Net Nitrogen Mineralization and Nitrification in Three Subtropical Forests of Southwestern China

摘要

Nitrogen is a limiting nutrient for plant growth in many forest ecosystems; however, information on N mineralization and nitrification in subtropical forests is generally lacking. To determine the effect of forest site on N mineralization and nitrification and the key contributing factors under subtropical climate, we studied the seasonal patterns of soil N mineralization and nitrification with closed in situ core incubation method in a mixed evergreen broadleaf forest, a pure Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) forest and a pure Zhennan (Phoebe zhennan S. Lee et F. N. Wei) forest in Dujiangyan, Sichuan province, southwestern China. Our results indicated that the rates and the seasonal patterns of net N mineralization and nitrification were similar among the three forest sites. The rates of both net N mineralization and nitrification were the highest in the winter season (December 2000 to April 2001), and negligible in spring and summer The variability in net N mineralization and nitrification and the specific environmental contributing factors, however, varied in different forest sites. The overall similarity in N mineralization and nitrification rates suggests that regional climate condition is the most dominant controlling factoron N mineralization and nitrification. At local scales, however, biodiversity may play an important role in patterns of N mineralization and nitrification; higher biodiversity could lead to higher and more stable N mineralization and nitrification.