Soil respiration characteristics under different site conditions in wind-water crisscross erosion region on Loess Plateau

Abstract: The wind and water erosion transitional belt of the Loess Plateau experiences intensive soil erosion, where the site conditions are complicated. The spatial heterogeneity of soil texture can alter spatial heterogeneity of soil respiration, with a consequent impact on carbon cycling of the ecosystem. The objective of this study was to investigate the soil respiration characteristics of two dominant shrubs (Caragana Korshinkii and Salix psammophila) under different site conditions, and elucidate the temperature sensitivity of soil respiration in the wind and water erosion transitional belt of the Loess Plateau. Experiments were performed with two site conditions (silt loam soil and sandy soil) for each shrub during the growing seasons from 2009 to 2010. Soil respiration was measured every other day with an ultra-light portable photosynthesis system (CI-340, CID Inc., USA) fitting with a soil respiration chamber (CI-301SR). Soil temperature at a depth of 5 cm depth was measured using a digital thermometer (Omega HH509R, Stamford, CT) adjacent to each PVC collar. Soil moisture in the 0 - 6 cm soil layer was measured using a frequency domain reflectometry (FDR) with a hand-held push probe (Theta probe type ML2X, Delta-T, UK). The root biomass was estimated by the sequential core method. The results showed that the soil respiration of C. korshinkii was larger in silt loam soil than in sandy soil, unlike S. psammophila. Soil water content and soil temperature were significant abiotic factors mediating the response of soil respiration of C. korshinkii to site conditions, whereas biotic factors (root biomass) were an important factor that could regulate the response of S. psammophila to site conditions. Under different site conditions, soil respiration of each shrub showed obviously seasonal changes. The soil respiration of C. korshinkii achieved their peak values in July or August. The maximum soil respiration of Salix psammophila was observed in August. Soil temperature could better explain seasonal changes of soil respiration of C. korshinkii, whereas soil water content could better explain seasonal changes of soil respiration of Salix psammophila. The relationship between soil respiration and soil temperature was better expressed by an exponential function under different site conditions. The Q10 of soil respiration was larger in silt loam soil than in sandy soil. This showed that the soil respiration of silt loam soil was more sensitive to soil temperature.