Resource colimitation governs plant community responses to altered precipitation

Abstract

Ecological theory and evidence suggest that plant community biomass and composition may often be jointly controlled by climatic water availability and soil nutrient supply. To the extent that such colimitation operates, alterations in water availability caused by climatic change may have relatively little effect on plant communities on nutrient-poor soils. We tested this prediction with a 5-y rainfall and nutrient manipulation in a semiarid annual grassland system with highly heterogeneous soil nutrient supplies. On nutrient-poor soils, rainfall addition alone had little impact, but rainfall and nutrient addition synergized to cause large increases in biomass, declines in diversity, and near-complete species turnover. Plant species with resource-conservative functional traits (low specific leaf area, short stature) were replaced by species with resource-acquisitive functional traits (high specific leaf area, tall stature). On nutrient-rich soils, in contrast, rainfall addition alone caused substantial increases in biomass, whereas fertilization had little effect. Our results highlight that multiple resource limitation is a critical aspect when predicting the relative vulnerability of natural communities to climatically induced compositional change and diversity loss.biodiversity | climate change | resource colimitation | functional traits | low-productivity ecosystems C urrent and predicted climatic changes are expected to considerably alter the water balance experienced by terrestrial ecosystems. Climate change can lead to increases or decreases in mean annual rainfall, shifts in seasonal and annual rainfall variability, changes in the frequency and magnitude of extreme precipitation events, shifts from snow to rain, declining snowpack, and temperature-driven increases in the climatic water deficit (1-3). These water-related changes are expected to exert dramatic impacts on the primary productivity, species composition, trophic relationships, diversity, and ecosystem functioning of natural communities (4-8), especially in arid and semiarid ecosystems (9-11). Water-related climatic changes are expected to outweigh the direct effects of increased temperatures on many natural communities (12). Despite the pervasiveness of the projected ecological impacts of changed water availability, very little is known about the factors that make some natural communities more vulnerable or resistant than others (13,14). An important step toward improving downscaled forecasts of climate change impacts on natural communities is to test explicit, theorybased predictions about the effects of altered water availability.Because water is a resource for plants, the concept of limiting resources is a potentially important principle for making successful predictions about altered water availability. Classically, "Liebig's law of the minimum" suggests that plant productivity is limited by the single resource that is in scarcest supply relative to demand (15). This theory was developed for agricultural systems, and although its simple logi...

Nitrogen deposition magnifies the sensitivity of desert steppe plant communities to large changes in precipitation

“…The PCA and the change in the relative AGB of the PFGs also indicated that the shift patterns were mainly derived from precipitation changes. The findings agree with some other studies reported that altered precipitation notably shifted plant community composition in semiarid grasslands (Eskelinen & Harrison, ; Yang et al, ). However, the sensitivity of plant community composition to precipitation changes could be mediated by other limited resource such as N, largely depending on environmental conditions such as soil nutrient pools (Eskelinen & Harrison, ).…”

Responses of peatland vegetation to 15‐year water level drawdown as mediated by fertility level

“…Fen and bog vegetation respond contrastingly to WLD; while fen communities were pushed from their initial states to vegetation succession, ombrotrophic communities showed higher inter‐annual variation but stayed within their initial state over the sixteen years following drainage. This pattern found here for peatland vegetation agrees with the general theory first grounded in grasslands and forests (Davis, Grime, & Thompson, ; Eskelinen & Harrison, ; Roberts & Gilliam, ) that mesic communities are more sensitive than nutrient‐poor communities to environmental perturbation.…”

Responses of soil microbial functional genes to global changes are indirectly influenced by aboveground plant biomass variation

“…Predicting ecosystem responses to global change is a fundamental issue in ecology. It has been well documented that the aboveground plant community is sensitive to precipitation change (Cleland et al, 2013;Eskelinen and Harrison, 2015) and N deposition (Stevens et al, 2004;Clark and Tilman, 2008), particularly in arid and semi-arid grassland ecosystems, where water and N are generally considered to be limiting resources (Harpole et al, 2007;Yang et al, 2011;Xu et al, 2012b). A growing body of evidence suggests that higher precipitation increases plant species richness (Bai et al, 2008;Xu et al, 2015b), whereas N fertilization is reported as the main driver of the loss of species richness (Gough et al, 2000;Stevens et al, 2004;Yang et al, 2011).…”