Fabian J?rg FischerHarry Jon Foord OwenTommaso JuckerEmily Rebecca Lines...
16页
查看更多>>摘要：Abstract How ecologists think about above‐ground forest structure and dynamics is fundamentally shaped by the data we can collect. This has historically been limited to what is possible with simple equipment such as a tape measure, which has often led to the three‐dimensional complexity of the form of trees being reduced to the diameter of a trunk, and perhaps the height of the tree. While simple and pragmatic, this trunk‐centric framework has some obvious limitations, as many of the major processes that influence how trees grow and interact with one another happen up in the canopy. For instance, the structural complexity of individual trees' leaf and branch arrangements and how trees fill canopy space are direct drivers of individual tree and whole‐forest productivity and dynamics, but remain poorly studied because they have traditionally been challenging to measure. However, recent advances in remote sensing and data processing are revolutionising our ability to accurately measure tree and forest structure from leaves to landscapes. Not only do we have access to more accurate data on structure, but we also have data spanning a much broader range of spatial, temporal and ecological scales, and new avenues of research that challenge how we understand forests are emerging. Synthesis. Here, we review the new opportunities these technologies bring us to measure the physical structure of trees and highlight the technological developments needed to maximise their value to the field of forest ecology. Today, perhaps for the first time, how ecologists choose to study above‐ground forest structure and dynamics is limited more by creativity than by what we can measure.
Ilaíne Silveira MatosOliver BinksCleiton B. EllerBianca B. Zorger...
11页
查看更多>>摘要：Abstract Occult precipitation events (fog, dew and light rain) can alter plant water and nutritional status, both directly through the aerial uptake of surface water and nutrients, and indirectly via redistribution of atmospheric resources to the soil. However, current frameworks that explain niche segregation, species interactions and coexistence still consider that ground‐rooted plants obtain resources almost exclusively via root absorption from soil. Here, we expand the plant hydrological niches model to incorporate both soil and atmospheric resource‐axes, thus providing a more complete picture of how ground‐rooted terrestrial plants obtain, remobilise, share and compete for water and soluble nutrients. First, we describe how plants with different water acquisition strategies access directly or indirectly atmospheric resources. Then, we discuss how the use of such resources may promote spatiotemporal niche segregation, contributing to shape species distribution and abundance within plant communities. We illustrate this argument with examples from arid, mesic and wet vegetation types. Finally, we examine how climate and land‐use changes may influence plant hydrological niches, potentially altering community structure. Synthesis. Understanding how available atmospheric resources influences niche segregation in plant communities is a crucial step towards better predictions of species responses (e.g. changes in distribution, abundance and interactions) to climate change.
Kerissa Fuccillo BattleAnna DuhonConrad R. VispoTheresa?M. Crimmins...
18页
查看更多>>摘要：Abstract Understanding the breadth and complexity of changes in phenology is limited by the availability of long‐term historical data sets with broad geographic range. We compare a recently discovered historical data set of plant phenology observations collected across the state of New York (1826–1872) to contemporary volunteer‐contributed observations (2009–2017) to evaluate changes in plant phenology between time periods. These multi‐site, multi‐taxa phenology data matched with temperature data uniquely extend historical observations back in time prior to the major atmospheric effects of the Industrial Revolution. The majority of the 36 trees, shrubs and forbs that comprised our analysable data set flowered and leafed out earlier in contemporary years than in the early to mid‐19th century. This shift is associated with a warming trend in mean January‐to‐April temperatures, with flowering and leafing advancing on average 3?days/°C earlier. On average, plants flowered 10.5?days earlier and leafed out 19?days earlier in the contemporary period. Urban areas exhibit more advanced phenology than their rural counterparts overall, and insect‐pollinated trees show more advanced phenology than wind‐pollinated trees and seasonality and growth form explain significant variation in flowering phenology. The greatest rates of temperature sensitivity and change between time periods for flowering are seen in early‐season species, particularly trees. Changes in the timing of leaf out are the most advanced for trees and shrubs in urban areas. Synthesis. Citizen science observations across two centuries reveal a dramatic, climate‐driven shift to earlier leaf out and flowering. The magnitude of advancement varies across settings, species and functional groups, and illustrates how long‐term monitoring and citizen science efforts are invaluable for ecological forecasting and discovery.
Erika BuscardoJózsef GemlSteven K. SchmidtHelena Freitas...
15页
查看更多>>摘要：Abstract Animals represent an overlooked source of horizontal redistribution of primary production and concentration of elements in ecosystems. For example, the high nutrient concentration of excretions by animals creates a mosaic of short‐term nutrient hotspots. However, how this impacts soil microbial communities, especially fungi, and in turn plant species diversity remains little known. This study quantified the temporal dynamics of soil mineral nitrogen (N) availability and its relationship with soil fungal community and functional group composition in simulated high‐N patches in an Amazonian rain forest. We hypothesised that (H1) changes in local resource dynamics would increase the abundance of pathotrophs and reduce that of saprotrophs and that, (H2) compared with previously reported bacterial community dynamics, fungi would be more resilient after a pulse disturbance event. A single urea pulse was applied and the relationship between fungal community composition and functional groups and soil N availability were determined before and twice after the urea treatment. An increase in mineral N availability and soil pH two months after the applied urea pulse was found to be associated with significant changes in fungal community composition and the abundance of functional groups. There was a notable decrease in the relative abundance of saprotrophs, accompanied by an increase in plant pathogenic fungi. Five months after the treatment, no differences were detected either in mineral N availability and soil pH or the composition of fungal communities and functional groups between the control and urea treatment. Synthesis. By locally favouring the abundance of plant pathogens, temporally short‐lived, but frequent high‐N patches created by animal excretions could potentially be involved in maintaining spatially and temporally variable soil microbial diversity and thus contributing to high plant community diversity in tropical rain forests as predicted by the Janzen–Connell hypothesis. The tendency of soil fungal communities in this study to return to their initial composition after 5?months suggests that they are resilient to perturbation by N pulse, and more so than previously observed in bacterial communities.
Alexander Suárez‐Mari?oGerardo Arceo‐GómezCristopher AlborVíctor Parra‐Tabla...
12页
查看更多>>摘要：Abstract Co‐flowering communities are usually characterized by high plant generalization but knowledge of the underlying factors leading to high levels of generalization and pollinator sharing, and how these may contribute to network structure is still limited. Flowering phenology and floral trait similarity are considered among the most important factors determining plant generalization and pollinator sharing. However, these have been evaluated independently even though they can act in concert with each other. Moreover, the importance of flowering phenology and floral similarity, via their effects on plant generalization, in the structure of plant–pollinator networks has been scarcely studied. Here, we aim to evaluate the effect of flowering phenology and floral similarity in mediating the degree of pollinator sharing and plant generalization in two coastal communities and uncover their importance as drivers of plant–pollinator network structure. We recorded flower production per species, as well as the identity and frequency of floral visitors along the entire flowering season. We estimated the degree of flowering overlap, the degree of floral similarity (using floral traits associated with size and colour) and the degree of pollinator sharing among plant species within both communities. Structural equation models (SEM) showed a positive effect of flowering overlap on pollinator sharing and plant generalization. Pollinator sharing and plant generalization positively affected network nestedness. Furthermore, SEM showed a direct positive effect of flowering overlap on network modularity. The SEM analyses also revealed a significant interaction effect of floral similarity and flowering overlap on pollinator sharing, with consequences for network nestedness in one community. Synthesis. Our results highlight the importance of integrating multiple axes of differentiation such as flowering phenology and floral similarity into our understanding of the drivers of plant–pollinator network structure.
查看更多>>摘要：Abstract Successful management of fire‐prone woody ecosystems is challenging and requires knowledge of the spatial arrangement of the trees and how the tree distribution patterns influence the nature and consequences of subsequent fires. In open tree landscapes, trees are often aggregated, and the ability of trees within the clumps to survive fires plays a significant role in determining subsequent landscape dynamics. If positive interactions exist among neighbouring trees, this will help maintain the patterns of clumped trees. However, the tree‐aggregated landscape will continue to exist only if the positive neighbour interactions persist consistently over time. In cases where disturbances are episodic, detecting these interactions is only possible through long‐term studies. Data reported here are from a 25‐year study involving the annual tree censusing of a large grid‐plot in a frequently burned open oak landscape dominated by Quercus macrocarpa and Quercus ellipsoidallis. The results showed that while having neighbours reduced tree growth, neighbours consistently facilitated survival, irrespective as to whether the neighbours were conspecifics or heterospecifics. Trees of all sizes in close proximity to neighbours were considerably more likely to survive fire throughout the study. This neighbour facilitation is likely the result of a reduction of both herbaceous and woody fuel within clumps. Synthesis. This is the first study to document consistent neighbour facilitation among trees experiencing repeated stressors over an extended time period. Our findings support the literature documenting positive neighbour effects among plants in stressful and highly disturbed environments, in accordance with the stress‐gradient hypothesis. While aggregated tree regeneration is typically viewed as the primary cause for the development of tree clumps in fire‐prone ecosystems, our study showed that aggregated tree survival, by itself, can also be an important driver of post‐fire tree clumping. Our results support the growing literature emphasizing the importance of landscape heterogeneity as a driver of resilience in fire‐prone tree ecosystems, and the value of maintaining or creating this heterogeneity during forest management.
Pieter SanczukEmiel De LombaerdeStef HaesenKoenraad Van?Meerbeek...
13页
查看更多>>摘要：Abstract Biological communities are reshuffling owing to species range shifts in response to climate change. This process inherently leads to novel assemblages of interacting species. Yet, how climatic change and local dynamics in biotic interactions jointly affect range shifts is still poorly understood. We combine a unique long‐term transplant competition‐exclusion experiment with species distribution models (SDMs) to test the effects of biotic interactions on understorey species range shifts under climate change in European temperate forests. Using a time series of 18?years of individual‐level demographic data of four common understorey plant species transplanted beyond their cold range edge to plots with and without interspecific competition, we built integral projection models (IPMs) and analysed the effects of competition on five key vital rates and population growth (λ). We assessed the results of the transplant experiment in the context of the modelled species' current and future potential distributions. We find that species' population performances in the transplant experiment decreased with lower predicted habitat suitability from the SDMs. The population performance at the transplant sites was mediated by biotic interactions with the local plant community: for two species with intermediate levels of predicted habitat suitability at the transplant sites, competition effects could explicitly differentiate between net population growth (λ?>?1) or shrinkage (λ?<?1). Synthesis. Our findings contest the long‐standing idea that at cold range edges, mainly abiotic factors structure species' distributions. We conclude that biotic interactions, through acting on local population dynamics, may impact species distributions at the continental scale. Hence, predicting climate‐change impacts on biodiversity redistributions ultimately requires us to also integrate dynamics in biotic interactions.
Lucas Loram‐Louren?oFernanda Santos FarneseRauander Douglas Ferreira Barros AlvesPriscila Ferreira Batista...
18页
查看更多>>摘要：Abstract Even after complete stomatal closure, plants lose water through the leaf cuticles and bark. This residual water conductance of leaves (gleaf‐res) and stems (gbark) can negatively impact plant water balance and affect plant survival in seasonally dry environments. However, little is known about the costs and benefits associated with such water leaks, especially on stem level. Here, we characterized the structural and functional determinants of the variability in gbark across tropical savanna species to elucidate how variations in this trait are related to contrasting growth strategies. The high variability in gbark across species was associated with morphoantomical properties of the outer bark (thickness, density and lenticel investment), and such characteristics influenced both stem transpiration and respiration, suggesting the existence of a trade‐off between water conservation and oxygen permeability, which reflected contrasting growth and dehydration tolerance strategies. For instance, species with higher gbark and gleaf‐res presented a fast resource acquisition strategy but were more prone to drought‐induced mortality by hydraulic failure. However, model simulations revealed that the relative contribution of gleaf‐res and gbark to overall water balance depended on whether leaves were less or more resistant to cavitation than the stems. Synthesis. By combining correlative studies, experimental results and a modelling exercise, we provide a new understanding of the costs and benefits associated with the variability in gbark across tropical savanna species and a new perspective for studies of water relations and carbon economics in species from a hyperdiverse savanna.
查看更多>>摘要：Abstract Water is the most limiting resource for plant survival and growth in arid environments, but the diversity of water‐use strategies among coexisting species in dryland communities is not well understood. There is also growing interest in assessing whether a whole‐plant coordination exists between traits related to water‐use and the leaf economic spectrum (LES). We used water stable isotopes (δ2H, δ18O) to quantify water uptake proportions from different soil depths by 24 species in a Mediterranean shrubland. Leaf traits associated with water‐use efficiency, stomatal regulation (δ13C, δ18O) and the LES (SLA, N, P, K concentrations) were also measured. We assessed potential trade‐offs between the above‐mentioned leaf traits, water uptake depth and their relationship with species abundance. We found distinct ecohydrological niche segregation among coexisting species. Bayesian models showed that our shrubland species used a median of 37% of shallow soil water (0–30?cm) and 63% of deep water (30–100?cm). Still, water source proportions varied considerably among species, as shallow soil water‐use ranged from a minimum of 6.4% to a maximum of 68%. Interspecific variability in foliar carbon investment (SLA) and nutrient concentrations was remarkably high, indicating diverse nutrient‐use strategies along the LES. Leaf δ18O, δ13C and δ15N values also differed widely among species, revealing differences in stomatal regulation, water‐use efficiency and nitrogen acquisition mechanisms. After accounting for evolutionary history effects, water uptake depth was coordinated with the LES: species using shallower soil water from fertile topsoil layers exhibited a more acquisitive carbon‐ and nutrient‐use strategy, whereas water uptake from deeper but less fertile soil layers was linked to a more conservative nutrient‐use strategy. Leaf‐level water‐use traits significantly influenced species abundance, as water‐savers with tight stomatal regulation and high water‐use efficiency were dominant. Synthesis. Greater utilisation of water stored in nutrient‐rich topsoil layers favoured a more acquisitive nutrient‐use strategy, whereas a deeper water uptake pattern appeared to constrain access to nutrients. Our findings thus suggest a largely inescapable trade‐off and coordination between soil water uptake depth and carbon‐ and nutrient‐use strategies in low‐fertility drylands.
NSTL
Wiley