三倍体毛白杨-黑麦草复合生态系统林木细根与草根的分解及养分动态

在天全县的退耕还林地中，对三倍体毛白杨细根与黑麦草草根的分解及其N、P、K、Ca和Mg养分动态进行了研究.结果表明，细根直径0～1、1～2和0～2 mm及草根的分解速率与时间呈负指数关系，第1年干重损失率分别为76.17%、69.80%、73.44%和79.53%，分解50%所需的时间分别为217、266、254和172 d.细根分解过程中，N和Ca浓度增加，而P、K、Mg浓度下降；草根分解过程中，其养分元素的浓度变化整体上没有规律.细根分解过程中P、K和Mg的养分残留率与其干重残留率的变化趋势相似，分解前期下降较快，随后下降比较平缓，N和Ca的养分残留率下降则比较平缓，并且养分的分解速率均以P最快，其次是K和Mg，而N和Ca最慢；草根分解过程中N、P、K、Ca 和Mg的养分残留率初期下降比较快，随后趋于平缓，并且元素分解速率呈不规则变化，其中Ca分解速率最慢，其它元素的分解速率相近.

Decomposition of Triploid populus tomentosa fine root and Lolium multiflorum grass root in a composite ecosystem and their nutrient dynamics

This paper studied the root decomposition and its nutrient dynamics of Triploid populus tomentosa and Lolium multiflorum in a plantation converted from farmland at Tianquan County of Sichuan Province. The results showed that the weight loss rate of fine root and grass root showed an exponential relationship with time, with an annual loss of 76.17%, 69.80%, 73.44% and 79.53% for fine roots of 0 approximately 1, 1 approximately 2 and 0 approximately 2 mm in diameter and grass root, respectively. During the decomposition of fine roots, their N and Ca contents increased, while P, K and Mg contents were in adverse. The nutrient contents of grass root during its decomposition had an irregular variation. The remaining percentage of fine root P, K and Mg had the same trend as root weight loss during its decomposition, while that of N and Ca had a slight decrease. For grass root, its N, P, K, Ca and Mg contents declined rapidly at the initial stage of decomposition, and then decreased slowly with irregular deposition rate.