N Mineralization and Nitrification in a Primary Lithocarpus xylocarpus Forest and Degraded Vegetation in the Ailao Mountain, Yunnan Province

摘要

Using the closed-top tube incubation method, we examined the soil nitrogen (N) mineralizationand nitrification in the primary Lithocarpus xylocarpus forest, a secondary oak forest and a tea plantationin the Ailao Mountain, Yunnan Province, China. This study was conducted in the dry season fromNovember 20, 1998 to May 15, 1999. Results showed that there were significant differences among thethree vegetation types in both net N mineralization and nitrification rates, and they also demonstratedtemporal variation. The net ammonification rate (RA) was much higher than net nitrification rate (RN), andthe latter was about 0.5%-10% of the former. Our results indicated that incubation period, vegetation typeand the location of plot all interactively affected RA, RN and net mineralization rate (RM). We providedevidence that anthropogenic disturbances could result in changes of ecosystems processes such as Nmineralization and nitrification rates. It is obvious that tea plantation and secondary growth forest havemore physically (mainly temperature and moisture) controlled N transformation processes than thewell-preserved primary L. xylocarpus forest, implying that the conservation of primary forest ecosystemsin the Ailao Mountain region should be emphasized.