Effects Of Phyllostachys Edulis Expansion On Nitrogen Mineralization And Its Availability Of Evergreen Broad-Leaved Forest

There is controversy as to whether or not Phyllostachys edulis expansion affect soil nitrogen availability and mineralization. Here, by space-time substitution method and PVC tube closed-top in situ incubation method, we measured some variables associated with N mineralization, including organic N content, inorganic N content, N mineralization rate, N uptake rate, N reture from litterfall between Ph. edulis-broadleaf mixed forest (PBMF, formed by Ph. edulis encroachment) and adjacent evergreen broad-leaved forests (EBF) in Dagangshan mountain, Jiangxi Province. The results are as followed:(1) When EBF conversed to PBMF, the soil total N, organic matter, C/N increased by 42.2%,99.51% and 40.09%, but soil pH and soil bulk density decreased by 5.61% and 18.75, respectively.(2) Compared with EBF, the soil hydrolysable-N, non-hydrolysable-N in PBMF were 31.57% and 111.11% higher, respectively, and the compenonts of soil hydrolysable-N, including ammonium-N, amino sugar-N, amino acid-N and hydrolysable unidentified-N in PBMF were also 24.14%,85.71%,31.82%,31.43% higher, respectively.(3) The Phyllostachys edulis expansion has little effects on inorganic N pool, the NH4+-N was the main inorganic form.(4) The Phyllostachys edulis expansion caused net annual N ammonification increased but nitrification rate and mineralization decreased. the net annual N ammonification was 26.66% greater in PBMF than in EBF, However, the net annual N nitrification rate and N mineralization rate were 104.60% and 33.40% lower.(5) When EBF conversed to PBMF, the forest NH4+-N uptake rate increased by 9.56%, but the forest NO3--N and inorganic nitrogen uptake rate decreased by 90.64% and 35.06%, respectively.(6) When EBF conversed to PBMF, the N return from litterfall reduced from 11.47 g·m-2 to 5.30 g·m-2, lowering by 53.79%.The findings will contribute to the effects of Phyllostachys edulis expansion on nitrogen cycling in forest ecosystem, and it was also an important part for the ecological benefits assessment of vegetation change when EBF changed to PBMF...