Asymmetric responses of soil respiration in three temperate steppes along a precipitation gradient in northern China revealed by soil-monolith transplanting experiment

Responses and feedbacks of ecosystem carbon (C) cycling in the terrestrial biosphere to climate change pose the major challenge for Earth System Model projections. However, whether ecosystem C cycling among diverse vegetation types shows different sensitivities and the associated underlying mechanisms remain elusive. As part of a 5-year (2014-2018) soil monolith transplant experiment, this study was designed to examine the influences of night warming, decreased precipitation, and increased precipitation on soil respiration in the three temperate steppes (i.e. desert, typical, and meadow steppes) along a precipitation gradient on the Mongolian Plateau. Over the 5 years, night warming had no effect on soil respiration in any of the three steppes. Decreased precipitation reduced soil respiration, whereas increased precipitation stimulated it in each steppe. In addition, the sensitivity of soil respiration to increased precipitation was larger than that to decreased precipitation, suggesting a positive asymmetry of soil respiration in response to changing precipitation. The soil respiration responses were predominately determined by both soil water availability and belowground net primary productivity in the desert and typical steppes, but by soil total C alone in the meadow steppe. These findings not only improve mechanistic understanding on the responses of soil respiration in various grassland ecosystems, but also facilitate the extrapolation from local to regional scale for the robust projections of terrestrial C-climate change feedbacks.