Abstract
The mechanisms underlying the retention of inorganic N in acidic forest soils in southern China are not well understood. Here, we simultaneously quantified the gross N transformation rates of various subtropical acidic forest soils located in southern China (southern soil) and those of temperate forest soils located in northern China (northern soil). We found that acidic southern soils had significantly higher gross rates of N mineralization and significantly higher turnover rates but a much greater capacity for retaining inorganic N than northern soils. The rates of autotrophic nitrification and NH3 volatilization in acidic southern soils were significantly lower due to low soil pH. Meanwhile, the relatively higher rates of NO3− immobilization into organic N in southern soils can counteract the effects of leaching, runoff, and denitrification. Taken together, these processes are responsible for the N enrichment of the humid subtropical forest soils in southern China.
Highlights
The mechanisms underlying the retention of inorganic N in acidic forest soils in southern China are not well understood
We simultaneously quantified the gross N transformation rates of various subtropical acidic forest soils located in southern China and those of temperate forest soils located in northern China
The inorganic N was dominated by NH41 in southern soils, while the NH41 contents were similar to the NO32 contents of northern soils
Summary
The mechanisms underlying the retention of inorganic N in acidic forest soils in southern China are not well understood. The relatively higher rates of NO32 immobilization into organic N in southern soils can counteract the effects of leaching, runoff, and denitrification. Taken together, these processes are responsible for the N enrichment of the humid subtropical forest soils in southern China. Previous investigations have demonstrated that humid subtropical and tropical acidic soils have low autotrophic and relatively high heterotrophic nitrification rates[9,10]. The mechanisms underlying the retention of inorganic N in humid subtropical forest soils have not been quantitatively investigated in detail based on N transformation dynamics
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