Species Interactions Reverse Grassland Responses to Changing Climate

Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
Science (Impact Factor: 33.61). 03/2007; 315(5812):640-2. DOI: 10.1126/science.1136401
Source: PubMed


Predictions of ecological response to climate change are based largely on direct climatic effects on species. We show that,
in a California grassland, species interactions strongly influence responses to changing climate, overturning direct climatic
effects within 5 years. We manipulated the seasonality and intensity of rainfall over large, replicate plots in accordance
with projections of leading climate models and examined responses across several trophic levels. Changes in seasonal water
availability had pronounced effects on individual species, but as precipitation regimes were sustained across years, feedbacks
and species interactions overrode autecological responses to water and reversed community trajectories. Conditions that sharply
increased production and diversity through 2 years caused simplification of the food web and deep reductions in consumer abundance
after 5 years. Changes in these natural grassland communities suggest a prominent role for species interactions in ecosystem
response to climate change.

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    • "Therefore, relating the temporally and spatially heterogeneous abiotic conditions that animals experience in situ can better inform species responses to future climate change (Hannah et al. 2014;Sears & Angilletta 2015). Field experiments that manipulate rainfall and temperature are ideal for testing the effects of climate change on microhabitat use of free ranging ectotherms (Suttle, Thomsen & Power 2007;Davis & DeNardo 2009). Moreover, studies that incorporate a wide range of rainfall gradients can allow for testing a spectrum of species responses to climate change, which is needed to assess climate change related risks (Kayler et al. 2015). "

    Full-text · Dataset · Jan 2016
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    • "In semi-arid environments, water availability is a key driver of plant productivity (Collins et al. 2014), and changes in this resource can negatively impact trophic interactions and animal activity (Voigt et al. 2003; Suttle, Thomsen & Power 2007). Chronic water stress can result in bottom-up trophic effects that alter trophic interactions and behaviours, disrupting ecosystem and community dynamics (Voigt et al. 2003; Suttle, Thomsen & Power 2007; Smith, Knapp & Collins 2009; McCluney et al. 2012). For example, cricket and spider foraging decisions are based on water needs rather than nutrition during dry conditions, with spiders consuming more water-rich resources, increasing predator–prey interactions when water is limiting (McCluney & Sabo 2009). "

    Full-text · Article · Oct 2015 · Functional Ecology
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    • "of competitors are unlikely. However, environmental change can rapidly disrupt coexistence in some cases (Jiang and Morin 2004;Stevens et al. 2004;Suttle et al. 2007). In a resource competition model, coexistence requires that the rate of resource supply is greater than the minimum amount required for positive population growth, and also that the ratio of resources supplied falls between the resource use ratios of the focal species and its competitor (see inequality (8) and Fig. 2). "
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    ABSTRACT: Anthropogenic environmental change can affect species directly by altering physiological rates or indirectly by changing competitive outcomes. The unknown strength of competition-mediated indirect effects makes it difficult to predict species abundances in the face of ongoing environmental change. Theory developed with phenomenological competition models shows that indirect effects are weak when coexistence is strongly stabilized, but these models lack a mechanistic link between environmental change and species performance. To extend existing theory, we examined the relationship between coexistence and indirect effects in mechanistic resource competition models. We defined environmental change as a change in resource supply points and quantified the resulting competition-mediated indirect effects on species abundances. We found that the magnitude of indirect effects increases in proportion to niche overlap. However, indirect effects also depend on differences in how competitors respond to the change in resource supply, an insight hidden in nonmechanistic models. Our analysis demonstrates the value of using niche overlap to predict the strength of indirect effects and clarifies the types of indirect effects that global change can have on competing species.
    Full-text · Article · Oct 2015 · The American Naturalist
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