Soil Net Organic Nitrogen Mineralization Kinetics in Response to Short- and Long-Term Land-Use Conversion of Woodland to Tea Fields

摘要

In recent years, with growing demand for tea consumption, tea cultivation area in China has been increasingly expanded, largely as a result of land-use conversion from woodland into tea field. Up to now, however, soil net nitrogen mineralization kinetics in response to short-and long-term land-use conversion of woodland to tea field remain unclear. Thus, a laboratory aerobic incubation test under constant temperature in combination with a double-pool exponential model were conducted to explore soil organic net nitrogen mineralization dynamics, and quantify soil net nitrogen mineralization kinetics from different planting ages of tea fields (1, 2, 3, 4, 5, and 30 years old, named T1, T2, T3, T4, T5, and T30 correspondingly) that converted from Masson pine woodland and adjacent woodland (W30, 30 years old). The results showed that land-use conversion exerted great influence on soil physicochemical properties. Though there were no differences in soil total nitrogen (TSN) and total phosphorus (TP) contents between W30 and TN, the TSN and TP were strongly affected by long-tern land-use conversion. The double-pool exponential model fitted soil net nitrogen mineralization data well (R-adj(2) ranged from 0.75 to 0.99; RMSE ranged from 0.18 to 0.99). The fitted parameter of soil active mineralization organic nitrogen pool (N-0) and soil active nitrogen mineralization rate constant (k(1)) for the woodland soil were 9.09 +/- 2.32 mg N kg(-1) and 0.24 +/- 0.13 d(-1), respectively. The N-0 for the tea plantation within two years of the growth stage presented decreasing tendencies, which indicated that soil nitrogen mineralization was stimulated after land-use conversion, and then showed increasing trends with the increasing tea planting ages. Besides, two stepwise regression models developed in this study showed that the nitrogen mineralized kinetic parameters could be well predicted by soil physicochemical properties. In conclusion, soil net nitrogen mineralization is greatly influenced by agricultural land-use conversion and planting ages.