Explore the vast range of titles available.

Dynamic Vegetation Models (DVMs) are designed to be suitable for simulating forest succession and species range dynamics under current and future conditions based on mathematical representations of the three key processes regeneration, growth, and mortality However, mortality formulations in DVMs are typically coarse and often lack an empirical basis, which increases the uncertainty of projections of future forest dynamics and hinders their use for developing adaptation strategies to climate change. Thus, sound tree mortality models are highly needed. We developed parsimonious, species-specific mortality models for 18 European tree species using >90,000 records from inventories in Swiss and German strict forest reserves along a considerable environmental gradient. We comprehensively evaluated model performance and incorporated the new mortality functions in the dynamic forest model ForClim. Tree mortality was successfully predicted by tree size and growth. Only a few species required additional covariates in their final model to consider aspects of stand structure or climate. The relationships between mortality and its predictors reflect the indirect influences of resource availability and tree vitality, which are further shaped by species-specific attributes such as maximum longevity and shade tolerance. Considering that the behavior of the models was biologically meaningful, and that their performance was reasonably high and not impacted by changes in the sampling design, we suggest that the mortality algorithms developed here are suitable for implementation and evaluation in DVMs. In the DVM ForClim, the new mortality functions resulted in simulations of stand basal area and species composition that were generally close to historical observations. However, ForClim performance was poorer than when using the original, coarse mortality formulation. The difficulties of simulating stand structure and species composition, which were most evident for Fagus sylvatica L. and in long-term simulations, resulted from feedbacks between simulated growth and mortality as well as from extrapolation to very small and very large trees. Growth and mortality processes and their species-specific differences should thus be revisited jointly, with a particular focus on small and very large trees in relation to their shade tolerance.

The widespread use of plastics has led to an omnipresence in soils. We aim to understand whether transformation of polyethylene (PE) and polyethylene terephthalate (PET) in the atmosphere alters their surface properties which, after input of microplastics to soil, leads to an increase of reactive surfaces in soils. PE and PET particles (sieved 200–400 µm) were exposed to accelerated UV degradation. Changes in particle size and surface morphology were measured (using electron microscopy) and compared to pH-dependent variation in surface charge parameters (zeta potential and cation exchange capacity). Fourier transform infrared spectroscopy and X-ray photoemission spectroscopy detected the formation of functional groups and surface atomic composition. After 2000 hours of degradation, PE particles reduced in size from 375 ± 117 µm to 8 ± 7 µm, while PET particles showed only a slight decrease in size, from 653 ± 219 µm to 484 ± 274 µm. Reduction of particle sizes correlated with increased absolute zeta potential and a decrease of the isoelectric point. Hydrated surface charge of degraded PE after 2000 hours was unstable under alkaline conditions, related to the formation of carbonyl groups on its surface and increase in hydrophilicity. PET showed fewer surface chemical changes. Especially for degraded PE incorporated in soil, the alteration of its surface can exhibit comparatively one-tenth of the cation sorption power of clay in alkaline environments (≈7.5 vs. 77 cmol c / kg at pH 9), while degraded PET remained comparatively low (≈1.1 cmol c / kg). This study demonstrates that PE undergoes substantial physicochemical changes during UV degradation, increasing its reactivity, while PET remains relatively stable. These findings highlight the need for further studies to differentiate and understand the effects of diverse plastic types on soil ecosystems.

At interphase, de-condensed chromosomes have a non-random three-dimensional architecture within the nucleus, however, little is known about the extent to which nuclear organisation might influence expression or vice versa . Here, using imprinting as a model, we use 3D RNA- and DNA-fluorescence-in-situ-hybridisation in normal and mutant mouse embryonic stem cell lines to assess the relationship between imprinting control, gene expression and allelic distance from the nuclear periphery. We compared the two parentally inherited imprinted domains at the Dlk1-Dio3 domain and find a small but reproducible trend for the maternally inherited domain to be further away from the periphery however we did not observe an enrichment of inactive alleles in the immediate vicinity of the nuclear envelope. Using Zfp57KO ES cells, which harbour a paternal to maternal epigenotype switch, we observe that expressed alleles are significantly further away from the nuclear periphery. However, within individual nuclei, alleles closer to the periphery are equally likely to be expressed as those further away. In other words, absolute position does not predict expression. Taken together, this suggests that whilst stochastic activation can cause subtle shifts in localisation for this locus, there is no dramatic relocation of alleles upon gene activation. Our results suggest that transcriptional activity, rather than the parent-of-origin, defines subnuclear localisation at an endogenous imprinted domain.

Climate change-induced weather extremes are increasing the intensity and frequency of disturbance events, posing a major threat to forests globally. In Central Europe, hotter and drier summers, such as those during the 2018–2020 drought period, have led to widespread forest damage. To adapt forests to a hotter and drier future it is important to identify sites more vulnerable to canopy mortality during drought, but high-resolution tree mortality data across continuous landscapes are still sparse. This study addresses this research gap by utilising a high-resolution (single-tree-level), spatially continuous dataset covering the entire Central European country of Luxembourg. We used generalized additive models (GAMs) to explore the contribution of biotic and abiotic drivers to the observed canopy mortality of conifer and broadleaf forests during the 2018–2020 summer droughts. Specifically, we assessed drivers related to forest structure, mortality clustering and spread, and topographic conditions to understand how they relate to spatial variability in canopy mortality. In total, the model explained 44.7 % of spatial variation in canopy mortality in conifers and 25.3 % in broadleaf forests. Environmental drivers related to clustered mortality, showed the strongest influence on canopy mortality in conifer forests, indicating that bark beetle infestation shaped spatial mortality patterns under drought. Forest height also emerged as an important driver associated with increased canopy mortality in both forest types. In contrast, topography- and soil-related drivers showed only limited influence on canopy mortality. Our study highlights the potential of using high-resolution canopy mortality data across a national-scale landscape to unravel how abiotic and biotic processes shape spatial variation in forest mortality under severe drought conditions.

In mouse and human, genes subjected to genomic imprinting have been shown to function in development, behavior, and post-natal adaptations. Failure to correctly imprint genes in human is associated with developmental syndromes, adaptive, and metabolic disorders during life as well as numerous forms of cancer. In recent years researchers have turned to RNA-seq technologies applied to reciprocal hybrid strains of mice to identify novel imprinted genes, causing a threefold increase in genes reported as having a parental origin-specific expression bias. The functional relevance of parental origin-specific expression bias is not fully appreciated especially since many are reported with only minimal parental bias (e.g. 51:49). Here, we present an in-depth meta-analysis of previously generated RNA-seq data and show that the methods used to generate and analyze libraries greatly influence the calling of allele-specific expression. Validation experiments show that most novel genes called with parental-origin-specific allelic bias are artefactual, with the mouse strain contributing a larger effect on expression biases than parental origin. Of the weak novel genes that do validate, most are located at the periphery of known imprinted domains, suggesting they may be affected by local allele- and tissue-specific conformation. Together these findings highlight the need for robust tools, definitions, and validation of putative imprinted genes to provide meaningful information within imprinting databases and to understand the functional and mechanistic implications of the process.

Large uncertainties characterize forest development under global climate change. Although recent studies have found widespread increased tree mortality, the patterns and processes associated with tree death remain poorly understood, thus restricting accurate mortality predictions. Yet, projections of future forest dynamics depend critically on robust mortality models, preferably based on empirical data rather than theoretical, not well-constrained assumptions. We developed parsimonious mortality models for individual beech (Fagus sylvatica L.) trees and evaluated their potential for incorporation in dynamic vegetation models (DVMs). We used inventory data from nearly 19,000 trees from unmanaged forests in Switzerland, Germany, and Ukraine, representing the largest dataset used to date for calibrating such models. Tree death was modelled as a function of size and growth, i. e., stem diameter (dbh) and relative basal area increment (relBAI), using generalized logistic regression accounting for unequal re-measurement intervals. To explain the spatial and temporal variability in mortality patterns, we considered a large set of environmental and stand characteristics. Validation with independent datasets was performed to assess model generality. Our results demonstrate strong variability in beech mortality that was independent of environmental or stand characteristics. Mortality patterns in Swiss and German strict forest reserves were dominated by competition processes as indicated by J-shaped mortality over tree size and growth. The Ukrainian primeval beech forest was additionally characterized by windthrow and a U-shaped size-mortality function. Unlike the mortality model based on Ukrainian data, the Swiss and German models achieved good discrimination and acceptable transferability when validated against each other. We thus recommend these two models to be incorporated and examined in DVMs. Their mortality predictions respond to climate change via tree growth, which is sufficient to capture the adverse effects of water availability and competition on the mortality probability of beech under current conditions.

Recent climate warming has fueled interest into climate-driven range shifts of tree species. A common approach to detect range shifts is to compare the divergent occurrences between juvenile and adult trees along environmental gradients using static data. Divergent occurrences between life stages can, however, also be caused by ontogenetic effects. These include shifts of the viable environmental conditions throughout development ('ontogenetic niche shift') as well as demographic dependencies that constrain the possible occurrence of subsequent life stages. Whether ontogenetic effects are an important driver of divergent occurrences between juvenile and adult trees along large-scale climatic gradients is largely unknown. It is, however, critical in evaluating whether impacts of environmental change can be inferred from static data on life stage occurrences. Here, we first show theoretically, using a two-life stage simulation model, how both temporal range shift and ontogenetic effects can lead to similar divergent occurrences between adults and juveniles (juvenile divergence). We further demonstrate that juvenile divergence can unambiguously be attributed to ontogenetic effects, when juveniles diverge from adults in opposite direction to their temporal shift along the environmental gradient. Second, to empirically test whether ontogenetic effects are an important driver of divergent occurrences across Europe, we use repeated national forest inventories from Sweden, Germany and Spain to assess juvenile divergence and temporal shift for 40 tree species along large-scale climatic gradients. About half of the species-country combinations had significant juvenile divergences along heat sum and water availability gradients. Only a quarter of the tree species had significant detectable temporal shifts within the observation period. Furthermore, significant juvenile divergences were frequently associated with opposite temporal shifts, indicating that ontogenetic effects are a relevant cause of divergent occurrences between life stages. Our study furthers the understanding of ontogenetic effects and challenges the practice of inferring climate change impacts from static data.

1. Selective hunting can affect demographic characteristics and phenotypic traits of the targeted species. Hunting systems often involve harvesting quotas based on sex, age and/or size categories to avoid selective pressure. However, it is difficult to assess whether such regulations deter hunters from targeting larger \"trophy\" animals with longer horns that may have evolutionary consequences. 2. Here, we compile 44,088 annually resolved and absolutely dated measurements of Alpine ibex (Capra ibex) horn growth increments from 8,355 males, harvested between 1978 and 2013, in the eastern Swiss Canton of Grisons. We aim to determine whether male ibex with longer horns were preferentially targeted, causing animals with early rapid horn growth to have shorter lives, and whether such hunting selection translated into long-term trends in horn size over the past four decades. 3. Results show that medium- to longer-homed adult males had a higher probability of being harvested than shorter-horned individuals of the same age and that regulations do affect the hunters' behaviour. Nevertheless, phenotypic traits such as horn length, as well as body size and weight, remained stable over the study period. 4. Although selective trophy hunting still occurs, it did not cause a measurable evolutionary response in Grisons' Alpine ibex populations; managed and surveyed since 1978. Nevertheless, further research is needed to understand whether phenotypic trait development is coinfluenced by other, potentially compensatory factors that may possibly mask the effects of selective, long-term hunting pressure.

Numerous studies have shown reduced performance in plants that are surrounded by neighbours of the same species 1 , 2 , a phenomenon known as conspecific negative density dependence (CNDD) 3 . A long-held ecological hypothesis posits that CNDD is more pronounced in tropical than in temperate forests 4 , 5 , which increases community stabilization, species coexistence and the diversity of local tree species 6 , 7 . Previous analyses supporting such a latitudinal gradient in CNDD 8 , 9 have suffered from methodological limitations related to the use of static data 10 – 12 . Here we present a comprehensive assessment of latitudinal CNDD patterns using dynamic mortality data to estimate species-site-specific CNDD across 23 sites. Averaged across species, we found that stabilizing CNDD was present at all except one site, but that average stabilizing CNDD was not stronger toward the tropics. However, in tropical tree communities, rare and intermediate abundant species experienced stronger stabilizing CNDD than did common species. This pattern was absent in temperate forests, which suggests that CNDD influences species abundances more strongly in tropical forests than it does in temperate ones 13 . We also found that interspecific variation in CNDD, which might attenuate its stabilizing effect on species diversity 14 , 15 , was high but not significantly different across latitudes. Although the consequences of these patterns for latitudinal diversity gradients are difficult to evaluate, we speculate that a more effective regulation of population abundances could translate into greater stabilization of tropical tree communities and thus contribute to the high local diversity of tropical forests. An analysis of tree survival data from forest sites worldwide shows that in the tropics, rare tree species experience stronger stabilizing density dependence than common species, wheras no correlation of stabilizing density dependence and abundance exists in the temperate zone.

The area covered by boreal forests accounts for ∼16% of the global and 22% of the Northern Hemisphere landmass. Changes in the productivity and functioning of this circumpolar biome not only have strong effects on species composition and diversity at regional to larger scales, but also on the Earth's carbon cycle. Although temporal inconsistency in the response of tree growth to temperature has been reported from some locations at the higher northern latitudes, a systematic dendroecological network assessment is still missing for most of the boreal zone. Here, we analyze the geographical patterns of changes in summer temperature and precipitation across northern Eurasia >60 °N since 1951 AD, as well as the growth trends and climate responses of 445 Pinus, Larix and Picea ring width chronologies in the same area and period. In contrast to widespread summer warming, fluctuations in precipitation and tree growth are spatially more diverse and overall less distinct. Although the influence of summer temperature on ring formation is increasing with latitude and distinct moisture effects are restricted to a few southern locations, growth sensitivity to June-July temperature variability is only significant at 16.6% of all sites (p ≤ 0.01). By revealing complex climate constraints on the productivity of Eurasia's northern forests, our results question the a priori suitability of boreal tree-ring width chronologies for reconstructing summer temperatures. This study further emphasizes regional climate differences and their role on the dynamics of boreal ecosystems, and also underlines the importance of free data access to facilitate the compilation and evaluation of massively replicated and updated dendroecological networks.