A Comparative Study of Manipulative and Natural Temperature Increases in Controlling Wetland Plant Litter Decomposition

Abstract

Manipulative experiments and space-for-time substitutions are two main approaches used to infer the impacts of future climate change on ecological processes, such as litter decomposition. The potential limitations of these approaches are well-recognized. Here, we address the congruence between these two approaches by comparing decomposition rates of leaf litter from four wetland plant species in response to (i) in-situ experimental warming (manipulative warming), and (ii) broad-scale spatial gradients (natural warming) over one-year observation of 2019. Manipulative warming was achieved by using open-top chambers (OTCs), and natural warming was followed along an altitudinal gradient from a high altitude site to a low site. Litter decomposition rates increased with temperature increasing in both OTC- and gradient-based approaches. However, litter decomposed faster along with the decreasing altitude than predicted by the manipulated rise in temperature, especially for those plants being resistant to decompose. For the gradient-based approach, the interaction effects between temperature and precipitation explained up to 44.1% of litter decomposition dynamics and served as a key to differentiate these two approaches. These results support the view that space-for-time substitution over broad-scale spatial gradients may magnify the responses of certain ecological processes to further climate warming. Our work is the first study to compare the characteristics of decomposition of wetland plant litter types in OTC- and natural gradient-based warming experiments.