Soil temperature and bacterial diversity regulate the impact of irrigation and fertilization practices on ecosystem respiration

Abstract

AbstractUnderstanding ecosystem respiration (Reco) response to various management practices is important for the sustainable development of solar greenhouse systems, which represent a large and profitable industry in Northwest China. A tomato (Lycopersicon esculentum Mill.)–cucumber (Cucumis sativus L.)–tomato rotation experiment was conducted with four treatments including two irrigation levels (regular irrigation [RI] and low irrigation [LI]) and two N fertilizer sources (organic‐N fertilizer [N1] and inorganic‐N fertilizer [N2]). Ecosystem respiration and soil variables were measured multiple times. Mean Reco flux was 511, 319, and 437 mg m–2 h–1 for tomato‐2016, cucumber‐2016, and tomato‐2017, respectively. Soil temperature was the most important factor affecting Reco magnitude. Tomato seasons with higher temperature had significantly greater Reco flux than the cucumber season. Organic‐N fertilizer application can stimulate Reco flux, cumulative Reco, and Reco intensity mainly by providing favorable soil N and C condition for soil bacterial growth and activity, whereas the difference between irrigation levels was inconsistent. The fitted exponential function describing the relationship between Reco and soil temperature showed that the temperature sensitivity decreased from tomato‐2016 to tomato‐2017 for all treatments, corresponding to the continuously reduced soil bacterial alpha diversity. Soil bacterial Shannon index was an effective prediction factor for Reco in the relatively warmer and drier season, with an R2 >.8 during tomato‐2017. The RIN1 treatment consistently had the greatest cumulative Reco and the highest soil bacterial alpha diversity throughout the rotation. Further studies are needed on the mechanisms of how the change of soil properties would regulate the response of Reco to soil abiotic and biotic factors.