Evidence for Edge Enhancements of Soil Respiration in Temperate Forests

Abstract

Forest fragmentation impacts carbon uptake and storage; however, the magnitude and direction of fragmentation impacts on soil respiration remain poorly characterized. We quantify soil respiration rates along edge‐to‐interior transects in two temperate broadleaf forests in the eastern United States that vary in climate, species composition, and soil type. We observe average soil respiration rates 15–26% higher at the forest edge compared to the interior, corresponding to large gradients in soil temperature. We find no significant difference in the sensitivity of soil respiration to temperature between the forest edge and interior. Fragmentation and resultant shifts in microenvironment alter forest productivity and soil respiration near forest edges. Ecosystem models do not currently represent edge dynamics, but given the prevalence of landscape fragmentation and its effect on carbon cycling along forest edges, this omission likely introduces an important source of uncertainty in our understanding of terrestrial carbon dynamics with a changing landscape and climate. Plain Language Summary Forests continuously release carbon dioxide into the atmosphere via the decomposition of soil organic matter and biological activities of belowground organisms in a process known as soil respiration. When intact forests are broken up (either naturally or by humans), the remaining fragments experience distinct environmental conditions near the edges. Previous work shows that temperate forests can capture and store more atmospheric carbon per unit area near forest edges; however, it is unknown how the presence of forest edges impacts the rate of carbon loss via soil respiration. Here we measure soil respiration rates along forest edges, where the local soil temperatures tend to be warmer than the forest interior. We find that near the edges, soil respiration rates are higher than the forest interior. We attribute the increased soil respiration rate to warmer forest edge soil temperatures. Our results suggest that estimates of soil respiration in the temperate forest region may be underestimating biological emissions of carbon dioxide. Altogether, our research identifies an important phenomenon previously unaccounted for in our understanding of the carbon cycle with important implications for estimating forest carbon exchanges in fragmented landscapes, particularly as the climate continues to warm.