Patterns of soil nitrogen mineralization under a land‐use change from desert to farmland

摘要

Abstract Understanding how soil nitrogen (N) mineralization (N min ) responds to environmental changes is critical for improving ecosystem management, especially in a resource‐constrained region. Intensive land exploitation in arid land has profound influences on soil ecosystems and thus on soil N min . A local‐scale field investigation was conducted to reveal the temporal dynamics of N min under land‐use change from desert to farmland, and to verify the mechanisms controlling N min change during this process in a typical desert oasis region. The results showed that N min ranged from −0.14 to 2.69 mg N kg −1 day −1 , with an average value of 0.74 mg N kg −1 day −1 . N min in old oasis farmland (OOF) was significantly higher than that in GCF (Gobi desert conversion farmland) and SCF (sandy desert conversion farmland), and the average change rates of N min were 0.036 and 0.032 mg N kg −1 day −1 year −1 in GCF and SCF, respectively. Structural equation modelling (SEM) was used to test whether the measured variables affected N min , and the results showed that soil organic matter (SOM), bulk density (BD) and sand content were the main soil factors affecting N min . These soil factors, together with farmland type and cropping time, can explain 31% of the variation in N min . Our observations revealed that N min changed substantially under the land conversion process from desert to farmland, and our findings will help with assessments and predictions of future N cycles in desert oasis regions in response to land‐use change. Highlights We used N min as an observed variable to evaluate the dynamics of the soil evolution process under a land‐use change from desert to farmland. Cropping year was identified by using map image data to reveal temporal trend of N min . N min was primarily affected by soil organic matter, bulk density and sandy content. Intensive land exploitation in arid land profoundly influences soil N min .