ALBERT

Description: Temperature is highly variable across space and time at multiple scales, shapes landscape pattern, and dictates ecological processes. While our knowledge of ecological phenomena is vast relative to many landscape metrics, thermal patterns which shape landscape mosaics are largely unknown. To address this disconnect, we investigated the thermal landscape by measuring black bulb temperature ( T bb ) at intervals as small as 15 min across 3 yr in a mixed-grass shrub vegetation community. We found that the thermal landscape was highly heterogeneous displaying a prevalence for thermal extremes (i.e., T bb  〉 50°C) and that T bb was driven by the synergism of environmental, terrain, and vegetation factors. Specifically, variation of T bb on the landscape was best predicted by the inclusion of ambient temperature ( T air ), solar radiation ( S rad ), low woody cover, and tall woody cover as variables. Moreover, models of single vegetation parameters (i.e., bare ground, low woody, or tall woody cover) each had greater relative importance than those containing a single terrain variable (i.e., slope or aspect) based on AIC, providing evidence that vegetation is a key driver of T bb on the landscape. Within the thermally heterogeneous landscape, tall woody cover moderated T bb by 10°C more than bare ground, herbaceous, or low woody cover during peak diurnal heating (14:00), and was the only cover type that remained 〈50°C on average. Given that tall woody cover comprises only about 7% of the landscape in our study, these findings have direct conservation implications for species inhabiting shrub communities, specifically that the distribution of tall woody cover is a spatially limited but key predictor of potential thermal refugia on the landscape. Our findings also demonstrate that local interactions between vegetation and temperature can create thermal patterns that shape dynamic landscape mosaics across space and time. Furthermore, we show that structural heterogeneity can maximize thermal complexity across landscapes which can provide greater potential thermal options for organisms. However, our modeled climate projections suggest that far greater thermal extremes will be possible across increasingly larger swaths of the landscape in the future, making assessments and quantifications of thermal landscapes increasingly critical.

Description: Abstract Ecological theory predicts that diversity decreases variability in ecosystem function. We predict that, at the landscape scale, spatial variability created by a mosaic of contrasting patches that differ in time‐since‐disturbance will decrease temporal variability in aboveground plant biomass. Using data from a multi‐year study of seven grazed tallgrass prairie landscapes, each experimentally managed for one to eight patches, we show that increased spatial variability driven by spatially‐patchy fire and herbivory reduces temporal variability in aboveground plant biomass. This pattern is associated with statistical evidence for the portfolio effect and a positive relationship between temporal variability and functional group synchrony as predicted by metacommunity variability theory. As disturbance from fire and grazing interact to create a shifting mosaic of spatially‐heterogeneous patches within a landscape, temporal variability in aboveground plant biomass can be dampened. These results suggest that spatially‐heterogeneous disturbance regimes contribute to a portfolio of ecosystem functions provided by biodiversity, including wildlife habitat, fuel, and forage. We discuss how spatial patterns of disturbance drive variability within and among patches. This article is protected by copyright. All rights reserved.

Description: Numerical simulations of thermal convection in the Earth's mantle often employ a pseudo-plastic rheology in order to mimic the plate-like behavior of the lithosphere. Yet the benchmark tests available in the literature are largely based on simple linear rheologies in which the viscosity is either assumed to be constant or weakly dependent on temperature. Here we present a suite of simple tests based on non-linear rheologies featuring temperature-, pressure-, and strain rate dependent viscosity. Eleven different codes based on the finite volume, finite element, or spectral methods have been used to run five benchmark cases leading to stagnant lid, mobile lid, and periodic convection in a 2-D square box. For two of these cases, we also show resolution tests from all contributing codes. In addition, we present a bifurcation analysis, describing the transition from a mobile lid regime to a periodic regime, and from a periodic regime to a stagnant lid regime, as a function of the yield stress. At a resolution of around 100 cells or elements in both vertical and horizontal directions, all codes reproduce the required diagnostic quantities with a discrepancy of at most ∼ 3% in the presence of both linear and non-linear rheologies. Furthermore they consistently predict the critical value of the yield stress at which the transition between different regimes occurs. As the most recent mantle convection codes can handle a number of different geometries within a single solution framework, this benchmark will also prove useful when validating viscoplastic thermal convection simulations in such geometries. This article is protected by copyright. All rights reserved.

Description: Long-distance movements are important adaptive behaviors that contribute to population, community, and ecosystem connectivity. However, researchers have a poor understanding of the characteristics of long-distance movements for most species. Here, we examined long-distance movements for the lesser prairie-chicken ( Tympanuchus pallidicinctus ), a species of conservation concern. We addressed the following questions: (1) At what distances could populations be connected? (2) What are the characteristics and probability of dispersal movements? (3) Do lesser prairie-chickens display exploratory and round-trip movements? (4) Do the characteristics of long-distance movements vary by site? Movements were examined from populations using satellite GPS transmitters across the entire distribution of the species in New Mexico, Oklahoma, Kansas, and Colorado. Dispersal movements were recorded up to 71 km net displacement, much farther than hitherto recorded. These distances suggest that there may be greater potential connectivity among populations than previously thought. Dispersal movements were displayed primarily by females and had a northerly directional bias. Dispersal probabilities ranged from 0.08 to 0.43 movements per year for both sexes combined, although these movements averaged only 16 km net displacement. Lesser prairie-chickens displayed both exploratory foray loops and round-trip movements. Half of round-trip movements appeared seasonal, suggesting a partial migration in some populations. None of the long-distance movements varied by study site. Data presented here will be important in parameterizing models assessing population viability and informing conservation planning, although further work is needed to identify landscape features that may reduce connectivity among populations.

Description: High-throughput sequencing has been proposed as a method to genotype microsatellites and overcome the four main technical drawbacks of capillary electrophoresis: amplification artifacts, imprecise sizing, length homoplasy, and limited multiplex capability. The objective of this project was to test a high-throughput amplicon sequencing approach to fragment analysis of short tandem repeats and characterize its advantages and disadvantages against traditional capillary electrophoresis. We amplified and sequenced 12 muskrat microsatellite loci from 180 muskrat specimens and analyzed the sequencing data for precision of allele calling, propensity for amplification or sequencing artifacts, and for evidence of length homoplasy. Of the 294 total alleles, we detected by sequencing, only 164 alleles would have been detected by capillary electrophoresis as the remaining 130 alleles (44%) would have been hidden by length homoplasy. The ability to detect a greater number of unique alleles resulted in the ability to resolve greater population genetic structure. The primary advantages of fragment analysis by sequencing are the ability to precisely size fragments, resolve length homoplasy, multiplex many individuals and many loci into a single high-throughput run, and compare data across projects and across laboratories (present and future) with minimal technical calibration. A significant disadvantage of fragment analysis by sequencing is that the method is only practical and cost-effective when performed on batches of several hundred samples with multiple loci. Future work is needed to optimize throughput while minimizing costs and to update existing microsatellite allele calling and analysis programs to accommodate sequence-aware microsatellite data. The primary advantages of fragment analysis by sequencing are the ability to precisely size fragments, resolve length homoplasy, multiplex many individuals and many loci into a single high-throughput run, and compare data across projects and across labs (present and future) with minimal technical calibration. A significant disadvantage of fragment analysis by sequencing is that the method is only practical and cost-effective when performed on batches of several hundred samples with multiple loci or in collaboration with multiple species or projects.

Description: Ecological theory predicts that diversity decreases variability in ecosystem function. We predict that, at the landscape scale, spatial variability created by a mosaic of contrasting patches that differ in time-since-disturbance will decrease temporal variability in aboveground plant biomass. Using data from a multi-year study of seven grazed tallgrass prairie landscapes, each experimentally managed for one to eight patches, we show that increased spatial variability driven by spatially-patchy fire and herbivory reduces temporal variability in aboveground plant biomass. This pattern is associated with statistical evidence for the portfolio effect and a positive relationship between temporal variability and functional group synchrony as predicted by metacommunity variability theory. As disturbance from fire and grazing interact to create a shifting mosaic of spatially-heterogeneous patches within a landscape, temporal variability in aboveground plant biomass can be dampened. These results suggest that spatially-heterogeneous disturbance regimes contribute to a portfolio of ecosystem functions provided by biodiversity, including wildlife habitat, fuel, and forage. We discuss how spatial patterns of disturbance drive variability within and among patches. This article is protected by copyright. All rights reserved.

Description: Large, complex coastal regions often require a combination of interventions to lower the risk of flooding to an acceptable level. In practice, a limited number of strategies are considered and interdependencies between interventions are often simplified. This paper presents the Multiple Lines of Defence Optimization System (MODOS)‐model. This quick, probabilistic model simulates and evaluates the impact of many flood risk reduction strategies while accounting for interdependencies amongst measures. The simulation includes hydraulic calculations, damage calculations, and the effects of measures for various return periods. The application and potential of this model is shown with a conceptual and simplified case study, based on the Houston‐Galveston Bay area. The analyses demonstrate how the MODOS‐model identifies trade‐offs within the system and shows how flood risk, cost, and impact respond to flood management decisions. This improved understanding of the impact of design and planning choices can benefit the discussions in finding the optimal flood risk reduction strategy for coastal regions.

Description: Seasonally flooded subtropical pastures are major methane (CH 4 ) sources, where transient flooding drives episodic and high magnitude emissions from the underlying landscape. Understanding the mechanisms that drive these patterns is needed to better understand pasture CH 4 emissions and their response to global change. We investigated belowground CH 4 dynamics in relation to surface fluxes using laboratory water table manipulations and compared these results to field-based eddy covariance measurements to link within-soil CH 4 dynamics to ecosystem fluxes. Ecosystem CH 4 fluxes lag flooding events, and this dynamic was replicated in laboratory experiments. In both cases, peak emissions were observed during water table recession. Flooding of surface organic soils and precipitation driven oxygen pulses best explained the observed time lags. Precipitation oxygen pulses likely delay CH 4 emissions until groundwater dissolved oxygen is consumed, and emissions were temporally linked to CH 4 production in surface soil horizons. Methane accumulating in deep soils did not contribute to surface fluxes and is likely oxidized within the soil profile. Methane production rates in surface organic soils were also orders of magnitude higher than in deep mineral soils, suggesting that over longer flooding regimes CH 4 produced in deep horizons is not a significant component of surface emissions. Our results demonstrate that distinct CH 4 dynamics may be stratified by depth and flooding of surface organic soils drives CH 4 fluxes from subtropical pastures. These results suggest that small changes in pasture water table dynamics can drive large changes in CH 4 emissions if surface soils remain saturated over longer time scales.

Description: Ecological theory predicts that diversity decreases variability in ecosystem function. We predict that, at the landscape scale, spatial variability created by a mosaic of contrasting patches that differ in time since disturbance will decrease temporal variability in aboveground plant biomass. Using data from a multi-year study of seven grazed tallgrass prairie landscapes, each experimentally managed for one to eight patches, we show that increased spatial variability driven by spatially patchy fire and herbivory reduces temporal variability in aboveground plant biomass. This pattern is associated with statistical evidence for the portfolio effect and a positive relationship between temporal variability and functional group synchrony as predicted by metacommunity variability theory. As disturbance from fire and grazing interact to create a shifting mosaic of spatially heterogeneous patches within a landscape, temporal variability in aboveground plant biomass can be dampened. These results suggest that spatially heterogeneous disturbance regimes contribute to a portfolio of ecosystem functions provided by biodiversity, including wildlife habitat, fuel, and forage. We discuss how spatial patterns of disturbance drive variability within and among patches.

Description: Habitat selection by animals is influenced by and mitigates the effects of predation and environmental extremes. For birds, nest site selection is crucial to offspring production because nests are exposed to extreme weather and predation pressure. Predators that forage using olfaction often dominate nest predator communities; therefore, factors that influence olfactory detection (e.g., airflow and weather variables, including turbulence and moisture) should influence nest site selection and survival. However, few studies have assessed the importance of olfactory cover for habitat selection and survival. We assessed whether ground-nesting birds select nest sites based on visual and/or olfactory cover. Additionally, we assessed the importance of visual cover and airflow and weather variables associated with olfactory cover in influencing nest survival. In managed grasslands in Oklahoma, USA, we monitored nests of Northern Bobwhite ( Colinus virginianus ), Eastern Meadowlark ( Sturnella magna ), and Grasshopper Sparrow ( Ammodramus savannarum ) during 2015 and 2016. To assess nest site selection, we compared cover variables between nests and random points. To assess factors influencing nest survival, we used visual cover and olfactory-related measurements (i.e., airflow and weather variables) to model daily nest survival. For nest site selection, nest sites had greater overhead visual cover than random points, but no other significant differences were found. Weather variables hypothesized to influence olfactory detection, specifically precipitation and relative humidity, were the best predictors of and were positively related to daily nest survival. Selection for overhead cover likely contributed to mitigation of thermal extremes and possibly reduced detectability of nests. For daily nest survival, we hypothesize that major nest predators focused on prey other than the monitored species’ nests during high moisture conditions, thus increasing nest survival on these days. Our study highlights how mechanistic approaches to studying cover informs which dimensions are perceived and selected by animals and which dimensions confer fitness-related benefits. Weather-related factors and predation are major sources of nest failure for birds. Nest site selection can be used to mitigate these adverse effects. We examined how visual cover variables and variables related to olfactory cover (e.g., airflow and moisture) influence nest survival and whether visual and olfactory cover is selected at nest sites of grassland-nesting birds. Nests were selected with more overhead visual concealment, and nests were more likely to succeed during high moisture conditions (high humidity and precipitation events). We surmise that overhead cover was used to mitigate thermal extremes and that during high moisture conditions predators focused foraging attention to prey other than the monitored species’ nests, thus increasing nest survival.