Plant functional trait response to environmental drivers across European temperate forest understorey communities

• Functional traits respond to environmental drivers, hence evaluating trait‐environment relationships across spatial environmental gradients can help to understand how multiple drivers influence plant communities. Global‐change drivers such as changes in atmospheric nitrogen deposition occur worldwide, but affect community trait distributions at the local scale, where resources (e.g. light availability) and conditions (e.g. soil pH) also influence plant communities.
• We investigate how multiple environmental drivers affect community trait responses related to resource acquisition (plant height, specific leaf area (SLA), woodiness, and mycorrhizal status) and regeneration (seed mass, lateral spread) of European temperate deciduous forest understoreys. We sampled understorey communities and derived trait responses across spatial gradients of global‐change drivers (temperature, precipitation, nitrogen deposition, and past land use), while integrating in‐situ plot measurements on resources and conditions (soil type, Olsen phosphorus (P), Ellenberg soil moisture, light, litter mass, and litter quality).
• Among the global‐change drivers, mean annual temperature strongly influenced traits related to resource acquisition. Higher temperatures were associated with taller understoreys producing leaves with lower SLA, and a higher proportional cover of woody and obligate mycorrhizal (OM) species. Communities in plots with higher Ellenberg soil moisture content had smaller seeds and lower proportional cover of woody and OM species. Finally, plots with thicker litter layers hosted taller understoreys with larger seeds and a higher proportional cover of OM species.
• Our findings suggest potential community shifts in temperate forest understoreys with global warming, and highlight the importance of local resources and conditions as well as global‐change drivers for community trait variation.

     

格氏栲天然林林窗植物群落功能性状的变异

林窗是森林更新演替的重要环节, 揭示林窗环境下功能性状变异来源及其相对贡献, 有助于阐明植物对林窗环境的响应。该研究以中亚热带格氏栲(Castanopsis kawakamii)天然林为对象, 设置9个不同大小的林窗样地, 运用方差分解探讨林窗、物种和个体对叶性状变异的相对贡献, 采用线性回归分析不同大小林窗下群落性状变化及种间和种内性状变异的重要性。研究发现: (1)格氏栲天然林林窗植物比叶面积、叶干物质含量、叶厚和叶绿素含量由种间性状变异主导, 叶氮含量由种内性状变异主导, 叶磷含量受林窗大小影响最大。(2)群落叶磷含量与林窗大小具有显著正相关关系, 土壤温度和水解氮含量对群落叶磷含量具有显著正效应, 土壤有效磷含量具有显著负效应。(3)沿林冠开放度的群落叶磷含量变化主要由种内性状变异引起, 优势种扮演着重要角色。结果表明, 格氏栲天然林林窗环境下植物功能性状仍以种间性状变异为主(平均41%), 但沿林窗环境梯度的群落性状变化主要源自种内性状变异, 通过植物表型可塑性响应环境改变, 优势种作用明显。     

A global meta‐analysis of the relative extent of intraspecific trait variation in plant communities

Recent studies have shown that accounting for intraspecific trait variation (ITV) may better address major questions in community ecology. However, a general picture of the relative extent of ITV compared to interspecific trait variation in plant communities is still missing. Here, we conducted a meta‐analysis of the relative extent of ITV within and among plant communities worldwide, using a data set encompassing 629 communities (plots) and 36 functional traits. Overall, ITV accounted for 25% of the total trait variation within communities and 32% of the total trait variation among communities on average. The relative extent of ITV tended to be greater for whole‐plant (e.g. plant height) vs. organ‐level traits and for leaf chemical (e.g. leaf N and P concentration) vs. leaf morphological (e.g. leaf area and thickness) traits. The relative amount of ITV decreased with increasing species richness and spatial extent, but did not vary with plant growth form or climate. These results highlight global patterns in the relative importance of ITV in plant communities, providing practical guidelines for when researchers should include ITV in trait‐based community and ecosystem studies.     

Effect of forest fragmentation on the woody flora of the highlands of Chiapas, Mexico

This study was conducted in the Chiapas Highlands, a tropical mountain region where traditional agricultural practices have resulted in a mosaic landscape of forest fragments embedded in a matrix of secondary vegetation and crop fields. The question addressed was how may woody species richness be affected by forest fragment attributes derived from traditional land-use patterns. Species inventories of total woody species, canopy and understorey trees, and shrubs were obtained in 22 forest fragments (5 ha). Multiple regression analyses were applied to examine the effects of size, matrix, isolation and shape of the forest fragments on richness of these species guilds. Fragment size was correlated with shape (r = 0.75) and isolation (r = –0.69), and isolation was correlated with shape (r = –0.75). Total species richness, and number of shrubs and understorey trees in fragments were related to isolation; moreover, additive effects of fragment shape were found for shrubs. The number of canopy species was not related to any fragment variable. Matrix did not help to explain species richness, possibly due to the landscape structure created by the traditional land-use patterns. In addition to size and isolation, we point out the need of considering shape and matrix as additional fragmentation attributes, along with social and economic factors, if we are ever going to be successful in our management and conservation actions.     

Landscape variation of liana communities in a Neotropical rain forest

We studied local and landscape variation of liana communities across habitats differing in soil and topography in the Lacandon tropical rain forest, southeast Mexico. All liana stems 1 cm diameter breast height (DBH) were sampled within each one of eight 0.5 ha plots. Two plots were sampled in each of the following habitats: alluvial-terrace, flood plain, low-hill, and karst-range. In the whole sampled area, we recorded 2092 liana stems ha^–1 representing a total basal area of 1.95 m² ha^–1 and 90 species within 34 families. Lianas showed a strong clumped spatial pattern and a high taxonomic diversity at the scale of 50 m². On average (± s.e.), we found 10.4±0.6 stems, 4.4±0.2 species and 3.4±0.2 families per 50-m² quadrat. Bignonaceae (19 species), Malpighiaceae (9), and Fabaceae (8) comprised about 40% of total number of recorded species, and almost 50% of the total liana biomass, as expressed by an importance value index that combines species relative abundance, spatial frequency and basal area. Nineteen families (56%) were represented by just one species and Cydista (Bignoniaceae) and Machaerium (Fabaceae) were the most diverse genera with four species each. In the landscape, lianas showed a geometric diversity-dominance relationship with only three species (Combretum argenteum, Hiraea fagifolia and Machaerium floribundum) accounting for more than 50% of total biomass. More than 30% of the species were rare (<15 stems ha^–1) and showed low spatial frequency (recorded in just one of the eight plots). Liana communities differed in structure and composition among sites and habitats. Among sites, lianas exhibited four-fold variation both in stem density and basal area and two-fold variation in species richness. Liana density was significantly and positively correlated with treefall disturbance. Ordination analysis indicated a strong habitat differentiation of lianas at the family and species levels. Most species with non-random distribution among habitats (69% from 25 species) were significantly most abundant in low-hill or flood plain sites, and some (12%) were preferentially found at the karst-range sites. The karst-range habitat was well differentiated from the others in species composition and structure, and shared only 50% of common species with other habitats.Soil water availability, treefall dynamics, as well as tree host identity and abundance may play an important role in the organisation of the liana communities at the Lacandon forest.