Dominant Forest Tree Research Articles

Resilience of genetic diversity in forest trees over the Quaternary

The effect of past environmental changes on the demography and genetic diversity of natural populations remains a contentious issue and has rarely been investigated across multiple, phylogenetically distant species. Here, we perform comparative population genomic analyses and demographic inferences for seven widely distributed and ecologically contrasting European forest tree species based on concerted sampling of 164 populations across their natural ranges. For all seven species, the effective population size, Ne, increased or remained stable over many glacial cycles and up to 15 million years in the most extreme cases. Surprisingly, the drastic environmental changes associated with the Pleistocene glacial cycles have had little impact on the level of genetic diversity of dominant forest tree species, despite major shifts in their geographic ranges. Based on their trajectories of Ne over time, the seven tree species can be divided into three major groups, highlighting the importance of life history and range size in determining synchronous variation in genetic diversity over time. Altogether, our results indicate that forest trees have been able to retain their evolutionary potential over very long periods of time despite strong environmental changes.

Biotechnology and Genomic Approaches to Mitigating Disease Impacts on Forest Health

Outbreaks of insects and diseases are part of the natural disturbance regime of all forests. However, introduced pathogens have had outsized impacts on many dominant forest tree species over the past century. Mitigating these impacts and restoring these species are dilemmas of the modern era. Here, we review the ecological and economic impact of introduced pathogens, focusing on examples in North America. We then synthesize the successes and challenges of past biotechnological approaches and discuss the integration of genomics and biotechnology to help mitigate the effects of past and future pathogen invasions. These questions are considered in the context of the transgenic American chestnut, which is the most comprehensive example to date of how biotechnological tools have been used to address the impacts of introduced pathogens on naïve forest ecosystems.

Runs of homozygosity reveal contrasting histories of inbreeding across global lineages of the edible porcini mushroom, Boletus edulis.

Inbreeding, the mating of individuals that are related through common ancestry, is of central importance in evolutionary and conservation biology due to its impacts on individual fitness and population dynamics. However, while advanced genomic approaches have revolutionised the study of inbreeding in animals, genomic studies of inbreeding are rare in plants and lacking in fungi. We investigated global patterns of inbreeding in the prized edible porcini mushroom Boletus edulis using 225 whole genomes from seven lineages distributed across the northern hemisphere. Genomic inbreeding was quantified using runs of homozygosity (ROHs). We found appreciable variation both among and within lineages, with some individuals having over 20% of their genomes in ROHs. Much of this variation could be explained by a combination of elevation and latitude, and to a lesser extent by predicted habitat suitability during the last glacial maximum. In line with this, the majority of ROHs were short, reflecting ancient common ancestry dating back approximately 200-1700 generations ago, while longer ROHs indicative of recent common ancestry (less than approximately 50 generations ago) were infrequent. Our study reveals the inbreeding legacy of major climatic events in a widely distributed forest mutualist, aligning with prevailing theories and empirical studies of the impacts of historical glaciation events on the dominant forest tree species of the northern hemisphere.

Effective population size of adult and offspring cohorts as a genetic monitoring tool in two stand-forming and wind-pollinated tree species: Fagus sylvatica L. and Picea abies (L.) Karst.

AbstractGenetic diversity is considered to be a prerequisite for adaptation and adaptability as it is a key element of biological diversity. However, the monitoring of genetic diversity has tended to be ignored in biodiversity monitoring. We report a comprehensive genetic monitoring effort in two dominant forest tree species, which was started with a baseline survey in 12 European beech populations and 10 Norway spruce populations in Germany. The standardized experimental design is based on collecting samples of at least 250 adult trees, and 400 natural regeneration and 400 seed samples and their genotyping with 15–16 high-resolution SSR markers. In addition to commonly used mean values across the markers to quantify genetic diversity, we placed special emphasis on various marker-based, pedigree-based and demographic models for estimating the contemporary effective population size Ne of the different generations. In both beech and spruce, no variation in genetic diversity with mean values across markers was detectable between the studied stands and between age cohorts. We detected that stable allelic diversity in progeny generations is ensured by sufficient gene flow from surrounding forests. However, estimates of effective population size show marked differentiation among populations and among age cohorts. Natural regeneration samples appear to converge on the parent generation, while seed samples show a clear bottleneck effect. The Ne parameter can be used to derive conclusions for sustainable natural regeneration management in forest stands and for seed stand approvals including adequate seed collections for appropriate artificial regenerations.The sibship frequency-based method for Ne estimates is presented as much more robust than the widely used LD estimates, which often fail for samples with too weak relatedness. Despite the distinct kinship structure in our monitoring plots, the contemporary effective population size proves to be an essential parameter for assessing the integrity of the reproductive system.

Molecular identification and functional characterization of an environmental stress responsive glutaredoxin gene ROXY1 in Quercus glauca

Quercus glauca is a valuable natural resource with both economic and ecological values. It is one of the dominant forest tree species widely distributed in Southern China. As a perennial broadleaf plant, Q. glauca inevitably encounters numerous stresses from environment. Glutaredoxins (GRXs) are a kind of small oxidoreductases that play an important role in response to oxidative stress. CC-type GRXs also known as ROXYs are specific to land plants. In this study, we isolated a CC-type GRX gene, QgROXY1, from Q. glauca. Expression of QgROXY1 is induced by a variety of environmental stimuli. QgROXY1 protein localizes to both cytoplasm and nucleus; whereas the nucleus localized QgROXY1 could physically interact with the basic region/leucine zipper motif (bZIP) transcription factor AtTGA2 from Arabidopsis thaliana. Transgenic A. thaliana ectopically expressing QgROXY1 is hypersensitive to exogenously applied salicylic acid. Induction of plant defense gene is significantly impaired in QgROXY1 transgenic plants that results in enhanced susceptibility to infection of Botrytis cinerea pathogen, indicating the evolutionary conserved function among ROXY homologs in weedy and woody plants. This is the first described function for the ROXYs in tree plants. Through this case study, we demonstrated the feasibility and efficacy of molecular technology applied to characterization of gene function in tree species.

High phenotypic variation found within the offspring of each mother tree in Fagus sylvatica regardless of the environment or source population

AbstractAimClimate change challenges temperate forest trees by increasingly irregular precipitation and rising temperatures. Due to long generation cycles, trees cannot quickly adapt genetically. Hence, the persistence of tree populations in the face of ongoing climate change depends largely on phenotypic variation, that is the capability of a genotype to express variable phenotypes under different environmental conditions, known as plasticity. We aimed to quantify phenotypic variation of central Europe's naturally dominant forest tree across various intraspecific scales (individuals, mother trees (families), populations) to evaluate its potential to respond to changing climatic conditions.LocationEurope.Time Period2016–2019.Major Taxa StudiedEuropean beech (Fagus sylvatica L.).MethodsWe conducted a fully reciprocal transplantation experiment with more than 9000 beech seeds from seven populations across a Europe‐wide gradient. We compared morphological (Specific Leaf Area), phenological (leaf unfolding) and fitness‐related (growth, survival) traits across various biological scales: within single mother trees, within populations and across different populations under the contrasting climates of the translocation sites.ResultsThe experiment revealed significant phenotypic variation within the offspring of each mother tree, regardless of geographic origin. Initially, seedling height growth varied among mother trees and populations, likely due to maternal effects. However, the growth performance successively aligned after the first year. In summary, we observed a consistent growth response in different beech populations to diverse environments after initial maternal effects.Main ConclusionsThe study strikingly demonstrates the importance of considering intraspecific variation. Given the surprisingly broad spectrum of phenotypes each mother tree holds within its juvenile offspring, we conclude that Fagus sylvatica might have the potential for medium‐term population persistence in face of climate change, provided that this pattern persists into later life stages. Hence, we also suggest further investigating the inclusion of passive adaptation and natural dynamics in the adaptive management of forests.

Fundamental but underrepresented: root carbon stocks in African montane forests

African montane forests harbor some of the greatest biodiversity worldwide, with high levels of species endemism. However, the loss of these forests through fragmentation, deforestation and climate change has been rapidly increasing in recent years. Montane forests in Africa are more susceptible to changes in climate than their lowland counterparts, yet their ecological value is still underrepresented. These montane forests have recently been highlighted as a major aboveground carbon (C) stock. The estimated 149.4 Mg C ha−1 from aboveground live trees surpasses estimates from the Intergovernmental Panel on Climate Change for these endangered forests, and exceeds reported values for neotropical montane and lowland forests by up to 70%. Despite the tremendous implications of these findings, coordinated and available research on the C storage potential of the other share of African montane forest biomass, that is in tree roots, is largely missing. Broadly estimated from the allometry of aboveground C stocks and from root:shoot ratios in lowland forests, more than 60 Mg C ha−1 can be stored in African montane forest roots, about 40% more than previously determined. While this broad estimation points at the potential importance of root C stocks in African montane forests, it also unveils a far-reaching knowledge gap. Here, we advocate for a more quantitative representation of the root C stock from dominant forest tree species of African tropical montane forests and ultimately for a better grasp on tree C stocks from this endangered ecosystem.

Global change explains reduced seeding in a widespread New Zealand tree: indigenous Tūhoe knowledge informs mechanistic analysis

IntroductionClimate change is expected to exacerbate the pressures faced by already fragile ecosystems. Negative impacts on the localized and culturally significant plant and animal species within these ecosystems will have cascading effects for the indigenous communities that interact with those species. Understanding how climate change affects culturally important seed crops may be particularly important, as seeds are critical for forest regeneration as well as providing sustenance for wildlife and people. In the central North Island/Te Ika-a-Māui of Aotearoa-New Zealand, Tūhoe elders of the Tuawhenua region have observed declines in seed production by the large-fruited locally dominant forest tree Beilschmiedia tawa (tawa, Lauraceae) over the last half century, which could be related to climate change.MethodsWe used seed trap data from six sites throughout the geographic range of tawa to measure trends in seed crop size from 1986 to 2020 and to determine which weather factors affect seed crops. We then used these weather predictors to hindcast how tawa seeding may have changed in Tuawhenua forests from 1910–2019, based on historic weather data.ResultsSeed trap data showed a decline in seeding through time across tawa’s range, and that seeding was lower at more northerly sites. Seed crops were synchronous among trees within sites, but were strongly asynchronous among sites. High seed crops were associated with cooler summer and winter temperatures, and with high rainfall. In the Tuawhenua region, increases in summer and winter temperatures appear to have contributed to the declines in tawa seed crops observed by elders, with the model predicting that years with heavy fruiting have become less frequent after 1940.DiscussionOur study provides strong evidence that tawa is undergoing changing seedfall patterns in response to changing climate. The biggest weather drivers of seeding that we identified in tawa were winter and summer temperature, both of which were negatively associated with crop size. Both winter and summer temperatures have increased in Tuawhenua in the last 100 years suggesting a possible mechanism to explain observations of long-term declines in tawa seedfall observed by Tūhoe elders of the Tuawhenua region, with ecological and cultural implications.

Chromosome-scale genome assembly and insights into the metabolome and gene regulation of leaf color transition in an important oak species, Quercus dentata.

Quercus dentata Thunb., a dominant forest tree species in northern China, has significant ecological and ornamental value due to its adaptability and beautiful autumn coloration, with color changes from green to yellow into red resulting from the autumnal shifts in leaf pigmentation. However, the key genes and molecular regulatory mechanisms for leaf color transition remain to be investigated. First, we presented a high-quality chromosome-scale assembly for Q. dentata. This 893.54 Mb sized genome (contig N50 = 4.21 Mb, scaffold N50 = 75.55 Mb; 2n = 24) harbors 31 584 protein-coding genes. Second, our metabolome analyses uncovered pelargonidin-3-O-glucoside, cyanidin-3-O-arabinoside, and cyanidin-3-O-glucoside as the main pigments involved in leaf color transition. Third, gene co-expression further identified the MYB-bHLH-WD40 (MBW) transcription activation complex as central to anthocyanin biosynthesis regulation. Notably, transcription factor (TF) QdNAC (QD08G038820) was highly co-expressed with this MBW complex and may regulate anthocyanin accumulation and chlorophyll degradation during leaf senescence through direct interaction with another TF, QdMYB (QD01G020890), as revealed by our further protein-protein and DNA-protein interaction assays. Our high-quality genome assembly, metabolome, and transcriptome resources further enrich Quercus genomics and will facilitate upcoming exploration of ornamental values and environmental adaptability in this important genus.

Genomic vulnerability to climate change in Quercus acutissima, a dominant tree species in East Asian deciduous forests.

Understanding the evolutionary processes that shape the landscape of genetic variation and influence the response of species to future climate change is critical for biodiversity conservation. Here, we sampled 27 populations across the distribution range of a dominant forest tree, Quercus acutissima, in East Asia, and applied genome-wide analyses to track the evolutionary history and predict the fate of populations under future climate. We found two genetic groups (East and West) in Q.acutissima that diverged during Pliocene. We also found a heterogeneous landscape of genomic variation in this species, which may have been shaped by population demography and linked selections. Using genotype-environment association analyses, we identified climate-associated SNPs in a diverse set of genes and functional categories, indicating a model of polygenic adaptation in Q.acutissima. We further estimated three genetic offset metrics to quantify genomic vulnerability of this species to climate change due to the complex interplay between local adaptation and migration. We found that marginal populations are under higher risk of local extinction because of future climate change, and may not be able to track suitable habitats to maintain the gene-environment relationships observed under the current climate. We also detected higher reverse genetic offsets in northern China, indicating that genetic variation currently present in the whole range of Q.acutissima may not adapt to future climate conditions in this area. Overall, this study illustrates how evolutionary processes have shaped the landscape of genomic variation, and provides a comprehensive genome-wide view of climate maladaptation in Q.acutissima.

Host Specificity and Seasonal Variation in the Colonization of Tubakia sensu lato Associated with Evergreen Oak Species in Eastern Japan.

Foliar fungal endophytes are ubiquitous and hyperdiverse, and tend to be host-specific among dominant forest tree species. The fungal genus Tubakia sensu lato is comprised of foliar pathogens and endophytes that exhibit host preference for Quercus and other Fagaceae species. To clarify interspecific differences in ecological characteristics among Tubakia species, we examined the endophyte communities of seven evergreen Quercus spp. at three sites in eastern Japan during summer and winter. Host tree species was the most significant factor affecting endophyte community composition. Tubakia species found at the study sites were divided into five specialists and three generalists according to their relative abundance in each host species and their host ranges. Specialists were dominant on their own host in summer, and their abundance declined in winter. To test the hypothesis that generalists are more widely adapted to their environment than specialists, we compared their spore germination rates at different temperatures. Spores of generalist Tubakia species were more tolerant of colder temperatures than were spores of specialist Tubakia species, supporting our hypothesis. Seasonal and site variations among Tubakia species were also consistent with our hypothesis. Host identity and ecology were significantly associated with endophyte community structure.

Inter-Individual Budburst Variation in Fagus sylvatica Is Driven by Warming Rate.

The onset of the growing season in temperate forests is relevant for forest ecology and biogeochemistry and is known to occur earlier with climate change. Variation in tree phenology among individual trees of the same stand and species, however, is not well understood. Yet, natural selection acts on this inter-individual variation, which consequently affects the adaptive potential to ongoing environmental changes. Budburst dates of 146 mature individuals of Fagus sylvatica, the dominant natural forest tree of central Europe, were recorded over 12 years in one forest stand of 1 ha in the Müritz National Park, Germany. The tree-specific location, topographical differences, as well as social status, were measured to explain the inter-individual variation in budburst. Furthermore, inter-individual differences in bud dormancy were quantified. Additional phenology and weather data across Germany from 405 sites over a 25-year period was used to put the insights from the single stand into perspective. Consistent phenological ranking over the years with respect to early and late flushing trees was observed within the single forest stand, with 23 trees consistently flushing 3–6 days earlier and 22 trees consistently flushing 3–10 days later than the median. Trees flushing consistently early varied most in their spring budburst dates and were less dormant than late-flushing trees already in mid-winter. The higher variation in earlier flushing trees was best explained by a slower warming rate during their budburst period in the observed stand as well as across Germany. Likewise, years with a lower warming rate during the budburst period were more variable in budburst dates. The rate of warming during spring time is crucial to accurately project future within-species variation and the resulting adaptive potential in spring phenology of dominant forest tree species.

Linked selection, ancient polymorphism, and ecological adaptation shape the genomic landscape of divergence in Quercus dentata

AbstractMultiple evolutionary forces contribute to heterogeneous genomic landscapes; however, disentangling their relative contributions is challenging. We sampled nine populations across the distribution of Quercus dentata, a dominant forest tree in East Asia, and used whole‐genome sequencing data to investigate mechanisms underlying divergence. We identified two genetic groups (north and south) that diverged ~1.84 million years ago, consistent with the uplift of the Qinling Mountains during the Pleistocene. The north group experienced a bottleneck during the middle–late Pleistocene and expanded from multiple refugia. The south group experienced a more severe bottleneck and showed high population differentiation, probably due to long‐term isolation and habitat fragmentation. We detected genomic islands with elevated relative differentiation (FST) scattered across the genome. Among these, 65.9% showed reduced absolute divergence (dXY) consistent with linked selection, while the remaining (34.1%) showed elevated dXY suggestive of divergent sorting of ancient polymorphisms. The recombination rate in genomic islands was lower than background, suggesting the importance of genome structure in shaping the genomic landscape. We detected 108 single nucleotide polymorphisms significantly associated with environmental factors, 12 of which clustered in a region of ~500 kb. This region showed multiple signals of positive selection in the north group, including the enrichment of XP‐extended haplotype homozygosity scores, an elevated population branch statistic, and an excess of high‐frequency derived alleles. In addition, we found that linkage disequilibrium was low and derived haplotypes declined rapidly in this region, indicating selection on standing variation. Our results clarify the evolutionary processes driving genomic divergence in Q. dentata.

Assessment of leaf morphological, physiological, chemical and stoichiometry functional traits for understanding the functioning of Himalayan temperate forest ecosystem

Leaf functional traits support plant survival and growth in different stress and disturbed conditions and respond according to leaf habit. The present study examined 13 leaf traits (3 morphological, 3 chemical, 5 physiological, and 2 stoichiometry) of nine dominant forest tree species (3 coniferous, 3 deciduous broad-leaved, 3 evergreen broad-leafed) to understand the varied response of leaf habits. The hypothesis was to test if functional traits of the conifers, deciduous and evergreen differ significantly in the temperate forest and to determine the applicability of leaf economic theory i.e., conservative vs. acquisitive resource investment, in the temperate Himalayan region. The attributes of the functional traits i.e., leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), leaf water content (LWC), stomatal conductance (Gs), and transpiration (E) followed the order deciduous > evergreen > coniferous. Leaf carbon and leaf C/N ratio showed the opposite pattern, coniferous > evergreen > deciduous. Chlorophyll (Chl) and photosynthetic rate (A) were highest for evergreen species, followed by deciduous and coniferous species. Also, structural equation modelling determined that morphological factors were negatively related to physiological and positively with chemical factors. Nevertheless, physiological and chemical factors were positively related to each other. The physiological traits were mainly regulated by stomatal conductance (Gs) however the morphological traits were determined by LDMC. Stoichiometry traits, such as leaf C/N, were found to be positively related to leaf carbon, and leaf N/P was found to be positively related to leaf nitrogen. The result of the leaf functional traits relationship would lead to precise prediction for the functionality of the temperate forest ecosystem at the regional scale.

Divergent Responses of Dominant Forest Tree Species to Manipulated Canopy and Understory N Additions in Terms of Foliage Stoichiometric, Photosynthetic, and Hydraulic Traits

AbstractNitrogen (N) deposition effects on the stoichiometric balance and photosynthetic and hydraulic couplings in subtropical forests has drawn wide attentions. The previously adopted understory application of N fertilization is criticized because it might ignore foliar N retention for different species. This paper reports a fertilizing application from the canopy (CAN) and under the canopy (UAN) in a phosphorus (P) limited ecosystem. Foliage stoichiometric, photosynthetic, and hydraulic traits of six dominant species were measured and analyzed. Both treatments equally enhanced foliage N and N/P, but not foliage P, who was highly species‐specific depending on tree height, which implied enhanced P limitation. Decreased isotope abundance of 15N (δ15N) that approaching to the level in the urea fertilizer under CAN suggested the existence of canopy retention of N. Besides, N response sensitivity of N, P and δ15N that positively related to tree height (H) under CAN indicated different exposure to the added N, which promoted stoichiometric imbalance among species. The photosynthetic traits represented by net photosynthesis (An) increased under both treatments. A divergent foliar photosynthetic and hydraulic traits variation was identified by significant decreased stomatal conductance (gs) and An/gs for CAN treatments, which induced the elevated isotope abundance of 13C (δ13C). Correspondingly, foliage hydraulic traits that shifted to water use efficiency axis were identified only under CAN in principal component analysis. Overall, our results proved that the canopy absorption and species heterogeneity should be considered regarding foliar safety versus efficiency trade‐off in response to nitrogen additions in the future.

Genetic Differentiation and Demographic History of Three Cerris Oak Species in China Based on Nuclear Microsatellite Makers

Knowledge of interspecific divergence and population expansions/contractions of dominant forest trees in response to geological events and climatic oscillations is of major importance to understand their evolution and demography. However, the interspecific patterns of genetic differentiation and spatiotemporal population dynamics of three deciduous Cerris oak species (Q. acutissima, Q. variabilis and Q. chenii) that are widely distributed in China remain poorly understood. In this study, we genotyped 16 nuclear loci in 759 individuals sampled from 44 natural populations of these three sibling species to evaluate the plausible demographical scenarios of the closely related species. We also tested the hypothesis that macro- and microevolutionary processes of the three species had been triggered and molded by Miocene–Pliocene geological events and Quaternary climatic change. The Bayesian cluster analysis showed that Q. acutissima and Q. chenii were clustered in the same group, whereas Q. variabilis formed a different genetic cluster. An approximate Bayesian computation (ABC) analyses suggested that Q. variabilis and Q. acutissima diverged from their most common ancestor around 19.84 Ma, and subsequently Q. chenii diverged from Q. acutissima at about 9.6 Ma, which was significantly associated with the episodes of the Qinghai–Tibetan Plateau (QTP). In addition, ecological niche modeling and population history analysis showed that these three Cerris oak species repeatedly underwent considerable ‘expansion–contraction’ during the interglacial and glacial periods of the Pleistocene, although they have varying degrees of tolerance for the climatic change. Overall, these findings indicated geological and climatic changes during the Miocene–Pliocene and Pleistocene as causes of species divergence and range shifts of dominant tree species in the subtropical and warm temperature areas in China.

How Spatial Resolution Affects Forest Phenology and Tree-Species Classification Based on Satellite and Up-Scaled Time-Series Images

The distribution of forest tree species provides crucial data for regional forest management and ecological research. Although medium-high spatial resolution remote sensing images are widely used for dynamic monitoring of forest vegetation phenology and species identification, the use of multiresolution images for similar applications remains highly uncertain. Moreover, it is necessary to explore to what extent spectral variation is responsible for the discrepancies in the estimation of forest phenology and classification of various tree species when using up-scaled images. To clarify this situation, we studied the forest area in Harqin Banner in northeast China by using year-round multiple-resolution time-series images (at four spatial resolutions: 4, 10, 16, and 30 m) and eight phenological metrics of four deciduous forest tree species in 2018, to explore potential impacts of relevant results caused by various resolutions. We also investigated the effect of using up-scaled time-series images by comparing the corresponding results that use pixel-aggregation algorithms with the four spatial resolutions. The results indicate that both phenology and classification accuracy of the dominant forest tree species are markedly affected by the spatial resolution of time-series remote sensing data (p < 0.05): the spring phenology of four deciduous forest tree species first rises and then falls as the image resolution varies from 4 to 30 m; similarly, the accuracy of tree species classification increases as the image resolution varies from 4 to 10 m, and then decreases as the image resolution gradually falls to 30 m (p < 0.05). Therefore, there remains a profound discrepancy between the results obtained by up-scaled and actual remote sensing data at the given spatial resolutions (p < 0.05). The results also suggest that combining phenological metrics and time-series NDVI data can be applied to identify the regional dominant tree species across different spatial resolutions, which would help advance the use of multiscale time-series satellite data for forest resource management.

Drivers and implications of distance decay differ for ectomycorrhizal and foliar endophytic fungi across an anciently fragmented landscape.

Fungal communities associated with plants often decrease in similarity as the distance between sampling sites increases (i.e., they demonstrate distance decay). In the southwestern USA, forests occur in highlands separated from one another by warmer, drier biomes with plant and fungal communities that differ from those at higher elevations. These disjunct forests are broadly similar in climate to one another, offering an opportunity to examine drivers of distance decay in plant-associated fungi across multiple ecologically similar yet geographically disparate landscapes. We examined ectomycorrhizal and foliar endophytic fungi associated with a dominant forest tree (Pinus ponderosa) in forests across ca. 550 km of geographic distance from northwestern to southeastern Arizona (USA). Both guilds of fungi showed distance decay, but drivers differed for each: ectomycorrhizal fungi are constrained primarily by dispersal limitation, whereas foliar endophytes are constrained by specific environmental conditions. Most ectomycorrhizal fungi were found in only a single forested area, as were many endophytic fungi. Such regional-scale perspectives are needed for baseline estimates of fungal diversity associated with forest trees at a landscape scale, with attention to the sensitivity of different guilds of fungal symbionts to decreasing areas of suitable habitat, increasing disturbance, and related impacts of climate change.

High plasticity in germination and establishment success in the dominant forest tree Fagus sylvatica across Europe

AbstractAimDistribution ranges of temperate tree species are shifting poleward and upslope into cooler environments due to global warming. Successful regeneration is crucial for population persistence and range expansion. Thus, we aimed to identify environmental variables that affect germination and seedling establishment of Europe's dominant forest tree, to compare the importance of plasticity and genetic variation for regeneration, and to evaluate the regeneration potential at and beyond the southern and northern distribution margins.LocationEurope.Time period2016–2018.Major taxa studiedEuropean beech (Fagus sylvatica (L.)).MethodsWe investigated how germination, establishment and juvenile survival change across a reciprocal transplantation experiment using over 9,000 seeds of beech from 7 populations from its southern to its northern distribution range margins.ResultsGermination and establishment at the seedling stage were highly plastic in response to environmental conditions. Germination success increased with warmer and declined with colder air temperature, whereas establishment and survival were hampered under warmer and drier conditions. Germination differed among populations and was positively influenced by seed weight. However, there was no evidence of local adaptation in any trait.Main conclusionsThe high plasticity in the early life‐history traits found irrespective of seed origin may allow for short‐term acclimatization. However, our results also indicate that this plasticity might not be sufficient to ensure the regeneration of beech in the future due to the low survival found under dry and hot conditions. The future climatic conditions in parts of the distribution centre and at the rear edge might thus become limiting for natural regeneration, as the likelihood of extreme heat and drought events will increase. By contrast, at the cold distribution margin, the high plasticity in the early life‐history traits may allow for increasing germination success with increasing temperatures and may thus facilitate natural regeneration in the future.

A summer and winter’s tale: factors influencing avian community composition and species abundances in lowland subtropical floodplain forests in central eastern Australia

The ecology of avian community assembly in subtropical climate areas with seasonal and year-to-year variability is complex and poorly understood. To test for variation in year–year and seasonal (summer–winter) avian community composition and species abundances, we established 10 transects (200 m long) and sampled twice yearly for 7 years. To differentiate year–year and seasonal (summer–winter) patterns from the potential disturbance effects caused by human activities associated with music festivals (events), we monitored community composition and species abundances on sites close to disturbance areas (impact) and sites distant from disturbances (control). Impacts from large scale music events included loud noise, and thousands of vehicle and people movements on a daily basis. Raw count, abundance-weighted, and feeding guild data were analysed using multivariate and univariate methods. Seasonal (summer–winter) patterns of food resource availability in dominant forest trees (fruit and nectar resources) were identified. We found strong signals for the influence of seasonality and seasonal resource availability on community composition and feeding guild representation (nectivores and frugivores). We detected somewhat weaker effects for location relative to disturbance (control vs impact) and weak effects for sample timing associated with disturbance from the events. Avian community composition showed high similarity between control and impact sites, was dynamic in space and time (year to year) and showed strong local and regional trends in response to seasonality. Avian species abundances were greater in less disturbed (control) forest habitats, highlighting the fundamental value of conservation reserves in protecting higher quality avian habitats.