Landscape position influences soil respiration variability and sensitivity to physiological drivers in mixed‐use lands of Southern California, USA. Issue 10 (10th October 2016) - Crum, Steven M.
Abstract: Linking variation in ecosystem functioning to physiological and landscape drivers has become an important research need for understanding ecosystem responses to global changes. We investigate how these contrasting scale‐dependent ecosystem drivers influence soil respiration ( Rs ), a key ecosystem process, using in situ landscape surveys and experimental subsidies of water and labile carbon. Surveys and experiments were conducted in summer and winter seasons and were distributed along a coastal to desert climate gradient and among the dominant land use classes in Southern California, USA. We found that Rs decreased from lawn to agricultural and wildland land uses for both seasons and along the climate gradient in the summer while increasing along the climate gradient in the winter. Rs variation was positively correlated with soil temperature and negatively to soil moisture and substrate. Water additions increased Rs in wildland land uses, while urban land uses responded little or negatively. However, most land uses exhibited carbon limitation, with wildlands experiencing largest responses to labile carbon additions. These findings show that intensively managed land uses have increased rates, decreased spatial variation, and decreased sensitivity to environmental conditions in Rs compared to wildlands, while increasing aridity has the opposite effect. In linking scales, physiological drivers were correlated with Rs but landscape position influenced Rs by altering both the physiological drivers and the sensitivity to the drivers. Systematic evaluation of physiological and landscape variation provides a framework for understanding the effects of interactive global change drivers to ecosystem metabolism across multiple scales. Key Points: Managed land uses have increased rates and decreased spatial variation and sensitivity to environmental conditions in soil respiration Variation in soil respiration was positively correlated with soil temperature and negatively to soil moisture and substrate Wetting increased soil respiration in wildlands, while urban land uses responded little or negatively. Most land uses responded to substrate