Contrary responses of soil heterotrophic and autotrophic respiration to spring and summer drought in alfalfa on the Loess Plateau

作者：Houkun Chu, Hong Wei Ni, Jingyong Ma, Yuying Shen · 发表于：Geoderma · 年份：2023 · DOI：10.1016/j.geoderma.2023.116722 · 被引用次数：9 · 研究领域：Soil Carbon and Nitrogen Dynamics、Soil erosion and sediment transport、Soil and Unsaturated Flow

Climate change has increased the intensity and frequency of seasonal droughts, which could fundamentally affect the terrestrial carbon (C) cycle. However, as the second-largest terrestrial C flux, soil respiration (Rs) and its heterotrophic (Rh) and autotrophic (Ra) components in response to seasonal drought are unclear. To investigate the effect of seasonal drought on the patterns and mechanisms of Rs and its components, a two-year continuous Rs measurement experiment was conducted in typical rain-fed managed alfalfa (Medicago sativa L.) fields on the Loess Plateau in China. The results showed that the ranges of Rs, Rh and Ra in the four seasons of managed alfalfa fields on the Loess Plateau were 0.45–3.70, 0.13–2.27, and 0.33–2.14 μmol m−2 s−1, respectively. There was no significant difference in the average annual Rs between the two years (P > 0.05). Both spring and summer droughts significantly decreased Rs; however, the seasonal Rh and Ra had different patterns under spring and summer droughts. Spring drought significantly reduced the seasonal Rh by 35.19 % but increased Ra by 20.35 %. In contrast, summer drought significantly increased the seasonal Rh by 45.51 % but decreased the Ra by 35.05 %. The differential response of Ra to seasonal drought was attributed to the opposite responses of the leaf area index (LAI) and photosynthetic rate to spring and summer drought, while Rh was related to the contrasting microorganism responses to spring drought and the pulse effect o...