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

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.