关键词: 氮素流失, 污染, 径流, 淋溶, 控制策略

Abstract: Since the 50 years implementation of strict fire suppression policy, the natural fire pattern in Great Xing’an Mountains changed greatly, and the species composition and age structure of the forests altered significantly. To understand the responses of the forests in Great Xing’an Mountains to the long term fire suppression could supply a sound basis for the sustainable development of forestry in this area. By using a spatially explicit landscape simulation model (LANDIS), the long-term (300 years) responses of forest landscape in Great Xing’an Mountains to the scenarios of natural fire (before 1950) and fire suppression (after 1950) were simulated, and the changes in fuel load, fire hazard, and forest tree species abundance under the two scenarios were compared. The simulation results showed that under fire suppression scenario, larch (Larix gmelinii) forest area increased significantly, while birch (Betula platyphylla) forest area was in adverse. Meanwhile, over-matured larch forest area increased, while young larch and birch forest areas decreased. Fire suppression prolonged the interval of fire, decreased the times of fire, increased the chance of catastrophic fire, and made the fire risk rapidly increased to a dangerous level. Under natural fire scenario, fire risk maintained at a relatively low level. Therefore, if the present strict fire suppression policy still implemented, extensive fuels management measures such as prescribed burning and coarse fuel load reduction should be adopted to decrease the occurrence chance of catastrophic fire. How to evaluate the effect of prescribed burning and coarse fuel load reduction in Great Xing’an Mountains, and to find the ways of keeping balance among fire suppression, maximal timber production, and sound ecological function, should be the issues to be urgently solved.

Key words: Nitrogen loss, Leaching, Pollution, Runoff, BMP practices