Hierarchical effects of environmental filters on the functional structure of plant communities: a case study in the French Alps
TL;DR: This paper tested the relative infl uence of multiple environmental factors on various metrics of plant functional trait structure and components of functional trait diversity in 82 vegetation plots in the Guisane Valley, French Alps to suggest that predicting plant community responses will require a hierarchical multi-facet approach.
Abstract: Understanding the inf l uence of the environment on the functional structure of ecological communities is essential to predict the response of biodiversity to global change drivers. Ecological theory suggests that multiple environmental factors shape local species assemblages by progressively fi ltering species from the regional species pool to local communities. ! ese successive fi lters should infl uence the various components of community functional structure in di" erent ways. In this paper, we tested the relative infl uence of multiple environmental fi lters on various metrics of plant functional trait structure (i.e. ‘ community weighted mean trait ’ and components of functional trait diversity, i.e. functional richness, evenness and divergence) in 82 vegetation plots in the Guisane Valley, French Alps. For the 211 sampled species we measured traits known to capture key aspects of ecological strategies amongst vascular plant species, i.e. leaf traits, plant height and seed mass (LHS). A comprehensive information theory framework, together with null model based resampling techniques, was used to test the various environmental e" ects. Particular community components of functional structure responded di" erently to various environmental gradients, especially concerning the spatial scale at which the environmental factors seem to operate. Environmental factors acting at a large spatial scale (e.g. temperature) were found to predominantly shape community weighted mean trait values, while fi ne-scale factors (topography and soil characteristics) mostly infl uenced functional diversity and the distribution of trait values among the dominant species. Our results emphasize the hierarchical nature of ecological forces shaping local species assemblage: large-scale environmental fi lters having a primary e" ect, i.e. selecting the pool of species adapted to a site, and then fi lters at fi scales determining species abundances and local species coexistence. ! is suggests that di" erent components of functional community structure will respond di" erently to environmental change, so that predicting plant community responses will require a hierarchical multi-facet approach.
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TL;DR: It is shown that both traits and phylogeny inform community assembly patterns in alpine plant communities across an elevation gradient, because they represent complementary information.
Abstract: Species enter and persist in local communities because of their ecological fit to local conditions, and recently, ecologists have moved from measuring diversity as species richness and evenness, to using measures that reflect species ecological differences. There are two principal approaches for quantifying species ecological differences: functional (trait-based) and phylogenetic pairwise distances between species. Both approaches have produced new ecological insights, yet at the same time methodological issues and assumptions limit them. Traits and phylogeny may provide different, and perhaps complementary, information about species' differences. To adequately test assembly hypotheses, a framework integrating the information provided by traits and phylogenies is required. We propose an intuitive measure for combining functional and phylogenetic pairwise distances, which provides a useful way to assess how functional and phylogenetic distances contribute to understanding patterns of community assembly. Here, we show that both traits and phylogeny inform community assembly patterns in alpine plant communities across an elevation gradient, because they represent complementary information. Differences in historical selection pressures have produced variation in the strength of the trait-phylogeny correlation, and as such, integrating traits and phylogeny can enhance the ability to detect assembly patterns across habitats or environmental gradients.
301 citations
Cites background from "Hierarchical effects of environment..."
...…and phylogeny-based work has gone further, testing if environmental gradients, which provide strong filters, affect © 2013 John Wiley & Sons Ltd/CNRS phylogenetic or functional distances in assemblages at different points along a gradient (Cavender-Bares & Wilczek 2003; de Bello et al. 2013)....
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TL;DR: This novel approach could revolutionize FD-based research by allowing quantification of the various FD components from organismal to macroecological scales, and allowing seamless transitions between scales.
Abstract: Owing to the conceptual complexity of functional diversity (FD), a multitude of different methods are available for measuring it, with most being operational at only a small range of spatial scales. This causes uncertainty in ecological interpretations and limits the potential to generalize findings across studies or compare patterns across scales. We solve this problem by providing a unified framework expanding on and integrating existing approaches. The framework, based on trait probability density (TPD), is the first to fully implement the Hutchinsonian concept of the niche as a probabilistic hypervolume in estimating FD. This novel approach could revolutionize FD-based research by allowing quantification of the various FD components from organismal to macroecological scales, and allowing seamless transitions between scales.
284 citations
Cites background from "Hierarchical effects of environment..."
...The TPD-based approach explicitly considers species abundances and ITV, is sensitive to gaps in the functional volume, and is less sensitive to outliers [47], making it preferable to pre-existing methods that use the convex hull volume in the calculation of FRic and FDiv [14]....
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...Functional richness (FRic; A) is the amount of functional volume occupied by a TPD, which can be estimated as the sum of the hypervolumes (or range in the single-trait case) of the cells where TPD is greater than 0, and is therefore independent of species abundances....
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...With respect to the hypervolume method [47], FRic has the advantage of being expressed in the same units as the trait data, making directly comparable the results from different studies....
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...In addition, TPDbased FEve can vary independently of evenness in species abundances, being a pure indicator of evenness in the abundance of traits [19], and is also not trivially correlated with FRic [67]....
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...In general, any application requiring predictions of trait values from a (A) Func onal richness FRic1 Low FRic2 High FRic1 High FRic2 Low (B) Func onal evenness FEve1 High FEve2 Low FEve1 High FEve2 Low (C) Func onal divergence FDiv1 Low FDiv2 High FDiv1 Low FDiv2 High (D) Func onal dissimilari es 0.61 0.93 0.83 0.41 0.86 1 0.51 0.3 0.89 0.76 Di ss im ila ri es 0.72 0.93 0.88 0.83 0.94 1 0.53 0.61 0.89 0.94 Di ss im ila ri es (E) Trait simula ons Figure 2....
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04 Jul 2017
TL;DR: Overall, the findings suggest that mixed forests are more resistant to natural disturbances that are relatively small-scale and selective in their effect, however, benefits provided by mixtures are less evident for larger-scale disturbances.
Abstract: Forests are frequently exposed to natural disturbances, which are likely to increase with global change, and may jeopardize the delivery of ecosystem services. Mixed-species forests have often been shown to be more productive than monocultures, but it is unclear whether this results from mixed stands being in part more resistant to various biotic and abiotic disturbance factors. This review investigates the relationships between tree diversity and stand resistance to natural disturbances and explores the ecological mechanisms behind the observed relationships. Mixed forests appear to be more resistant than monocultures to small mammalian herbivores, soil-borne fungal diseases and specialized insect herbivores. Admixing broadleaves to conifers also increases the resistance to fire and windstorms when compared to pure conifer stands. However, mixed forests may be more affected by drought depending on the species in the mixture. Overall, our findings suggest that mixed forests are more resistant to natural disturbances that are relatively small-scale and selective in their effect. However, benefits provided by mixtures are less evident for larger-scale disturbances. Higher tree diversity translates into increased resistance to disturbances as a result of ecological trait complementarity among species, reduction of fuel and food resources for herbivores, enhancement of diversion or disruption processes, and multi-trophic interactions such as predation or symbiosis. To promote resistance, the selection of tree species with different functional characteristics appears more important than increasing only the number of species in the stand. Trees with different levels of susceptibility to different hazards should be intermixed in order to reduce the amount of exposed resources and to generate barriers against contagion. However, more research is needed to further improve associational resistance in mixed forests, through a better understanding of the most relevant spatial and temporal scales of species interactions and to optimize the overall provision of ecosystem services.
259 citations
ETH Zurich1, IFREMER2, University of Zurich3, University of Marburg4, Paul Sabatier University5, Swiss Federal Institute of Aquatic Science and Technology6, Swedish University of Agricultural Sciences7, University of Fribourg8, University of Grenoble9, Imperial College London10, Université de Sherbrooke11
TL;DR: This review of studies investigating variation in network structures along environmental gradients highlights how methodological decisions about standardization can influence their conclusions, and warns against a comparison of studies that rely on distinct forms of standardization.
Abstract: Knowledge of species composition and their interactions, in the form of interaction networks, is required to understand processes shaping their distribution over time and space. As such, comparing ecological networks along environmental gradients represents a promising new research avenue to understand the organization of life. Variation in the position and intensity of links within networks along environmental gradients may be driven by turnover in species composition, by variation in species abundances and by abiotic influences on species interactions. While investigating changes in species composition has a long tradition, so far only a limited number of studies have examined changes in species interactions between networks, often with differing approaches. Here, we review studies investigating variation in network structures along environmental gradients, highlighting how methodological decisions about standardization can influence their conclusions. Due to their complexity, variation among ecological networks is frequently studied using properties that summarize the distribution or topology of interactions such as number of links, connectance, or modularity. These properties can either be compared directly or using a procedure of standardization. While measures of network structure can be directly related to changes along environmental gradients, standardization is frequently used to facilitate interpretation of variation in network properties by controlling for some co-variables, or via null models. Null models allow comparing the deviation of empirical networks from random expectations and are expected to provide a more mechanistic understanding of the factors shaping ecological networks when they are coupled with functional traits. As an illustration, we compare approaches to quantify the role of trait matching in driving the structure of plant-hummingbird mutualistic networks, i.e. a direct comparison, standardized by null models and hypothesis-based metaweb. Overall, our analysis warns against a comparison of studies that rely on distinct forms of standardization, as they are likely to highlight different signals. Fostering a better understanding of the analytical tools available and the signal they detect will help produce deeper insights into how and why ecological networks vary along environmental gradients.
178 citations
Cites background from "Hierarchical effects of environment..."
...…species richness (e.g. Whittaker, Willis & Field, 2001; Macpherson, 2002), functional structure (Cornwell & Ackerly, 2009; Pellissier et al., 2010; de Bello et al., 2013), phylogenetic diversity (Graham et al., 2009; Pellissier et al., 2012) or multiple dimensions simultaneously (; Weinstein et…...
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...As emphasized by de Bello et al. (2013), null models are not ‘magic wands’, and a linear dependence between the SES and the original raw metric is frequently observed....
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King Juan Carlos University1, Sewanee: The University of the South2, Centre national de la recherche scientifique3, Institut national de la recherche agronomique4, Université du Québec à Trois-Rivières5, Academy of Sciences of the Czech Republic6, Federal University of Rio Grande do Norte7, Max Planck Society8
TL;DR: The results revealed that communities characterized by a low variance can also exhibit low kurtosis values, indicating that functionally contrasting species can co-occur even in communities with narrow ranges of trait values.
Abstract: 1. The environmental filtering hypothesis predicts that the abiotic environment selects species with
similar trait values within communities. Testing this hypothesis along multiple – and interacting –
gradients of climate and soil variables constitutes a great opportunity to better understand and predict
the responses of plant communities to ongoing environmental changes.
2. Based on two key plant traits, maximum plant height and specific leaf area (SLA), we assessed
the filtering effects of climate (mean annual temperature and precipitation, precipitation seasonality),
soil characteristics (soil pH, sand content and total phosphorus) and all potential interactions on the
functional structure and diversity of 124 dryland communities spread over the globe. The functional
structure and diversity of dryland communities were quantified using the mean, variance, skewness
and kurtosis of plant trait distributions.
3. The models accurately explained the observed variations in functional trait diversity across the
124 communities studied. All models included interactions among factors, i.e. climate–climate (9%
of explanatory power), climate–soil (24% of explanatory power) and soil–soil interactions (5% of
explanatory power). Precipitation seasonality was the main driver of maximum plant height, and
interacted with mean annual temperature and precipitation. Soil pH mediated the filtering effects of
climate and sand content on SLA. Our results also revealed that communities characterized by a low
variance can also exhibit low kurtosis values, indicating that functionally contrasting species can
co-occur even in communities with narrow ranges of trait values.
4. Synthesis. We identified the particular set of conditions under which the environmental filtering
hypothesis operates in drylands world-wide. Our findings also indicate that species with functionally
contrasting strategies can still co-occur locally, even under prevailing environmental filtering. Interactions
between sources of environmental stress should be therefore included in global trait-based
studies, as this will help to further anticipate where the effects of environmental filtering will impact
plant trait diversity under climate change.
137 citations
References
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Book•
19 Jun 2013
TL;DR: The second edition of this book is unique in that it focuses on methods for making formal statistical inference from all the models in an a priori set (Multi-Model Inference).
Abstract: Introduction * Information and Likelihood Theory: A Basis for Model Selection and Inference * Basic Use of the Information-Theoretic Approach * Formal Inference From More Than One Model: Multi-Model Inference (MMI) * Monte Carlo Insights and Extended Examples * Statistical Theory and Numerical Results * Summary
36,993 citations
"Hierarchical effects of environment..." refers methods in this paper
...CWM, FRic, FEve, FDiv) were quantified using generalised additive models in an information-theory approach (Burnham and Anderson 2002)....
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...…variables on species diversity (i.e. species richness and Simpson index) and on the different metrics of the functional structure of the communities (i.e. CWM, FRic, FEve, FDiv) were quantified using generalised additive models in an information-theory approach (Burnham and Anderson 2002)....
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Book•
01 Jan 2004TL;DR: In this paper, the authors focus on the pressure humanity is placing on the natural world, and on the continued ability of ecosystems to deliver the services on which we all depend, and develop strategies to ameliorate its impact.
Abstract: Summary As prehistoric cave paintings illustrate, our species has had an enduring appreciation of the variety and abundance of life on Earth. Today, however, concern is focused on the pressure humanity is placing on the natural world, and on the continued ability of ecosystems to deliver the services on which we all depend. To understand the extent of this ‘biodiversity crisis’ and develop strategies to ameliorate its impact, it is essential to be able to accurately measure biological diversity (a term often contracted to biodiversity) and make informed predictions about how and why this diversity varies over space and time.
7,082 citations
Macquarie University1, University of Minnesota2, Stanford University3, Simón Bolívar University4, Wageningen University and Research Centre5, Smithsonian Environmental Research Center6, University of Alaska Fairbanks7, VU University Amsterdam8, University of Zurich9, Centre national de la recherche scientifique10, Curtin University11, Tohoku University12, University of Wisconsin–Eau Claire13, Landcare Research14, University of Concepción15, University of Cape Town16, University of Tartu17, Polish Academy of Sciences18, University of Tokyo19, Utrecht University20, University of Western Australia21, Charles Darwin University22, Ural State University23, University of Toronto24, Texas A&M University25, University of Córdoba (Spain)26
TL;DR: Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.
Abstract: Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.
6,360 citations
TL;DR: It is asserted that community ecology should return to an emphasis on four themes that are tied together by a two-step process: how the fundamental niche is governed by functional traits within the context of abiotic environmental gradients; and how the interaction between traits and fundamental niches maps onto the realized niche in the context a biotic interaction milieu.
Abstract: There is considerable debate about whether community ecology will ever produce general principles. We suggest here that this can be achieved but that community ecology has lost its way by focusing on pairwise species interactions independent of the environment. We assert that community ecology should return to an emphasis on four themes that are tied together by a two-step process: how the fundamental niche is governed by functional traits within the context of abiotic environmental gradients; and how the interaction between traits and fundamental niches maps onto the realized niche in the context of a biotic interaction milieu. We suggest this approach can create a more quantitative and predictive science that can more readily address issues of global change.
3,715 citations
Book•
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01 Jan 1999
TL;DR: In this article, a taxonomic index (genera) of alpine plants is presented, with a brief review of water relations and water relations of alpin plants in the alpine life zone.
Abstract: 1 Plant ecology at high elevations.- The concept of limitation.- A regional and historical account.- The challenge of alpine plant research.- 2 The alpine life zone.- Altitudinal boundaries.- Global alpine land area.- Alpine plant diversity.- Origin of alpine floras.- Alpine growth forms.- 3 Alpine climate.- Which alpine climate.- Common features of alpine climates.- Regional features of alpine climates.- 4 The climate plants experience.- Interactions of relief, wind and sun.- How alpine plants influence their climate.- The geographic variation of alpine climate.- 5 Life under snow: protection and limitation.- Temperatures under snow.- Solar radiation under snow.- Gas concentrations under snow.- Plant responses to snowpack.- 6 Alpine soils.- Physics of alpine soil formation.- The organic compound.- The interaction of organic and inorganic compounds.- 7 Alpine treelines.- About trees and lines.- Current altitudinal positions of climatic treelines.- Treeline-climate relationships.- Intrazonal variations and pantropical plateauing of alpine treelines.- Treelines in the past.- Attempts at a functional explanation of treelines.- A hypothesis for treeline formation.- Growth trends near treelines.- Evidence for sink limitation.- 8 Climatic stress.- Survival of low temperature extremes.- Avoidance and tolerance of low temperature extremes.- Heat stress in alpine plants.- Ultraviolet radiation - a stress factor.- 9 Water relations.- Ecosystem water balance.- Soil moisture at high altitudes.- Plant water relations - a brief review of principles.- Water relations of alpine plants.- Desiccation stress.- Water relations of special plant types.- 10 Mineral nutrition.- Soil nutrients.- The nutrient status of alpine plants.- Nutrient cycling and nutrient budgets.- Nitrogen fixation.- Mycorrhiza.- Responses of vegetation to variable nutrient supply.- 11 Uptake and loss of carbon.- Photosynthetic capacity of alpine plants.- Photosynthetic responses to the environment.- Daily carbon gain of leaves.- The seasonal carbon gain of leaves.- C4 and CAM photosynthesis at high altitudes.- Tissue respiration of alpine plants.- Ecosystem carbon balance.- 12 Carbon investments.- Non-structural carbohydrates.- Lipids and energy content.- Carbon costs of leaves and roots.- Whole plant carbon allocation.- 13 Growth dynamics and phenology.- Seasonal growth.- Diurnal leaf extension.- Rates of plant dry matter accumulation.- Functional duration of leaves and roots.- 14 Cell division and tissue formation.- Cell size and plant size.- Mitosis and the cell cycle.- From meristem activity to growth control.- 15 Plant biomass production.- The structure of alpine plant canopies.- Primary productivity of alpine vegetation.- Plant dry matter pools.- Biomass losses through herbivores.- 16 Plant reproduction.- Flowering and pollination.- Seed development and seed size.- Germination.- Alpine seed banks and natural recruitment.- Clonal propagation.- Alpine plant age.- Community processes.- 17 Global change at high elevation.- Alpine land use.- The impact of altered atmospheric chemistry.- Climatic change and alpine ecosystems.- References (with chapter annotation).- Taxonomic index (genera).- Geographical index.- Color plates.- Plant life forms.- The alpine life zone.- Environmental stress.- The human dimension.
2,971 citations