Decoupling Between Functional Diversity and Stability of Decomposer Functions in Natural and Agroecosystems Can Favor Resistance to Land-Use Change.

Functional diversity in producers and consumers can not only promote ecosystem functions but also impart additional desirable features, such as stability of functions and how they are translated into services. These connections between diversity, functions, and stability are seen across various natural ecosystems in the terrestrial, marine, and freshwater realms. Yet, it remains challenging to extend these linkages to agroecosystems-because producers and consumers play widely different ecological roles here compared to natural ecosystems. Microbial decomposer functions, however, are common to both natural and agroecosystems. But the linkages between functional diversity in decomposers, their functions, and stability remain inadequately known. We take advantage of human land-use in the Trans-Himalayas where the natural reference grazing ecosystem with native plants and herbivores is repurposed into two distinct agroecosystems to grow livestock or crops. Here, we answer three questions: (a) whether land-use change alters the intensity of decomposer functions, (b) whether land-use change homogenizes decomposer functions, and (c) whether land-use change alters the stability of decomposer functions. Variation in decomposer functions was not attributable to background spatial autocorrelation or variation in edaphic conditions. We find that the intensity of the individual decomposer functions was higher under crops compared to the native state, but the intensity remained comparable under livestock. Land-use had no net effect on multifunctionality. The functional diversity was lower under crops and was comparable under livestock. We find that land-use did not affect the temporal stability of the decomposer biomass. Structural equation models further suggested that functional diversity is decoupled from the stability of decomposer biomass. These results indicate that decomposer functions can be resistant to change in land-use. Therefore, ecological resistance in decomposer functions can offer the basis for stewardship of agroecosystems since homogenization can result in ecosystems becoming more susceptible to environmental fluctuations, such as those foreseen by future climate projections.