森林草原过渡区森林凋落物分解初期规律研究

Study on The Rules of Early Forest Litter Decomposition in Forest-steppe Transition Zone

为了探索内蒙古大兴安岭南段森林草原过渡区凋落物分解规律和调节生态系统物质循环和能量流动的载体作用,本文采用网袋法对杨桦次生林凋落物分解状况进行了研究,结果表明：经过非生长季的冻融破碎过程白桦和山杨林的凋落物失重率分别变为51.34%和38.71%,生长季的分解变化不大,总体与土壤温度和含水量显著相关;凋落物失重模式分别为：y白=0.312e-0.4721t（R2=0.9347）;y山=0.035e-0.3502t（R2=0.9601）。凋落物N、P、K 3种养分元素及有机碳含量的迁移规律从前1年的秋季到第2年的秋季基本呈＂释放—富集＂模式,生长季刚开始时养分动态均呈下降趋势,开始富集的转折点基本在分解210~240 d左右,到分解360 d时富集最大。由此可知：凋落物分解、养分元素迁移过程可能不以微生物分解为主导,降雨淋溶、物理破碎等非生物因素可能作用显著。

Forest- steppe transition zone is a region influenced sensitively by climate change and fragile ecological environment, and is the media of adjusting the material cycle and energy flow of litter decomposition dynamics in e- cosystem, which is important to the nutrient balance system. The article discusses the litter decomposition of the secondary forest of poplar and birch that is part of the forest - steppe transition zone in the south of the Greater Xing＇ an Mountains of Inner Mongolia by use of net bag method and lab analysis. The results show that after freez- ing and thawing process of non - growing season, the weight loss rates of forest litters of Betula platyphylla and Pob- ulus davidiana are 51.34% and 38.71% separately. The weight loss of forest litters has little change, which is di- reedy related to soil temperature and moisture in the growing season. And the pattern of weight loss is Ybich = 0. 312e - 0. 4721t （ R2 = 0. 9347） and YpoCar = 0. 035e -- 0. 3502t （ R2 = 0. 9601 ）. The transform rule of N, P, K and total organic carbon content basically appeared a releasing -enriching pattern from the former autumn to the next autumn. Nutrient dynamics decreased in early growing season, and the turning point of enrichment was at 210 - 240 d after decomposition, and the maximum enrichment was at 360 d after decomposition. So, the litter decom- position and the transform process of nutrients can＇ t be controlled by microbial decomposition, but it was associated with some abiotic factors such as rainfall, eluviation and physical breaking.