Functional richness outperforms taxonomic richness in predicting ecosystem functioning in natural phytoplankton communities

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Functional structure of biological communities predicts ecosystem multifunctionality

The accelerating rate of change in biodiversity patterns, mediated by ever increasing human pressures and global warming, demands a better understanding of the relationship between the structure of biological communities and ecosystem functioning (BEF). Recent investigations suggest that the functional structure of communities, i.e. the composition and diversity of functional traits, is the main driver of ecological processes. However, the predictive power of BEF research is still low, the integration of all components of functional community structure as predictors is still lacking, and the multifunctionality of ecosystems (i.e. rates of multiple processes) must be considered. Here, using a multiple-processes framework from grassland biodiversity experiments, we show that functional identity of species and functional divergence among species, rather than species diversity per se, together promote the level of ecosystem multifunctionality with a predictive power of 80%. Our results suggest that primary productivity and decomposition rates, two key ecosystem processes upon which the global carbon cycle depends, are primarily sustained by specialist species, i.e. those that hold specialized combinations of traits and perform particular functions. Contrary to studies focusing on single ecosystem functions and considering species richness as the sole measure of biodiversity, we found a linear and non-saturating effect of the functional structure of communities on ecosystem multifunctionality. Thus, sustaining multiple ecological processes would require focusing on trait dominance and on the degree of community specialization, even in species-rich assemblages.     

青藏高原高寒草地生物多样性与生态系统功能的关系

生物多样性和生态系统功能(BEF)之间的关系是目前陆地生态系统生态学研究的热点, 对于生态系统的高效利用与管理意义重大, 而且对于退化生态系统功能的恢复及生物多样性的保护有重要的指导作用。高寒草地是青藏高原生态系统的主体, 近年来, 在气候变化与人为干扰等因素的驱动下, 高寒草地生态系统功能严重衰退。为此, 本文在综述物种多样性和生态系统功能及其相互关系研究进展的基础上, 首先从地下生态学过程研究、全球变化对生态系统多功能性的影响等方面解析了目前关于草地生物多样性和生态系统功能研究中存在的问题。继而, 从不同草地类型、草地退化程度、放牧、模拟气候变化、刈割、施肥、封育和补播等干扰利用方式对高寒草地物种多样性与生态系统功能的影响进行了全面的评述。并指出了高寒草地BEF研究中存在的不足, 今后应基于物种功能多样性开展高寒草地BEF研究, 全面且综合地考虑非生物因子(养分资源、外界干扰、环境波动等)对生物多样性与生态系统功能之间关系的影响, 关注尺度效应和要素耦合在全球气候变化对高寒草地BEF研究中的作用。最后, 以高寒草地BEF研究进展和结论为支撑依据, 综合提出了高寒草地资源利用和生物多样性保护的措施与建议: 加强放牧管理, 保护生物多样性; 治理退化草地, 维持生物多样性功能; 加强创新保护理念, 增强生态系统功能。     

Functional diversity is positively associated with biomass for lake diatoms

1. Recent work has emphasised the benefit of using functional measures when relating biodiversity to ecosystem functioning. In this study, we investigated the extent to which functional and taxonomic diversity might be related to summed biovolume in community assemblages of 212 species of diatoms collected from 65 temperate lakes in western and central Quebec, Canada. 2. We quantified functional diversity as both the total path‐length of a functional dendrogram (FD) and the variance in species traits (TV) for a given community. Selected traits included both size and responses to a set of environmental variables known to be influential for diatom communities. 3. Species richness, as well as both FD and TV, was positively associated with total diatom biovolume at the level of the entire diatom community, suggesting that diversity in response types (particularly to total phosphorus and pH) is important for diatom community production. 4. Although functional measures of diversity did not provide enhanced explanatory power over species richness, we argue that an exploration of functional traits potentially allows greater insight into the mechanisms underlying biodiversity–ecosystem functioning relations, indicating which traits might be most influential in driving community biomass production.     

Trophic complementarity drives the biodiversity–ecosystem functioning relationship in food webs

The biodiversity–ecosystem functioning (BEF) relationship is central in community ecology. Its drivers in competitive systems (sampling effect and functional complementarity) are intuitive and elegant, but we lack an integrative understanding of these drivers in complex ecosystems. Because networks encompass two key components of the BEF relationship (species richness and biomass flow), they provide a key to identify these drivers, assuming that we have a meaningful measure of functional complementarity. In a network, diversity can be defined by species richness, the number of trophic levels, but perhaps more importantly, the diversity of interactions. In this paper, we define the concept of trophic complementarity (TC), which emerges through exploitative and apparent competition processes, and study its contribution to ecosystem functioning. Using a model of trophic community dynamics, we show that TC predicts various measures of ecosystem functioning, and generate a range of testable predictions. We find that, in addition to the number of species, the structure of their interactions needs to be accounted for to predict ecosystem productivity.     

生态学的多样性指数:功能与系统发育

生物多样性是生态学的核心问题。传统的多样性指数仅包含物种数和相对多度的信息,这类基于分类学的多样性指数并不能很好地帮助理解群落构建和生态系统功能。不同物种对群落构建和生态系统功能所起到的作用类型和贡献也不完全相同,且物种在生态过程中的作用和贡献往往与性状密切相关,因此功能多样性已经成为反映物种群落构建、干扰以及环境因素对群落影响的重要指标。同时,由于亲缘关系相近的物种往往具有相似的性状,系统发育多样性也可以作为功能多样性的一个替代。功能多样性和系统发育多样性各自具有优缺点,但二者均比分类多样性更能揭示群落和生态系统的构建、维持与功能。     

Traits of dominant plant species drive normalized difference vegetation index in grasslands globally

Aim

Theoretical, experimental and observational studies have shown that biodiversity–ecosystem functioning (BEF) relationships are influenced by functional community structure through two mutually non-exclusive mechanisms: (1) the dominance effect (which relates to the traits of the dominant species); and (2) the niche partitioning effect [which relates to functional diversity (FD)]. Although both mechanisms have been studied in plant communities and experiments at small spatial extents, it remains unclear whether evidence from small-extent case studies translates into a generalizable macroecological pattern. Here, we evaluate dominance and niche partitioning effects simultaneously in grassland systems world-wide.

Location

Two thousand nine hundred and forty-one grassland plots globally.

Time period

2000–2014.

Major taxa studied

Vascular plants.

Methods

We obtained plot-based data on functional community structure from the global vegetation plot database “sPlot”, which combines species composition with plant trait data from the “TRY” database. We used data on the community-weighted mean (CWM) and FD for 18 ecologically relevant plant traits. As an indicator of primary productivity, we extracted the satellite-derived normalized difference vegetation index (NDVI) from MODIS. Using generalized additive models and deviation partitioning, we estimated the contributions of trait CWM and FD to the variation in annual maximum NDVI, while controlling for climatic variables and spatial structure.

Results

Grassland communities dominated by relatively tall species with acquisitive traits had higher NDVI values, suggesting the prevalence of dominance effects for BEF relationships. We found no support for niche partitioning for the functional traits analysed, because NDVI remained unaffected by FD. Most of the predictive power of traits was shared by climatic predictors and spatial coordinates. This highlights the importance of community assembly processes for BEF relationships in natural communities.

Main conclusions

Our analysis provides empirical evidence that plant functional community structure and global patterns in primary productivity are linked through the resource economics and size traits of the dominant species. This is an important test of the hypotheses underlying BEF relationships at the global scale.     

Resilience and stability of a pelagic marine ecosystem

The accelerating loss of biodiversity and ecosystem services worldwide has accentuated a long-standing debate on the role of diversity in stabilizing ecological communities and has given rise to a field of research on biodiversity and ecosystem functioning (BEF). Although broad consensus has been reached regarding the positive BEF relationship, a number of important challenges remain unanswered. These primarily concern the underlying mechanisms by which diversity increases resilience and community stability, particularly the relative importance of statistical averaging and functional complementarity. Our understanding of these mechanisms relies heavily on theoretical and experimental studies, yet the degree to which theory adequately explains the dynamics and stability of natural ecosystems is largely unknown, especially in marine ecosystems. Using modelling and a unique 60-year dataset covering multiple trophic levels, we show that the pronounced multi-decadal variability of the Southern California Current System (SCCS) does not represent fundamental changes in ecosystem functioning, but a linear response to key environmental drivers channelled through bottom-up and physical control. Furthermore, we show strong temporal asynchrony between key species or functional groups within multiple trophic levels caused by opposite responses to these drivers. We argue that functional complementarity is the primary mechanism reducing community variability and promoting resilience and stability in the SCCS.     

Functional traits composition predict macrophytes community productivity along a water depth gradient in a freshwater lake

Functional trait composition of plant communities has been proposed as a helpful key for understanding the mechanisms of biodiversity effects on ecosystem functioning. In this study, we applied a step‐wise modeling procedure to test the relative effects of taxonomic diversity, functional identity, and functional diversity on macrophytes community productivity along water depth gradient. We sampled 42 plots and 1513 individual plants and measured 16 functional traits and abundance of 17 macrophyte species. Results showed that there was a significant decrease in taxonomic diversity, functional identity (i.e., stem dry mass content, leaf [C] and leaf [N]), and functional diversity (i.e., floating leaf, mean Julian flowering date and rooting depth) with increasing water depth. For the multiple‐trait functional diversity (FD) indices, functional richness decreased, while functional divergence increased with water depth gradient. Macrophyte community productivity was strongly determined by functional trait composition within community, but not significantly affected by taxonomic diversity. Community‐weighted means (CWM) showed a two times higher explanatory power relative to FD indices in determining variations in community productivity. For nine of sixteen traits, CWM and FD showed significant correlations with community productivity, although the strength and direction of those relations depended on selected trait. Furthermore, functional composition in a community affected productivity through either additive or opposite effects of CWM and FD, depending on the particular traits being considered. Our results suggested both mechanisms of mass ratio and niche complementarity can operate simultaneously on variations in community productivity, and considering both CWM and FD would lead to a more profound understanding of traits–productivity relationships.     

Environmental conditions influence the plant functional diversity effect on potential denitrification

Global biodiversity loss has prompted research on the relationship between species diversity and ecosystem functioning. Few studies have examined how plant diversity impacts belowground processes; even fewer have examined how varying resource levels can influence the effect of plant diversity on microbial activity. In a field experiment in a restored wetland, we examined the role of plant trait diversity (or functional diversity, (FD)) and its interactions with natural levels of variability of soil properties, on a microbial process, denitrification potential (DNP). We demonstrated that FD significantly affected microbial DNP through its interactions with soil conditions; increasing FD led to increased DNP but mainly at higher levels of soil resources. Our results suggest that the effect of species diversity on ecosystem functioning may depend on environmental factors such as resource availability. Future biodiversity experiments should examine how natural levels of environmental variability impact the importance of biodiversity to ecosystem functioning.     

微生物性状揭示物种分布格局、群落构建机制和生态系统功能

微生物性状是指与其存活、生长和繁殖紧密相关的一系列核心属性,这些属性能够反映微生物对环境变化的响应,进而影响微生物的物种分布格局、群落构建机制以及相应的生态系统功能。越来越多的研究表明,相比于微生物分类学信息,微生物性状可以在种群、群落和生态系统尺度等视角扩展我们对微生物生态过程的理解,并提供生态模式的机理性解释。本文回顾微生物性状研究的发展历程,总结近年来基于微生物性状研究的前沿科学问题,比如微生物性状的分类和测定方法、基于性状的功能多样性定义及应用、性状与物种分布格局和群落构建机制的关系、性状对生物多样性和生态系统功能的影响以及对环境变化的响应等。尽管微生物性状研究已经延伸到生态学领域的各个方面,有力推动着各个前沿科学问题的研究发展,但是仍然面临很多机遇与挑战。因此,本文也从研究方法和研究方向等方面对未来基于微生物性状的研究提出了展望。     

绿弯菌的研究现状及展望

绿弯菌是一个深度分支的门级别细菌类群,广泛分布于生物圈各种生境。现已生效发表的绿弯菌构成9个纲,但仅包含56个种;基于分子生态学的研究结果表明尚有大量绿弯菌类群仍是未培养状态。绿弯菌形态多样,营养方式和代谢途径十分丰富,参与了C、N、S等一系列重要生源元素的生物地球化学循环过程。研究该类群不仅有助于认识环境中微生物的多样性及其代谢特征,从而更好的理解微生物参与的生态学过程,还有助于揭示微生物对环境的适应及其进化。本文主要综述了绿弯菌的发现历史、营养、代谢及其在元素循环中的作用,并总结了其分离培养和潜在应用价值,最后展望了未来的研究方向,旨在为深入探究绿弯菌的进化、培养和驱动地球化学元素循环等研究提供参考。     

Functional diversity changes during tropical forest succession

Functional diversity (FD) ‘those components of biodiversity that influence how an ecosystem operates or functions’ is a promising tool to assess the effect of biodiversity loss on ecosystem functioning. FD has received ample theoretical attention, but empirical studies are limited. We evaluate changes in species richness and FD during tropical secondary forest succession after shifting cultivation in Mexico. We also test whether species richness is a good predictor of FD. FD was calculated based on a combination of nine functional traits, and based on two individual traits important for primary production (specific leaf area) and carbon sequestration (wood density). Stand basal area was a good predictor of successional changes in diversity and FD, in contrast to fallow age. Incidence-based FD indices increased logarithmically with stand basal area, but FD weighted by species’ importance values lacked pattern with succession. Species richness and diversity are strong predictors of FD when all traits were considered; linear relationships indicate that all species are equally functionally complementary, suggesting there is little functional redundancy. In contrast, when FD was calculated for individual traits and weighted for abundances, species richness may underestimate FD.Selection of functional trait(s) critically determines FD, with large consequences for studies relating biodiversity to ecosystem functioning. Careful consideration of the traits required to capture the ecosystem process of interest is thus essential.     

植物群落功能多样性计算方法

以性状为基础的功能多样性指数在预测生态系统功能中起到越来越重要的作用.本文对近年来陆续出现的植物群落功能多样性指数进行综述.依据物种多样性指数的组成,功能多样性指数分为功能丰富度、功能均匀度和功能离散度指数.介绍了这3类指数的计算方法,有助于更好、更准确地理解“生物多样性-环境-生态系统功能”的关系.     

亚热带森林生物多样性与生态系统功能实验研究基地(BEF-China)研究进展

生物多样性与生态系统功能的关系(BEF)及其内在机制是当前生物多样性研究领域的热点问题。长期以来,以草地生态系统为主的BEF研究积累了大量研究成果,而基于森林生态系统的相关研究则相对较少。亚热带森林生物多样性与生态系统功能实验研究基地(BEF-China)是目前包含树种最多、涉及多样性水平最高的大型森林控制实验样地。该文总结了基于BEF-China平台的研究进展,特别是生物多样性对生态系统生产力、养分循环以及多营养级相互作用关系等方面的影响,并提出了未来BEF-China的研究应注重高通量测序和遥感等新兴技术的应用,在生物多样性的多维度、生态系统的多种组分与多种功能以及BEF研究的多种尺度等交叉方向上持续开展深入研究。针对BEF-China研究成果的梳理有助于理解驱动亚热带森林生物多样性与生态系统功能关系的内在机理,为生物多样性保护和生态修复提供科学依据。     

On the importance of the negative selection effect for the relationship between biodiversity and ecosystem functioning

Much of our knowledge on biodiversity and ecosystem functioning comes from studies examining the effects of biodiversity on biomass production within a trophic group. A large number of these studies have found that increasing biodiversity tends to increase biomass production, leading many ecologists to believe that there exists a general positive relationship between biodiversity and ecosystem functioning. Here we argue that such a positive relationship may not be general, particularly for ecosystem functions other than biomass. Our argument centers on the potential importance of the negative selection effect, which operates where competitively dominant species do not contribute significantly to the function of interest. We suggest that negative selection effects may be potentially common for non-biomass functions, for which species competitive ability may often be a poor indictor of its functional impact. We conclude that diverse (positive, negative, and neutral) BEF relationships are possible for non-biomass functions and that for a particular function, the exact form of the BEF relationship may depend on how species functional impacts relate to their competitive abilities in the community.     

Field observed relationships between biodiversity and ecosystem functioning during secondary succession in a tropical lowland rainforest

The relationship between biodiversity and ecosystem functioning (BEF) is one of the most concerned topics in ecology. However, most of the studies have been conducted in controlled experiments in grasslands, few observational field studies have been carried out in forests. In this paper, we report variations of species diversity, functional diversity and aboveground biomass (AGB) for woody plants (trees and shrubs) along a chronosequence of four successional stages (18-year-old fallow, 30-year-old fallow, 60-year-old fallow, and old-growth forest) in a tropical lowland rainforest recovered after shifting cultivation on Hainan Island, China. Fifty randomly selected sample plots of 20 m × 20 m were investigated in each of the four successional stages. Four functional traits (specific leaf area, wood density, maximum species height and leaf dry matter content) were measured for each woody plants species and the relationships between species/functional diversity and AGB during secondary succession were explored. The results showed that both plant diversity and AGB recovered gradually with the secondary succession. AGB was positively correlated with both species and functional diversity in each stage of succession. Consistent with many controlled experimental results in grasslands, our observational field study confirms that ecosystem functioning is closely related to biodiversity during secondary succession in species rich tropical forests.     

荒漠植物性状权衡策略及功能多样性研究进展

荒漠植物是干旱区具有独特功能性状与资源权衡表征的地带性植物。植物功能性状及其多样性格局与资源权衡策略对群落结构优化和生态系统功能改善起着关键作用。该综述主要从荒漠植物组织、器官功能性状特征、功能性状权衡策略、功能多样性组分及测度3个方面梳理了荒漠植物性状权衡策略与功能多样性研究的进展脉络：1）荒漠植物独特的根、茎、叶功能性状特征揭露了植被对环境变化的响应以及对生态系统功能的影响,基于植物功能性状的研究有助于解决许多生态学的关键性问题;2）作为植物功能性状之间存在的最普遍的联系,权衡策略是经过自然筛选后形成的性状组合,关键性状已经被发掘并创造性的提出了"经济谱"概念。荒漠植物研究过程中,应分析其根、茎、叶的特征属性筛选关键性状,着眼于关键性状间及整株植物性状间的权衡策略;3）功能多样性是影响生态系统运行和发挥作用的生物多样性的重要组成部分,荒漠植物功能多样性能预测和指示群落中物种对于荒漠生态系统功能发挥和过程变化的影响。功能多样性的组分可以从不同角度反映群落的生态位占据状况和资源利用程度,指数的选择要体现在群落内部物种的功能特征之间的差异程度,同时要考虑这些物种自身在群落内的优势程度。本研究为未来荒漠植物功能性状及多样性研究梳理了一些新的研究方向和内容,期望为荒漠植物生理生态学研究的选题和发展提供一些新的思路。     

Functional diversity (FD), species richness and community composition

Functional diversity is an important component of biodiversity, yet in comparison to taxonomic diversity, methods of quantifying functional diversity are less well developed. Here, we propose a means for quantifying functional diversity that may be particularly useful for determining how functional diversity is related to ecosystem functioning. This measure of functional diversity “FD” is defined as the total branch length of a functional dendrogram. Various characteristics of FD make it preferable to other measures of functional diversity, such as the number of functional groups in a community. Simulating species' trait values illustrates how the relative importance of richness and composition for FD depends on the effective dimensionality of the trait space in which species separate. Fewer dimensions increase the importance of community composition and functional redundancy. More dimensions increase the importance of species richness and decreases functional redundancy. Clumping of species in trait space increases the relative importance of community composition. Five natural communities show remarkably similar relationships between FD and species richness.     

Advancing biodiversity–ecosystem functioning science using high-density tree-based experiments over functional diversity gradients

Increasing concern about loss of biodiversity and its effects on ecosystem functioning has triggered a series of manipulative experiments worldwide, which have demonstrated a general trend for ecosystem functioning to increase with diversity. General mechanisms proposed to explain diversity effects include complementary resource use and invoke a key role for species’ functional traits. The actual mechanisms by which complementary resource use occurs remain, however, poorly understood, as well as whether they apply to tree-dominated ecosystems. Here we present an experimental approach offering multiple innovative aspects to the field of biodiversity–ecosystem functioning (BEF) research. The International Diversity Experiment Network with Trees (IDENT) allows research to be conducted at several hierarchical levels within individuals, neighborhoods, and communities. The network investigates questions related to intraspecific trait variation, complementarity, and environmental stress. The goal of IDENT is to identify some of the mechanisms through which individuals and species interact to promote coexistence and the complementary use of resources. IDENT includes several implemented and planned sites in North America and Europe, and uses a replicated design of high-density tree plots of fixed species-richness levels varying in functional diversity (FD). The design reduces the space and time needed for trees to interact allowing a thorough set of mixtures varying over different diversity gradients (specific, functional, phylogenetic) and environmental conditions (e.g., water stress) to be tested in the field. The intention of this paper is to share the experience in designing FD-focused BEF experiments with trees, to favor collaborations and expand the network to different conditions.