Response of Soil Respiration to Precipitation Variation in Alfalfa Grassland on the Western Loess Plateau: Hysteresis and Diel Q₁₀

Response of Soil Respiration to Precipitation Variation in Alfalfa Grassland on the Western Loess Plateau: Hysteresis and Diel Q₁₀

Soil respiration (Rs) plays an important role in the terrestrial carbon cycle, but how precipitation variation affects Rs in alfalfa grassland is poorly understood. To explore the effects of precipitation variation on Rs, this experiment was conducted by using rainfall shelters to simulate 30% precipitation reduction (P-30), normal precipitation (CK) and 30% precipitation increase (P+30) for an alfalfa (Medicago sativa) grassland in the Qingyang city, Gansu province, China. Rs was measured continuously using an automated soil respiration system (model LI-8100A with an LI-8150 multiplexer, LI-COR, Nebraska, USA) during the overwintering preparation period of alfalfa. The results showed that the Rs under P-30 and P+30 conditions were significantly higher than under CK treatment by 12.3% and 21.8% (P< 0.05), respectively. The Q₁₀ (temperature sensitivity of soil respiration) under P-30 condition was significantly higher than P+30 treatment by 12.3%. The mean time lag between Rs and soil temperature (Ts) was 2hrs in three precipitation treatments, with Rs getting to the peak earlier than Ts. The Q₁₀ decreases with increasing volumetric water content (VWC), and Rs increases with temperature increasing during the overwintering preparation period of alfalfa. Therefore, the effects of precipitation variation on Rs, identified in this study, will facilitate the assessment and simulation of ecosystem carbon cycling of artificial alfalfa grassland ecosystem on the Loess Plateau.