Soil heterogeneity modulates responses to multiple global environmental changes in model grassland communities
An important part of ecological research has been devoted to understand and predict how plant species and assemblages respond to changes in the availability and spatiotemporal heterogeneity of resources like water, light and nutrients. In the natural world, spatial heterogeneity in the availability of soil-based resources at various scales (soil heterogeneity) is the norm, rather than the exception, in most ecosystems. Albeit soil heterogeneity is a key feature of most terrestrial ecosystems, and plays a crucial role in shaping their structure, productivity, composition and diversity, it has often been ignored when evaluating the effects of global change drivers on plant performance and associated ecosystem processes. Thus, it is virtually unknown whether observed plant responses to global change drivers are modified by soil heterogeneity. This chapter synthesizes a series of multifactorial microcosm experiments aiming to evaluate the joint effects of soil heterogeneity and global change drivers (biotic diversity, nutrient availability, [CO2] and changes in rainfall patterns) on the response of individuals and assemblages (in terms of biomass production and allocation and nutrient uptake patterns) formed by different combinations of Lolium perenne L., Plantago lanceolata L., Trifolium repens L., Anthoxanthum odoratum L. and Holcus lanatus L. We tested the hypothesis that soil heterogeneity modulates the magnitude of the response of both individuals and assemblages to multiple global change drivers (i.e., that individual and assemblage responses to soil heterogeneity and global change drivers will not be predictable from the observed responses to any one of the evaluated factors in isolation). In all the experiments conducted we did find a series of two-and three-term interactions determining key responses at both the individual and assemblage level. Thus, our working hypothesis was supported by our results. Our synthesis strongly suggest that single-factor studies should not be used to extrapolate how grassland ecosystems may respond to global change, which is composed of multiple-and potentially interacting-drivers. © 2013 by Nova Science Publishers, Inc. All rights reserved.
