Net Nitrogen Mineralization and Nitrification at Different Landscape Positions in a Lowland Subtropical Rain Forest in Taiwan

摘要

Although soil N transformation rate measurements are needed to assess plant availability and N losses in a forest ecosystem, little data is available on lowland subtropical rain forests. The objective of this study is to determine the rates of N mineralization and nitrification in different seasons (January and August in 2006) and at different landscape positions (footslope and summit) in the Nanjenshan forest of southern Taiwan, where the vegetation types and soil properties vary among the differentlandscape positions. According to our 28-d in situ incubation experiments, although there were larger soil C, soil N, and microbial N pools at the summit position, the footslope soils showed higher net N mineralization and nitrification rates, as expressed on a per unit C or N basis. Laboratory incubation results indicated that the N mineralization was more responsive to temperature change than to moisture change in the Nanjenshan forest soils. Our results suggested that the substrate properties at thefootslope position contributed to a higher net N mineralization and nitrification rate and that the differences between the N transformation rates at different landscape positions might be related to the types of vegetation.