ALBERT

Beschreibung: Key message Flow rates were quantified on detached pedicels and conductances calculated. Flow rates and conductances were independent of time and temperature, increased with the pressure applied and slightly decreased during development. Abstract Water uptake is thought to contribute to cracking of sweet cherry fruit. Water uptake/loss occurs not only through the fruit surface but also through the xylem and phloem of the pedicel. The objectives here were: (1) to quantify the hydraulic conductance of the pedicel xylem and (2) to identify the factors affecting pedicel xylem conductance. Using a modified pressure probe, water was forced through excised pedicels. The rates of axial flow were quantified gravimetrically by collecting water at the pedicel’s distal end in a pre-weighed Eppendorf tube. Applying pressure to the proximal end of a pedicel induced a constant axial flow of water through it. The introduction of air embolisms to the xylem markedly decreased axial conductance from 1.3 ± 0.1 × 10 −10  m 3 MPa −1 s −1 to near zero. Steam girdling had no effect on axial conductance indicating the water flows to be through the xylem, not significantly through the phloem in our ex situ arrangement. Compared with a petiole, the pedicel conductance was 50-fold lower. A cross-section of a pedicel near its distal end revealed about 10 vascular bundles that diverged from a complete ring closer to the proximal end. Conductance estimates from the numbers and sizes of xylem vessels using Hagen–Poiseuille’s law exceed those determined experimentally by about three to fourfold. Conductance of pedicels decreased slightly in developing fruit and then remained about constant until maturity. Surprisingly, there was no significant effect of temperature on conductance. The conductance estimates may be used to model xylem water flows through the pedicel.

Beschreibung: Key message The premature leaf withering in Quercus subpyrenaica during the especially dry summers of 2011 and 2012 is interpreted as a mechanism for protecting the stem from xylem cavitation. Abstract The Mediterranean basin has been proposed as an area especially vulnerable to the effect of global climate change, with a greater probability of extreme drought events which can trigger massive forest decline episodes. The impact of extreme droughts on tree mortality in these territories can be magnified by several local factors, such as soil depth, which can predispose some species or individuals to be the damaged. During the summer of 2011 and 2012 many individuals of the deciduous Q. subpyrenaica in the Spanish Pre-Pyrenees showed a premature leaf withering in patches interspersed with non-affected areas. In this study, we have demonstrated that during 2011 and 2012 an extreme drought episode coincided with this phenomenon. The ultimate mechanism explaining the premature withering in Q. subpyrenaica was the hydraulic failure in the vascular system of the leaves in those trees growing in the poorest soil conditions. This mechanism, identified as an example of vulnerability segmentation, preserved the integrity of the stems and buds and allowed the new foliage production during the following spring. As a negative consequence, this drought avoidance strategy shortens the vegetative period, which may threaten the long-term growth and survival of these trees.

Beschreibung: Key message This study shows that functional grouping of the species based on nitrogen fixing ability along with initial leaf litter C/P, C/N, P and N could help us predicting leaf litter decomposition rate. Abstract Grouping species into functional groups is a good approach to understanding exotic plants impacts on ecosystem functioning in their new environment. One key plant trait that has large ecosystem-level consequences is the ability of plants to fix atmospheric nitrogen into plant available forms. Most previous studies have reported faster leaf litter decomposition rates of nitrogen fixing than non-nitrogen-fixing species, supporting the separation of these as functional groups. Here, we present a multispecies monitoring of litter decomposability of seven tree species in a 1 year decomposition experiment in outdoor litter bed common garden experiment in river floodplain in South Western Iran. We tested within- and between-functional-groups for rates of leaf litter decomposition and nutrient dynamics. Our results highlight that nitrogen-fixing trees and non-nitrogen-fixing trees can be distinguished based on specific leaf area and leaf litter traits. The interesting results were that the leaf litter decomposition rates of the two functional groups were related to different initial leaf litter traits. Leaf litter decomposition rates of nitrogen-fixing trees were related to initial leaf litter C/P, C/N, N, P and Ca, while leaf litter decomposition rates of non-nitrogen-fixing trees were only related to initial leaf litter Ca. Whereas specific leaf area was the best predictor of leaf litter decomposition rates among all the species. Therefore, our results revealed that both initial leaf litter traits and functional groups were predicting leaf litter decomposition rates.

Beschreibung: Key message The CO 2 effect on the root production of a broad-leaved community was insignificant when grown in brown forest soil, however, it was positively large when grown in volcanic ash soil. Abstract We evaluated the root response to elevated CO 2 fumigation of 3 birches ( Betula sp.) and 1 deciduous oak ( Quercus sp.) grown in immature volcanic ash soil (VA) or brown forest soil (BF). VA is a nutrient-poor, phosphorus-impoverished soil, broadly distributed in northern Japan. Each species had been exposed to either ambient (375–395 μmol mol −1 ) (aCO 2 ) or elevated (500 μmol mol −1 ) (eCO 2 ) CO 2 during the daytime (more than 70 μmol m −2  s −1 ) over 4 growing seasons. The results suggest that eCO 2 did not cause an increase in total root production when the community had grown in fertile BF soil, however, it did cause a large increase when the community was grown in infertile VA soil. Yet, carbon allocation to plant roots was not affected by eCO 2 in either the BF or VA soils. Rhizo-morphogenesis appeared to occur to a greater extent under eCO 2 . It seems that the saplings developed a massive amount of fine roots under the VA and eCO 2 conditions. Unexpectedly, eCO 2 resulted in a larger total root mass when the community was grown in VA soil than when grown in BF soil (eCO 2  × VA vs. eCO 2  × BF). These results may hint to a site-specific potential of communities to sequester future atmospheric carbon. The growing substance of plants is an important factor which root response to eCO 2 depends on, however, further studies are needed for a better understanding.

Beschreibung: Key message Analysis of tree-ring anatomical features of co-occurring Sycamore maple and Italian alder showed species-specific xylem hydraulic traits revealing functional adaptation to climate at their southernmost distribution limit. Abstract The impact of rising temperature and changing rainfall patterns is expected to alter the drought resistance limits of Mediterranean plants. Water shortage negatively affects plant hydraulic conductance, increasing plant vulnerability to drought-induced xylem embolism. This phenomenon may force maple-alder ecosystems, affecting the competitive balance between these two species at their southernmost distribution limit. By developing a tree-ring series of xylem anatomical features, we evaluated the relationship between the climate and the functional xylem anatomy of sycamore and alder woody species that coexist in the same area. We hypothesized that variation in xylem anatomy between the two species is driven by plasticity and trade-offs between safety from drought-induced embolism and water transport efficiency. Sycamore maple and Italian alder had several distinctive anatomical traits, revealing successful plant hydraulic properties, such as hydraulic conductivity and vulnerability to embolism. Surprisingly, the xylem hydraulic architecture of maple did not reflect the trade-off between the efficiency of the conducting system and safety against embolism, whereas a shift towards a more efficient xylem configuration was observed for alder during periods of water shortage. Alder trees primarily adjusted their architecture by reducing the size of larger vessels, which are more vulnerable to embolism. In particular, a strong trade-off between xylem traits in alder facilitated high xylem plasticity, allowing rapid hydraulic adjustment to annual climatic variability. This response may represent an important determinant of individual performance, and may have the potential to shape the functional diversity and ecology of this forest community.

Beschreibung: Key message Leaf relative water content, leaf area, leaf fresh weight, and SPAD chlorophyll meter readings along with Co - rbcL and Co - rbcS expression can be used for evaluating Camellia oleifera responses to combined drought and heat stress and subsequent recovery after rainfall events. Abstract Leaf characteristics, soluble protein and total soluble sugar contents as well as Rubisco-related gene expression in three cultivars of C. oleifera were measured during a combined drought and heat stress period and after subsequent rainfall events. Leaf relative water content (RWC) was significantly correlated with leaf area (LA), leaf fresh weight (FW), SPAD chlorophyll meter readings, and the levels of Co - rbcL and Co - rbcS expression. Results suggest that leaf RWC, LA, leaf FW, SPAD readings together with Co - rbcL and Co - rbcS expression can be used for evaluating responses of C. oleifera cultivars to combined drought and heat stress and subsequent recovery after rainfall events. Rubisco activase might be used for evaluating plant recovery after rainfall. This study identified cultivars differing in tolerance to the combined stress and recovery. Information derived from this study should be valuable for improving survivability and productivity of C. oleifera cultivars.

Beschreibung: Key message Pith diameter is a good parameter to solve dating architecture problems. Abstract Plant architecture can be used to study plant development retrospectively thanks to time-dependent morphological markers, particularly those corresponding to the winter break in temperate regions. The Aleppo Pine and the Turkish Pine are polycyclic species, thus they usually develop several consecutive growth units per year, making it sometimes difficult to date them. In this study, we show that keeping track of the pith diameter profile, to date each shoot, is an efficient method. The pith diameter is larger on the first growth unit than on the last growth unit of the year. Moreover, a pairwise comparison showed that the pith diameter undergoes a decrease along the annual shoot from the first growth unit to the last. As pith diameter decreases upwards the annual shoot, it can be used for dating. Pith diameter progresses from 1 year to another too: there is an increase in the early years of life, corresponding to the tree’s establishment phase. Lastly, we found a positive relationship between the basal pith diameter of an annual shoot and its length. The variability around this relationship could reflect environmental conditions, especially climate conditions.

Beschreibung: • Key message Xylem and soil CO 2 fluxes in coppiced oak forests increase with clonal size, suggesting larger expenditures of energy for root respiration. An imbalance between root demand and shoot production of carbohydrates may contribute to the degradation of abandoned coppices. • Context Our understanding of root respiration is limited, particularly in root-resprouting species with many stems and a large system of interconnected roots resulting from long-term coppicing. • Aims We tested the hypothesis that clone size influences the internal flux of CO 2 dissolved in xylem sap ( F T ) from roots into the stem and soil CO 2 efflux ( F S ) as indicators of root respiration. We predicted that large clones would exhibit higher F T per stem and F S than small clones due to larger root system per stem in large clones. • Methods Genetic analyses were performed to elucidate clonal grouping. F T was measured continuously for 100 days in 16 similar-sized stems of Quercus pyrenaica belonging to two large and two small clones. F S was measured in 20 clones of varying size. • Results F T per stem and F S were higher in large clones. F T was 2 % of the root-respired CO 2 that diffused through soil to the atmosphere. • Conclusions Relative to other studies, the contribution of F T to root respiration was very low, pointing to large differences depending on species or site. Higher stem F T and F S in large clones compared with small clones suggest greater carbon consumption by roots in large clones, pointing to a root/shoot biomass and physiological imbalance resulting from long-term coppicing that would partially explain the degradation of currently abandoned stands of Q. pyrenaica .

Beschreibung: Key message Radial growth responses of gap-edge trees to GT intensity greatly depends on microclimate condition (soil temperature and PAR) within gaps and their abilities in competing and utilizing the limited resources. Abstract Gap-model thinning (GT) is an effective management technique to improve the productivity of dense monoculture plantation. However, how GT intensity influence inter- and intra-annual radial growth of the gap-edge trees remains an open question. In order to explore this question, we implemented an experiment with four treatments (control and gap sizes of 74, 109, and 196 m 2 ) in a 30-year-old spruce ( Picea asperata ) plantation in 2008. We used dendrochronological method to explore dynamic of the basal area increment (BAI) of gap-edge trees ( n  = 127) from 2009 to 2012 after GT treatments. We found that effects of GT on the BAI of gap-edge trees highly depended on GT intensity and their crown classes. The large gaps significantly increased the BAI of gap-edge trees and further the latewood growth responded more sensitively than the earlywood, whereas the influences of the small and intermediate gaps were weak; the large gaps effectively improved the BAI of the dominant trees, following by the intermediate, but not for the suppressed trees. Our results also displayed that the earlywood increment was strongly related to the soil temperature in spring and the latewood formation was influenced by the photosynthetically active radiation in autumn. It was eventually concluded that dynamic radial growth of gap-edge trees were driven by the improved microclimate caused by GT and their abilities in competing and utilizing resources. The present study highlights the importance of setting appropriate GT intensity and choosing the felled trees in GT operation.

Beschreibung: Key message Water use patterns of understorey vegetation are species-dependent. Calluna vulgaris showed little or no regulation of transpiration in response to soil water depletion or air vapour pressure deficit, unlike Pteridium aquilinum , Rubus sp. and Molinia caerulea . Context Evapotranspiration at forest stand scale is the sum of three components: overstorey and understorey transpiration, and evaporation from soil. During periods of soil water shortage, evapotranspiration of trees declines significantly, but the response of understorey vegetation is less well known. Some reports suggest that understorey vegetation can sometimes be the main source of water depletion in a forest stand during drought episodes. Aims We assessed transpiration in response to decreased soil water content (SWC) and increased vapour pressure deficit (VPD) in the atmosphere for four understorey species with contrasting patterns of resource capture. Methods Potted plants of Pteridium aquilinum , Molinia caerulea , Calluna vulgaris and Rubus sect. Fruticosi were grown under two radiation levels combined with three levels of SWC. Temperature, radiation, VPD and transpiration were monitored. Results Calluna vulgaris displayed a water spender behaviour with little or no regulation of transpiration during soil water depletion and increased VPD, whereas Pteridium aquilinum showed a low transpiration rate whatever the conditions. Rubus sect. Fruticosi gradually decreased transpiration during soil water depletion and increased VPD, whereas Molinia caerulea responded strongly to soil water depletion but only moderately to VPD. Conclusion This study highlights the importance of adding identity and water use strategy of understorey species to the tree canopy component to establish a reliable forest water balance.

Beschreibung: Key message Among apple viruses, the present study identified Apple stem grooving virus infection in Bauhinia variegata . CP gene of the isolate clustered with kiwi isolate, however, differing in biological characteristics. Abstract Bauhinia variegata , widely distributed in Kangra district (Himachal Pradesh, India), was found to exhibit severe virus-like symptoms, which included chlorosis, chlorotic and necrotic spots, mottling, leaf distortion and grooves on the stem. Symptomatic leaf samples collected from three different locations in the district, viz. CSIR-IHBT (Palampur), CSK HPKV (Palampur) and Dharamshala were analyzed by DAS-ELISA, dot blot hybridization and RT-PCR for the presence of ASGV infection. The combined results of three detection techniques showed 9 out of 30 samples to be positive for the virus. To understand the incidence of other major apple viruses, samples were also analyzed by multiplex RT-PCR. However, only ASGV was detected from the samples. Complete CP gene from four of the positive samples was amplified by RT-PCR and confirmed through sequencing and BLAST analysis of the amplicons. Phylogenetically, three isolates (abbreviated as BAU1, BAU2 and BAU18) clustered with apple isolates from India, Brazil and China, while one (BAU16) clustered separately. All the four isolates shared 94–99 % sequence identity at amino acid level and 87–98 % sequence identity at nucleotide level with all the other isolates from various geographical locations and differing hosts. To the best of our knowledge, this is a first report describing ASGV infection on B. variegata, its molecular characterization, and diversity analysis and incidence study. The tree probably acts as a reservoir of ASGV as it is found actively growing around apple nursery plantations, while no other apple virus was diagnosed from Bauhinia.

Beschreibung: Key message This paper provides an important direct proembryogenic mass initiation and plant regeneration method that might be supportive and stable for gene transformation and commercial production of Torreya grandis . Abstract Torreya grandis is an important and commercially valuable tree that is utilized as a source of essential oil and nuts. Propagation researches of T. grandis have been focused on micropropagation and somatic embryogenesis which derived from callus but limited data regarding direct somatic embryogenesis and plant regeneration are available in the literature. This study investigated the effects of plant growth regulators combinations on direct proembryogenic masses initiation and plant regeneration. Proembryogenic masses were initiated from cotyledons and hypocotyls of immature zygotic embryos directly. The frequency of direct proembryogenic masses initiation (52.6 %) was significantly greater than other treatments when the explants were cultured on Schenk and Hildebrandt medium which supplemented with 0.1 mg l −1 N6-benzylaminopurine, 0.1 mg l −1 Kinetin and 0.1 mg l −1 2,4-dichlorophenoxyacetic acid. Combined application of Abscisic acid and Polyethylene glycol 6000 stimulated cotyledons formation and resulted in morphologically superior somatic embryos. Schenk and Hildebrandt medium supplemented with 10 mg l −1 Abscisic acid and 20 mg l −1 Polyethylene glycol 6000 was optimum (88 %) for somatic embryos maturation. Highest germinated somatic embryos percentage (35.6 %) was obtained on Schenk and Hildebrandt medium supplemented with 2000 mg l −1 activated charcoal, with root and shoot lengths of 2.3 and 1.9 cm, respectively. As proembryogenic masses were initiated without the formation of callus, this study will aid to establish stable genetic transformation and will also be useful in improving understanding of the somatic embryogenesis of T. grandis.

Beschreibung: Key message Influence of climate warming and resin collection on the growth of Masson pine. Abstract Using tree-ring analysis coupled with the resin tapping history and climate data, we investigated the effects of climate warming and resin collection on the radial growth of Masson pine ( Pinus massoniana ) in southern China. Fifty Masson pine trees from untapped (LDC) and tapped (WLS) stands were sampled from Changting, southern China. The radial growth of Masson pine at the LDC site was positively influenced by previous November and current February temperature and current July precipitation. There is an abrupt change point of the LDC series in 2002, which may be linked with regional climate warming. An increasing trend in the LDC series over the last 20 years is also found. Resin collection had a negative effect on the radial growth of Masson pine at the WLS site, especially on old trees. The positive effect of climate warming on the radial growth of Masson pine was offset by the negative effect of the resin collection. Therefore, in order to keep timber production, the unplanned resin collection should be forbidden.

Beschreibung: Key message Under increasing short-term drought stress, E. camaldulensis plantlets showed reduced stomatal conductance, then decreased carboxylation efficiency, and finally, reduced quantum efficiency of photosynthesis and chlorophyll content. Abstract We evaluated the physiological responses of a drought-tolerant (DT) clone and a drought-sensitive (DS) clone of Eucalyptus camaldulensis to drought stress. We evaluated leaf gas exchange, chlorophyll fluorescence, chlorophyll content, and biomass of 4-month-old eucalyptus plantlets during a graduated series of drought stress treatments over 24 days. The plantlets were grown in half-strength Hoagland’s solution, and drought stress was imposed by adding polyethylene glycol (PEG 6000) to the nutrient solution. The plantlets were subjected to three stepwise levels of drought stress, each 8 days long. The osmotic potential of the nutrient solution was −70, −140, and −280 kPa under mild, moderate, and severe drought stress, respectively. Compared with unstressed plantlets, the drought-stressed plantlets of both clones showed significant decreases in leaf gas exchange, chlorophyll fluorescence parameters, and biomass accumulation. The limitation of photosynthesis under mild drought stress was mainly because of reduced stomatal conductance. The reduction in the photosynthetic rate ( P n ) under moderate to severe drought stress was because of both stomatal and non-stomatal limitation; that is stomatal closure, reduced carboxylation efficiency, reduced quantum efficiency, and decreased chlorophyll content. Both clones used stomatal control as an avoidance mechanism under drought stress. The differences between the two clones were already shown under mild drought stress. Compared to its non-stressed condition, the DS clone showed larger decreases in P n , stomatal conductance, and transpiration rate than the DT clone. The stepwise scheme in imposing drought stress can differentiate the drought response traits in E. camaldulensis .

Beschreibung: Key message The growth of Japanese larch seedlings is regulated by the presence of nutrients as well as ectomycorrhizal symbiosis. Abstract The mountain slope of an active volcano is a severe environment for the regeneration of larch ( Larix kaempferi Sarg. hereafter larch) seedlings. To determine parameters affecting the growth of larch seedlings, we analyzed stoichiometry of elements in the soils and plant organs, ectomycorrhizal (ECM) colonization, and photosynthetic abilities. These parameters were compared with two different elevations. From nutrient analysis of plant organs from larch seedlings grown on the slope of a volcano, potassium (K) was insufficient compared with the seedlings grown in other habitats. Symbiosis with ECM fungi enabled the uptake of nutrients, especially phosphorous (P) and nitrogen (N). The main factor affecting the differences in relative height growth rate (RHGr) of larch was attributed to ECM colonization. There was a positive relationship between ECM colonization and concentrations of P or N in needles. Larch seedlings with high rates of ECM colonization showed high concentrations of P and N, and had high photosynthetic rates. At lower elevation sites, concentrations of N and K in needles were low with high density of individuals. Moreover, larch showed a high accumulation of aluminum (Al) and iron (Fe) even though the amount of these elements in the soil was small. These seedlings exhibited a suppressed photosynthetic rate and RHGr. Symbiosis with ECM fungi could suppress the excessive uptake of Al and Fe.

Beschreibung: Key message The surface area and dry biomass of leaves can be satisfactorily estimated from simple dimension measurements. These data are useful for estimating carbon allocation in trees using functional–structural growth models. Abstract Leaf area and leaf dry biomass are key parameters linked to plant production and they are used in functional–structural plant models to simulate plant growth, but they are difficult to ascertain. Measuring leaf dimensions (length and width) to estimate them provides a non-destructive and rapid approach that can be used in the field. This was tested on teak ( Tectona grandis ) in Togo. Leaves were sampled to maximize variability in sizes along two categories of axes and at different ranks on the growth units. Two different equations were determined to estimate leaf area and dry biomass from leaf dimensions. The relation between leaf area ( A ) and the product of length ( L ) × width (Wi) was defined by the linear equation A  = 0.60 ×  L  × Wi whereas dry biomass (We) was predicted by a power law We = 0.004 × ( L  × Wi) 1.11 . This method could also be tested and applied to other species.

Beschreibung: Key message Variations in stable carbon and oxygen isotope compositions of co-occurring plant species reflect their different water use strategies and indicate the importance of screening species’ WUE i to plan climate change adaptation strategies. Abstract The different abilities of plant species to cope with drought have been associated with structural and ecophysiological constraints. In this paper, we evaluate interspecific differences in intrinsic water use efficiency (WUE i ) and the ratio of photosynthesis (A) to stomatal conductance (g s ) in three co-occurring Mediterranean shrubs: two broad-leaved evergreen ( Pistacia lentiscus and Phillyrea angustifolia ) and one needle-like-leaved evergreen ( Juniperus phoenicea ). We used δ 13 C in rings to assess inter-annual changes in WUE i while the influence of the stomatal conductance was explored through δ 18 O. Our results indicate consistent differences in WUE i in the three species, largely determined by leaf traits and differences in stomatal conductance control. Juniperus phoenicea could be the most threatened by the current trend of increasing temperature and summers drought. Phillyrea angustifolia and P. lentiscus seem to be less affected by drought stress because of their tighter stomatal control and high survival rate under field conditions. Our study shows that shrubs with different leaf traits employ different plant ecophysiological strategies under drought stress.

Beschreibung: Key message In tropical forests, co-occurring woody monocot and dicot species adapted different water use strategies highly depending on their investment in the hydraulic conduit properties. Abstract We studied the hydraulic efficiency of palms and broad-leaved tropical tree species from a moist tropical lowland forest in the Central Brazilian Amazon. Therefore, we harvested 34 trees and 10 açai palms and measured vessel size and frequency at diameter at breast height and additionally at the base of the crown shaft for the palms. Further, we assessed the active xylem area to estimate the hydraulic conductivity through Hagen Poiseuille’s adapted theoretical equation. Mean vessel diameter in dicot trees was 127.62 ± 49.22 μm with an average 9.09 ± 6.50 vessels per mm 2 . Mean conduits sizes at the base ( h  = 0.10 m) of palm trees were larger with 288.20 ± 32.96 μm and less frequent with 1.40 ± 0.46 vessels per mm 2 . Hydraulic conductivity was on average 3.31 ± 4.59 kg m −1  s −1  MPa −1 for dicot trees. Mean hydraulic conductivity in açai palms was 20.45 ± 10.6 kg m −1  s −1  MPa −1 at the base, and increased to 124.73 ± 55.2 kg m −1  s −1  MPa −1 at the crown base. Hydraulic conductivity at the base of the crown was higher than in the base of the trunk due to the high density of vessels in a small cross-section in this height. Furthermore, we found a species-independent relationship between vessel diameter and frequency. We conclude that the differences found in the hydraulic efficiency give some evidence that palms have a lower occurrence of embolism and cavitation than trees, which is due to stiffer and stronger conduit pathways and efficient drought-avoiding strategies. The differences in hydraulic architecture between palms and trees imply different water use patterns thus varying niche differentiation, but this does not consequently need to be an excluding factor for coexistence in the same environment.

Beschreibung: Key message Through a stochastic programming framework, risk preferences can be included in forest planning. The value of utilizing stochastic programming is always positive; however, the value depends on the information quality and risk preferences of the decision maker. Context Harvest scheduling requires decisions be taken based on imperfect information and assumptions regarding the future state of the forest and markets. Aims The aim of this study is to incorporate elements of risk management into forest management, so that the decision maker can understand the risks associated with utilizing the imperfect data. Methods Incorporation of uncertainty is done through stochastic programming. This allows for the decision maker’s attitude towards risk to be incorporated into the development of a solution. By means of a simple even-flow problem formulation, a method of using stochastic programming to incorporate explicit trade-off between objective function value and risk of not meeting the constraints has been developed. Results The different models highlight the importance of including uncertainty in management of forest resources. In general, as the decision maker becomes more risk averse, the incorporation of uncertainty into the model becomes more important. Conclusions The use of stochastic programming allows for additional information to be included in the formulation, and this allows for the decision maker to account for downside risk.

Beschreibung: Key message Sloped terrains tend to produce trees with higher radial variation in wood density while at high wind speeds, the wood tends to present higher stiffness and lower MFA in Eucalyptus. Abstract Few studies have investigated the influence of environmental conditions on the within-tree variation in Eucalyptus wood traits. The genotype and environment effects and their interactions influence the wood properties. Their evaluations are crucial to estimate the genotype values and to select with efficiency. Thus, the aim of this study was to better understand the effect of ground slope and wind speed on the spatial variation of basic density ( ρ ), stiffness (MOE) and microfibril angle (MFA) of Eucalyptus wood. Wood discs cut along the trunk were sampled from one-hundred fifty 6-year-old Eucalyptus grandis  ×  E. urophylla hybrids growing in three contrasting growing conditions influenced by ground slope and wind regime. Near infrared (NIR) calibrations previously developed for ρ , MOE and MFA were used to predict in our discs. 2-D plots presenting the spatial variation of predicted wood traits were compared. The higher the ground slope, the greater the magnitude of radial variation in ρ , principally in the medium zone of the trunk. The spatial variation of wood stiffness seems to be sensitive to two environmental conditions. The MFA radial decreases were more pronounced where the wind speed was higher. At the base and top of the trees, however, there was no significant effect of growing conditions on the radial variation of the wood properties considered here.

Beschreibung: Key message The use of mean characteristics of communities to infer absolute species variations may well constitute another “silent clash of paradigms” Austin (Oikos 86:170–178, 1999 ) in community ecology. We discuss this issue based on a recent paper on floristic thermophilization in forests.

Beschreibung: Key Message Annals of Forest Science is publishing a series of review papers to celebrate 50 years of activities as a journal in forest and wood science. The reviews emphasize the extent to which forest and wood sciences changed and developed as a large array of disciplines devoted to complex objects with sometimes many conflicting issues.

Beschreibung: Key message We provided a precise quantitative analysis of the factors at the origin of bark damage during harvesting operations and developed a model able to predict them accurately. The major factors were the distance of trees to skid trails, the intensity of removals, the harvesting system as well as the interactions between the distance of trees to skid trails with harvesting systems, the average skidding distance, the tree species and tree height. • Context During timber harvesting, trees in the remaining stand may suffer bark damage resulting from tree-felling or log manipulation. Although a multitude of case studies and empirical observations provide qualitative and quantitative information with respect to the potential causal factors, the basic quantitative relationship between major factors of influence and the resulting degree of bark damage remains largely unclear. • Aims The objective was to provide a precise quantitative analysis of impact factors explaining the occurrence of bark damage during harvesting operations. • Methods Three different modelling approaches were tested: boosted regression tree (BRT), a generalised linear mixed effects model (GLMM) and Bayesian Markov chain Monte Carlo generalised linear mixed models (MCMCglmm). • Results The major factors with a significant impact on the occurrence of bark damage were the distance of trees to skid trails, the intensity of removals, the harvesting system and the interaction term between the distance of trees to skid trails with harvesting systems, average skidding distance, tree species and tree height. • Conclusion The final model includes the relevant major factors impacting on the infliction of bark damage during practical harvesting operations. Furthermore, it discriminates well with respect to the occurrence of bark damage, and it provides managers with a rational and conclusive tool for optimising harvesting operations.

Beschreibung: Key message We show that Pinus pinaster provenance affects both seed germination and seedling recruitment after fire. This information is crucial for managers to select the best seed-provisioning populations when implementing reforestation programs to assist the natural post-fire regeneration of the species. Context Reforestation programs to assist natural regeneration of maritime pine ( Pinus pinaster Aiton) forests after wildfires very often neglect the fire-adaptive traits of the selected seed-source populations, threatening future stand resilience to fire. Aim We investigate the influence of seed provenance and weight on the rate and timing of seed germination, and on early seedling growth of P. pinaster after fire. Methods We simulated conditions during fire by experimentally submitting free seeds from three P. pinaster provenances with contrasting levels of serotiny (from 〈6 to 〉58 % of trees bearing serotinous cones within the population) to six combinations of temperature and exposure time. We fitted GLMs and LMs to test for differences among provenances in reproductive performance after the thermal shock treatments. Results Heavy seeds derived from the very low serotinous population exhibited greater tolerance to heat (higher germination rate, lower germination time, and higher seedling length) than the lighter ones from the highly serotinous population. Conclusion The seeds enclosed in serotinous cones are, however, the only ones protected from high fire-induced temperatures, delaying release until favourable post-burn conditions for germination and seedling establishment. Therefore, selecting the best fire-adapted populations with the optimal serotiny level as seed-provisioning sources should be encouraged to ensure forest regrowth in fire-prone areas.

Beschreibung: Key message Although first flowering in trees causes clear changes in main stem morphological trends, we prove that it does not totally explain changes in wood density trends. Abstract The phase change produced by a tree’s first flowering event (that marks the limit between juvenile and mature stage) causes changes in the morphological trends of the main stem. As has been documented in a number of tree species, the number of growth units per annual shoot, the annual shoot length, and the growth unit length are some of the variables that exhibit abrupt changes when first flowering occurs. Considering the strong impact of first flowering on tree morphology—and considering also trends that have been observed in wood density and related variables, we tested the relationship between the first flowering event and wood density trend changes in Pinus radiata D. Don at three different site conditions with differing climates. The relationship was studied using different criteria to select the proper variables and methodology. Some interesting relationships between first flowering and certain variables were found, particularly the variables earlywood density, latewood density accumulated, latewood proportion, and ring area. However, these relationships were not consistent among the three sites. Overall, there is not enough evidence to conclude that the first flowering causes or contributes to changes in wood density trends. Our findings suggest that studies should be conducted on the relationship between the architectural development of the crown and changes in internal wood characteristics. We corroborate the suggestion as reported by Burdon et al. (For Sci 50:399–415, 2004) of adopting the terms corewood and outerwood instead of juvenile and mature wood.

Beschreibung: Key message CHX had remarkable inhibition on P. edulis photosynthesis, and the reflectance indexes and F 685 / F 735 had the potential value for quantifying the effects of antibiotics on trees. Abstract To reveal the effects of antibiotics on photosynthesis and provide help for remote sensing the influence of antibiotics on trees, we investigated the effects of cycloheximide (CHX) on Phyllostachys edulis . In CHX treatment, the photosynthetic pigment content in P. edulis was decreased markedly, which led to the increase in the reflectance spectra in visible region. CHX reduced the donor side and acceptor side of photosystem II (PSII), density of reaction centers, quantum production and electron transport in PSII, and raised the dissipation of absorbed light energy. Besides the dissipation, the absorbed light energy can be emitted as fluorescence with two main peaks in the red (685 nm) and far-red (735 nm) region, respectively. In 0.50 mM CHX treatment, a significant decline in the height and area of the peak at 685 nm might result from Chl loss reducing the light absorption and lower photochemical reaction in PSII. When fourth derivative analysis of fluorescence emission spectra was performed, the changes of the peaks at 718, 735 and 750 nm might result from the decline of absorbed solar radiation caused by the reduced pigment content and/or the damages to the PSI. In CHX treatment, a remarkable increase in intercellular CO 2 concentrations and light compensation point and decrease in light saturation point demonstrated that the CO 2 assimilation ability was decreased. Those results suggested that the photosynthesis in trees can be reduced after they were watered with wastewater containing CHX. The reflectance indexes and F 685 / F 735 ( H 685 / H 735 and A 685 / A 735 ) were markedly affected by CHX, demonstrating that they had the potential value for quantifying the effects of antibiotics on trees.

Beschreibung: Key message The effect of unexpected low temperature on coexisting species in inland locations was examined; frost tolerance simulation over a 2-year period was used to determine bottlenecks where competition can arise. Abstract The effect of frost events on natural regeneration of Mediterranean mixed forests under a scenario of climate change is not well known. The expected increase in mean annual temperature and the greater inter- and intra-annual variability in frosts occurrence can significantly damage natural regeneration leading to death, with a decisive effect on species composition and forest dynamics. We investigated seasonal variations in frost tolerance of three Mediterranean species ( Pinus pinea , Quercus ilex and Juniperus oxycedrus ) co-occurring in inland locations in Spain. Our aim was to assess seasonal inter-specific differences in frost sensitivity or tolerance. First, we applied the relative electrolyte leakage method (REL) to estimate the frost tolerance of these species every 3–4 weeks during the 9-month period in which frost events can occur in a year. Second, we explored the REL relationship with environmental variables impacting frost acclimation/deacclimation, i.e., absolute minimum and maximum temperatures and photoperiod. Third, we built a REL model to predict seasonal variations in REL performance of young trees. We simulated REL through a 2-year period, thus defining seasonal bottlenecks in which the dynamics of regeneration can be affected by frost events. Our results showed contrasting behaviors between species, highlighting a greater sensitivity to cold of P. pinea compared to the other two species. The three species are most vulnerable in autumn; however, the different strategies to cope with unfavorable conditions adopted by Q. ilex and J. oxycedrus (e.g., stress tolerance and/or resprouting ability) give these species a competitive advantage over P. pinea .

Beschreibung: Key message This review gives a comprehensive overview of adaptations of mangrove root system to the adverse environmental conditions and summarizes the ecological importance of mangrove root to the ecosystem. Abstract In plants, the first line of defense against abiotic stress is in their roots. If the soil surrounding the plant root is healthy and biologically diverse, the plant will have a higher chance to survive in stressful conditions. Different plant species have unique adaptations when exposed to a variety of abiotic stress conditions. None of the responses are identical, even though plants have become adapted to the exact same environment. Mangrove plants have developed complex morphological, anatomical, physiological, and molecular adaptations allowing survival and success in their high-stress habitat. This review briefly depicts adaptive strategies of mangrove roots with respect to anatomy, physiology, biochemistry and also the major advances recently made at the genetic and genomic levels. Results drawn from the different studies on mangrove roots have further indicated that specific patterns of gene expression might contribute to adaptive evolution of mangroves under high salinity. We also review crucial ecological contributions provided by mangrove root communities to the ecosystem including marine fauna.

Beschreibung: Key message Traditional coppice conversion to high forest through periodic thinning requires a long period to attain the regeneration stage. We showed that anticipating seed cutting can accelerate the progression of the stands towards more adult stand conditions , compared with traditional management. The application of different active management options in the same landscape can contribute to increase landscape diversity . Context In southern European beech forests, coppice is a widespread management system, especially due to the past uses. The existence of large areas either abandoned or under protracted transitory stage raises questions concerning environmental and economic revenues related to the different management options. Aims We evaluated the effectiveness of anticipating seed cutting in beech coppices to accelerate the coppice transition to high forest, compared with traditional management (periodic thinning) and natural evolution pattern (unthinned control). Methods We used an exploratory analysis of ecological variables related to structure, dynamics, and productivity of the stands (growth efficiency, leaf area index, litter production, transmittance, and canopy heterogeneity), which were monitored during 10 years in beech coppices in Central Italy. Results Anticipating seed cutting produced stronger modification in canopy structure, improving growth efficiency as a result of higher resource availability, supporting higher seed production which accelerated the progression of the stand towards more adult stand conditions, compared with traditional management and unthinned control. Conclusion The application of different active management options can increase landscape heterogeneity under the conditions in which increasing landscape diversity represents a priority management issue, while simultaneously allowing environmental and economic revenues.

Beschreibung: Key message This paper for the first time provides insights into the important roles of the miRNAs during blooming period in Populus simonii   ×   P. nigra. Abstract MicroRNAs (miRNAs) are small RNAs that act as regulators of eukaryotic gene expression at the post-transcriptional level. Using high-throughput sequencing technology, we analyzed miRNAs in Populus. simonii  ×  P. nigra at three stages of male flower bud development (pollen at the tetrad, uninucleate, and binucleate stages, respectively), using shoot tips and vegetative buds as controls. In total, 305 differentially expressed miRNAs from 49 families were identified. Among the 49 families, 17 were highly or moderately conserved in other species. A higher number of differentially expressed miRNAs were down-regulated in male flower buds compared with vegetative organs. Quantitative real-time PCR showed that almost all miRNAs have the same expression pattern as in the cluster results. Gene ontology enrichment analysis provided an indication of the possible functions of the miRNAs in male flower bud development.

Beschreibung: Key message Borneo’s tropical heath (kerangas) forest has limited soil nutrient availability, and high variation in aboveground structure and fine-root biomass. This variation depends on altitude and soil nitrogen availability. Abstract To elucidate the biotic and abiotic factors affecting the variation in fine-root biomass (FRB, 〈2 mm diameter) of trees growing under nutrient-poor environments in Sabah, North Borneo, we investigated FRB in different forests with varying soil nitrogen (N) availability. We selected two study sites at different altitudes: the Maliau Basin (ca. 1000 m asl) and Nabawan (ca. 500 m asl). Both sites included tropical heath (kerangas) forest, on infertile soils (podzols) with a surface organic horizon overlying a bleached (eluviated) mineral horizon, and taller forests on more fertile non-podzolic soils. FRB was obtained from each plot by soil coring (to a depth of 15 cm). FRB increased with decreasing soil inorganic N content (NH 4 –N and NO 3 –N), tree height, and aboveground biomass. Thus, higher proportions of carbon resources were allocated to fine-roots in stands with lower N availability. FRB was significantly greater at the Maliau Basin than at Nabawan, reflecting lower soil N availability at higher altitude. Our results demonstrate high variation in FRB among the heath forests, and suggest that fine-root development is more prominent under a cooler climate where N availability limits tree growth owing to slower decomposition. The variation in N availability under the same climate (i.e., at the same altitude) appears to be related to the extent of soil podzolization.

Beschreibung: Key message After a flooding period, Populus deltoides plants compensate for the reduced growth under flooding by substituting the leaf area loss instead of increasing the leaf photosynthetic activity. Abstract Flooding stress induces changes in trees at plant and leaf level that can reduce growth and productivity. In this work, we explored changes in leaf traits related to productivity during the post-flooding period in three poplar clones with different degrees of flooding sensibility. Our hypothesis was that changes in leaf traits could lead to a higher photosynthetic activity in the post-flooding period to compensate for the reduction in carbon fixation under flooding. Plants were grown in pots in a greenhouse. Flooding was induced by filling the pots with tap water up to 5 cm over the surface soil for 28 days. After this period, flooding ended and plant recovery was followed for 44 days. Flooding decreased total leaf area, stomatal conductance and photosynthetic rate, but leaf size, stomatal, leaf area, chlorophyll and Rubisco content were not affected. Stomatal index was reduced in one clone and leaf thickness was increased in another one. During the post-flooding period, the formerly flooded plants of all clones produced leaves with increased area and thickness compared to the control plants, but specific leaf area and chlorophyll and Rubisco content were not altered. Stomatal index was only decreased in one clone. The leaves expanded in the post-flooding period did not increase their photosynthetic capacity, but had a higher water use efficiency and a lower stomatal conductance. The plants compensated for the reduced growth under flooding by substituting the leaf area loss instead of increasing the photosynthetic activity.

Beschreibung: Key message In the Qinling Mountains of north-central China, subalpine fir treelines exhibited a significant upward movement on the northern slope, but only a slight change on the southern slope over the past 200   years, supporting the idea that pattern and timing of treeline change are contingent on local environmental conditions. Abstract Variability in the response of altitudinal treelines to climate change might be contingent on species-specific characteristics and on different climate. The objective of this study was to examine the pattern, timing and variability in response of Abies fargesii treeline to climate warming among topographically similar, but climatically different sites. Rectangular plots were established across subalpine fir treeline ecotones on the northern and southern slopes of the Qinling Mountains. Dendroecological techniques were used to examine treeline patterns and dynamics at 50-year intervals. The results showed that despite the differences in regional climate, all the plots studied displayed a recent rapid recruitment trend. Tree recruitment was favored by high spring–summer temperatures on the northern slope and by high summer temperatures on the southern slope. Subalpine fir treelines exhibited a significant upward movement on the northern slope, but only a slight change on the southern slope over the past 200 years. The variability in changes of treeline position on the northern and southern slope can be attributed to the differences in regional climate conditions, supporting the idea that pattern and timing of treeline change is contingent on local environmental conditions.

Beschreibung: Key message SSR marker characterization of Indian mango cultivars revealed two distinct groups of populations with geographical affiliation. Six SSR loci with low PI have been identified as universal markers for mango characterization. Abstract In this study, genetic diversity and population structure of mango cultivars were assessed by employing fourteen simple sequence repeat markers, with high polymorphic information content. A set of 387 mango accessions from different regions of India was used. Model-based structure analysis revealed the presence of two subpopulations comprising the cultivars from ‘South-West’ region and ‘North-East’ region. A similar clustering pattern was observed in the dendrogram analysis, with two major groups identified that were further sub-grouped based on their genetic relatedness. Analysis of molecular variance showed a significant variance component among and within mango sub-populations derived from the structure analysis. The proportion of genetic differentiation among individuals within the two populations was found to be significant with a F ST value of 0.248. The extent of genetic diversity was found to be higher in case of ‘South and West’ population than ‘North and East’ population. Six SSR loci with low probability of identity values have been chosen as universal markers for mango characterization. Our results highlight genetic diversity encompassed by mango cultivars and genetic distinctness of ‘South-West’ and ‘North-East’ region cultivars.

Beschreibung: Key message Despite variable dynamics of genetic diversification at the different altitudinal levels, strong gene flow tends to standardize larch genetic diversity: the larch forest distributed along the altitudinal gradient can be regarded as a single population. Context While in forest tree species many studies focus on the structure of the genetic diversity at the natural range and at the forest stand levels, few studies have worked at intermediate levels like the landscape level. Aims We tried to determine to what degree altitude variation can affect the genetic diversity and the local structure of the genetic diversity of European larch ( Larix decidua Miller) at the landscape level. Methods Using microsatellite markers, we determined the between- and within-plot genetic structure and the spatial genetic structure (SGS) of four altitudinal plots distributed between 1,350 and 2,300 m a.s.l. in a European larch forest located in the French Alps. Results A homogenous neutral genetic structure was detected along this gradient. The intensity of the SGS was found to be stronger at 2,300 m and decreased at the 2,000-m plot. It was low or non-existent at the 1,700- and 1,350-m altitudinal levels. Conclusion Our results suggest that the genetic structure observed at the landscape level in this European larch forest was only slightly affected by climatic variation, human activities, or historical events. However, the variation of intensity of the SGS within the altitudinal plots indicates the existence of variable genetic dynamics, despite the globally uniform genetic structure along the altitudinal gradient.

Beschreibung: Key message Late-successional red spruce performed relatively better than faster growing black spruce under elevated carbon dioxide; this may be related to species’ shade tolerance. Abstract We compared growth, components of growth, and biomass allocation between two largely sympatric spruces, red spruce ( Picea rubens Sarg.; RS) and black spruce ( Picea mariana (Mill.) B.S.P.; BS) using 12 populations from across eastern Canada grown under ambient CO 2 (aCO 2 ) and elevated CO 2 (eCO 2 ) to evaluate absolute and relative responses to this increasing greenhouse gas. The 12 populations originated from continental to maritime environments, with seed collected from two proximate pairs of RS and BS stands from each of three provinces of eastern Canada—Ontario (ON), New Brunswick (NB), and Nova Scotia (NS)—considered here as provenances. Over 4 years, BS displayed increasingly greater height growth compared with RS. By the end of the 4th year, BS on average had 127 % greater total mass and 50 % greater root-collar diameter than RS. Bud flush was earlier for BS than RS, and BS bud flush occurred in the following order: ON, NB, NS. Under eCO 2 , BS and RS allocated more mass to stem (stem + branches), and further analysis showed that 25 % of this difference in biomass allocation was attributable to increasing tree size, with the balance directly due to eCO 2 . As expected, BS allocated more to aboveground than belowground mass than RS due their respective status as early- and late-successional species. However, under eCO 2 , BS partitioned more belowground and RS more aboveground than under aCO 2 . Black spruce had greater growth efficiency (GE; stem mass to needle mass ratio) than RS; GE increased with eCO 2 , and the increase was greater for BS than RS. Elevated CO 2 resulted in a relative biomass enhancement of 10.8 and 18.0 % for BS and RS, respectively. This does not support the theory that faster growing species will have a competitive advantage compared with inherently slower growing plants under eCO 2 , but agrees with other observations that shade-tolerant species have greater response ratios to eCO 2 than shade-intolerant species. Also, despite high possibility of hybridization and introgression between the two species, particularly in the highly fragmented and small remnant populations from ON, the findings show that ON and NB remain true to species type for the major growth parameters, allometry, growth efficiencies, and physiological traits and that the provenance variation is mostly consistent with findings from common-garden studies.

Beschreibung: Key message Sex and site conditions modulate intra- and inter-annual secondary growth and its climatic sensitivity in a dioecious Mediterranean conifer. Abstract Divergent evolutionary pressures associated with differential reproductive costs in dioecious trees may lead to sex-related variation in non-reproductive functions. Sex-related differences may be site-dependent, with different outcomes depending on environmental conditions. We explored the effects of sex and environmental conditions on the climatic control of annual secondary growth and intra-annual wood density fluctuations (IADF) of a dioecious conifer ( Juniperus thurifera L.) growing in two sites with contrasting hydrological conditions under a continental Mediterranean climate. Different sex-related strategies had variable effects on relative secondary growth, with females outperforming males under more favorable hydrological conditions, and males outperforming females under water-limited conditions. Ring width and IADF formation were driven by climatic factors occurring at different temporal scales. Tree-ring growth depended on factors acting prior to the initiation of the xylogenesis and to conditions directly affecting the duration and pace of cambial activity, and ring width, therefore, integrated a complex signal of factors occurring over a relatively long period, and on an annual cycle. In contrast, IADFs responded to singular short-term events that alleviated drought and promoted cambial reactivation during the summer arrest. Female trees showed a more opportunistic water use, displayed in the stronger ring-width response to June–July conditions. Enhanced cambial sensitivity in females set a lower threshold for IADF occurrence, leading to a higher frequency of IADFs irrespective of site. Intra-annual and inter-annual female growth patterns reflect an opportunistic strategy to benefit from favorable climatic windows.

Beschreibung: Key message When areas of interest experience little change, remote sensing-based maps whose dates deviate from ground data can still substantially enhance precision. However, when change is substantial, deviations in dates reduce the utility of such maps for this purpose. Context Remote sensing-based maps are well-established as means of increasing the precision of estimates of forest inventory parameters. The general practice is to use maps whose dates correspond closely to the dates of ground data. However, as national forest inventories move to continuous inventories, deviations between map and ground data dates increase. Aims The aim was to assess the degree to which remote sensing-based maps can be used to increase the precision of estimates despite differences between map and ground data dates. Methods For study areas in the USA and Norway, maps were constructed for each of two dates, and model-assisted regression estimators were used to estimate inventory parameters using ground data whose dates differed by as much as 11 years from the map dates. Results For the Minnesota study area that had little change, 7-year differences in dates had little effect on the precision of estimates of proportion forest area. For the Norwegian study area that experienced considerable change, 11-year differences in dates had a detrimental effect on the precision of estimates of mean biomass per unit area. Conclusions The effects of differences in map and ground data dates were less important than temporal change in the study area.

Beschreibung: Key message This study is an important contribution to understanding of the dormancy dynamics of apple buds grown in contrasting climates, highlighting the main factors possibly involved in their control and the key role of rehydration. Abstract The aim of this study was to compare the dormancy dynamics and the physiological status of vegetative and floral buds of apple cultivars grown during cold and mild winters. Long shoots bearing vegetative buds and short shoots bearing floral buds were regularly collected during two successive cycles at Marsillargues, France (2011/12, 2012/13) and Palmas, Paraná, Brazil (2012, 2013). The dormant state in vegetative buds was evaluated by the single-node cutting test and in floral buds by the Tabuenca’s test. The first approach highlighted important differences in the dormancy dynamics in both sites, clearly showing that: (1) the entry and the maximum level of dormancy are strongly correlated with cold winter temperatures; (2) the three classical phases of dormancy dynamics are difficult to differentiate under a mild winter climate; and (3) endodormancy, if it actually exists, is very weak and lasts only for a short time. Distinct temporal changes between both sites were found for flower primordia fresh and dry weight. The ecodormant state was linked to significant changes in dry weight and the capacity to quickly reach a water content of around 77 % according to the Tabuenca’s test. High temperatures in Brazil allowed a quick transition between endodormancy and ecodormancy compared to France where the rehydration period was long. The weak endodormancy associated with a quasi-absence of ecodormancy could explain the strong spatio-temporal heterogeneity of budburst and flowering under a mild winter climate. This may be useful for understanding the future phenology of trees under global warming conditions and for the selection of adapted cultivars.

Beschreibung: Key message This study developed and tested models to predict the belowground biomass and root/shoot ratio using aboveground field measures. The predictive power of such indirect measurement is useful for a rapid and reliable assessment of the biomass of the Mediterranean species. Context Forest biomass estimation has been simplified by the availability of indirect methodologies for automatic measuring. However, most of the information on forest root systems is largely unexplored due to the difficulty in estimating belowground biomass (BGB) at large scale. A plausible approach to investigating forest BGB is to establish a relationship between a number of dendrometric parameters related to the aboveground vegetation (AGB) (e.g., tree diameter and height) and the belowground component of the total biomass. Aims This work presents findings for indirect measurements of BGB in the typical Mediterranean landscapes focusing on sclerophyllous vegetation, specifically Phillyrea latifolia L. The purpose of the present study is twofold: (a) to develop a model explaining the BGB distribution of P. latifolia based on field data for dendrometric parameters, and (b) to understand how the ratio between BGB and AGB varies according to stem diameter as a proxy of plant growth. Methods A total of 50 P. latifolia plants were randomly selected in the study areas and considered for excavation. Individual plants were analyzed to determine AGB and BGB development. A number of models were developed and tested to predict the BGB and root/shoot ratio using aboveground field measures. Allometric equations were employed to predict the AGB and BGB and relative partitioning in the Phillyrea community. Results Models for P. latifolia AGB and BGB estimation that include crown diameter and stem height measures augment the models’ predictive power. When used alone, the predictive power of the root collar diameter appears to be overestimated, while its effect is stronger for a subset of observations with larger crown diameter and stem height. The root/shoot ratio values of plant species typically related to the Mediterranean context seem to be largely superior to the ratio values of trees and forests. Conclusions The model is ideally suited to incorporate indirectly measured tree height for a rapid and reliable assessment of the biomass of single Mediterranean species. Further research might include replication of the same studies in different geographic areas of the Mediterranean and in-depth analyses of AGB.

Beschreibung: Key message High root productions, especially in the fine roots, estimated by ingrowth cores were confirmed in mangrove forests. The zonal variation in root production was caused by inundation regime and soil temperature. Abstract Mangrove forests have high net primary productivity (NPP), and it is well known that these trees allocate high amounts of biomass to their root systems. In particular, fine root production (FRP) comprises a large component of the NPP. However, information on root production remains scarce. We studied FRP in three zones ( Avicennia , Rhizophora , and Xylocarpus ) of a mangrove forest in eastern Thailand using ingrowth cores (0–30 cm of soil depth). The root biomass and necromass were periodically harvested from the cores and weighed during the one-year study. The FRP was determined by summation of the fine root biomass (FRB) and root necromass. The results showed that the FRB clearly increased in the wet and cool dry seasons. Magnitude of FRB in the Rhizophora and Xylocarpus zones was 1171.07 and 764.23 g/m 2 /30 cm, respectively. The lowest FRB (292.74 g/m 2 /30 cm) was recorded in the Avicennia zone locating on the river edge where there is a greater frequency of inundation than the other zones. Root necromass was high in the Rhizophora and Xylocarpus zones, and accumulated noticeably when soil temperatures rapidly declined during the middle of the wet season to cool dry season. However, root necromass in the Avicennia zone varied within a small range. We attributed the small accumulation of root necromass in the Avicennia zone to the relative high soil temperature that likely caused a high root decomposition rate. The average FRP (3.403–4.079 ton/ha/year) accounted for 74.4, 81.5, and 92.4 % of the total root production in the Avicennia , Rhizophora , and Xylocarpus zone, respectively. The root production and causative factors (i.e., soil temperature and inundation regime) are discussed in relation to the carbon cycle of a mangrove forest.

Beschreibung: Key message This is the first time to show that alpine Cassiope fastigiata shrubs form distinct annual growth rings and record climatic signals. Abstract Cassiope species grow as dwarf shrubs at high latitudes and high elevations. Unlike in the High Arctic, not much is known about their age and growth on the Tibetan Plateau and in the Himalayas. There, Cassiope fastigiata could potentially serve as indicator species for climate change. The objective of our study, therefore, was to investigate its dendroecological potential. For this purpose, 20 shoots were collected both on the south-eastern Tibetan Plateau (site 1) and in the central Himalayas (site 2). Cross-sections of 8–10 μm in thickness were cut and the widths of the clearly distinguishable growth rings were measured. No missing outer rings were detected at the shoot base when serial sectioning was applied. Of the 40 shoots, 19 at site 1 and 10 at site 2 showed similar growth patterns. The remaining shoots were excluded from further analyses. C. fastigiata formed up to 30 annual growth rings whose width varied from 13 to 150 μm. Its growth at both sites was positively associated with temperature in late winter/early spring, and at site 2 additionally with precipitation in late autumn of the preceding year and spring of the current year. Our study confirmed that C. fastigiata forms distinct annual growth rings. The growth response to precipitation at site 1 and the lack thereof at site 2 result from differences in hydrology between the south-eastern Tibetan Plateau and the central Himalayas.

Beschreibung: Key message High-throughput sequencing and subsequent analysis indicated that miRNAs play crucial roles in floral thermogenesis of Magnolia denudata flowers. Abstract Animal-like thermogenic activity in flowers has been reported in several families of seed plants. Many studies have explored the ecological significance of thermogenesis in pollination biology; however, the molecular mechanisms regulating floral thermogenesis remain unclear. To characterize the roles of miRNA in floral thermogenesis, we analyzed miRNA expression in Magnolia denudata flowers during thermogenic and non-thermogenic stages. High-throughput sequencing and subsequent analysis revealed 82 conserved and 32 novel miRNAs in M. denudata flowers. A total of 187 EST sequences were predicted to be targets of 63 miRNAs. The target genes fell into 15 KOG functional classes and were involved in 25 KEGG pathways, suggesting that miRNAs play extensive regulatory roles in biological processes of M. denudata flowers. Among the identified miRNAs, 17 were differentially expressed between thermogenic and non-thermogenic stages and thus were thought to play roles in regulating floral thermogenesis in M. denudata . GO enrichment analysis revealed that target genes of these thermogenesis-related miRNAs were enriched in the functional groups ‘polyprenyl transferase activity’ and ‘photosynthetic electron transport’. Considering the important roles of polyprenyl transferase in the respiratory chain and the fact that floral thermogenesis of M. denudata flowers is associated with sunlight, we can infer that miRNAs play crucial roles in floral thermogenesis of M. denudata flowers by regulating cellular respiration and light reactions.

Beschreibung: Key message Spring temperature is a major limiting factor at the beginning of the growing season, the timing of growth initiation can increase by about 7   days/°C. During the growing season, impacts of climate variables on radial   growth are similar along an altitudinal gradient. Abstract Altitude is considered as an important factor affecting tree growth in mountain forest ecosystems. In this paper, the results of a 2-year field study along an altitudinal gradient in the cold and arid central Qilian Mountains, northwestern China, are reported. Twelve Qilian juniper trees ( Sabina przewalskii Kom.) were monitored with high-resolution dendrometers at three altitudes ranging from 2,865 to 3,550 m. At each altitude, a local weather station was installed close to the studied trees. We identified correlations between intra-annual growth patterns derived from the Gompertz equation with local air temperature and precipitation data. The timing of growth initiation became earlier and the growing season duration increased with decreasing altitude. The onset of radial growth occurred between early May and early June, and the growing season terminated between mid-July and late August, resulting in a growing season duration that decreased from 107 to 41 days as elevation increased. June is the most important growth period at each altitude. Spring temperature, which is strongly associated with elevation, is a critical factor determining the initiation of radial growth. The timing of growth initiation was delayed by 3–4 days per 100 m elevation. When associated with the modeled altitudinal spring temperature lapse rate of −0.48 °C/100 m, the onset of the growing season increased by about 7 days/°C. However, during the growing season, daily stem radial increments showed a positive correlation with precipitation and a negative correlation with daily maximum air temperature at all altitudes. Our study provides new data revealing the basic growth processes of Qilian juniper trees and provides significant information to quantify the responses of tree growth to future global warming.

Beschreibung: Key message We demonstrate that, beyond leaf phenology, the phenological cycles of wood and fine roots present clear responses to environmental drivers in temperate and boreal trees. These drivers should be included in terrestrial ecosystem models. Context In temperate and boreal trees, a dormancy period prevents organ development during adverse climatic conditions. Whereas the phenology of leaves and flowers has received considerable attention, to date, little is known regarding the phenology of other tree organs such as wood, fine roots, fruits, and reserve compounds. Aims Here, we review both the role of environmental drivers in determining the phenology of tree organs and the models used to predict the phenology of tree organs in temperate and boreal forest trees. Results Temperature is a key driver of the resumption of tree activity in spring, although its specific effects vary among organs. There is no such clear dominant environmental cue involved in the cessation of tree activity in autumn and in the onset of dormancy, but temperature, photoperiod, and water stress appear as prominent factors. The phenology of a given organ is, to a certain extent, influenced by processes in distant organs. Conclusion Inferring past trends and predicting future trends of tree phenology in a changing climate requires specific phenological models developed for each organ to consider the phenological cycle as an ensemble in which the environmental cues that trigger each phase are also indirectly involved in the subsequent phases. Incorporating such models into terrestrial ecosystem models (TEMs) would likely improve the accuracy of their predictions. The extent to which the coordination of the phenologies of tree organs will be affected in a changing climate deserves further research.

Beschreibung: Key message Spatial heterogeneity of soil resources is linked to tree patch distribution in Mediterranean cork oak woodlands. Tree patch distribution modifies soil traits by varying litterfall inputs due to different tree covers. Context The spatial heterogeneity of soil resources affects the structure and functioning of the different plant communities on ecosystems. In Mediterranean oak woodlands, the scattered trees play a key role in this spatial heterogeneity and might strongly influence ecosystem functioning and its productivity. Aims To assess the influence of the spatial pattern of trees and litter nutrient content on the spatial heterogeneity of soil properties. Methods We used a combination of geostatistical techniques and a linear mixed model to evaluate the spatial heterogeneity of soil and the seasonal and spatial variability of litter nutrient content, respectively. Results Soil parameters showed a high spatial heterogeneity. Tree cover was positively related with soil pH, and the organic matter, N, K, and Ca soil content. The return of nutrients to the soil via leaf fall had a marked seasonality and a high spatial variability, but this spatial variability had no effect on the spatial pattern of soil resources. Conclusion The spatial heterogeneity of soil in cork oak woodlands is mainly driven by tree patches distribution. The importance of the spatial heterogeneity of soil resources and the spatial pattern of trees on the functioning of the dehesa ecosystem makes it necessary to include them in plant nutrition studies and modeling approaches in these ecosystems.

Beschreibung: Key message Seed storage temperature influences root anatomy of the endangered Populus nigra , and consequently may alter nutrient absorption. A lower temperature during seed storage (−20 and −196 °C) may preserve the potential for a suitable root system development after germination. Context Seed storage conditions can be an important determinant of later seedling growth of Populus nigra L., an endangered tree species. Aims We tested whether long-term seed storage temperature, −10, −20 or −196 °C, affects the pattern of seedling root traits responsible for resource acquisition as compared to seedlings of fresh seeds. Methods We analysed the morphology, anatomy, degree of mycorrhizal colonization, and biochemical composition of roots developed from seed stored for 24 months at five different temperatures (from 3 to −196 °C) commonly used to preserve genetic resources. Results Except for root anatomy, we found no relationship between seed storage temperature and the root traits of seedlings. Among the various storage conditions, the proportion of roots with primary development in the first four orders was similar in seedlings developed from fresh seeds of from seeds stored at −196 or −20 °C. Nitrogen content in the roots was positively correlated with the proportion of (i) roots with primary development and (ii) the cortex width in the root diameter. Conclusions Higher temperatures during seed storage reduced the proportion of roots with absorptive function (with primary development). Therefore, for preservation of P. nigra seeds we recommend lower temperatures such as −20 and −196 °C.

Beschreibung: Key message Earlywood width in Quercus crispula increased from 1970 to 2004 without changes of vessel anatomy and ring growth. Abstract The increase in diameter of a tree stem is an important indicator of forest productivity. Xylem traits, such as the number and cross-sectional area of earlywood vessels, are also critical parameters of forest growth because of the physiological and structural contribution of xylem to the growth of the tree stem. Forest productivity appears to be affected by climate change and, indeed, trees might be expected to acclimate to gradual long-term climate change. The aim of this study was to identify long-term changes in increases in stem diameter and in earlywood vessels by examining tree rings of Quercus crispula . Focusing on 20 mature specimens of Q. crispula , we examined annual ring growth from 1970 to 2004 and measured earlywood traits, namely, the width, cross-sectional area (henceforth referred to as area) and number of earlywood vessels, by digital image analysis. We developed a hierarchical Bayesian model for detection of long-term trends in these traits. We found that earlywood width, as well as the total number and area of earlywood vessels, increased during the 35 years under analysis. One possible cause of these changes might be the long-term elevation of temperatures in early spring, which determine the timing of the onset of cambial reactivation from winter dormancy. In contrast to the long-term changes, short-term, yearly changes in earlywood traits fluctuated to a smaller extent than yearly changes in tree ring width. Therefore, the observed long-term changes in earlywood appear to represent acclimation to long-term climate change.

Beschreibung: Key message The extension of damage and anatomical changes in riparian trees after flood impact can be quantified with X-ray computed tomography and variogram analyses. Abstract This paper combines X-ray computed tomography (XRCT) images and variogram analyses to document the response of riparian trees to mechanical damage caused by floods. Changes in wood anatomy and density have been described in the past to occur as a result of severe cambial tissue damage. However, knowledge is still fragmentary insofar as the spatial extent of responses is concerned and in terms of causative factors controlling the magnitude of response. Here, we present a novel approach combining non-destructive XRCT images with geostatistical tools to describe the extension of anatomical changes in 30 specimens of 3 Mediterranean riparian species ( Alnus glutinosa (L.) Gaertn., Fraxinus angustifolia Vahl. and Salix atrocinerea Brot.) scarred by floods. We visually assess tree and wound characteristics (i.e., wound size, decayed area, callus length, callus mark) as well as the health state of trees prior to wounding. In parallel, we systematically computed 1D variograms using XRCT images so as to quantify relative tangential changes in wood density after wounding. Based on non-parametric statistical tests and Principal Component Analyses (PCA), we identify possible controls of macroscopic anatomical features on tangential affected area (TAA) and decay processes. Reactions in trees are controlled differently between species, but are driven above all by the health state of the tree prior to wounding. In view of the expected increase in the frequency of hydrogeomorphic processes and/or changes in the availability of sediments in a future greenhouse climate, wounding of trees is expected to occur more frequently in riparian forests, which could have negative effects on the sustainability of riparian vegetation.

Beschreibung: Key message We adjusted generic models for species-rich forest types and specific models for 15 species. Regression assumptions, lack of fitness and goodness of fit and comparison between models were assessed analytically. Generic models produced estimates not less reliable than species-specific models. Logarithmic models presented the best results of adjustment and evenness of residual variance. Context Assessment of dendrometric variables is important to obtain accurate estimates of stand attributes as biomass and carbon stock estimates. Some of them, as tree height and stem volume, are difficult and expensive to measure; volume models, calibrated on large datasets in tropical and subtropical forests, are rare. Aims This study aimed to construct stem volume models for native tree species in three forest types in southern Brazil, to select models with best fitness, to assess agreement between measured and predicted datasets and to compare species-specific and generic models. Methods Data from 418 sample plots were used to adjust generic models for forest types and specific models for 15 species. Regression assumptions, modelling efficiency, lack of fitness, goodness of fit and comparison between species-specific and generic models were assessed by analytical methods. Results Logarithmic models presented the best results of adjustment and evenness of residual variance. Lack of fit F test showed acceptable adjust quality for nearly all species-specific and generic models; R 2 adj * and modelling efficiency measure presented values close to 1 for all fitted models; model identity F test showed differences between specific and generic models in some cases. Conclusion Since regression assumptions were satisfied and because of their quality of fit, the fitted models compose useful tools for predicting total stem volume (with bark) for forest remnants in southern Brazil. Stratification of datasets by forest type for model fitting showed to be necessary, but, commonly, generic models for forest types produced estimates not less reliable than species-specific models.

Beschreibung: Key message Hypocotyl semi-dwarfism in BP was only due to less cell number. Daylight was required to inhibit cell division in the mutant. ABA, IAA and cytokinins would be involved. Abstract Coffea arabica ‘Laurina’ is a natural mutant of Coffea arabica ‘Bourbon’ (B) and is known under the trade name ‘Bourbon Pointu’ (BP). Under daylight, the laurina mutation leads to pleiotropic effects, including semi-dwarf hypocotyls. At the opposite, semi-dwarfism of BP seedlings disappeared under darkness conditions. The first step was to describe the morphological impact of the mutation in seedlings growing under daylight by comparison with seedlings growing under darkness. As the hypocotyl length was mainly affected, the second step was to investigate histological modifications in the organ comparing B and BP seedlings growing under daylight. Result of this investigation indicated that the mutation does not impact on cell length. Moreover, cytometry analyses showed absence of endoreduplication. Actually, the mutation influenced the cell number and this effect appeared before the 40th day after sowing. The length difference of hypocotyls between B and BP was due to lower cell number in BP, indicating possible involvement of phytohormones. Investigations showed the decrease of cytokinin and auxin levels in BP compared to B, while the cytokinin/auxin ratio remained constant in both varieties. By contrast, abscisic acid content increased in BP. Concurrently these results indicate the lowering of cell division, due to the mutation.

Beschreibung: Key message We found that indiscriminately using tree-ring MXD data with inhomogeneous temporal distribution from different elevations might cause biased chronologies. A mean-adjusting method was developed to overcome this bias. Abstract Here we analyse maximum latewood density (MXD) of Pinus sylvestris L. (Scots pine), from deadwood (dry) and subfossil wood (from lakes) collected along an elevation gradient in and close to the central Scandinavian Mountains, in the province of Jämtland, Sweden. Focusing on two common time periods (900–1150 CE and 1300–1550 CE), the mean absolute MXD of deadwood samples showed an inverse relationship with elevation, i.e. the absolute MXD decreases with elevation. However, the MXD values of the subfossil samples did not show such a consistent relationship with elevation. It was also noted that the differences in mean absolute MXD values among sites of different elevations in a given period were larger than among sites of similar elevation between the two time periods, where the former was assumed to be warmer than the latter. Using a theoretical model and a real example, it was shown that indiscriminately using MXD data with inhomogeneous temporal distribution from different elevations may cause biased chronologies, which can have significant effects on subsequent interpretations of past climate variability. A mean-adjusting method was developed to overcome this bias, and its usefulness was demonstrated by comparing two chronologies built on mean-adjusted and unadjusted MXD samples. It was concluded that unadjusted samples from different elevations with inhomogeneous temporal distribution can distort the long-term trend in a final chronology, while this bias can be alleviated if mean-adjusted samples are used.

Beschreibung: Key message The olive pollen production showed a variation related to temperature and rainfall during dormancy period. A correlation was found between the number of olive tree inflorescences and airborne pollen counts. Abstract Analysis of pollen production in crops such as the olive is of particular agronomical value, in that it can help to predict final harvest outcomes. Since olive pollen is a major cause of allergy in the Mediterranean region, this analysis can also provide health-related benefits. The present study analyzed flower and pollen production in ‘Cornicabra’ olive cultivar, charting its correlation with airborne pollen counts, with phenological findings such as onset of pre-flowering period, and with environmental factors such as temperature and rainfall, elevation and northern vs. southern exposure of floral structures on the tree crown. Findings confirmed spatiotemporal variations for most of the parameters studied. Mean pollen grain production per flower of olive tree was 1.10 × 10 5  ± 0.25 × 10 5 . Variations in the production of flowering branches, inflorescences, flowers and pollen reflected internal regulation processes linked to alternate bearing as well as year-on-year variations in weather conditions. Temperature and rainfall during dormancy were the weather-related variables most influencing flower, inflorescence and flowering-branch production. Early attainment of chilling requirements during dormancy was associated with increased production, coinciding with earlier budburst. A correlation was found between the number of inflorescences—and thus overall flower production—and airborne pollen counts. Production parameters also varied as a function of olive grove location, although that variability was not clearly attributable to the elevation. The correlation between production parameters and northern vs. southern exposure on the olive tree crown was significant only for flowering branches, whose production varied depending on their location on the tree crown.

Beschreibung: Key message The effects on large-area volume estimates of uncertainty in individual tree volume model predictions were negligible when using simple random sampling estimators for large-area estimation, but non-negligible when using stratified estimators which reduced the effects of sampling variability. Context Forest inventory estimates of tree volume for large areas are typically calculated by adding model predictions of volumes for individual trees at the plot level and calculating the per unit area mean over plots. The uncertainty in the model predictions is generally ignored with the result that the precision of the large-area volume estimate is optimistic. Aims The primary objective was to estimate the effects on large-area volume estimates of volume model prediction uncertainty due to diameter and height measurement error, parameter uncertainty, and model residual variance. Methods Monte Carlo simulation approaches were used because of the complexities associated with multiple sources of uncertainty, the non-linear nature of the models, and heteroskedasticity. Results The effects of model prediction uncertainty on large-area volume estimates of growing stock volume were negligible when using simple random sampling estimators. However, with stratified estimators that reduce the effects of sampling variability, the effects of model prediction uncertainty were not necessarily negligible. The adverse effects of parameter uncertainty and residual variance were greater than the effects of diameter and height measurement errors. Conclusion The uncertainty of large-area volume estimates that do not account for model prediction uncertainty should be regarded with caution.

Beschreibung: Key message In droughted oak foliage, water shortage and carbon starvation caused structural injury varying in severity between cell types and indicative of adaptive reversible and degenerative irreversible processes. Abstract Warmer temperatures as a consequence of climate change have already started to affect forest ecosystems, enhancing drought frequency and severity. Also depending on drought chronicity and ontological tissue development, tree foliage can respond to drought by enhancing structural acclimation and thus delay injury. More comprehensive characterization of micromorphological responses in foliage is needed for evaluating the tolerance of forest trees in the future. In the present study, structural reactions in foliage of three oak species exposed to acute summer drought were analyzed using transmitted light, fluorescence and electron microscopy. Oak leaves withstood drought stress for a considerable length of time before injury in the form of necrotic leaf margins appeared. In the leaf parts still asymptomatic, structural changes indicative of water stress and carbon starvation were observed. In the epidermis, autophagic processes—with exocytosis of degraded material—contributed to cell wall thickening. However, they also accelerated the degeneration of cell content whereas stomatal guard cells often remained unscathed. In mesophyll, the material in autolytic vesicles was internalized in vacuoles, which contributed to maintaining the cell turgescence. Plugging of xylem and phloem cells with polysaccharidic and proteinic material was mechanistically related to necrosis of leaf margins. These structural changes were indicative of reversible adaptive and irreversible degenerative processes. The functionality of upper mesophyll and stomata was prioritized, allowing foliage to resume gas exchange within hours of rewatering. Hence, extensive structural changes within still asymptomatic parts of the foliage were accountable in increasing the drought tolerance of the oaks.

Beschreibung: Key message Warmer summer conditions result in increased terpene emissions except under severe drought, in which case they strongly decrease. Abstract Water stress results in a reduction of the metabolism of plants and in a reorganization of their use of resources geared to survival. In the Mediterranean region, periods of drought accompanied by high temperatures and high irradiance occur in summer. Plants have developed various mechanisms to survive in these conditions by resisting, tolerating or preventing stress. We used three typical Mediterranean tree species in Israel, Pinus halepensis L., Quercus calliprinos and Quercus ithaburensis Webb, as models for studying some of these adaptive mechanisms. We measured their photosynthetic rates ( A ), stomatal conductance ( g s ), and terpene emission rates during spring and summer in a geophysical gradient from extremely dry to mesic from Yatir (south, arid) to Birya (north, moist) with intermediate conditions in Solelim. A and g s of P. halepensis were threefold higher in Birya than in Yatir where they remained very low both seasons. Quercus species presented 2–3-fold higher A and g s but with much more variability between seasons, especially for Q. ithaburensis with A and g s that decreased 10–30-fold from spring to summer. Terpene emission rates for pine were not different regionally in spring but they were 5–8-fold higher in Birya than in Yatir in summer ( P  〈 0.05). Higher emissions were also observed in Solelim for the drought resistant Q. ithaburensis ( P  〈 0.001) but not for Q. calliprinos . α-Pinene followed by limonene and 3-carene were the dominant terpenes. Warmer summer conditions result in increased Terpene emission rates except under severe drought, in which case they strongly decrease.

Beschreibung: Key message We investigated the variability of the relationships between climate and tree-ring growth along an altitudinal gradient and the temporal instability of the relationships under warming for Changbai larch ( Larix olgensis Henry) in northeast of China. Abstract Growth response of trees to climate has been found to vary with elevation, but their relationships might also be altered with ongoing global climate change. We developed residual chronologies of tree-ring growth parameters at three sites to investigate variability of the interactions between climate and tree-ring growth for Changbai larch ( Larix olgensis Henry) along an altitudinal gradient on the northern slopes of the Changbai Mountains area in Northeastern China. The results indicate that temperature and precipitation are linked differently to the formation of the annual ring width of Changbai larch at different elevations. Tree-ring density of Changbai larch is mainly positively associated with temperature while negatively responding to precipitation. The relationships between temperature and tree-ring growth became unstable, however, after the notable warming of the late 1980s in the study area. Tree-ring width decreased at low elevation under drought stress, whereas showed more positive sensitivity to warming at higher altitudes. We found that the tree-ring density relationship with temperature also became unstable under the rising temperature regime. These findings could be applied in simulating tree-ring growth and forest distribution under various climatic and environmental scenarios.

Beschreibung: Key message Cell wall polysaccharidic composition changed between cotyledons, hypocotyls and roots. Neither the laurina mutation nor the presence of light had an impact on this composition. Abstract Coffea arabica ‘Laurina’, a natural mutant of Coffea arabica ‘Bourbon’ (B), is also known as ‘Bourbon Pointu’ (BP). In seedlings under daylight, the laurina mutation leads to semi-dwarf hypocotyls, but this effect disappears in darkness conditions. The first step of our work was to analyze the impact of the mutation on the monosaccharide cell wall composition in cotyledons, hypocotyls and roots in relation to growth conditions (daylight vs darkness). Secondly, the same type of comparison was carried out for caffeine and chlorogenic acid (CQA) contents. Cell wall polysaccharides (CWP) present in cotyledons, hypocotyls and roots were identified. Neither the laurina mutation nor the growth conditions had an impact on the CWP composition. By contrast, there were marked differences between cotyledons, hypocotyls and roots regarding their CWP composition, CQA and caffeine contents. Lastly, the mutation and the light did not modify the CQA content in the three organs, whereas the mutation, but the light, lowered the caffeine (CAF) content.

Beschreibung: Key message The post-fire growth responses and changes in wood C and N isotope composition depend on site water availability and fire severity in Mediterranean Aleppo pine forests. Abstract Mediterranean forests are subjected to recurrent wildfires and summer droughts. Under warmer and drier conditions, it is required to determine how Mediterranean pines recover after wildfires, and how this translates into changes in tree radial growth and function (e.g. intrinsic water-use efficiency—iWUE). We analysed four Aleppo pine areas located in SE Spain affected by 1994 wildfires and subjected to different water availability, ranging from mesic to semi-arid conditions. We combined dendrochronological analyses with δ 13 C and δ 15 N wood isotopes to quantify the changes in radial growth (expressed as Basal Area Increment—BAI) and functional responses (iWUE and N cycling) to three fire severities (unburned sites, low and medium severities). We expected that the post-fire release in nutrients and a reduction in competition for water would enhance radial growth. We found that fire did not significantly alter growth patterns at the driest sites, but increased BAI at the wettest sites. δ 13 C was significantly ( P  ≤ 0.01) more negative only in burned stands located at the wettest site indicating a decreased iWUE and thus improved water availability. However, the δ 15 N was higher in severely burned than in unburned plots from all sites but the wettest site, indicating a potential fertilization effect of fire in sites subjected to mild drought severity. Site water availability determined how fire affected subsequent modifications in growth and tree functioning of Aleppo pine forests, that is, changes in iWUE and N cycling. Therefore, site dryness should be explicitly considered to forecast the growth and functioning responses of Mediterranean pine forests to the predicted increasing recurrence of fire events due to global warming.

Beschreibung: Key message Interspecific variation in nitrogen isotope composition of roots and leaves of tree seedlings grown in a steady-state nitrogen environment reflects known variation in sites of assimilation and nitrogen source preference in three tree species. Abstract As a time-integrated measure of nitrogen use, discrimination against the heavier stable isotope ( 15 N) during the uptake and assimilation of inorganic nitrogen has the potential to provide information on interspecific differences in inorganic nitrogen source preference. Here, nitrogen isotope composition (δ 15 N) at natural abundance was measured for the roots and shoots from seedlings of three forest tree species: Populus tremuloides (aspen), Pinus contorta var. latifolia (pine) and Picea glauca (spruce). The seedlings were grown hydroponically with low (0.1 mM) or high (1.5 mM) concentrations of NO 3 − or NH 4 + , or in sand with NO 3 − , NH 4 + or an equal mix of NO 3 − and NH 4 + (0.1 mM). Whole-plant nitrogen isotope discrimination was observed in hydroponically grown seedlings but not in sand culture. Differences in δ 15 N between shoots and roots were greater in aspen when grown with NO 3 − (3.02 ‰) than with NH 4 + (1.27 ‰). There were no significant differences between the δ 15 N of leaves and roots for pine and spruce on either source. Although whole-plant nitrogen isotope discrimination was not observed in sand culture, shoot δ 15 N was, again, greater than root δ 15 N for NO 3 − -grown aspen. Interspecific variation in nitrogen isotope discrimination was observed in both hydroponics and sand culture. The differences in nitrogen isotope composition under steady-state conditions indicate that interspecific differences in nitrogen source preference are consistent with previous experiments using alternative methods to identify differences in nitrogen uptake and assimilation in the same tree species.

Beschreibung: Key message Mutational witches’ broom clones show a growth redistribution compared with normal clones. The main factor affecting the variations in mutant clone morphology is the strength of the mutation. Abstract Mutational witches’ broom is a fragment of the tree crown with abnormally dense branching and slower shoot growth, compared with those of a normal crown. Thousands of dwarf ornamental cultivars widely used in landscape design have been developed from mutational witches’ broom. In this study, crown morphology was compared between grafted clones of witches’ broom and normal clones from the same trees. The results quantify variations in crown structure between the mutants and normal clones. The sample materials were 10 pairs of grafted witches’ broom and normal crown clones of Pinus sibirica . The mutant and normal clones were discrete sets. Many morphological traits were affected in the mutants. Compared with the normal-crown clones, the mutants showed male sterility, decreased apical dominance, reduced shoot and needle length, and increased branching and seed cone bearing. In terms of morphogenic changes induced by the mutation, the shoots of the witches’ broom clones were bicyclic, generated seed cones that were much shorter than those of normal clones, and had acquired the ability to form lateral buds. The extent of interclonal variation was significantly greater among witches’ broom clones than among normal clones. Compared with the morphological traits of normal clones, those of the mutants were shifted in the same direction but to different extents. Therefore, mutational witches’ broom is the expression of a mutation that can be weak, medium, or strong. These results will be useful for unraveling the genetic basis of witches’ broom in conifers and for breeding new dwarf cultivars.

Beschreibung: Key message Only severe drought stress induced lower non-structural carbohydrate concentrations in Robinia pseudoacacia saplings, and non-structural carbohydrate reduction occurs solely in branches and stems at the end of the growing season. Abstract A better understanding of non-structural carbohydrate (NSC) dynamics in trees under drought stress is critical to elucidate the mechanisms underlying forest decline and tree mortality that result from extended periods of drought. We performed a continuous controlled drought pot experiment from May 14 to September 7, 2013 using Robinia pseudoacacia saplings under 14, 10, 8, and 6 % soil water content that represented the absence of drought (AD), moderate drought (MD), severe drought (SD), and very severe drought (VSD) stress, respectively. Growth, leaf gas exchange, and NSC concentrations in different sapling tissues were measured once a month. The results showed that net photosynthetic rates and the relative increments of basal diameter and height decreased with the intensification of drought stress. Saplings showed lower starch and NSC concentrations and higher soluble sugar concentrations and ratios of sugars to starch only under SD and VSD. The concentrations of starch and NSC were significantly decreased under SD and VSD solely in branches and stems at the end of the growing season. Our results indicated that the timescale of physiological processes plays an important role in NSC dynamics, and that only severe drought stress significantly decreases NSC concentrations, and NSC reduction occurs solely in branches and stems at the end of the growing season.

Beschreibung: Key message The potential of European National Forest Inventories to harmonise stem quality estimation in European forests was identified despite considerable differences in existing national approaches. Context Knowledge on stem quality and assortments structure in European forests is highly important for policy makers and the timber industry and also for carbon life cycle analysis due to the fact that different timber products have different end use and thus store carbon for different time periods. Aims The study aim was to evaluate the potential of European National Forest Inventories (NFI) to objectively report on the stem quality in European forests in a harmonised manner. Methods A comprehensive questionnaire was conducted as the first important step to evaluate the current status of stem quality assessment and assess the existing level of harmonisation. Results Direct stem quality assessment or classification is used in 19 out of 28 European NFIs. Only eight countries provide timber assortment estimates from their NFIs. In addition, different sampling strategies for stem quality assessment are used among NFIs. Tree parameters relevant for stem quality assessment on standing trees were identified for the purpose of harmonisation. Several methods towards harmonisation between European NFIs for the purpose of reporting on stem quality of European forests were suggested. Conclusion Current European NFIs are not capable of reporting the stem quality of European forests in a harmonised manner at this stage and considerable efforts will need to be taken before the harmonised stem quality estimation can be prepared. However, the inquiry also revealed that there is a potential to develop the harmonised estimations in future.

Beschreibung: Key message The tree species, elevation and climate change jointly influenced the tree-ring growth, directing us to carefully consider the comprehensive effects of these variables when performing large-scale and multi-species-based dendroclimatic studies. Abstract The rate of tree growth varies by species and is influenced by elevation and climate gradients. Assessing the influence of these variables on tree-ring growth can improve projections for tree growth under future climate conditions. Here, we evaluate the relationships between tree species, elevation, climate and tree-ring growth in the Qilian Mountains of northwest China by using the tree-ring records of Qinghai spruce ( Picea crassifolia ) and Qilian juniper ( Juniperus przewalskii ) trees. The rotated principal component analysis was applied to examine the individual tree growth and the associated influencing factors. The tree-ring chronologies were used to compare tree growth patterns and the climate–growth relationships between the two species and elevations. The results indicated that trees from the Qinghai spruce sites showed similar growth patterns and climate–growth relationships, even though the elevation differed. The Qilian juniper chronologies from the high and low elevation sites revealed different growth patterns during recent decades that were closely related to the discrepant climate–growth relationships with the temperatures and the recent warming trend. The differences in tree growth patterns between both species and elevation could be attributed to plant physiological traits. The results of this study demonstrate the impact of tree species, elevation and climate change on tree-ring growth, suggesting that accounting for the influences of these variables could improve large-scale and multi-species-based dendroclimatic studies.

Beschreibung: Key message The study developed equations for predicting aboveground and belowground biomass of planted and coppiced Eucalyptus globulus in NW Spain. It was the first published work considering site effects on aboveground biomass and first work for predicting root biomass, for this species in this region, where it covers about 310,000 ha . Context Eucalyptus globulus is a species of great economic relevance, being increasingly used for bioenergy. In Galicia (NW Spain), where most of the E. globulus in the country is growing, there are scarce studies modeling aboveground biomass fractions of that species, together with a lack of information on its belowground biomass. Aims The objective of this study was to develop new and more accurate allometries for predicting E. globulus tree aboveground biomass fractions and coarse belowground biomass in NW Spain. Methods Aboveground biomass models were calibrated by two approaches: nonlinear seemingly unrelated regressions (NSUR), using tree and stand variables, and nonlinear mixed effects ( nlme ) equations adding the site factor effect. Validation was made with an independent dataset (85 trees). Belowground biomass equations were constructed for planted and coppiced trees. Results Crown length and dominant height substantially improved the precision in leaf and branch biomass estimation (NSUR). An added value of our study was the modeling of root/shoot ratio, as a function of diameter of planted and coppiced trees, for first time in this species. Conclusion This study confirms the importance of site and stand stage to explain aboveground biomass variability. Although different belowground biomass accumulation patterns were observed for planted and coppice trees, aboveground biomass equations were common.

Beschreibung: Key message Presented Models describe the current growth rate. These models are good tools for growth prediction in the near future and will be compareable with further models; they will demonstrate the Norway spruce growth changes considering the climate change. Abstract Tree growth depends on genetic, climatic, microsite conditions and stand structure variations. A new evaluation method was carried out for studying mutual tree competition based on the social area of each trees. Nine Norway spruce ( Picea abies (L.) Karst.) stands were investigated. The objectives of this study were to quantify each individual tree basal area increment during the years 2008–2012 with respect to the social area of the individual trees, competition indexes and the dendrometric characteristics of the trees. The social area of the trees in the investigated plots varied from 0.06 to 43.04 m 2 where correlation coefficient ( R 2 ) with each individual basal area increment was significantly high. Distance characteristics [e.g. minimum weighted distance ( D i min ) and maximum weighted distance ( D i max )] provided a correlation coefficient (with individual tree basal area increments) varying from 0.69 to 0.84. Values of the R 2 between individual basal area increments and nearest trees dependent (NTD 6 ) competition indexes varied from 0.41 to 0.66, while for distance-dependent competition indexes it varied from 0.59 to 0.78. To facilitate 5-year individual basal area increment inventories ( I g5 ), linear models were used to develop the new specific functions. Individual tree growth models based on the distance measurement components and their combinations resulted in very high estimation accuracy. Therefore, the best model to determining basal area increment is the proven linear model using a social tree area, stem diameter at the breast height and crown length as input variables.

Beschreibung: Key message Throughfall nutrient fluxes were generally higher in a mixed stand than in a pure stand of Oriental beech. Throughfall fluxes were higher than bulk precipitation fluxes except for nitrogen and indicate higher canopy uptake of this element in the pure stand compared to the mixed stand . Context Oriental beech is an economically relevant tree species for Iran and adjacent countries. Yet little is known about nutrient cycling in Oriental beech stands and the influence of the degree of mixture with other species. Aim s We assessed the effect of seasons on nutrient fluxes in precipitation and whether throughfall chemistry differed between pure and mixed stands. Methods Bulk precipitation in the open field and throughfall were sampled during one whole month within each season from August 2013 to May 2014 in a pure (81 % of beech trees on average) and a mixed stand (57 % of beech trees) of Oriental beech. Samples were analysed for pH, nitrate (NO 3 − ), ammonium (NH 4 + ), phosphorus (P), calcium (Ca 2+ ), magnesium (Mg 2+ ) and potassium (K + ). Results Nutrient concentrations were generally higher in the growing season than in the dormant season, both in bulk precipitation and in throughfall. Nutrient fluxes were higher in fall and these peaks coincided with higher amounts of precipitation. The concentrations and fluxes of NH 4 + , NO 3 − , P, Ca 2+ , Mg 2+ and K + were generally higher in the mixed stand than in the pure stand in all seasons. Compared to the open field, throughfall fluxes were usually higher, except for NO 3 − and NH 4 + , indicating direct canopy uptake of nitrogen. Conclusion Canopy composition in Oriental beech stands (owing to differences in foliage chemistry) and seasons (owing to differences in precipitation regime and phenological stages) have a significant effect on throughfall nutrient fluxes.

Beschreibung: Key message Genetic diversity appears to be unaffected by disturbance in a stand of the light-demanding Neotropical tree V. michelii . Although spatial genetic structure is modified in post-disturbance cohorts, mixing of seeds from different mother trees in canopy gaps appears to efficiently maintain genetic admixture. Context The interplay between genetic and demographic processes has major consequences on population viability. Population size affects demographic trends, while genetic diversity insures viability by reducing risks of inbreeding depression and by maintaining adaptive potential. Yet, the consequences of increases in census size (as opposed to effective size) on genetic diversity of forest populations are poorly known. Aims We have studied the structure of genetic diversity in populations of saplings of the light-responsive tree, Virola michelii (Myristicaceae, the nutmeg family), in two plots having undergone different levels of canopy-gap opening disturbance. This allowed us to test the “intermediate disturbance” hypothesis, which generally applies to species diversity, at the intra-specific scale. Methods Levels and distribution of genetic diversity were compared between plots and between life stages. Sapling parentage was analysed to infer each adult tree’s contribution to regeneration. Results Genetic diversity was higher, and spatial genetic structure was stronger in the post-disturbance than in the control seedling population. Parentage analysis suggested that a limited number of parents contributed to most of the regeneration, but that efficient mixing of their progeny may have enhanced the diversity of saplings occupying canopy gaps. Conclusion A mixture of demo-genetic processes may contribute to maintain genetic diversity in spite of, or possibly due to, ecosystem disturbance in V. michelii .

Beschreibung: Key message Different environmental conditions affect tree senescence by different patterns of carbohydrate concentrations and have specific impact on the dissection of the photosynthetic apparatus. Abstract A proactive cultivation of Mediterranean broadleaf species, including oaks, has been suggested to fill possible temporal and spatial gaps in forestry created by Climate Change in Central Europe in the future. Climate can affect trees in several different ways, e.g., by modulating the course of leaf senescence. Senescence-associated processes, like regulation of carbohydrates and changes in chlorophyll fluorescence under drought stress conditions were studied with leaf tissue of drought-tolerant downy oak ( Quercus pubescens ). Two months of consistent drought stress in a frost-free greenhouse led to significantly earlier senescence and significant increased amounts of soluble sugars in the leaves of the drought-stressed group in comparison to a well-watered control group. Similar sugar accumulation was observed in trees outdoors, after exposure to frost. In contrast to monocarpic plants the accumulation of free sugars is neither triggering leaf senescence, nor is it a side effect of age-depending changes in Q. pubescens. Instead, sugar accumulation is induced by abiotical factors, like drought and frost. Furthermore, we suggest that the senescence process in the absence of drought stress or frost depends on the source status of the leaf, which, in term, is a function of light (through photosynthesis) and night temperature (through respiration). Contents of the storage metabolite starch decreased during late summer in all three groups. Drought-stressed plants showed a decline of the connectivity of photosystem II antenna, reflected as the L-band in the chlorophyll fluorescence induction curves, and stronger correlations between the declines in the capacity of photosynthetic dark reactions and electron transport-associated chlorophyll fluorescence parameters. We conclude that the disassembly of single parts of the photosynthetic apparatus during leaf senescence is a uniform process, but the onset of this process depends on abiotical environmental factors.

Beschreibung: Key message We compiled 2,458 biomass equations from 168 destructive sampling studies in Indonesia. Unpublished academic theses contributed the largest share of the biomass equations. The availability of the biomass equations was skewed to certain regions, forest types, and species. Further research is necessary to fill the data gaps in emission factors and to enhance the implementation of climate change mitigation projects and programs. Context Locally derived allometric equations contribute to reducing the uncertainty in the estimation of biomass, which may be useful in the implementation of climate change mitigation projects and programs in the forestry sector. Many regional and global efforts are underway to compile allometric equations. Aims The present study compiles the available allometric equations in Indonesia and evaluates their adequacy in estimating biomass in the different types of forest across the archipelago. Methods A systematic survey of the scientific literature was conducted to compile the biomass equations, including ISI publications, national journals, conference proceedings, scientific reports, and academic theses. The data collected were overlaid on a land use/land cover map to assess the spatial distribution with respect to different regions and land cover types. The validation of the equations for selected forest types was carried out using independent destructive sampling data. Results A total of 2,458 biomass equations from 168 destructive sampling studies were compiled. Unpublished academic theses contributed the majority of the biomass equations. Twenty-one habitat types and 65 species were studied in detail. Diameter was the most widely used single predictor in all allometric equations. The cumulative number of individual trees cut was 5,207. The islands of Java, Kalimantan, and Sumatra were the most studied, while other regions were underexplored or unexplored. More than half of the biomass equations were for just seven species. The majority of the studies were carried out in plantation forests and secondary forests, while primary forests remain largely understudied. Validation using independent data showed that the allometric models for peat swamp forest had lower error departure, while the models for lowland dipterocarp forest had higher error departure. Conclusion Although biomass studies are a major research activity in Indonesia due to its high forest cover, the majority of such activities are limited to certain regions, forest types, and species. More research is required to cover underrepresented regions, forest types, particular growth forms, and very large tree diameter classes.

Beschreibung: Key message Tested on data from Tanzania, both existing species-specific and common biomass models developed elsewhere revealed statistically significant large prediction errors. Species-specific and common above- and belowground biomass models for three mangrove species were therefore developed. The species-specific models fitted better to data than the common models. The former models are recommended for accurate estimation of biomass stored in mangrove forests of Tanzania. Context Mangroves are essential for climate change mitigation through carbon storage and sequestration. Biomass models are important tools for quantifying biomass and carbon stock. While numerous aboveground biomass models exist, very few studies have focused on belowground biomass, and among these, mangroves of Africa are hardly or not represented. Aims The aims of the study were to develop above- and belowground biomass models and to evaluate the predictive accuracy of existing aboveground biomass models developed for mangroves in other regions and neighboring countries when applied on data from Tanzania. Methods Data was collected through destructive sampling of 120 trees (aboveground biomass), among these 30 trees were sampled for belowground biomass. The data originated from four sites along the Tanzanian coastline covering three dominant species: Avicennia marina (Forssk.) Vierh, Sonneratia alba J. Smith, and Rhizophora mucronata Lam. The biomass models were developed through mixed modelling leading to fixed effects/common models and random effects/species-specific models. Results Both the above- and belowground biomass models improved when random effects (species) were considered. Inclusion of total tree height as predictor variable, in addition to diameter at breast height alone, further improved the model predictive accuracy. The tests of existing models from other regions on our data generally showed large and significant prediction errors for aboveground tree biomass. Conclusion Inclusion of random effects resulted into improved goodness of fit for both above- and belowground biomass models. Species-specific models therefore are recommended for accurate biomass estimation of mangrove forests in Tanzania for both management and ecological applications. For belowground biomass ( S. alba ) however, the fixed effects/common model is recommended.

Beschreibung: Key message The estimates of fine root production by net sheet method were not affected by the net material or the aperture size, but flexible nets are preferable to avoid an underestimation. Abstract The estimation of the fine root production is important for understanding the mechanisms of carbon cycling in ecosystems. The recently developed net sheet method allows the measurement of fine root production in forest ecosystems. The simplicity of this innovative technique reduces labor costs and causes little soil disturbance during installation. However, the protocols and methods are still poorly developed; for example, the effects of net material, mesh aperture size and firmness on the results remain unknown. Therefore, we measured the number and dry mass of fine roots grown through net sheets in forest soils to determine the effect of the net quality and type (polyamide, polyethylene, polyethylene terephthalate, stainless steel), mesh aperture size (2 and 4 mm) and firmness (firm and flexible) on the results. The study was conducted in managed and unmanaged Japanese cedar forests in Japan and in a mixed dipterocarp forest in Malaysia. No effect of net material or mesh aperture size on the number of roots grown through the net sheets or on root production was observed. A smaller number of roots grew through the firm type of nets than that of the flexible nets in the managed Japanese cedar and mixed dipterocarp forests. These results suggest that fine root production is not affected by the material of the net sheets or the mesh aperture size, but flexible nets are preferable to avoid an underestimation of fine root production.

Beschreibung: Key message Stomatal regulation involves beneficial effects of pruning mulch and irrigation on leaf photosynthesis in Prunus yedoensis and Ginkgo biloba under moderate drought. G. biloba showed conservative water use under drought. Abstract Leaf photosynthesis is highly sensitive to soil water stress via stomatal and/or biochemical responses, which markedly suppress the growth of landscape trees. Effective irrigation management to maintain leaf photosynthesis and information on species-specific photosynthetic responses to soil water stress are essential for the sustainable management of landscape trees in Japan, in which summer drought often occurs. In order to investigate effective irrigation management, we used plants with moderate soil water stress as controls, and examined the effects of daily irrigation and pruning mulch on leaf photosynthesis in container-grown Ginkgo biloba and Prunus yedoensis , which are the first and second main tall roadside trees in Japan. Stomatal conductance was significantly increased by pruning mulch and daily irrigation, with similar increases in leaf photosynthesis being observed in P. yedoensis and G. biloba . In order to obtain information on species-specific photosynthetic responses to soil water stress, we compared the responses of leaf photosynthesis and leaf water status to reductions in soil water content (SWC) between the two species. G. biloba maintained a constant leaf water potential, leaf water content, maximum carboxylation rate, and electron transport rate with reductions in SWC, whereas reductions were observed in P. yedoensis . We concluded that pruning mulch and irrigation effectively offset the negative impact of moderate water stress on leaf photosynthesis in summer in P. yedoensis and G. biloba via stomatal regulation, and also that G. biloba maintained its photosynthetic biochemistry and leaf water status better than P. yedoensis under severe water stress.

Beschreibung: Key message Our manuscript presents an approach to measure the maximum torsional shear and bending strains/stres ses of tree trunk. The measured strains are not affected by the direction of pulling force. Abstract Stem breakage is a common failure mode of standing trees. The stem of the tree with a lopsided crown is always subjected to bending and torsional combined deformation state under wind load. At a certain degree of torsional moment, the torsional stress exceeds the value of shearing strength of green timber resulting in longitudinal splitting. There is no valid experimental approach to measure shear strain of a trunk scientifically so far. In this paper, we propose an approach to measure the maximum torsional shear and bending strains of a stem which is under combined deformation state. It is that four strain meters are arranged on tree stem in a certain way. The measured strains are not affected by the direction of pulling force. We explain the principle of the measurement approach. To validate the measurement approach, tree-pulling tests are performed to model wind forces. The trunk strains are also converted to trunk stresses using Hooke’s Law. Analyses of the results demonstrate that the experimentally measured values are in good agreement with the theoretical values.

Beschreibung: Key message Species with low density of intact branches are likely to have higher growth rates than species with high density of intact branches, but at the cost of a lower water-use efficiency and larger sensitivity to xylem embolism. Abstract The hydraulic niche separation theory proposes that species co-exist by having a range of traits to allow differential access to resources within heterogeneous environments. Here, we examined variation in branch xylem anatomy and foliar carbon stable isotopes (δ 13 C) as a measure of water-use efficiency (WUE) in seven co-occurring species, Acacia aneura , Acacia bivenosa , Corymbia opaca , Eucalyptus camaldulensis , Erythrina vespertilio , Hakea sp., and Psydrax latifolia , in an arid zone open Corymbia savanna on the Ti Tree Basin, Northern Territory, Australia. We test the following hypotheses: (1) Species with large conductive areas exhibit a low density of intact branches, while species with small conductive areas have a significantly higher density of intact branches. (2) Species with smaller conductive areas exhibit more enriched values of δ 13 C and therefore have larger WUE than those with larger conductive areas and (3) there is an inverse correlation between theoretical sapwood hydraulic conductivity and vessel implosion resistance. The results of this study demonstrated significant variation in density of intact branches, ranging from 0.38 to 0.80 g cm −3 and this variation was largely explained by variation in sapwood conductive area. Species with low conductive areas ( P. latifolia , Hakea sp. and Acacia species) exhibited large values of WUE ( r 2  = 0.62, p  〈 0.05). These species are likely to be less vulnerable to cavitation by having small conductive areas and thicker fibre walls. We demonstrated a significant ( r 2  = 0.83, p  = 0.004) negative correlation between theoretical sapwood hydraulic conductivity and vessel implosion resistance. These results are discussed in relation to hydraulic niche separation.

Beschreibung: Key message For long-term environmental investigations, tree-ring δ 15 N values are inappropriate proxies for foliar δ 15 N for both Fagus sylvatica and Picea abies under moderate N loads. Abstract Currently it is unclear whether stable nitrogen isotope signals of tree-rings are related to those in foliage, and whether they can be used to infer tree responses to environmental changes. We studied foliar and tree-ring nitrogen (δ 15 N) and carbon (δ 13 C) isotope ratios in European beech ( Fagus sylvatica L.) and Norway spruce ( Picea abies L.) from six long-term forest monitoring sites in Switzerland together with data on N deposition and soil N availability, as well as a drought response index over the last two decades. For both species, tree-ring δ 15 N and δ 13 C values were less negative compared to foliar δ 15 N and δ 13 C values, most likely due to recycling and reallocation of N within the tree and fractionation processes associated with the transport of sucrose and the formation of tree-rings, respectively. Temporal trends recorded in foliar δ 15 N were not reflected in tree-ring δ 15 N, with much higher variations in tree-rings compared to foliage. Soil N availability and N deposition were partially able to explain changes in foliar δ 13 C, while there were no significant correlations between environmental variables and either tree-ring or foliar δ 15 N. Our results suggest an uncoupling between the N isotopic composition of tree-rings and foliage. Consequently, tree-ring δ 15 N values are inappropriate proxies of foliar δ 15 N values under low-to-moderate N deposition loads. Furthermore, at such low levels of deposition, tree-ring δ 15 N values are not recommended as archives of tree responses to soil C/N or bulk N deposition.

Beschreibung: Key message Present study recommends DBH as independent variable of the derived allometric models and Biomass   =   a   +   b DBH 2 has been selected for total above-ground biomass, nutrients and carbon stock. Abstract Kandelia candel (L.) Druce is a shrub to small tree of the Sundarbans mangrove forest of Bangladesh. The aim of the study was to derive the allometric models for estimating above-ground biomass, nutrient and carbon stock in K. candel . A total of eight linear models with 64 regression equations were tested to derive the allometric models for biomass of each part of plant; and nutrients and carbon stock in total above-ground biomass. The best fitted allometric models were selected by considering the values of R 2 , CV, R mse , MS error , S a , S b , F value, AICc and Furnival Index. The selected allometric models were Biomass = 0.014 DBH 2  + 0.03; √Biomass = 0.29 DBH − 0.21; √Biomass = 0.66 √DBH − 0.57; √Biomass = 1.19 √DBH − 1.02; Biomass = 0.21 DBH 2  + 0.12 for leaves, branches, bark, stem without bark and total above-ground biomass, respectively. The selected allometric models for Nitrogen, Phosphorous, Potassium and Carbon stock in total above-ground biomass were N = 0.39 DBH 2  + 0.49, P = 0.77 DBH 2  + 0.14, K = 0.87 DBH 2  + 0.07 and C = 0.09 DBH 2  + 0.05, respectively. The derived allometric models have included DBH as a single independent variable, which may give quick and accurate estimation of the above-ground biomass, nutrient and carbon stock in this species. This information may also contribute to a broader study of nutrient cycling, nutrient budgeting and carbon sequestration of the studied forest.

Beschreibung: Key message Wood fibres are as sensitive to environmental conditions as vessels in tree rings with intra-annual density fluctuations (IADFs) in Mediterranean species. Abstract Forecasted environmental changes are likely to increase the frequency of intra-annual density fluctuations (IADFs) in Mediterranean tree rings. The interpretation of intra-annual anatomical variability of tree rings with IADFs can be useful to understand plant-growth response to environmental changes with seasonal resolution. We analysed the intra-annual variability of quantitative traits of both vessels and fibres in the woods of Arbutus unedo L. and Erica arborea L. to compare the sensitivity of different cell types to environmental variations. We applied digital image analysis on microphotographs of semi-thin sections of tree rings formed at sites with different soil water availability. Wood of both species showed good adaptability that allows anatomical traits of vessels and fibres to be harmonised by changing the water transport capacity and wood strength, promoting the efficiency or safety of water transport according to water availability during wood formation. The size of fibres showed trends of variation similar to vessels. Not all parameters of vessels were accurate indicators of the IADF presence. In conclusion, parameters of fibres, which offer advantages during automatic measurement, showed the same sensitivity to environmental fluctuations as vessels. Thus, they could be good indicators of summer drought to describe and interpret the ecological meaning of IADFs in tree rings.

Beschreibung: Key message We estimated aboveground biomass of large mangrove trees from terrestrial Lidar measurements. This makes the first attempt to extend mangrove biomass equations validity range to trunk diameter reaching 125   cm. Abstract Accurately determining biomass of large trees is crucial for reliable biomass analyses in most tropical forests, but most allometric models calibration are deficient in large trees data. This issue is a major concern for high-biomass mangrove forests, especially when their role in the ecosystem carbon storage is considered. As an alternative to the fastidious cutting and weighing measurement approach, we explored a non-destructive terrestrial laser scanning approach to estimate the aboveground biomass of large mangroves (diameters reaching up to 125 cm). Because of buttresses in large trees, we propose a pixel-based analysis of the composite 2D flattened images, obtained from the successive thin segments of stem point-cloud data to estimate wood volume. Branches were considered as successive best-fitted primitive of conical frustums. The product of wood volume and height-decreasing wood density yielded biomass estimates. This approach was tested on 36 A. germinans trees in French Guiana, considering available biomass models from the same region as references. Our biomass estimates reached ca. 90 % accuracy and a correlation of 0.99 with reference biomass values. Based on the results, new tree biomass model, which had R 2 of 0.99 and RSE of 87.6 kg of dry matter. This terrestrial LiDAR-based approach allows the estimates of large tree biomass to be tractable, and opens new opportunities to improve biomass estimates of tall mangroves. The method could also be tested and applied to other tree species.

Beschreibung: Key message Cloning and functional analysis of CcBBM gene. Abstract Baby boom (BBM), as a transcription factor of AP2/ERF family, has great potence in promoting somatic embryogenesis. In this study, a BBM gene from somatic embryos of camphor tree ( Cinnamomum camphora L.), named CcBBM , was cloned and characterized. A partial fragment of 560 bp of CcBBM was amplified by degenerate PCR based on the two conserved AP2 domains of other annotated BBMs. Full-length cDNA of CcBBM was obtained by a cloning strategy combing degenerate PCR and RACE technique. The open-reading frame of CcBBM is 2169 bp in length, which encodes 722 amino acids. A comparison of the deduced amino acid sequence of CcBBM with BBM from other species showed high similarities, ranging from 51 to 80 %. The mRNA levels of CcBBM in different tissues were detected by semi-quantitative reverse transcription PCR (RT-PCR). CcBBM was expressed in most tissues, with highest expression level in somatic embryos, followed by roots, young fruits and flowers. Ectopic expression of CcBBM gene in Arabidopsis exhibited a variety of deformed and variegated leaves and short roots. No spontaneous somatic embryogenesis was observed in 35S :: CcBBM transgenic plants. These results will help us understand the role of CcBBM in somatic embryogenesis in camphor tree.

Beschreibung: Key message Physicochemical conditions present during the initiation of somatic embryogenesis in Pinus radiata determine the rate of embryogenic cell lines generated as well as the final number of somatic embryos. Abstract The effect of physical and chemical conditions during the initiation and proliferation stages of somatic embryogenesis in radiata pine was investigated. The first objective was to assess if different temperatures and/or water availability during the initiation or proliferation of embryogenic tissue impacted the success rate during each stage of somatic embryogenesis. The second objective was to determine what stage has a greater influence on subsequent stages of development. Some treatments (18 °C, 4 g L −1 gellan gum) resulted in a higher percentage of initiation whereas others (28 °C, 2 g L −1 gellan gum) gave rise to lower initiation. Our results indicated that initiation at different temperatures affected the subsequent stages of somatic embryogenesis. Thus, these embryogenic tissues were influenced by the environmental conditions present at initiation. We were able to successfully regenerate somatic embryos from cell lines initiated under all the environmental conditions tested.

Beschreibung: Key message Compared with annual tree-ring cellulose δ 18 O, intra-annual cellulose δ 18 O has potential to reconstruct precipitation with higher resolution and stronger signal intensity. Abstract Annual tree-ring cellulose oxygen isotope values (δ 18 O) of Fokienia hodginsii provide a promising proxy of monsoon-season precipitation in Southeast China. Measuring intra-annual cellulose δ 18 O values may reveal the seasonal variability of precipitation and the associated climate influences. Here, we examine intra-annual variation of cellulose δ 18 O values in Fokienia hodginsii and Cryptomeria fortune from Fujian Province, Southeast China. Both species exhibited considerable intra-annual variations in cellulose δ 18 O (range ~6 ‰) with a consistent pattern of enriched values near the annual ring boundary and depleted values in the central portion of the ring. Seasonal patterns in the tree-ring δ 18 O values generally followed changes in precipitation δ 18 O values. Compared with annual tree-ring cellulose δ 18 O, intra-annual cellulose δ 18 O has potential to reconstruct precipitation with higher resolution and stronger signal intensity. July tree-ring cellulose δ 18 O is significantly correlated ( r  = −0.58, p  〈 0.05) with July precipitation, and June–August tree-ring cellulose δ 18 O and annual tree-ring cellulose δ 18 O, respectively, explain 52 and 41 % of the actual variance of April–August precipitation. In addition, May–October cellulose δ 18 O values during El Niño years are higher than in La Niña years, and April to October rainfall is lower in El Niño years than in La Niña years. Combining the significant correlations between inter-annual cellulose δ 18 O values and sea surface temperatures in the central tropical Pacific, our results support the hypothesis that El Niño–Southern Oscillation affects tree-ring cellulose δ 18 O in Southeast China by modulating seasonal precipitation.

Beschreibung: Key message In rupestrian savannas in southeastern Brazil Clusia arrudae Planchon & Triana in the dry season performed CAM-cycling with very little gas exchange in the early morning followed by a long depression during the rest of the day. CAM-cycling is considered as a survival strategy under drought and the productivity of the plant which is quite abundant must rely on performance of C 3 -photosynthesis in more favorable seasons. Abstract In rupestrian savannas in the Serra do Cipó (19°14′48.9″S, 43°30′36.0″W) at 1300 m a.s.l. and in the Serra de São José (21°08′S, 44°17′W) at 1010–1030 m a.s.l. in southeastern Brazil Clusia arrudae Planchon & Triana is abundant. As CAM is frequent in the genus Clusia we supposed that it would perform CAM as a drought adaptation at the very dry rupestrian savanna sites in the dry season. At the Serra do Cipó site as control we studied the obligate C 3 -species Eremanthus glomerulatus Less. Both species are sympatric at this site. Eremanthus glomerulatus performed C 3 -photosynthesis with a midday depression. The patterns of C. arrudae were completely different so that genuine C 3 -photosynthesis was excluded, but they were also not typical of CAM. The stomata were almost closed during the night. Some stomatal opening and net CO 2 uptake occurred in the early morning hours followed by a long depression with stomatal closure throughout the rest of the day. Nevertheless, photo inhibition was limited and photosynthetic electron transport rate remained high during this time indicating that photosynthetic excitation energy was required and suggesting that CO 2 assimilation was continuing behind closed stomata based on internal sources of CO 2 . There was some nocturnal accumulation of organic acids (malic and citric acids) which could represent a source of CO 2 during the light period. Overall, the observations can be best explained by the performance of CAM-cycling by C. arrudae . However, leaf carbon gain of C. arrudae was much inferior to that of E. glomerulatus . CAM-cycling appears to be a strategy for protection from photoinhibitory damage and survival under strong conditions of drought. Steeper more vertical leaf positions observed would assist reducing overheating during stomatal closure at high irradiance. The abundance of C. arrudae suggests that the plant must have other means to sustain productivity such as full C 3 -photosynthesis in the more favorable seasons.

Beschreibung: Key message There are specific diurnal light variation patterns and negligible seasonal variation within tree crowns. Crown-mediated regulation of temporal light regimes can be important for whole plant function in Mediterranean evergreens. Abstract The light environment within a tree crown can be characterized by specific variation patterns arising from the structural features of the crown. Within-crown light variation patterns can be important for plant productivity, but this has yet to be assessed in natural settings. The spatio-temporal variations of direct and diffuse photosynthetic photon flux density (PPFD), their proportions and sunfleck frequency within the crowns of isolated adult wild olive trees ( Olea europaea L.) were investigated. Trees growing in contrasting Mediterranean conditions (continental vs. coastal) at the same latitude were compared. Instantaneous diffuse and total PPFD were measured with sunshine sensors in three crown layers (outer-, middle- and inner-crown) in the south-facing part of the crown, at two points of the diurnal (mid-morning and midday) and seasonal (summer and winter) cycles. Direct PPFD and the proportion of direct to total PPFD vary diurnally within the crown as a result of an increase in sunfleck frequency during midday and in self-shading during mid-morning, in both summer and winter conditions. Conversely, the lack of seasonal variation in the three light attributes is better explained by a greater average crown transmittance in winter conditions. The interplay between crown architecture heterogeneity and varying solar position renders identifiable patterns of temporal variations in the light environment within tree crowns. These patterns suggest that trees can benefit from the light heterogeneity typical of Mediterranean environments by developing conservative architectural layouts.

Beschreibung: Key message Cambial activity of ~100-year-old Qilian juniper trees initiated before the middle of May at an elevation of 3200   m a.s.l.; June and July were the main stem radial increment period. Around the middle of August, all xylem cell differentiation periods are completed. Precipitation or relative humidity is the main limiting factor for tree radial growth on the northeastern Tibetan Plateau. Abstract Previous studies have found that annual tree-ring width series of Qilian juniper ( Sabina przewalskii Kom.) in the northeastern Tibetan Plateau (TP) are mostly moisture controlled, irrespective of site elevation. Knowing precisely the cambial growth dynamics during a vegetation period can lead to a better understanding of the climatic factors driving regional tree growth patterns. We observed wood formation with micro-cores taken at weekly intervals from late April to early October 2013, and monitored daily stem radial changes with high-resolution electronic point dendrometers in 30-min intervals. Dormant cambium contained 5–6 cell layers in the cambium zone. Cambial activity initiated before the middle of May in all the monitored trees. About three quarters of the total cell production or radial growth formed during June and July. Lignification of secondary walls of new xylem cells continued from end of May to middle of August. After the middle of August, the cambium entered into the inactive period. Dendrometer measurements confirmed that June and July were the main stem radial increment period. Nonparametric Kendall’s Tau correlations indicate that daily relative humidity and precipitation significantly influence stem growth in May. No obvious relationships were detected in June. In July, significant negative influences of maximum temperature and positive effects of relative humidity prevailed. Overall, growing season precipitation or associated relative humidity is the limiting factor for tree stem radial increments on the intra-annual scale. Our results present a thorough understanding of Qilian juniper xylogenesis and its climate forcing within the whole growing season on the northeastern TP.

Beschreibung: Key message The structure of petals and volatile compounds from fresh Styrax tonkinensis cut flowers were investigated by using micro-techniques and a headspace solid-phase micro-extraction technique coupled with GC–MS. Abstract Styrax tonkinensis is a fast-growing woody plant that is used for timber and as a medicinal plant. In the present study, the structures of the flower petals of S. tonkinensis were investigated and volatile compounds emitted from the petals were identified. Light microscopy, scanning and transmission electron microscopy were used to describe petal structure. The volatile constituents were analyzed using a headspace GC–MS technique. Results indicated that glandular hairs and 8–9 layers of parenchyma cells in the cream-white petals play a key role in emitting the fragrance. An analysis of the volatile components emitted by the cut flowers of S. tonkinensis at two stages of flower development (prior to and at anthesis) indicated that monoterpenes, such as 1,3,6-octatriene, 3,7-dimethyl-( Z ), and α-pinene, were the most abundant volatile components in all samples.

Beschreibung: Key message Pruning significantly reduced stem CO 2 efflux, but had little effect on soil CO 2 efflux and root respiration. Pruning did not alter temperature sensitivity of CO 2 efflux from stem and soil. Abstract Pruning is one of the common silvicultural practices for Chinese fir ( Cunninghamia lanceolata ) plantations to produce knot-free wood. However, little is known about the effects of pruning on stem and soil CO 2 efflux in Chinese fir plantations. In this study, we experimentally manipulated the canopy of Chinese fir by pruning the lower 50 % of the green crown length in a Chinese fir plantation. We monitored the effects of pruning on the stem and soil CO 2 efflux, stem radial growth, xylem sap flow, and nonstructural carbohydrate (NSC) concentrations. Our results showed that pruning resulted in the significant reduction of stem CO 2 efflux, particularly during the growing season. Despite the removal of the lower 50 % of the green crown length, we did not observe a pronounced reduction in soil CO 2 efflux and its components. Moreover, pruning had only little effect on sap flow. No significant difference was observed in the NSC concentrations between treatments in the stem cores and fine roots. We speculated that the different responses of stem and soil CO 2 efflux to pruning in the Chinese fir (sprouting species) plantation may have resulted from the different carbon allocations between aboveground and belowground tissues. However, further studies are required to confirm if our findings could be applied to other tree species or ecosystems.

Beschreibung: Key message We developed two additive systems of biomass equations based on diameter and tree height for nine hardwood species by SUR, and used a likelihood analysis to evaluate the model error structures. Abstract In this study, a total of 472 trees were harvested and measured for stem, root, branch, and foliage biomass from nine hardwood species in Northeast China. Two additive systems of biomass equations were developed, one based on tree diameter ( D ) only and one based on both tree diameter ( D ) and height ( H ). For each system, three constraints were set up to account for the cross-equation error correlations between four tree component biomass, two sub-total biomass, and total biomass. The model coefficients were simultaneously estimated using seemly unrelated regression (SUR). Likelihood analysis was used to verify the error structures of power functions in order to determine if logarithmic transformation should be applied on both sides of biomass equations. Jackknifing model residuals were used to validate the prediction performance of biomass equations. The results indicated that (1) stem biomass accounted for the largest proportion (62 %) of the total tree biomass; (2) the two additive systems of biomass equations obtained good model fitting and prediction, of which the model R a 2 was 〉0.89, and the mean absolute percent bias (MAB %) was 〈35 %; (3) the system of biomass equations based on both D and H significantly improved model fitting and performance, especially for total, aboveground, and stem biomass; and (4) the anti-log correction was not necessary in this study. The established additive systems of biomass equations can provide reliable and accurate estimation for individual tree biomass of the nine hardwood species in Chinese National Forest Inventory.

Beschreibung: Key message This study provides new data and an alternative framework to the debate of tree carbon economy in a context of increasing stress. Abstract For long-living trees, the resilience in times of stress is directly linked to the amount of accessible reserves. Despite the simplicity of this principle, the understanding of how carbon reserves limit growth and/or induce mortality under global change is still debated. In this study, we quantify how anatomical properties of rays—one of the main container for carbon reserves in tree stems—vary among sites, individuals, and annual rings of Larix gmelinii growing in contrasting sites in Siberia to verify if (1) the ray proportion and anatomical structure is linked to the environment, and/or (2) to changes in other wood tissues. Our observations have highlighted that ray proportion mainly varies among individuals, but little among sites and consecutive annual rings. We also observed that ray size and density scale to the wood structure with a relatively constant ratio of ~2.5 rays per tracheid, independent of site conditions. These results suggest that the functional connection between the anatomy of rays and tracheid is unaffected by environment and highlight the importance of considering allometric relations in ecological comparisons. Comparative studies of long-term trajectory of ray proportion of living and dead trees might unravel observed variability among individuals validating the link between long-term depleted reserves and mortality.

Beschreibung: Key message Reduced growth but high NSC after severe defoliation of evergreen trees can be explained by three, non-exclusive processes: critical loss of non-C reserves, hormonal changes, and prioritisation of C storage over growth. Abstract In an attempt to simulate processionary moth impact on pines, we explored the extent to which late winter defoliation affects growth and carbon reserves in the following season. In separate treatments we removed 100, and 50 % of needles of whole trees and defoliated single branches in naturally grown, 2–3-m-tall Pinus pinaster trees in Italy. Shoot and stem growth (lateral shoot length and basal area increment, respectively) were substantially reduced after 100 % defoliation (−45 % for shoots, −84 % for stems). In 50 % defoliated trees only stem growth was reduced (−37 %), and in trees with a single branch defoliated, growth remained unaffected. Although substantial carbon and nitrogen reserves were removed from defoliated trees prior to bud break, non-structural carbohydrates (NSC) concentrations in branches and needles fell below control values only during the first half of the growing season, and considerable amounts of NSC persisted throughout the year. By the end of the dry and hot Mediterranean summer, NSC concentrations in branch xylem, branch phloem, previous year needles, stem sapwood and root xylem were similar among all treatments. Reduced growth and high late season NSC after defoliation can be explained by (1) a critical loss of reserves other than C (e.g. N and P), (2) hormonal changes which affected cambial activity, or (3) a prioritisation of carbon storage over growth, with all three mechanisms potentially contributing to the observed growth and NSC response.

Beschreibung: Key message More than half of the dead trees fell down within decade. Besides, DBH effect on snag longevity varied by tree species and was not detected for some species. Management of long-lived snags in temperate mixed forests should be reconsidered. Context Snags (standing dead trees) provide essential habitats for many species. Those with large diameter at breast height (DBH) are prioritized for retention; one of the reasons is that snag longevity (recruitment to falling down) increases with increasing DBH in conifer-dominated forests. Despite its importance, the DBH effect on hardwood snags is inadequately understood. Aims The aim of this study is to investigate whether and how the DBH effect varies by tree species in mixed conifer–hardwood forests. Methods We checked the current status (standing or falling) of dead trees that had been recorded in 37 permanent plots and applied a generalized linear mixed model. We used tree species, time since death, DBH, and interaction terms as variables. Results Half of the dead trees with a DBH of 25 cm were estimated to have fallen down within 1–6 years for most of the species. While snag longevity increased with increasing DBH in Abies sachalinensis and Phellodendron amurense , we detected no such effect in Picea and three hardwood species. Conclusions For highly decayed or long-lived snags, retaining large snags is not always effective. Managers of species-rich mixed forests should consider the variability of the DBH effects and management of dead wood before and after tree mortality.

Beschreibung: Key message In modelling regeneration patterns , parametric regression is recommended because it can account for the spatial and temporal correlation present in the data , whereas decision trees allow more complex interactions and can be used to reduce the number of variables . Context The establishment of seedlings after regeneration fellings is key to guaranteeing the development and persistence of the forest. Depending on the objective pursued, data available or type of forest, a number of different methods have been employed to assess the relationship between seedling establishment and both environmental and stand factors. Most authors have conducted their analyses using parametric regression or point pattern analysis. Aim We analysed the way in which light, stand conditions, edaphic and topographic variables affect the regeneration of Pinus sylvestris L. in Central Spain. We used different methods to analyse the same data set. The strengths and weaknesses of each method were discussed. Methods We used two parametric approaches: generalized linear mixed model regression using a negative binomial followed by the variant explanatory variables reduction prior to regression as well as three nonparametric approaches not commonly employed in forest regeneration: nonmetric multidimensional scaling, regression trees and random forests algorithm. Results The parametric regression identified a larger number of variables associated with the regeneration process and the inclusion of a random effect in the model allowing the consideration of the spatial variability among plots. However, decision trees captured the complex interaction among variables, which typical parametric methods were unable to detect. Conclusion Different statistical methods gave similar insights into the underlying ecological process. However, different statistical premises with inference implications can be noticed. This may give misinterpretation of the model depending on the nature of the data. The choice of a given method should be made according to the nature of the data and the achievement of desirable results.

Beschreibung: Key message The long-term effect of forest fires in the regeneration of Pinus canariensis was studied. Forest fires had little long-term effects on seed production, seedling germination and seedling mortality. The characteristics of different forest stands across the island had influence in some of the regeneration parameters studied. Context Despite the importance of forest regeneration dynamics after wildfires, little is known about its long-term evolution after a fire. Aims We tested the effect of fire on the long-term regeneration dynamics of P. canariensis . Method In a forest fire chronosequence of five fire ages (time elapsed since the last fire) plus an unburned stand, we monitored seed production, seedling germination and mortality during 2 years. Results We detected significant differences among forest stands in seed production, seedling density and mortality but not in germination and turnover. These differences were unrelated to fire age. Seed production was conditioned by the number of large adults and elevation, germination by diameter at breast height (DBH) and soil nitrogen content and mortality by DBH. Conclusion We detected no long-term effect of fire on the regeneration of P. canariensis in natural pine forest; however, during the first years after fire, modification of nitrogen availability in soil can reduce germination. Stand conditions in natural pine forests appear to mainly control regeneration dynamics. The regeneration strategies and fire-resistance traits of this species have ensured its persistence in the long term.

Beschreibung: Key message During outbreak, a discrepancy between larval performance and the main host used for egg laying was found in Orgyia trigotephras . It results mostly from intraspecific competition, but reduced egg mortality on the less suitable host plant may play a secondary role . Context Host range of polyphagous herbivores often comprises plants of low nutritional quality, which may however provide other benefits to the animal. Understanding the effect of host plants use on insect fitness and its population dynamics are central questions in insect-plant ecology . O. trigotephras Boisduval is a polyphagous Mediterranean defoliator. During outbreaks, larvae are frequently found on two unrelated host species, Pistacia lentiscus L. and Quercus coccifera L. Aim The aim of this study was to clarify the effect of population density on host use and the effects of host tree on insect performance. Methods The realized fecundity and egg mortality were measured during 3 years showing different population levels of the defoliator. Larval performance on the two host species was analyzed. Results Larvae fed on Q. coccifera had faster development, lower mortality, higher female/male ratio, and higher fecundity than larvae fed on P. lentiscus . Yet, at high population densities, under high intraspecific competition, P. lentiscus was the most used for egg laying. During outbreak, higher levels of parasitism by Aprostocetus sp. and predation by Coccidiphila rungsella Nel and Brusseaux were found on eggs laid on Q. coccifera compared to those laid on P. lentiscus . Conclusions The results indicate a discrepancy between host use and larvae performance, possibly ruled by resources exploitation and intraspecific competition. The reduced egg predation on P. lentiscus during outbreaks might also provide an indirect benefit to the insect.

Beschreibung: Key message Low winter temperatures induce an increase in the soil-to-trunk hydraulic resistance of field-grown olive trees resulting in a significant disturbance of their water relations. Abstract A disturbance of water relations in response to chilling have long been observed in potted plants growing under controlled conditions, but information is lacking for field plants. The aim of this study was to assess the effects of winter low temperatures on the water relations of mature olive trees. To this end, water potential, sap flux density, soil temperature and meteorological data were monitored in a hedgerow olive orchard near Córdoba, southern Spain, throughout two consecutive winters. Water stress symptoms were found in terms of midday Ψ, despite adequate water supply and low evaporative demand. These effects were associated with changes in the soil-to-trunk hydraulic resistance ( R root ), which increased by December–January to much higher values than those previously reported in the literature, particularly in the year of higher fruit load. The contribution of viscosity ( η ) to the observed R root dynamics was almost negligible as deduced from measurements of soil temperature, so the high winter values of R root were likely to have originated from other causes such as reductions in membrane permeability and root growth. The findings of this work raise new major issues that deserve further research such as the impact of the winter water stress on stomatal conductance and photosynthesis rates in mature olive trees.

Beschreibung: Key message Here, we isolated a NAC transcription factor PtoVNS11 from Populus tomentosa Carr. Molecular characterization showed that PtoVNS11 was involved in the regulation of secondary cell wall formation in poplar. Abstract NAC domain transcription factors are important regulators that activate the secondary wall biosynthesis in wood formation. In this study, we isolated a NAC domain transcription factor PtoVNS11 from Populus tomentosa Carr. PtoVNS11 shares high identity with SND1 of Arabidopsis thaliana (59.6 %) and PtrWND1B (97.9 %) of P. trichocarpa . Gene expression analyses showed that PtoVNS11 gene was mainly accumulated in xylem and stem of poplar. Further, GUS expression driven by the PtoVNS11 promoter was observed in vascular tissues of vegetative and reproductive organs in transgenic Arabidopsis . Promoter deletion analysis revealed that the fragment (−283 to −171) with the secondary wall NAC-binding element was required for tissue-specific expression of the PtoVNS11 gene. Subcellular localization analysis showed that PtoVNS11:GFP fusion protein was localized in the nucleus. Transgenic poplar plants carrying 35S:PtoVNS11 exhibited dwarf phenotypes with shorter internode as compared to wild-type plants. PtoVNS11 overexpression resulted in massive deposition of lignin and increased thickening of secondary walls in transgenic poplar. Transcription analysis showed that the expression levels of many wood-associated genes were up-regulated in transgenic plants overexpressing PtoVNS11 . Taken together, our results indicate that PtoVNS11 may be involved in the regulation of the secondary wall biosynthesis during wood formation in poplar.