such as shelled pteropods, by promoting dissolution of aragonite shells. Study of shell dissolution requires an accurate and sensitive method for assessing shell damage. Shell dissolution was induced through incubations in CO 2 -enriched seawater for 4 and 14 days. We describe a procedure that allows the level of dissolution to be assessed and classified into three main types: Type I with partial dissolution of the prismatic layer; Type II with exposure of underlying crossed-lamellar layer, and Type III, where crossed-lamellar layer shows signs of dissolution. Levels of dissolution showed a good correspondence to the incubation conditions, with the most severe damage found in specimens held for 14 days in undersaturated condition (Ω ~ 0.8). This methodology enables the response of small pelagic calcifiers to acidified conditions to be detected at an early stage, thus making pteropods a valuable bioindicator of future ocean acidification.

Beschreibung: Predicting the impacts of ocean acidification on coastal ecosystems requires an understanding of the effects on macroalgae and their grazers, as these underpin the ecology of rocky shores. Whilst calcified coralline algae (Rhodophyta) appear to be especially vulnerable to ocean acidification, there is a lack of information concerning calcified brown algae (Phaeophyta), which are not obligate calcifiers but are still important producers of calcium carbonate and organic matter in shallow coastal waters. Here we compare ecological shifts in sub-tidal rocky shore systems along CO 2 gradients created by volcanic seeps in the Mediterranean and Papua New Guinea, focussing on abundant macroalgae and grazing sea urchins. In both the temperate and tropical systems the abundances of grazing sea urchins declined dramatically along CO 2 gradients. Temperate and tropical species of the calcifying macroalgal genus Padina (Dictyoaceae, Phaeophyta) showed reductions in CaCO 3 content with CO 2 enrichment. In contrast to other studies of calcified macroalgae, however, we observed an increase in the abundance of Padina spp. in acidified conditions. Reduced sea urchin grazing pressure and significant increases in photosynthetic rates may explain the unexpected success of decalcified Padina spp. at elevated levels of CO 2 . This is the first study to provide a comparison of ecological changes along CO 2 gradients between temperate and tropical rocky shores. The similarities we found in the responses of Padina spp. and sea urchin abundance at several vent systems increases confidence in predictions of the ecological impacts of ocean acidification over a large geographical range .

Beschreibung: Changes in the seawater carbonate chemistry (ocean acidification) from increasing atmospheric carbon dioxide (CO 2 ) concentrations negatively affect many marine calcifying organisms, but may benefit primary producers under dissolved inorganic carbon (DIC) limitation. To improve predictions of the ecological effects of ocean acidification, the net gains and losses between the processes of photosynthesis and calcification need to be studied jointly on physiological and population levels. We studied productivity, respiration, and abundances of the symbiont-bearing foraminifera Marginopora vertebralis on natural CO 2 seeps in Papua New Guinea and conducted additional studies on production and calcification on the Great Barrier Reef (GBR) using artificially enhanced p CO 2 . Net oxygen production increased up to 90% with increasing p CO 2 , with temperature, light and pH together explaining 61% of the variance in production. Production increased with increasing light and increasing p CO 2 , and declined at higher temperatures. Respiration was also significantly elevated (~25%), while calcification was reduced (16-39%) at low pH/high p CO 2 compared to present day conditions. In the field, M. vertebralis was absent at three CO 2 seep sites at pH T otal levels below ~7.9 ( p CO 2 ~700 μatm), but it was found in densities of over 1000 m −2 at all three control sites. The study showed that endosymbiotic algae in foraminifera benefit from increased DIC availability, and may be naturally carbon limited. The observed reduction in calcification may have been caused either by increased energy demands for proton pumping (measured as elevated rates of respiration), or by stronger competition for DIC from the more productive symbionts. The net outcome of these two competing processes is that M. vertebralis cannot maintain populations under p CO 2 exceeding 700 μatm, thus are likely to be extinct in the next century.

Beschreibung: In the spring of 2010 temperatures averaged ~3 °C above the long term mean (March-May) across the northeastern United States. However, in mid-to-late spring much of this region experienced a severe frost event. The spring of 2010 therefore provides a case study on how future spring temperature extremes may affect northeastern forest ecosystems. We assessed the response of three northern hardwood tree species (sugar maple, American beech, yellow birch) to these anomalous temperature patterns using several different data sources and addressed four main questions: (1) Along an elevational gradient, how was each species affected by the late spring frost? (2) How did differences in phenological growth strategy influence their response? (3) How did the late spring frost affect ecosystem productivity within the study domain? (4) What are the potential long-term impacts of spring frost events on forest community ecology? Our results show that all species exhibited early leaf development triggered by the warm spring. However, yellow birch and American beech have more conservative growth strategies and were largely unaffected by the late spring frost. In contrast, sugar maples responded strongly to warmer temperatures and experienced widespread frost damage that resulted in leaf loss and delayed canopy development. Late spring frost events may therefore provide a competitive advantage for yellow birch and American beech at the expense of sugar maple. Results from satellite remote sensing confirm that frost damage was widespread throughout the region at higher elevations (〉 500 m). The frost event is estimated to have reduced gross ecosystem productivity by 70-153 g C m −2 , or 7–14% of the annual gross productivity (1061 ± 82 g C m −2 ) across 8753 km 2 of high-elevation forest. We conclude that frost events following leaf out, which are expected to become more common with climate change, may influence both forest composition and ecosystem productivity.

Beschreibung: Many species are locally adapted to decreased habitat quality at their range margins, and therefore show genetic differences throughout their ranges. Under contemporary climate change, range shifts may affect evolutionary processes at the expanding range margin due to founder events. Additionally, populations that are affected by such founder events will, in the course of time, become located in the range centre. Recent studies investigated evolutionary changes at the expanding range margin, but have not assessed eventual effects across the species’ range. We explored the possible influence of range shift on the level of adaptation throughout the species’ total range. For this we used a spatially explicit, individual-based simulation model of a woodland bird, parameterised after the middle spotted woodpecker ( Dendrocopus medius ) in fragmented habitat. We simulated its range under climate change, and incorporated genetic differences at a single locus that determined the individual's degree of adaptation to optimal temperature conditions. Generalist individuals had a large thermal tolerance but relatively low overall fitness, while climate specialists had high fitness combined with a small thermal tolerance. In equilibrium, the populations in the range centre were comprised of the specialists, while the generalists dominated the margins. In contrast, under temperature increase, the generalist numbers increased at the expanding margin and eventually also occupied the centre of the shifting range, while the specialists were located in the retracting margins. This was caused by founder events and led to overall maladaptation of the species, which resulted in a reduced metapopulation size and thus impeded the species’ persistence. We therefore found no evidence for a complementary effect of local adaptation and range shifts on species’ survival. Instead we showed that founder events can cause local maladaptation which can amplify throughout the species’ range, and, as such, hamper the species’ persistence under climate change.

Beschreibung: Whilst global environmental change in the Twenty First Century will undoubtedly have direct impacts on built heritage, it will also have important indirect effects through its influence on microbial, plant and animal life on heritage sites. Environmental change will affect both the structure of biotic communities and the function of such communities. Both impacts will, in turn, influence the deterioration and conservation of heritage sites. Changes in precipitation will exert a major, but as yet poorly understood, control on heritage biotas, whilst changes in atmospheric composition may also be important. Climatic changes will cause range shifts for some taxa, further influencing community composition. Whilst there are many unknowns, making prediction difficult, some scenarios can be proposed based on ecological response to stress and disturbance. This approach indicates some ‘hotspots’ at risk of experiencing dramatic shifts in biotic communities and their impacts, which may switch from biodeteriogenic to bioprotective or vice versa. Such hotspots include vulnerable sandstone and limestone heritage structures in areas of the Mediterranean, Middle East, Caribbean and Southern Africa.

Beschreibung: Agriculturally driven changes in soil phosphorus (P) are known to have persistent effects on local ecosystem structure and function, but regional patterns of soil P recovery following cessation of agriculture are less well understood. We synthesized data from 94 published studies to assess evidence of these land-use legacies throughout the world by comparing soil labile and total P content in abandoned agricultural areas to that of reference ecosystems or sites remaining in agriculture. Our meta-analysis shows that soil P content was typically elevated after abandonment compared to reference levels, but reduced compared to soils that remained under agriculture. There were more pronounced differences in the legacies of past agriculture on soil P across regions than between the types of land use practiced prior to abandonment (cropland, pasture, or forage grassland). However, consistent patterns of soil P enrichment or depletion according to soil order and types of post-agricultural vegetation suggest that these factors may mediate agricultural legacies on soil P. We also used mixed effects models to examine the role of multiple variables on soil P recovery following agriculture. Time since cessation of agriculture was highly influential on soil P legacies, with clear reductions in the degree of labile and total P enrichment relative to reference ecosystems over time. Soil characteristics (clay content and pH) were strongly related to changes in labile P compared to reference sites, but these were relatively unimportant for total P. The duration of past agricultural use and climate were weakly related to changes in total P only. Our finding of reductions in the degree of soil P alteration over time relative to reference conditions reveals the potential to mitigate these land-use legacies in some soils. Better ability to predict dynamics of soil nutrient recovery after termination of agricultural use is essential to ecosystem management following land-use change.

Beschreibung: The land-atmosphere exchange of methane (CH 4 ) and carbon dioxide (CO 2 ) in a high-Arctic wet tundra ecosystem (Rylekærene) in Zackenberg, north-eastern Greenland, was studied over the full growing season and until early winter in 2008 and from before snow melt until early winter in 2009. The eddy covariance technique was used to estimate CO 2 fluxes and a combination of the gradient and eddy covariance methods was used to estimate CH 4 fluxes. Small CH 4 bursts were observed during spring thawing 2009, but these existed during short periods and would not have any significant effect on the annual budget. Growing season CH 4 fluxes were well correlated with soil temperature, gross primary production, and active layer thickness. The CH 4 fluxes remained low during the entire autumn, and until early winter. No increase in CH 4 fluxes were seen as the soil started to freeze. However, in autumn 2008 there were two CH 4 burst events that were highly correlated with atmospheric turbulence. They were likely associated with the release of stored CH 4 from soil and vegetation cavities. Over the measurement period, 7.6 and 6.5 g C m −2 was emitted as CH 4 in 2008 and in 2009, respectively. Rylekærene acted as a C source during the warmer and wetter measurement period 2008, whereas it was a C sink for the colder and drier period of 2009. Wet tundra ecosystems, such as Rylekærene may thus play a more significant role for the climate in the future, as temperature and precipitation are predicted to increase in the high-Arctic.

Beschreibung: Anthropogenic nitrogen deposition has shifted many ecosystems from nitrogen ( N ) limitation to phosphorus ( P ) limitation. Although well documented in plants, no study to date has explored whether N deposition exacerbates P limitation at higher trophic levels, or focused on the effects of induced plant P limitation on trophic interactions. Insect herbivores exhibit strict N  :  P homeostasis, and should therefore be very sensitive to variations in plant N  :  P stoichiometry and prone to experiencing deposition-induced P limitation. In the current study, we investigated the effects of N deposition and P availability on a plant-herbivorous insect system. Using common milkweed ( Asclepias syriaca ) and two of its specialist herbivores, the monarch caterpillar ( Danaus plexippus ) and milkweed aphid ( Aphis asclepiadis ) as our study system, we found that experimental N deposition caused P limitation in milkweed plants, but not in either insect species. However, the mechanisms for the lack of P limitation were different for each insect species. The body tissues of A. asclepiadis always exhibited higher N  :  P ratios than that of the host plant, suggesting that the N demand of this species exceeds P demand, even under high N deposition levels. For D. plexippus , P addition increased the production of latex, which is an important defense negatively affecting D. plexippus growth rate. As a result, we illustrate that P limitation of herbivores is not an inevitable consequence of anthropogenic N deposition in terrestrial systems. Rather, species-specific demands for nutrients and the defensive responses of plants combine to determine the responses of herbivores to P availability under N deposition.

Beschreibung: Ecologists are increasingly recognizing the conservation significance of microrefugia, but it is inherently difficult to locate these small patches with unusual climates, and hence they are also referred to as cryptic refugia. Here we introduce a new methodology to quantify and locate potential microrefugia using fine-scale topoclimatic grids that capture extreme conditions, stable climates, and distinct differences from the surrounding matrix. We collected hourly temperature data from 150 sites in a large (200 km by 300 km) and diverse region of New South Wales, Australia, for a total of 671 days over 2 years. Sites spanned a range of habitats including coastal dune shrublands, eucalypt forests, exposed woodland ridges, sheltered rainforest gullies, upland swamps, and lowland pastures. Climate grids were interpolated using a regional regression approach based on elevation, distance to coast, canopy cover, latitude, cold-air drainage, and topographical exposure to winds and radiation. We identified extreme temperatures on two separate climatic gradients: the 5th percentile of minimum temperatures and the 95th percentile of maximum temperatures. For each gradient, climatic stability was assessed on three different time scales (intra-seasonal, intra-annual and inter-annual). Differences from the matrix were assessed using a moving window with a 5 km radius. We averaged the Z-scores for these extreme, stable and isolated climates to identify potential locations of microrefugia. We found that our method successfully predicted the location of communities that were considered to occupy refugia, such as rainforests that have progressively contracted in distribution over the last 2.5 million years, and alpine grasslands that have contracted over the last 15 thousand years. However, the method was inherently sensitive to the gradient selected and other aspects of the modelling process. These uncertainties could be dealt with in a conservation planning context by repeating the methodology with various parameterizations and identifying areas that were consistently identified as microrefugia.

Beschreibung: Global vegetation models predict rapid poleward migration of tundra and boreal forest vegetation in response to climate warming. Local plot and air-photo studies have documented recent changes in high-latitude vegetation composition and structure, consistent with warming trends. To bridge these two scales of inference, we analyzed a 24-year (1986-2010) Landsat time series in a latitudinal transect across the boreal forest-tundra biome boundary in northern Quebec province, Canada. This region has experienced rapid warming during both winter and summer months during the last forty years. Using a per-pixel (30 m) trend analysis, 30% of the observable (cloud-free) land area experienced a significant (p 〈 0.05) positive trend in the Normalized Difference Vegetation Index (NDVI). However, greening trends were not evenly split among cover types. Low shrub and graminoid tundra contributed preferentially to the greening trend, while forested areas were less likely to show significant trends in NDVI. These trends reflect increasing leaf area, rather than an increase in growing season length, because Landsat data were restricted to peak-summer conditions. The average NDVI trend (0.007/yr) corresponds to a leaf-area index (LAI) increase of ~0.6 based on the regional relationship between LAI and NDVI from the Moderate Resolution Spectroradiometer (MODIS). Across the entire transect, the area-averaged LAI increase was ~0.2 during 1986-2010. A higher area-averaged LAI change (~0.3) within the shrub-tundra portion of the transect represents a 20-60% relative increase in LAI during the last two decades. Our Landsat-based analysis subdivides the overall high-latitude greening trend into changes in peak-summer greenness by cover type. Different responses within and among shrub, graminoid, and tree-dominated cover types in this study indicate important fine-scale heterogeneity in vegetation growth. Although our findings are consistent with community shifts in low-biomass vegetation types over multi-decadal time scales, the response in tundra and forest ecosystems to recent warming was not uniform.

Beschreibung: Climate change may shrink and/or shift plant species ranges thereby increasing their vulnerability and requiring targeted conservation to facilitate adaptation. We quantified the vulnerability to climate change of plant species based on exposure, sensitivity and adaptive capacity and assessed the effects of including these components in complementarity-based spatial conservation prioritisation. We modelled the vulnerability of 584 native plant species under three climate change scenarios in an 11.9 million hectare fragmented agricultural region in southern Australia. We represented exposure as species’ geographic range under each climate change scenario as quantified using species distribution models. We calculated sensitivity as a function of the impact of climate change on species’ geographic ranges. Using a dispersal kernel, we quantified adaptive capacity as species’ ability to migrate to new geographic ranges under each climate change scenario. Using Zonation , we assessed the impact of individual components of vulnerability (exposure, sensitivity and adaptive capacity) on spatial conservation priorities and levels of species representation in priority areas under each climate change scenario. The full vulnerability framework proved an effective basis for identifying spatial conservation priorities under climate change. Including different dimensions of vulnerability had significant implications for spatial conservation priorities. Incorporating adaptive capacity increased the level of representation of most species. However, prioritising sensitive species reduced the representation of other species. We conclude that whilst taking an integrated approach to mitigating species vulnerability to climate change can ensure sensitive species are well-represented in a conservation network, this can come at the cost of reduced representation of other species. Conservation planning decisions aimed at reducing species vulnerability to climate change need to be made in full cognisance of the sensitivity of spatial conservation priorities to individual components of vulnerability, and the trade-offs associated with focussing on sensitive species.

Beschreibung: Species need to move to keep pace with changing climates, but we do not know if species can move at the required speed. Spread rates of native species may underestimate how fast species can move, we therefore assessed how fast Lessepsian species (marine non-native species that invaded the Mediterranean from the Red Sea through the Suez Canal) can spread to give a ‘best-case’ assessment of the effects of climate change on marine biodiversity. We show that about 20% of Lessepsian species could not spread fast enough to keep pace with climate change in about 20% of the global seas and this suggests that climate change may lead to biodiversity loss. The velocity of climate change on the seabed is much lower than at the sea surface, and as a result of this the proportion of species that keep pace with climate change at the seabed was much larger than at the sea surface. This suggests that locations at depth could act as refuges for slow dispersing species. Our analysis compared different estimates of the spreading abilities of marine species and showed that the estimate of spread rates strongly affects the predicted effect of climate change on biodiversity. Providing more accurate estimates of the spreading ability of marine species should therefore have priority if we want to predict the effect of climate change on marine biodiversity. This study is a first approximation of the potential scale and distribution of global marine biodiversity loss and can provide benchmark estimates of the spread rates that species could achieve in colonizing suitable habitat. Assisted colonization may be required to maintain biodiversity in the most strongly affected areas. © 2012 Blackwell Publishing Ltd

Beschreibung: Precise estimations of soil organic carbon (SOC) stocks are of decided importance for the detection of C sequestration or emission potential induced by land use changes. For Germany, a comprehensive, land use–specific SOC data set has not yet been compiled. We evaluated a unique data set of 1460 soil profiles in southeast Germany in order to calculate representative SOC stocks to a depth of 1 m for the main land use types. The results showed that grassland soils stored the highest amount of SOC, with a median value of 11.8 kg m −2 , whereas considerably lower stocks of 9.8 and 9.0 kg m −2 were found for forest and cropland soils, respectively. However, the differences between extensively used land (grassland, forest) and cropland were much lower compared with results from other studies in central European countries. The depth distribution of SOC showed that despite low SOC concentrations in A horizons of cropland soils, their stocks were not considerably lower compared with other land uses. This was due to a deepening of the topsoil compared with grassland soils. Higher grassland SOC stocks were caused by an accumulation of SOC in the B horizon which was attributable to a high proportion of C-rich Gleysols within grassland soils. This demonstrates the relevance of pedogenetic SOC inventories instead of solely land use–based approaches. Our study indicated that cultivation-induced SOC depletion was probably often overestimated since most studies use fixed depth increments. Moreover, the application of modelled parameters in SOC inventories is questioned because a calculation of SOC stocks using different pedotransfer functions revealed considerably biased results. We recommend SOC stocks be determined by horizon for the entire soil profile in order to estimate the impact of land use changes precisely and to evaluate C sequestration potentials more accurately.

Beschreibung: Ongoing global climate change presents serious challenges in conservation biology, forcing us to revisit previous tools and principles on the basis of how species may respond to novel climatic conditions. There is currently a major gap between predictions of species vulnerability and management strategies, despite the fact that linking these areas is fundamental for future biodiversity conservation. Here we evaluate what drives vulnerability to climate change in three Iberian endemic water beetles, representing three independent colonizations of the same habitat, employing comparative thermal physiology, species distribution models and estimations of species dispersal capacity. We derive conservation strategies for each species based on their differential capacity to persist and/or potential to shift their ranges in response to global warming. We demonstrate that species may be affected by climatic warming in very different ways, despite having broadly similar ecological and biogeographical traits. The proposed framework provides an effective complement to traditional species vulnerability assessments, and could aid the development of more effective conservation strategies in the face of global warming.

Beschreibung: Understanding how species and ecosystems respond to climate change requires spatially and temporally rich data for a diverse set of species and habitats, combined with models that test and predict responses. Yet current work is hampered by the long-known problems of inadequate management of data and insufficient description of analytical procedures, especially in the field of ecology. Despite recent institutional incentives to share data and new data archiving infrastructure, many ecologists do not archive and publish their data and code. Given current rapid rates of global change, the consequences of this are extreme: because an ecological dataset collected at a certain place and time represents an irreproducible set of observations, ecologists doing local, independent research possess, in their file cabinets and spreadsheets, a wealth of information about the natural world and how it is changing. Although large-scale initiatives will increasingly enable and reward open science, we believe that change demands action and personal commitment by individuals—from students and PIs. Here, we outline the major benefits of sharing data and analytical procedures in the context of global change ecology, and provide guidelines for overcoming common obstacles and concerns. If individual scientists and labs can embrace a culture of archiving and sharing we can accelerate the pace of the scientific method and redefine how local science can most robustly scale up to globally-relevant questions.

Beschreibung: Montane tropical rainforests are critically important areas for global bird diversity, but are projected to be highly vulnerable to contemporary climate change. Upslope shifts of lowland species may partially offset declines in upland species, but also result in a process of lowland biotic attrition. This latter process is contingent on the absence of species adapted to novel warm climates, and isolation from pools of potential colonisers. In the Australian Wet Tropics, species distribution modelling has forecast critical declines in suitable environmental area for upland endemic birds, but information is lacking for important neighbouring rainforest regions. Here we use expanded geographic coverage of data to model the realised distributions of 120 bird species found in north-eastern Australian rainforest, including species from potential source locations in the north and recipient locations in the south. We reaffirm previous conclusions as to the high vulnerability of this fauna to global warming, and extend the list of species whose suitable environmental area is projected to decrease. However, we find that expansion of suitable area for some species currently restricted to northern rainforests has the potential to offset biotic attrition in lowland forest of the Australian Wet Tropics. By examining contrasting dispersal scenarios, we show that responses to climate change in this region may critically depend on dispersal limitation, as climate change shifts the suitable environmental envelopes of many species south into currently unsuitable habitats. For lowland and northern species, future change in vegetation connectivity across contemporary habitat barriers is likely to be an important mediator of climate change impacts. In contrast, upland species are projected to become increasingly isolated and restricted. Their survival is likely to be more dependent on the viability of assisted migration, and the emergence and persistence of suitable environments at recipient locations. © 2012 Blackwell Publishing Ltd

Beschreibung: Emissions of the trace gas nitrous oxide (N 2 O) play an important role for the greenhouse effect and stratospheric ozone depletion, but the impacts of climate change on N 2 O fluxes and the underlying microbial drivers remain unclear. The aim of this study was to determine effects of sustained climate change on field N 2 O fluxes and associated microbial enzymatic activities, microbial population abundance and community diversity in an extensively managed, upland grassland. We recorded N 2 O fluxes, nitrification and denitrification, microbial population size involved in these processes and community structure of nitrite reducers ( nir K) in a grassland exposed for four years to elevated atmospheric CO 2 (+ 200 ppm), elevated temperature (+ 3.5°C) and reduction of summer precipitations (-20%) as part of a long-term, multifactor climate change experiment. Our results showed that both warming and simultaneous application of warming, summer drought and elevated CO 2 had a positive effect on N 2 O fluxes, nitrification, N 2 O release by denitrification and the population size of N 2 O reducers and NH 4 oxidizers. In situ N 2 O fluxes showed a stronger correlation with microbial population size under warmed conditions compared with the control site. Specific lineages of nir K denitrifier communities responded significantly to temperature. In addition, nir K community composition showed significant changes in response to drought. Path analysis explained more than 85% of in situ N 2 O fluxes variance by soil temperature, denitrification activity and specific denitrifying lineages. Overall, our study underlines that climate-induced changes in grassland N 2 O emissions reflect climate-induced changes in microbial community structure, which in turn modify microbial processes.

Beschreibung: Climate change may considerably impact the carbon (C) dynamics and C stocks of forest soils. To assess the combined effects of warming and reduced precipitation on soil CO 2 efflux, we conducted a two-way factorial manipulation experiment (4 °C soil warming + throughfall exclusion) in a temperate spruce forest from 2008 until 2010. Soil was warmed by heating cables throughout the growing seasons. Soil drought was simulated by throughfall exclusions with three 100 m 2 roofs during 25 days in July/August 2008 and 2009. Soil warming permanently increased the CO 2 efflux from soil whereas throughfall exclusion led to a sharp decrease in soil CO 2 efflux (45% and 50% reduction during roof installation in 2008 and 2009, respectively). In 2008, CO 2 efflux did not recover after natural rewetting and remained lowered until autumn. In 2009, CO 2 efflux recovered shortly after rewetting, but relapsed again for several weeks. Drought offset the increase in soil CO 2 efflux by warming in 2008 (growing season CO 2 efflux in t C ha −1 : control: 7.1 ± 1.0; warmed: 9.5 ± 1.7; warmed + roof: 7.4 ± 0.3; roof: 5.9 ± 0.4) and in 2009 (control: 7.6 ± 0.8; warmed + roof: 8.3 ± 1.0). Throughfall exclusion mainly affected the organic layer and the top 5 cm of the mineral soil. Radiocarbon data suggest that heterotrophic and autotrophic respiration were affected to the same extent by soil warming and drying. Microbial biomass in the mineral soil (0 - 5 cm) was not affected by the treatments. Our results suggest that warming causes significant C losses from the soil as long as precipitation patterns remain steady at our site. If summer droughts become more severe in the future, warming induced C losses will likely be offset by reduced soil CO 2 efflux during and after summer drought.

Beschreibung: A recent study (Wolf et al., 2010) suggests that short – lived pulses of N 2 O emission during spring thaw dominate the annual N 2 O budget and that grazing decreases N 2 O emissions during the spring thaw. To verify this we conducted year – round N 2 O flux measurements from June 2010 to May 2011 in Tianshan alpine grassland in central Asia. No pulse emissions of N 2 O were found at grazing management sites and nitrogen addition sites during the spring thaw. The contribution of the spring thaw to the total annual N 2 O budget was small and accounted for only 6.6% of the annual fluxes, with winter emissions accounting for 16.7% and growing season emissions accounting for 76.7%. The difference in N 2 O emissions attributable to grazing management was not significant ( p 〉 0.05). Nitrogen input tended to increase N 2 O emissions at N addition sites during the grass growing season compared with those at unfertilized sites. N 2 O fluxes showed a significant correlation with air temperature and also with both soil temperature and soil water content at 10 cm depth.

Beschreibung: In many terrestrial ecosystems, variation in aboveground net primary production (ANPP) is positively correlated with variation in interannual precipitation. Global climate change will alter both the mean and the variance of annual precipitation, but the relative impact of these changes in precipitation on mean ANPP remains uncertain. At any given site, the slope of the precipitation-ANPP relationship determines the sensitivity of mean ANPP to changes in mean precipitation, while the curvature of the precipitation-ANPP relationship determines the sensitivity of ANPP to changes in precipitation variability. We used 58 existing long-term data sets to characterize precipitation-ANPP relationships in terrestrial ecosystems and to quantify the sensitivity of mean ANPP to the mean and variance of annual precipitation. We found that most study sites have a nonlinear, saturating relationship between precipitation and ANPP, but these nonlinearities were not strong. As a result of these weak nonlinearities, ANPP was nearly 40 times more sensitive to precipitation mean than variance. A 1% increase in mean precipitation caused a -0.2% to 1.8% change in mean ANPP, with a 0.64% increase on average. Sensitivities to precipitation mean peaked at sites with a mean annual precipitation near 500 mm. Changes in species composition and increased intra-annual precipitation variability could lead to larger ANPP responses to altered precipitation regimes than predicted by our analysis.

Beschreibung: Anthropogenic acid deposition may lead to soil acidification, with soil buffering capacity regulating the magnitude of any soil pH change. However, little evidence is available from large-scale or long-term observations. Here we evaluated changes in soil pH across northern China's grasslands over a 20 year period using soil profiles obtained from China's Second National Soil Inventory during the 1980s and a more recent regional soil survey in 2001-2005. A transect from the central-southern Tibetan Plateau to the eastern Inner Mongolian Plateau, where Kriging interpolation provided robust predictions of the spatial distribution of soil pH, was then selected to examine pH changes during the survey period. Our results showed that soil pH in the surface layer had declined significantly over the last two decades, with an overall decrease of 0.63 units (95% confidence interval = 0.54-0.73 units). The decline of soil pH was observed in both alpine grasslands on the Tibetan Plateau and temperate grasslands on the Inner Mongolian Plateau. Soil pH decreased more intensively in low soil carbonate regions, while changes of soil pH showed no significant associations with soil cation exchange capacity. These results suggest that grassland soils across northern China have experienced significant acidification from the 1980s to the 2000s, with soil carbonates buffering the increase of soil acidity. The buffering process may induce a large loss of carbon from soil carbonates and thus alter the carbon balance in these globally important ecosystems.

Beschreibung: Current climate change exacerbates the environmental restrictions on temperate species inhabiting low latitude edges of their geographical ranges. We examined how temperature variations due to current and future climate change are likely to affect populations’ persistence of stream-dwelling brown trout Salmo trutta at the vulnerable southern periphery of its range. Analysis of 33 years of air temperature data (1975–2007) by time-series models indicated a significant upward trend and a pronounced shift in air temperature around 1986-1987. This warming is associated with an ongoing population decline of brown trout, most likely caused by a loss of suitable thermal habitat in lower latitudes since the 1980s. Population decrease may not be attributed to physical habitat modification or angler pressure, as carrying capacity remained stable and populations were not overexploited. We developed regional temperature models, which predicted that unsuitable thermal habitat for brown trout increased by 93% when comparing climate conditions between 1975–1986 and 1993–2004. Predictions from climate envelope models showed that current climate change may be rendering unsuitable 12% of suitable thermal habitat each decade, resulting in an overall population decrease in the lower reaches of around 6% per year. Furthermore, brown trout catches markedly decreased 20% per year. Projections of thermal habitat loss under the ecologically friendly B2 SRES scenario showed that brown trout may lose half of their current suitable habitat within the study area by 2040 and become almost extinct by 2100. In parallel to the upstream movement of brown trout thermal habitat, warm water species are increasing their relative abundance in salmonid waters. Empirical evidence was provided of how current climate change threatens some of the most healthy native brown trout populations in Southern Europe and how forthcoming climate change is expected to further decrease the conservation status of the species.

Beschreibung: Over the past 3 decades, North Sea Atlantic cod ( Gadus morhua ) have exhibited variable length-at-age along with declines in spawning stock biomass and timing of maturity. Multiple factors affecting growth and development in fish acted on this economically important stock over the same period including warming waters and an intensive fishery. Here, we employ North Sea cod as a model population, exploring how a physiologically relevant temperature metric (the growing degree-day, GDD; °C day) can be used to compare year-classes on a physiologically relevant time-scale, disentangling influences of climate (thermal history) on observed length-at-age trends. We conclude that the trends in North Sea cod length-at-age observed during the last three decades can be explained by a combination of temperature-dependent growth increases and a trend toward earlier maturation, the latter likely induced by the intensive fishing pressure, and possibly evidence of fisheries-induced evolution.

Beschreibung: Soil multitrophic interactions transfer energy from plants as the predominant primary producer to communities of organisms that occupy different positions in the food chain and are linked by multiple ecological networks, which is the soil food web. Soil food web sequesters carbon, cycles nutrients, maintains soil health to suppress pathogens, helps plants tolerate abiotic and biotic stress, and maintains ecosystem resilience and sustainability. Understanding the influence of climate change on soil multitrophic interactions is necessary to maintain these essential ecosystem services. But summarising this influence is a daunting task due to a paucity of knowledge and a lack of clarity on the ecological networks that constitute these interactions. The scant literature is fragmented along disciplinary lines, often reporting inconsistent findings that are context and scale-dependent. We argue for the differentiation of soil multitrophic interactions along functional and spatial domains to capture cross-disciplinary knowledge and mechanistically link all ecological networks to reproduce full functionalities of the soil food web. Distinct from litter mediated interactions in detritosphere or elsewhere in the soil, the proposed ‘pathogen suppression’ and ‘stress tolerance’ interactions operate in the rhizosphere. A review of the literature suggests that climate change will influence the relative importance, frequency and composition of functional groups, their trophic interactions and processes controlling these interactions. Specific climate change factors generally have a beneficial influence on pathogen suppression and stress tolerance, but findings on the overall soil food web are inconsistent due to a high level of uncertainty. In addition to an overall improvement in the understanding of soil multitrophic interactions using empirical and modelling approaches, we recommend linking biodiversity to function, understanding influence of combinations of climatic factors on multitrophic interactions and the evolutionary ecology of multitrophic interactions in a changing climate as areas that deserve most attention.

Beschreibung: Redd (nest) surveys for resident brook trout ( Salvelinus fontinalis ) were conducted annually in a mountain lake in northern New York for 11 years with multiple surveys conducted during the spawning season in eight of those years. Repeated surveys throughout the spawning season allowed us to fit an individually based parametric model and estimate the day of year on which spawning was initiated, reached its midpoint, and ended during each year. Spawning phenology was then assessed relative to (1) mean of maximum daily air temperature and (2) mean of maximum daily water temperature at the lake bottom during summer in each year using a linear model. Elevated temperatures in summer were correlated with a delay in spawning and a reduction in the total number of redds constructed. Increasing the summer mean of maximum daily air temperatures by 1 °C delayed spawning by approximately 1 week and decreased the total number of redds constructed by nearly 65. Lake spawning brook trout select redd sites based on the presence of discharging groundwater that is relatively constant in temperature within and across years, leading to relatively consistent egg incubation times. Therefore, delayed spawning is likely to delay fry emergence, which could influence emergence synchrony with prey items. This work highlights non-lethal and sub-lethal effects of elevated summer temperatures on native resident salmonids in aquatic environments with limited thermal refugia.

Beschreibung: To understand how environmental changes have influenced forest productivity, stemwood biomass ( B ) dynamics were analyzed at 1267 permanent inventory plots, covering a combined 209 ha area of unmanaged temperate-maritime forest in southwest British Columbia, Canada. Net stemwood production (Δ B ) was derived from periodic remeasurements of B collected over a 40-year measurement period (1959–1998) in stands ranging from 20 to 150 years old. Comparison between the integrated age response of net stemwood production, Δ B ( A ), and the age response of stemwood biomass, B ( A ), suggested a 58 ± 11% increase in Δ B between the first 40 years of the chronosequence period (1859–1898) and the measurement period. To estimate extrinsic forcing on Δ B , several different candidate models were developed to remove variation explained by intrinsic factors. All models exhibited temporal bias, with positive trends in (observed minus predicted) residual Δ B ranging between of 0.40 and 0.64% yr −1 . Applying the same methods to stemwood growth ( G ) indicated residual increases ranging from 0.43 and 0.67% yr −1 . Higher trend estimates corresponded with models that included site index (SI) as a predictor, which may reflect exaggeration of the age-decline in SI tables. Choosing a model that excluded SI, suggested that Δ B increased by 0.40 ± 0.18% yr −1 , while G increased by 0.43 ± 0.12% yr −1 over the measurement period. Residual G was significantly correlated with atmospheric carbon dioxide ( CO 2 ), temperature ( T ), and climate moisture index (CMI). However, models driven with climate and CO 2 , alone, could not simultaneously explain long-term and measurement-period trends without additional representation of indirect effects, perhaps reflecting compound interest on direct physiological responses to environmental change. Evidence of accelerating forest regrowth highlights the value of permanent inventories to detect and understand systematic changes in forest productivity caused by environmental change.

Beschreibung: Changes in winter time conditions at high-latitude ecosystems could severely affect the carbon exchange processes. Using a 15 year stream record combined with winter field measurements and laboratory experiment, we studied the regulation of dissolved organic carbon (DOC) concentration in stream water draining boreal mire during snow melt. The most unanticipated finding was that cold soils with deep soil frost resulted in increased snow melt DOC concentrations in the stream runoff. Wintertime field measurements of DOC concentrations below the mire soil frost showed that this phenomenon could be explained by freeze-out of DOC giving higher levels of DOC in the soil water below the ice as the soil frost developed downwards in the mire. Experimental freezing of water with a certain DOC concentration in the laboratory further corroborated the freeze-out of DOC. In this experiment, as much as 96% of the DOC was excluded from the ice, whereas the freeze-out in the mire was less effective (60%). The difference between the proportion of DOC retained in pure water relative to the proportion retained in peat water during freezing is probably due to trapped DOC in the solid peat soil matrix. A simple mass-balance model showed that to explain the higher stream DOC concentrations during a winter with deep soil frost, approximately 0.5% of the mire area needed to be hydrologically connected to the stream discharge. In the stream records, we also found that the DOC concentrations during snow melt episodic runoff were negatively related to increasing intensity of the snow melt episodes (dilution by low DOC snow melt water) and higher previous export of DOC.

Beschreibung: It is often assumed that daytime patterns of ecosystem carbon assimilation are mostly driven by direct physiological responses to exogenous environmental cues. Under limited environmental variability, little variation in carbon assimilation should thus be expected unless endogenous plant controls on carbon assimilation, which regulate photosynthesis in time, are active. We evaluated this assumption with eddy flux data, and we selected periods when net ecosystem exchange (NEE) was decoupled from environmental variability in seven sites from highly contrasting biomes across a 74° latitudinal gradient over a total of 36 site-years. Under relatively constant conditions of light, temperature, and other environmental factors, significant diurnal NEE oscillations were observed at six sites, where daily NEE variation was between 20% and 90% of that under variable environmental conditions. These results are consistent with fluctuations driven by the circadian clock and other endogenous processes. Our results open a promising avenue of research for a more complete understanding of ecosystem fluxes that integrates from cellular to ecosystem processes.

Beschreibung: We performed a detailed study on the carbon build-up over the 140-year-long chronosequence of the Damma glacier forefield, Switzerland, to gain insights into the organic carbon dynamics during the initial stage of soil formation and ecosystem development. We determined soil carbon and nitrogen contents and their stable isotopic compositions, as well as molecular-level composition of the bulk soils, and recalcitrance parameters of carbon in different fractions. The chronosequence was divided into three age groups, separated by small end moraines that resulted from two glacier re-advances. The net ecosystem carbon balance (NECB) showed an exponential increase over the last decades, with mean annual values that range from 100 g C m −2  yr −1 in the youngest part to over 300 g C m −2  yr −1 in a 60–80 years old part. However, over the entire 140-year chronosequence, the NECB is only 20 g C m −2  yr −1 , similar to results of other glacier forefield studies. The difference between the short- and long-term NECB appears to be caused by reductions in ecosystem carbon (EC) accumulation during periods with a colder climate. We propose that two complementary mechanisms have been responsible: 1) Reductions in net primary productivity down to 50% below the long-term mean, which we estimated using reconstructed effective temperature sums. 2) Disturbance of sites near the terminus of the re-advanced glacier front. Stabilization of soil organic matter appeared to play only a minor role in the coarse-grained forefield. We conclude that the forefield ecosystem, especially primary productivity, reacts rapidly to climate changes. The EC gained at warm periods is easily lost again in a cooling climate. Our conclusions may also be valid for other high mountain ecosystems and possibly arctic ecosystems.

Beschreibung: Predicting the impact of climate change on the damage niche of an agricultural weed at a local scale requires a process-based modelling approach that integrates local environmental conditions and the differential responses of the crop and weed to change. A simulation model of the growth and population dynamics of winter wheat and a competing weed, Sirius 2010, was calibrated and validated for the most economically damaging weed in UK cereals, Alopecurus myosuroides . The model was run using local-scale climatic scenarios generated by the LARS-WG weather generator and based on the HadCM3 projections for the periods 2046–2065 and 2080–2099 to predict the impact of climate change on the population dynamics of the weed and its effect on wheat yields. Owing to rising CO 2 concentration and its effect on radiation use efficiency of wheat, weed-free wheat yields were predicted to increase. The distribution of the weed was predicted to remain broadly similar with a possible northward shift in range. Local-scale variation in the impact of climate change was apparent owing to variation in soil type and water holding capacity. The competitive balance was shifted in favour of the deeper rooted crop under climate change, particularly on sites with lighter soils, owing to more frequent and severe drought stress events. Although the damage niche of A. myosuroides was predicted to reduce under climate change, it is likely that weeds with contrasting physiology, such as C4 species, will be better adapted to future conditions and pose a more serious threat.

Beschreibung: Rivers are among the world's most modified ecosystems, with poor water quality representing a prominent problem for over 200 years, especially in urban areas. In Western Europe, however, industrial decline, tighter regulation and improved wastewater treatment have combined over recent decades to create conditions conducive to extensive restoration and positive biological change. Here, we evaluate the river macroinvertebrate fauna of England and Wales in relation to water quality, physical habitat and climate over almost two decades. We predicted that biological recovery would be characterized by: (i) greater taxon richness and prevalence of pollution-sensitive taxa, (ii) larger changes in more heavily urbanized catchments, and (iii) temporal trends in assemblage structure that correlated with improving water quality. Family level richness increased on average by nearly 20% during 1991–2008, accompanied by a widespread shift towards taxa characteristic of well-oxygenated and less polluted waters. Changes were largest in the most urbanized catchments. A combination of natural gradients and anthropogenic pressures explained the variation among sites, whereas temporal changes correlated with improving water quality and variations in discharge. Positive trends were not universal, however, and there was localized deterioration in some streams draining upland areas and in the lowland south east. Our results are consistent with a large-scale ecological recovery of English and Welsh rivers since 1990, probably continuing a trend from the mid-20th century. Based on these results, we suggest: (i) freshwater communities are resilient to long-term anthropogenic pressures, (ii) biodiversity benefits can arise from investment and long-term restoration intended largely to enhance ecosystem services such as drinking water and sanitary concerns, and (iii) long-term monitoring data collected for statutory purposes–based in this case on nearly 50 000 samples–can address scientific questions at spatial and temporal extents seldom achieved in research programmes.

Beschreibung: Mechanisms to mitigate global climate change by sequestering carbon ( C ) in different ‘sinks' have been proposed as at least temporary measures. Of the major global C pools, terrestrial ecosystems hold the potential to capture and store substantially increased volumes of C in soil organic matter (SOM) through changes in management that are also of benefit to the multitude of ecosystem services that soils provide. This potential can only be realized by determining the amount of SOM stored in soils now, with subsequent quantification of how this is affected by management strategies intended to increase SOM concentrations, and used in soil C models for the prediction of the roles of soils in future climate change. An apparently obvious method to increase C stocks in soils is to augment the soil C pools with the longest mean residence times (MRT). Computer simulation models of soil C dynamics, e.g. RothC and Century, partition these refractory constituents into slow and passive pools with MRTs of centuries to millennia. This partitioning is assumed to reflect: (i) the average biomolecular properties of SOM in the pools with reference to their source in plant litter, (ii) the accessibility of the SOM to decomposer organisms or catalytic enzymes, or (iii) constraints imposed on decomposition by environmental conditions, including soil moisture and temperature. However, contemporary analytical approaches suggest that the chemical composition of these pools is not necessarily predictable because, despite considerable progress with understanding decomposition processes and the role of decomposer organisms, along with refinements in simulation models, little progress has been made in reconciling biochemical properties with the kinetically defined pools. In this review, we will explore how advances in quantitative analytical techniques have redefined the new understanding of SOM dynamics and how this is affecting the development and application of new modelling approaches to soil C .

Beschreibung: Many of the world's northern peatlands are underlain by rapidly thawing permafrost. Because plant production in these peatlands is often nitrogen (N)-limited, a release of N stored in permafrost may stimulate net primary production or change species composition if it is plant-available. In this study, we aimed to quantify plant-available N in thawing permafrost soils of subarctic peatlands. We compared plant-available N-pools and -fluxes in near-surface permafrost (0–10 cm below the thawfront) to those taken from a current rooting zone layer (5–15 cm depth) across five representative peatlands in subarctic Sweden. A range of complementary methods was used: extractions of inorganic and organic N, inorganic and organic N-release measurements at 0.5 and 11 °C (over 120 days, relevant to different thaw-development scenarios) and a bioassay with Poa alpina test plants. All extraction methods, across all peatlands, consistently showed up to seven times more plant-available N in near-surface permafrost soil compared to the current rooting zone layer. These results were supported by the bioassay experiment, with an eightfold larger plant N-uptake from permafrost soil than from other N-sources such as current rooting zone soil or fresh litter substrates. Moreover, net mineralization rates were much higher in permafrost soils compared to soils from the current rooting zone layer (273 mg N m −2 and 1348 mg N m −2 per growing season for near-surface permafrost at 0.5 °C and 11 °C respectively, compared to −30 mg N m −2 for current rooting zone soil at 11 °C). Hence, our results demonstrate that near-surface permafrost soil of subarctic peatlands can release a biologically relevant amount of plant available nitrogen, both directly upon thawing as well as over the course of a growing season through continued microbial mineralization of organically bound N. Given the nitrogen-limited nature of northern peatlands, this release may have impacts on both plant productivity and species composition.

Beschreibung: Many species are locally adapted to decreased habitat quality at their range margins, and therefore show genetic differences throughout their ranges. Under contemporary climate change, range shifts may affect evolutionary processes at the expanding range margin due to founder events. Additionally, populations that are affected by such founder events will, in the course of time, become located in the range centre. Recent studies investigated evolutionary changes at the expanding range margin, but have not assessed eventual effects across the species’ range. We explored the possible influence of range shift on the level of adaptation throughout the species’ total range. For this we used a spatially explicit, individual-based simulation model of a woodland bird, parameterised after the middle spotted woodpecker ( Dendrocopus medius ) in fragmented habitat. We simulated its range under climate change, and incorporated genetic differences at a single locus that determined the individual's degree of adaptation to optimal temperature conditions. Generalist individuals had a large thermal tolerance but relatively low overall fitness, while climate specialists had high fitness combined with a small thermal tolerance. In equilibrium, the populations in the range centre were comprised of the specialists, while the generalists dominated the margins. In contrast, under temperature increase, the generalist numbers increased at the expanding margin and eventually also occupied the centre of the shifting range, while the specialists were located in the retracting margins. This was caused by founder events and led to overall maladaptation of the species, which resulted in a reduced metapopulation size and thus impeded the species’ persistence. We therefore found no evidence for a complementary effect of local adaptation and range shifts on species’ survival. Instead we showed that founder events can cause local maladaptation which can amplify throughout the species’ range, and, as such, hamper the species’ persistence under climate change.

Beschreibung: Effects of climatic oscillations on populations in marine environments are produced mainly through the lower trophic levels. Marine mammals, as top predators, are affected indirectly by these fluctuations, showing variations in their survival, growth and reproduction. The main objective of this study was to determine whether we could detect the effect of climatic oscillations on Commerson's dolphins ( Cephalorhynchus c. commersonii ) off Tierra del Fuego, Argentina, by examining the presence and proportion of anomalous dentinal growth layer groups (GLGs). The relative deposition of anomalous GLGs was determined by calendar year from 1960 to 2005 and related to the Southern Annular Mode (SAM) and El Niño Southern Oscillation (ENSO) events and to mean annual sea surface temperatures (SST). Then, growth parameters between animals that did and did not show anomalous dentinal growth layer patterns in one or more of their GLGs were compared. The presence of anomalous GLGs was related to the SAM, increasing in frequency with negative values of the SAM. No relationship was found among anomalous GLGs, ENSO and SST. There were no significant differences in growth parameters between animals with and without anomalous GLGs. Using recording structures such as teeth provided a unique way of reconstructing time series to evaluate the effects of these climatic patterns on a top predator species in an area where no similar studies have been conducted, primarily due to a lack of suitable long-term data sets.