中文摘要：

采用埋袋法对水曲柳和落叶松粗根（5—10mm）、中根（2—5mm）、细根（〈2mm）的分解速率及其养分释放进行了为期2年的研究．结果表明，水曲柳粗根、中根和细根年分解系数分别为0．3649、0．4381和0．2720，落叶松依次分别为0．1967、0．1955和0．2464．通过养分分析发现，根系分解过程释放大量C和养分．分解150d后，两树种所有级别根系的可溶性糖释放均超过90％．水曲柳粗根和中根K的释放均在40％左右，细根K的释放为71％，落叶松所有级别的根系K的释放均在95％以上．在根系分解第2年。两树种粗根和中根N的释放在50％左右波动，P在40％左右波动，两树种细根N和P的释放均达到60％．因此，根系分解在C和养分循环中起重要作用，如果将其忽略，土壤有机质和养分元素的循环将会被严重低估．

英文摘要：

A two-year buried bag experiment with different sizes of Fraxinus mandshurica and Larix gmelinii roots showed that the coarse （5 -10 mm） , medium （2 -5 mm） and fine （ 〈2 mm） roots ofF. mandshurica had an annual decomposition coefficient of 0. 3649, 0.4381 and 0. 2720, while those of L. gmelinii had the coefficient of 0. 1967, 0. 1955 and 0. 2464, respectively. During root decomposition, large amounts of carbon and nutrients released. After buried into soil for 150 days, more than 90% of soluble sugar in all sizes of the two species roots was released, and about 40% , 71% and 95% of potassium was released from the coarse and medium, and fine roots of F. mandshurica, and all sizes of L. gmelinii roots, respectively. In the second year of the experiment, about 50% of nitrogen and 40% of phosphorus were released from the coarse and medium roots of the two species, and 60% of nitrogen and phosphorus were released from their fine roots. In the study of forest ecosystem＇ s carbon and nutrient cycles, root decomposition shouldn＇ t be ignored.