A trait-based approach to community assembly: partitioning of species trait values into within- and among-community components

Plant functional traits vary both along environmental gradients and among species occupying similar conditions, creating a challenge for the synthesis of functional and community ecology. We present a trait-based approach that provides an additive decomposition of species' trait values into alpha and beta components: beta values refer to a species' position along a gradient defined by community-level mean trait values; alpha values are the difference between a species' trait values and the mean of co-occurring taxa. In woody plant communities of coastal California, beta trait values for specific leaf area, leaf size, wood density and maximum height all covary strongly, reflecting species distributions across a gradient of soil moisture availability. Alpha values, on the other hand, are generally not significantly correlated, suggesting several independent axes of differentiation within communities. This trait-based framework provides a novel approach to integrate functional ecology and gradient analysis with community ecology and coexistence theory.     

Community Functional Responses to Soil and Climate at Multiple Spatial Scales: When Does Intraspecific Variation Matter?

Despite increasing evidence of the importance of intraspecific trait variation in plant communities, its role in community trait responses to environmental variation, particularly along broad-scale climatic gradients, is poorly understood. We analyzed functional trait variation among early-successional herbaceous plant communities (old fields) across a 1200-km latitudinal extent in eastern North America, focusing on four traits: vegetative height, leaf area, specific leaf area (SLA), and leaf dry matter content (LDMC). We determined the contributions of species turnover and intraspecific variation to between-site functional dissimilarity at multiple spatial scales and community trait responses to edaphic and climatic factors. Among-site variation in community mean trait values and community trait responses to the environment were generated by a combination of species turnover and intraspecific variation, with species turnover making a greater contribution for all traits. The relative importance of intraspecific variation decreased with increasing geographic and environmental distance between sites for SLA and leaf area. Intraspecific variation was most important for responses of vegetative height and responses to edaphic compared to climatic factors. Individual species displayed strong trait responses to environmental factors in many cases, but these responses were highly variable among species and did not usually scale up to the community level. These findings provide new insights into the role of intraspecific trait variation in plant communities and the factors controlling its relative importance. The contribution of intraspecific variation to community trait responses was greatest at fine spatial scales and along edaphic gradients, while species turnover dominated at broad spatial scales and along climatic gradients.     

Potential trajectories of old‐growth Neotropical forest functional composition under climate change

Quantifying relationships between plant functional traits and abiotic gradients is valuable for evaluating potential responses of forest communities to climate change. However, the trajectories of change expected to occur in tropical forest functional characteristics as a function of future climate variation are largely unknown. We modeled community level trait values of Costa Rican rain forests as a function of current and future climate, and quantified potential changes in functional composition. We calculated per‐plot community weighted mean (CWM) trait values for leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen (N) and phosphorus (P) content, and wood basic specific gravity (WSG), for tree and palm species in 127 0.25 ha plots. We modeled the response of CWM traits to current temperature and precipitation gradients using generalized additive modeling. We then predicted and mapped CWM traits values under current and future climate, and quantified potential changes under a global warming scenario (RCP8.5, year 2050). We calculated the area within the multi trait functional space occupied by forest plots under both current and future climate, and determined potential changes in functional space occupied by forest plots. Overall, precipitation predicted CWM traits better than temperature. Models indicated increases in CWM SLA, N and P, and a decrease in CWM LDMC under climate change. Lowland forest communities converged on a single direction of change towards more acquisitive CWM trait values, indicating a change in forest functional composition resulting from a changed climate. Functional space occupied by forest plots was reduced by 50% under the future climate. Functional composition changes may have further effects on forests ecosystem services. Assessing functional trait spatial‐gradients can help bridge the gap between species‐based biogeography and biogeochemical approaches to strengthen biodiversity and ecosystem services conservation efforts.     

Greater variation in boreal plant community composition and community-level traits at local- than regional-scale

Questions

Rapid climate change in northern latitudes is expected to influence plant functional traits of the whole community (community-level traits) through species compositional changes and/or trait plasticity, limiting our ability to anticipate climate warming impacts on northern plant communities. We explored differences in plant community composition and community-level traits within and among four boreal peatland sites and determined whether intra- or interspecific variation drives community-level traits.

Location

Boreal biome of western North America.

Methods

We collected plant community composition and functional trait data along dominant topoedaphic and/or hydrologic gradients at four peatland sites spanning the latitudinal extent of the boreal biome of western North America. We characterized variability in community composition and community-level traits of understorey vascular and moss species both within (local-scale) and among sites (regional-scale).

Results

Against expectations, community-level traits of vascular plant and moss species were generally consistent among sites. Furthermore, interspecific variation was more important in explaining community-level trait variation than intraspecific variation. Within-site variation in both community-level traits and community composition was greater than among-site variation, suggesting that local environmental gradients (canopy density, organic layer thickness, etc.) may be more influential in determining plant community processes than regional-scale gradients.

Conclusions

Given the importance of interspecific variation to within-site shifts in community-level traits and greater variation of community composition within than among sites, we conclude that climate-induced shifts in understorey community composition may not have a strong influence on community-level traits in boreal peatlands unless local-scale environmental gradients are substantially altered.     

Soil conditions drive changes in a key leaf functional trait through environmental filtering and facilitative interactions

Non-random patterns in the functional structure of communities are often interpreted as evidence for different forces governing their assemblage. However, community assembly processes may act antagonistically, countering each other's signatures on the functional structure of communities, which may lead to spurious inferences on the underlying mechanisms. To illustrate this issue, we assessed the joint effects of environmental filtering and facilitative interactions on a key leaf functional trait (i.e. specific leaf area, SLA) in Mediterranean dwarf-shrub communities, using a two-scale sampling approach. Specifically, we analyzed differences in community-weighted mean SLA values (CWM-SLA) between communities (community-scale) and between guilds within communities (guild-scale, i.e. individuals sampled in understorey, overstorey and open-ground conditions) across contrasted soil environments and elevational gradients. We found that communities on harsh edaphic conditions (i.e. dolomite habitats) showed significantly lower CWM-SLA values than communities on more fertile habitats. In contrast, elevation was a poor predictor of differences in CWM-SLA between the communities. This suggests that environmental filtering may influence leaf trait variation along soil gradients irrespective of elevation. On the other hand, communities on dolomite habitats showed strong differences in CWM-SLA between understorey (higher CWM-SLA) and either open-ground and overstorey guilds (lower CWM-SLA), whereas communities on more fertile soils showed no differences between the guilds. The strong differences in CWM-SLA between understorey and non-understorey guilds in dolomite communities suggest that facilitative interactions may be particularly at stake under stressful edaphic conditions, thus partially mitigating the effect of environmental filtering (i.e. low SLA values) on communities growing in harsh soils.     

Convergent succession of plant communities is linked to species’ functional traits

Functional traits reflecting the resource economy and growth strategy of plants vary widely both within and among ecosystems. Theory suggests that trait variation within a community may determine the relative abundance of species, though this idea requires more empirical support.We set up a long-term succession experiment in a nutrient-poor wetland, planting seedlings of twelve fenland species in different relative abundances and absolute densities, thereby creating 24 communities. The biomass of these species and the soil water and nutrient status of the system were monitored over ten years. Using these data, we could relate the changing relative abundance of species to five traits – leaf dry matter content (LDMC), leaf nitrogen concentration (LNC), specific leaf area (SLA), relative growth rate (RGR), and seed mass (SM).The initial communities converged after ten years to a common dominance–diversity structure, with two species accounting for 82% of total biomass. Soil water and nutrient conditions remained largely constant. By the end of the experiment, community trait structure had changed so that species functional traits were significantly related to their relative abundance. The most abundant species had high LDMC and SM, but low RGR and SLA, and varied little in LNC, suggesting that investment in leaf structure and retention of nutrients were most important for species dominance under low nutrient conditions. Our results provide experimental evidence that dominance–subdominance structures in plant communities are governed by functional traits.     

How soil and elevation shape local plant biodiversity in a Mediterranean hotspot

Elucidating how evolutionary and ecological factors drive the assemblage of communities in biodiversity hotspots remains an important challenge. This currently impedes our ability to predict the responses of communities to the ongoing global changes in these major world’s biodiversity reservoirs. Here, we focus on the Sierra Nevada mountain range, a core region of the Baetic-Rifan biodiversity hotspot in the western Mediterranean, and explore the relative importance of soil properties and elevation in shaping phylogenetic and functional diversity of shrub communities. We recorded the total number of each species in community transects across elevation gradients and contrasting soil conditions, and measured some ecologically relevant functional traits (specific leaf area, leaf carbon:nitrogen ratio, plant height and blooming duration). Phylogenetic distances among species were inferred from a genus-level time-calibrated molecular phylogeny. Elevation was the main factor predicting phylogenetic and functional alpha diversity of plant communities. Species in high-elevation communities were phylogenetically distant but functionally similar, being relatively smaller and having relatively short blooming durations, whilst species in low-elevation communities showed the opposite pattern. Beta diversity in SLA and leaf C:N ratio based on species incidences were positively correlated with a soil pH and micronutrient gradient. Specifically, communities that develop on soils of high pH and low micronutrient concentrations showed low SLA values and high leaf C:N ratios, whilst communities on soils of lower pH and high micronutrient concentrations showed the opposite pattern. We conclude that soil properties and elevation simultaneously shape the structure of Mediterranean shrub communities by differentially acting on the different dimensions of the species niches. Elevation seems to filter plant height and phenology-related traits whereas nutrient-related functional traits are more related to soil properties. Our study illustrates the primary role of environmental heterogeneity for the maintenance of diversity in Mediterranean mountain ecosystems.     

Variable effects on growth and defense traits for plant ecotypic differentiation and phenotypic plasticity along elevation gradients

Along ecological gradients, phenotypic differentiation can arise through natural selection on trait diversity and magnitude, and environment‐driven plastic changes. The magnitude of ecotypic differentiation versus phenotypic plasticity can vary depending on the traits under study. Using reciprocal transplant‐common gardens along steep elevation gradients, we evaluated patterns of ecotypic differentiation and phenotypic plasticity of several growth and defense‐related traits for two coexisting but unrelated plant species, Cardamine pratensis and Plantago major. For both species, we observed ecotypic differentiation accompanied by plasticity in growth‐related traits. Plants grew faster and produced more biomass when placed at low elevation. In contrast, we observed fixed ecotypic differentiation for defense and resistance traits. Generally, low‐elevation ecotypes produced higher chemical defenses regardless of the growing elevation. Yet, some plasticity was observed for specific compounds, such as indole glucosinolates. The results of this study may suggest that ecotypic differentiation in defense traits is maintained by costs of chemical defense production, while plasticity in growth traits is regulated by temperature‐driven growth response maximization.     

三峡库区消落带植物群落及其功能性状对水淹强度的响应

植物功能性状能表征其对资源的利用能力和对外界环境的响应,而水淹强度的不同使得三峡库区消落带不同高程的生境存在较大差异,因此开展不同水淹梯度下消落带植物群落生态策略及功能性状差异的研究,对全面理解植物对消落带不同生境的适应机理具有重要意义。研究选取受三峡水库水位变化影响的澎溪河流域,沿高程梯度对不同水淹强度下的植物群落及其功能性状指标进行分析。结果表明:(1)消落带植物群落处于演替的初级阶段,不同水淹梯度下的植物群落存在显著分化;(2)环境胁迫是决定消落带植物生态策略的主要因素,总体呈现较为集中的耐压策略,随着高程升高有逐渐向杂草策略转移的趋势;(3)随着高程升高,植物的高度、主茎干物质量、比根长及叶组织密度都有增大的趋势,比叶面积则相反。(4)各功能性状之间存在显著相关性,并通过形成不同的性状组合以适应不同强度水淹干扰的生境。消落带下部更倾向于投资于叶片使植物在出露期能快速获取资源和完成生活史,而消落带上部则更倾向于投资防御组织及根系以抵御干旱,研究结果可为消落带生物多样性保护及其生态系统修复提供理论依据。     

Within- and among-species variation in specific leaf area drive community assembly in a tropical cloud forest

Specific leaf area (SLA) is a key functional trait reflecting the trade-off between resource capture and conservation, and has been identified as playing an important role in plant community assembly. Mechanistic models of community assembly state that the assemblage of species in a local community is controlled by environment filters operating on functional traits. We measured within- and among-species variation of SLA, and environmental conditions in a tropical cloud forest to explore how variation in this functional trait contributes to community assembly. SLA variation at the species level was also decomposed into alpha (within assemblage variation), and beta (across assemblage variation) values. SLA decreased with increasing solar irradiance (approximated using plant height) within the three study sites, and differed among the three sites both for within- and among-species comparisons. Mean plot SLA, accounting for both within and among species across the three sites, increased significantly in relation to air temperature but not local photosynthetic photon flux density and soil total phosphorus. Alpha SLA decreased with increasing solar irradiance within the three sites and beta SLA differed among the three sites. Our results clearly demonstrate that light and air temperature are key environmental factors involved in organizing plant species within and among communities in tropical cloud forests. The strong relationship between both intra- and interspecific variation in SLA and environmental conditions strongly confirms the role of trait variation in the assembly of plant species in tropical cloud forest communities via environment filtering related to light availability and air temperature.     

Contrasting patterns of intraspecific trait variability in native and non-native plant species along an elevational gradient on Tenerife,Canary Islands

Background and AimsNon-native plant species are not restricted to lowlands, but increasingly are invading high elevations. While for both native and non-native species we expected variability of plant functional traits due to the changing environmental conditions along elevational gradients, we additionally assumed that non-native species are characterized by a more acquisitive growth strategy, as traits reflecting such a strategy have been found to correlate with invasion success. Furthermore, the typical lowland introduction of non-native species coming from multiple origins should lead to higher trait variability within populations of non-native species specifically at low elevations, and they might therefore occupy a larger total trait space.MethodsAlong an elevational gradient ranging from 55 to 1925 m a.s.l. on Tenerife, we collected leaves from eight replicate individuals in eight evenly distributed populations of five native and six non-native forb species. In each population, we measured ten eco-morphological and leaf biochemical traits and calculated trait variability within each population and the total trait space occupied by native and non-native species.Key ResultsWe found both positive (e.g. leaf dry matter content) and negative (e.g. leaf N) correlations with elevation for native species, but only few responses for non-native species. For non-native species, within-population variability of leaf dry matter content and specific leaf area decreased with elevation, but increased for native species. The total trait space occupied by all non-native species was smaller than and a subset of that of native species.ConclusionsWe found little evidence that intraspecific trait variability is associated with the success of non-native species to spread towards higher elevations. Instead, for non-native species, our results indicate that intermediate trait values that meet the requirements of various conditions are favourable across the changing environmental conditions along elevational gradients. As a consequence, this might prevent non-native species from overcoming abruptly changing environmental conditions, such as when crossing the treeline.     

Different trends in phylogenetic and functional structure of plant communities along an elevation gradient

The study of diversity gradients due to elevation dates back to the foundation of biogeography and ecology. Although elevation-driven patterns of plant diversity have been reported for centuries, uncertainty still exists about the assembly rules that drive these patterns. In this study, we revealed the causal factor of community assemblies for the diversity of tree and herb species along an elevation. To this end, we applied an integrated method using both functional traits and phylogeny, called the mean pairwise functional-phylogenetic distance, to understand the assembly rules for woody and herbaceous species communities along an elevation gradient. At higher elevation sites, woody and herbaceous communities were comprised of species having similar traits. The phylogenetic trends for woody species were consistent with the functional trends; closely related species co-occurred more frequently than expected at higher elevations. Phylogenetic trends for herb species were opposite to the functional trends; species with similar traits but having a random phylogenetic distribution co-occurred at higher elevations. We suggest that the community assembly rules for woody and herb species vary with elevation; and functional constraints due to environmental filtering at higher elevation act as assembly rules along gradients in both woody and herbaceous communities, even though their phylogenetic backgrounds differ.     

Leaf-trait responses to environmental gradients in moorland communities: contribution of intraspecific variation,species replacement and functional group replacement

The values of many important traits of plants in a community change along environmental gradients. Such changes may involve intraspecific variation and replacement by species that have different trait values. We hypothesized that they also involve the variation within and among functional groups (FGs) to the environmental dependence of trait values at the community level. We studied environmental dependence of trait values in 27 moorlands at various scales and analyzed to what extent intraspecific variation, species replacement within FGs and FG replacement contribute to the gradient of community trait values. The community structure in moorlands was influenced mainly by two environmental factors: temperature and water condition. Plants inhabiting sites with low temperature and low-pH generally tended to have lower maximum leaf height, greater leaf mass per area, and smaller leaf size. At the community level, site-mean of maximum leaf height and leaf size generally increased with increasing temperature and water pH. Our analysis demonstrated that the relative contributions of intraspecific variation, species replacement within FGs and FG replacement differed depending on combinations of the traits and environments. The contribution of FG replacement varied considerably among cases (0.6–34.5 %). Species replacement within FGs, which has received little attention in previous studies, was most responsible for the community-level changes (31.6–65.3 %) and intraspecific variation also made a large contribution (22.9–57.9 %). Understanding such various mechanisms involving intraspecific variation and species replacement should help us better predict how the structure and functioning of moorland plant communities will respond to climate change.     

Plant functional traits and community assembly along interacting gradients of productivity and fragmentation

Quantifying the association of plant functional traits to environmental gradients is a promising approach for understanding and projecting community responses to land use and climatic changes. Although habitat fragmentation and climate are expected to affect plant communities interactively, there is a lack of empirical studies addressing trait associations to fragmentation in different climatic regimes.In this study, we analyse data on the key functional traits: specific leaf area (SLA), plant height, seed mass and seed number. First, we assess the evidence for the community assembly mechanisms habitat filtering and competition at different spatial scales, using several null-models and a comprehensive set of community-level trait convergence and divergence indices. Second, we analyse the association of community-mean traits with patch area and connectivity along a south–north productivity gradient.We found clear evidence for trait convergence due to habitat filtering. In contrast, the evidence for trait divergence due to competition fundamentally depended on the null-model used. When the null-model controlled for habitat filtering, there was only evidence for trait divergence at the smallest sampling scale (0.25 m × 0.25 m). All traits varied significantly along the S–N productivity gradient. While plant height and SLA were consistently associated with fragmentation, the association of seed mass and seed number with fragmentation changed along the S–N gradient.Our findings indicate trait convergence due to drought stress in the arid sites and due to higher productivity in the mesic sites. The association of plant traits to fragmentation is likely driven by increased colonization ability in small and/or isolated patches (plant height, seed number) or increased persistence ability in isolated patches (seed mass).Our study provides the first empirical test of trait associations with fragmentation along a productivity gradient. We conclude that it is crucial to study the interactive effects of different ecological drivers on plant functional traits.     

Intraspecific trait variability shapes leaf trait response to altered fire regimes

Background and AimsUnderstanding impacts of altered disturbance regimes on community structure and function is a key goal for community ecology. Functional traits link species composition to ecosystem functioning. Changes in the distribution of functional traits at community scales in response to disturbance can be driven not only by shifts in species composition, but also by shifts in intraspecific trait values. Understanding the relative importance of these two processes has important implications for predicting community responses to altered disturbance regimes.MethodsWe experimentally manipulated fire return intervals in replicated blocks of a fire-adapted, longleaf pine (Pinus palustris) ecosystem in North Carolina, USA and measured specific leaf area (SLA), leaf dry matter content (LDMC) and compositional responses along a lowland to upland gradient over a 4 year period. Plots were burned between zero and four times. Using a trait-based approach, we simulate hypothetical scenarios which allow species presence, abundance or trait values to vary over time and compare these with observed traits to understand the relative contributions of each of these three processes to observed trait patterns at the study site. We addressed the following questions. (1) How do changes in the fire regime affect community composition, structure and community-level trait responses? (2) Are these effects consistent across a gradient of fire intensity? (3) What are the relative contributions of species turnover, changes in abundance and changes in intraspecific trait values to observed changes in community-weighted mean (CWM) traits in response to altered fire regime?Key ResultsWe found strong evidence that altered fire return interval impacted understorey plant communities. The number of fires a plot experienced significantly affected the magnitude of its compositional change and shifted the ecotone boundary separating shrub-dominated lowland areas from grass-dominated upland areas, with suppression sites (0 burns) experiencing an upland shift and annual burn sites a lowland shift. We found significant effects of burn regimes on the CWM of SLA, and that observed shifts in both SLA and LDMC were driven primarily by intraspecific changes in trait values.ConclusionsIn a fire-adapted ecosystem, increased fire frequency altered community composition and structure of the ecosystem through changes in the position of the shrub line. We also found that plant traits responded directionally to increased fire frequency, with SLA decreasing in response to fire frequency across the environmental gradient. For both SLA and LDMC, nearly all of the observed changes in CWM traits were driven by intraspecific variation.     

Trait variation and functional diversity maintenance of understory herbaceous species coexisting along an elevational gradient in Yulong Mountain,Southwest China

Characterizing trait variation across different ecological scales in plant communities has been viewed as a way to gain insights into the mechanisms driving species coexistence. However, little is known about how changes in intraspecific and interspecific traits across sites influence species richness and community assembly, especially in understory herbaceous communities. Here we partitioned the variance of four functional traits (maximum height, leaf thickness, leaf area and specific leaf area) across four nested biological scales: individual, species, plot, and elevation to quantify the scale-dependent distributions of understory herbaceous trait variance. We also integrated the comparison of the trait variance ratios to null models to investigate the effects of different ecological processes on community assembly and functional diversity along a 1200-m elevational gradient in Yulong Mountain. We found interspecific trait variation was the main trait variation component for leaf traits, although intraspecific trait variation ranged from 10% to 28% of total variation. In particular, maximum height exhibited high plasticity, and intraspecific variation accounted for 44% of the total variation. Despite the fact that species composition varied across elevation and species richness decreased dramatically along the elevational gradient, there was little variance at our largest (elevation) scale in leaf traits and functional diversity remained constant along the elevational gradient, indicating that traits responded to smaller scale influences. External filtering was only observed at high elevations. However, strong internal filtering was detected along the entire elevational gradient in understory herbaceous communities, possibly due to competition. Our results provide evidence that species coexistence in understory herbaceous communities might be structured by differential niche-assembled processes. This approach--integrating different biological scales of trait variation--may provide a better understanding of the mechanisms involved in the structure of communities.     

Plant Trait Variation along an Altitudinal Gradient in Mediterranean High Mountain Grasslands: Controlling the Species Turnover Effect

Assessing changes in plant functional traits along gradients is useful for understanding the assembly of communities and their response to global and local environmental drivers. However, these changes may reflect the effects of species composition (i.e. composition turnover), species abundance (i.e. species interaction), and intra-specific trait variability (i.e. species plasticity). In order to determine the relevance of the latter, trait variation can be assessed under minimal effects of composition turnover. Nine sampling sites were established along an altitudinal gradient in a Mediterranean high mountain grassland community with low composition turnover (Madrid, Spain; 1940 m–2419 m). Nine functional traits were also measured for ten individuals of around ten plant species at each site, for a total of eleven species across all sites. The relative importance of different sources of variability (within/between site and intra-/inter-specific functional diversity) and trait variation at species and community level along the considered gradients were explored. We found a weak individual species response to altitude and other environmental variables although in some cases, individuals were smaller and leaves were thicker at higher elevations. This lack of species response was most likely due to greater within- than between-site species variation. At the community level, inter-specific functional diversity was generally greater than the intra-specific component except for traits linked to leaf element content (leaf carbon content, leaf nitrogen content, δ¹³C and δ¹⁵N). Inter-specific functional diversity decreased with lower altitude for four leaf traits (specific leaf area, leaf dry matter content, δ¹³C and δ¹⁵N), suggesting trait convergence between species at lower elevations, where water shortage may have a stronger environmental filtering effect than colder temperatures at higher altitudes. Our results suggest that, within a vegetation type encompassing various environmental gradients, both, changes in species abundance and intra-specific trait variability adjust for the community functional response to environmental changes.     

东灵山地区不同森林群落叶功能性状比较

植物功能性状(plant functional trait)是近年来生态学研究的热点.其中叶功能性状(leaf functional trait)与植株生物量和植物对资源的获得、利用及利用效率的关系最为密切.研究了东灵山地区叶功能性状之间的关系、叶功能性状与地形因子的关系,并对不同群落叶功能性状进行了比较.通过Pearson相关分析发现,叶干物质含量(LDMC)与比叶面积(SLA)、叶氮浓度(LNC)、叶磷浓度(LPC)、叶钾浓度(LKC)负相关;叶大小与叶厚度正相关;SLA与 LNC、LPC、LKC正相关;LNC与LPC、LKC正相关;LPC与LKC正相关.通过灰色关联度分析发现,对叶大小、LNC、LKC来讲,海拔是各项地形因子中的首要影响因子;对LDMC、叶厚度来讲,坡度对其影响最大;对SLA、LPC来讲,坡位是其首要影响因子.依据乔木层的SLA和LDMC将5种群落分成3类,第一类是黑桦林和山杨林,第二类是辽东栎林,第三类是胡桃楸林和糠椴林.群落的分类情况符合该地带性植被优势度类型的分类情况,LDMC和SLA是最能体现群落间差异的叶功能性状.     

PLANT RESPONSES TO CLIMATE IN THE CAPE FLORISTIC REGION OF SOUTH AFRICA: EVIDENCE FOR ADAPTIVE DIFFERENTIATION IN THE PROTEACEAE

Local adaptation along environmental gradients may drive plant species radiation within the Cape Floristic Region (CFR), yet few studies examine the role of ecologically based divergent selection within CFR clades. In this study, we ask whether populations within the monophyletic white protea clade (Protea section Exsertae, Proteaceae) differ in key functional traits along environmental gradients and whether differences are consistent with local adaptation. Using seven taxa, we measured trait–environment associations and selection gradients across 35 populations of wild adults and their offspring grown in two common gardens. Focal traits were leaf size and shape, specific leaf area (SLA), stomatal density, growth, and photosynthetic rate. Analyses on wild and common garden plants revealed heritable trait differences that were associated with gradients in rainfall seasonality, drought stress, cold stress, and less frequently, soil fertility. Divergent selection between gardens generally matched trait–environment correlations and literature‐based predictions, yet variation in selection regimes among wild populations generally did not. Thus, selection via seedling survival may promote gradient‐wide differences in SLA and leaf area more than does selection via adult fecundity. By focusing on the traits, life stages, and environmental clines that drive divergent selection, our study uniquely demonstrates adaptive differentiation among plant populations in the CFR.