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

Abstract

AbstractUnderstanding how soil nitrogen (N) mineralization (Nmin) 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 Nmin. A local‐scale field investigation was conducted to reveal the temporal dynamics of Nminunder land‐use change from desert to farmland, and to verify the mechanisms controlling Nminchange during this process in a typical desert oasis region. The results showed that Nminranged from −0.14 to 2.69 mg N kg−1day−1, with an average value of 0.74 mg N kg−1day−1. Nminin 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 Nminwere 0.036 and 0.032 mg N kg−1day−1year−1in GCF and SCF, respectively. Structural equation modelling (SEM) was used to test whether the measured variables affected Nmin, and the results showed that soil organic matter (SOM), bulk density (BD) and sand content were the main soil factors affecting Nmin. These soil factors, together with farmland type and cropping time, can explain 31% of the variation in Nmin. Our observations revealed that Nminchanged 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.HighlightsWe used Nminas 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 Nmin.Nminwas primarily affected by soil organic matter, bulk density and sandy content. Intensive land exploitation in arid land profoundly influences soil Nmin.