Soil Nitrogen Mineralization And Its Availability Across Typical Stages Of Forest Community Succession Under Hilly Red Soil In Mid-subtropical Zone Of China

Soil nitrogen (N) transformation is one of key ecosystem processes, and soil N availability has a feedback to the community succession. Soil N transformation and N availability were in detail studied by continuous menstruate, in situ incubation associated with laboratory incubation under plant community succession sequences of Nanchang suburb in mid-subtropical zone which include shrubbery, coniferous forest, mixed forest and evergreen broad-leaved forest of China. The objectives were to describe the relationship between characteristic of vegetation and soil N pool and to provide scientific basis on vegetation restoration, forest ecosystems management and continuable development. The main conclusions drawn from the study were as follows:(1) The results of soil N transformation and its availability studied by PVC tubes and ion exchange resin bags methods all showed the tendency of shrubbery < coniferous forest < mixed forest < evergreen broad-leaved forest (P<0.05);(2) The concentrations of NH₄⁺-N in spring or summer were higher than that in autumn or winter, NO₃^--N showed opposite tendency and the concentrations of mineral N were highest in winter than in other seasons; ammonification rates were highest in spring, but nitrification rates were lowest in spring, net N mineralization rates showed different seasonal changes under different succession stages;(3) Soil NH₄⁺-N and ammonification rates were dominant in the primary stage of succession, reversely, NO₃^--N and nitrification rates were in the absolutely dominant in the advanced stage of succession.(4) The results showed that ammonification rates and N net mineralization rates were all increased with the temperatures, but no differences in nitrification rates; ammonification, nitrification and net mineralization rates were all highest in the half-saturation water of the soil, while no differences occurred in current water and saturation water; soil ammonification, nitrification and net mineralization rates all increased with forest succession by laboratory aerobic incubation of three factors, three levels and three repetitions methods.In a word, the ability of soil N supply and N availability would be enhanced with direct succession; global warming was in favor of increasing the ability of soil N supply; seasonal drought or strong rainfall would decrease it.