中亚热带丘陵红壤区森林演替典型阶段土壤氮磷有效性

在中亚热带典型丘陵红壤区选取裸露地、马尾松(Pinus massoniana)林地、针阔混交林地、常绿阔叶林地为研究对象,开展土壤氮(N)、磷(P)供应、有效性及其耦合过程的研究.结果表明,土壤有机C、全N、净矿化速率、中性磷酸酶活性表现为随森林演替进展呈现逐步提高的变化趋势;而土壤全P、C/N、C/P、氨化速率、硝化速率、树脂P、NaHCO3-P、NaOH-P、声波P、酸性P、总有效P、酸性磷酸酶活性未表现出此趋势;但反映N、P有效供应的指标,除氨化速率、树脂P和酸性磷酸酶外,在常绿阔叶林中均为最高.相关分析表明大部分N、P供应指标之间存在显著相关性(P<0.05).丘陵红壤区森林演替初级阶段P的限制性明显强于N,土壤N、P供应在森林演替进展过程中可以逐步得到优化而实现协调供应.以常绿阔叶林为中亚热带丘陵红壤区植被恢复的最终目标是可行和理想的.

Soil nitrogen and phosphorus availability in forest ecosystems at different stages of succession in the central subtropical region

Soil nitrogen (N) and phosphorus (P) content and availability were examined in four ecosystems representing different stages of forest succession: bare hillside, Masson pine (Pinus massoniana) forest, conifer\|broadleaf mixed forest and evergreen broad\|leaved forest. All sites were located on the luvisols red soil in the central subtropical region. Soil nitrogen and phosphorus data were obtained by closed\|top PVC tube incubation and Hedley P fractionation methods. The results indicated that soil organic carbon, total N, net N\|mineralization rate and neutral phosphatase activity increased with the successional stages. Soil total P, C/N ratio, C/P ratio, ammonification rate, nitrification rate, resin P, NaHCO3\|P, NaOH\|P, sonic P, acid P, total available P, and acidic phosphatase activity did not show distinct trends with successional stages. All soil nutrient measures except for ammonification rate, resin P and acidic phosphatase activity were greatest in the evergreen broad\|leaved forest. Strong correlations (P<0.05) were found among most of these measurements. In our study systems, P limitation to plant growth was stronger than N limitation at early successional stages and soil N and P availability were improved with forest successional development. Our data suggests that the evergreen broad\|leaved forest shall be considered as the final purpose of vegetation restoration in central subtropical region.