Biotic mechanisms of community stability shift along a precipitation gradient

Abstract

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract. Understanding how biotic mechanisms confer stability in variable environments is a fundamental quest in ecology, and one that is becoming increasingly urgent with global change. Several mechanisms, notably a portfolio effect associated with species richness, compensatory dynamics generated by negative species covariance and selection for stable dominant species populations can increase the stability of the overall community. While the importance of these mechanisms is debated, few studies have contrasted their importance in an environmental context. We analyzed nine long-term data sets of grassland species composition to investigate how two key environmental factors, precipitation amount and variability, may directly influence community stability and how they may indirectly influence stability via biotic mechanisms. We found that the importance of stability mechanisms varied along the environmental gradient: strong negative species covariance occurred in sites characterized by high precipitation variability, whereas portfolio effects increased in sites with high mean annual precipitation. Instead of questioning whether compensatory dynamics are important in nature, our findings suggest that debate should widen to include several stability mechanisms and how these mechanisms vary in importance across environmental gradients.

Temporal variability in aboveground plant biomass decreases as spatial variability increases

“…While compensatory effects among plant functional groups also stabilize productivity (Bai et al 2004, Gherardi andSala 2015), the portfolio effect is a main mechanism of stability in mesic grassland (Hallett et al 2014). Our study is a novel extension of the portfolio effect from plant species to functional groups in a metacommunity context.…”

Climate modifies response of non-native and native species richness to nutrient enrichment

“…Precipitation, temperature and water availability are three of the most common variables used to understand how climate shapes species distributions, diversity and trait variation [24,37,41]. Further, these three variables impact on plants' photosynthetic capacity, growth rates and biomass allocation [41,42].…”

“…Over time, species arrival and local environmental conditions will shape the composition of communities [25,35,36], and species characteristics will determine their success in different abiotic environments (including both mean conditions and variability) [24,25,37,38]. However, nutrient addition modifies environmental conditions, changing the composition of communities and reducing species diversity [4,5,8], often causing losses of rare, native, perennial and N-fixing species [8,39].…”

Inter-annual species-level variations in an abyssal polychaete assemblage (Sta. M, NE Pacific, 4000 m)

“…Compensatory dynamics as defined by Houlahan et al (2007), (hypothesis A) were tested using the variance ratio (VR) method (Ernest and Brown, 2001;Hallett et al, 2014;Klug et al, 2000;Schluter, 1984). Both species and functional group density, biomass and energy use rate were assessed in this manner (Eq.…”