Native temperature regime influences soil response to simulated warming

Anthropogenic climate change is expected to increase global temperatures and potentially increase soil carbon (C) mineralization, which could lead to a positive feedback between global warming and soil respiration. However the magnitude and spatial variability of belowground responses to warming are not yet fully understood. Some of the variability may depend on the native temperature regimes of soils. Soils from low temperature climates may release more C than will soils from high temperature climates because soils in cold climates are often C-rich and may experience more warming. We investigated whether soils from low native temperatures respired more than did soils from high native temperatures. We collected intact soil cores from three elevational transects along a latitudinal gradient in the forests of southern Appalachian Mountains. Soil cores were incubated for 292 days at low, medium, and high temperatures (separated by 3 °C each) with diurnal temperature and light regimes that simulated realistic temperature changes likely to occur within the next century. The native temperature regimes of soils negatively influenced soil respiration, such that soils from cold climates respired more in response to experimental warming than did soils from warm climates. Conversely, soils from warm climates mineralized the largest proportion of available soil C and available soil nitrogen in response to warming. Across all soils, modest experimental warming increased soil respiration, the proportion of available soil C that was being respired (respiration/soil C), and the proportion of soil nitrogen that was mineralized (N min/soil N). Taken together, these data suggest that soils from low native temperatures have a greater potential to release C in response to climate warming because the C stocks are larger and respiration rates will be higher than those in soils from high native temperatures.