Effect of microclimate on litter decomposition within the arctic region.

Abstract

Plant litter decomposition is a key process in the global carbon cycle, influencing carbon exchange between ecosystems and the atmosphere. Temperature and moisture are known climatic regulators of decomposition rate at broad spatial scales. However, their influence at finer spatial resolutions remains uncertain. Small-scale variation is particularly important to study in arctic sites, as they harbor extensive microclimatic variation. The Arctic region is predicted to experience the greatest change in climate compared to the global average, potentially causing decomposition rates to increase considerably. As arctic regions store nearly half of the terrestrial carbon, this could have profound effects on carbon cycling and the global climate. This study investigates the effects of microclimatic temperature and soil moisture on litter decomposition at three arctic sites (Latnjajaure, Disko Island and Svalbard). Decomposition rate (k), measured using the Tea Bag Index (TBI), was modeled as a function of small-scale variation in temperature and moisture using multiple linear regression. Site-specific models found no evidence that small-scale variation in moisture influenced decomposition rates at these sites, which may be due to moisture not being a limiting factor at the relatively low arctic temperatures. A combined model including all sites revealed an overall positive relationship between temperature and decomposition rate, suggesting that small-scale variation in temperature has a significant but relatively weak positive effect on decomposition rate that is constant across the Arctic. This study highlights the importance of including small-scale environmental variability into decomposition studies, but also suggests that factors other than temperature and moisture will likely have an important influence on decomposition and, by extension, carbon cycling under arctic climate change.