退耕还林地三倍体毛白杨与黑麦草复合模式细根和草根的分解动态

Fine Root and Grass Root Decomposition in an Intercropping System of Triploid Populus tomentosa and Lolium multiflorum Established on Land Converting from Farmland

在天全县的退耕还林地中,对三倍体毛白杨+黑麦草模式细根和草根的分解及其N、P、K、Ca、Mg养分释放动态进行研究。细根Φ0～1mm、Φ1～2mm、Φ0～2mm及草根的第1年干质量损失率分别为73.97%、69.80%、73.44%和79.53%,应用对数方程模拟细根和草根的分解过程,拟合程度较好(R2>0.9,P<0.01),分解50%所需的时间分别为210、252、243和185d。细根分解过程中,P、K、Mg的含量下降,N、Ca的含量增加。草根分解过程中,养分元素的含量都呈现出不规则的波动变化,整体上没有明显的规律性。在细根分解过程中,P、K、Mg的养分释放率与其干质量损失率的变化趋势相似,分解前期增加较快,随后上升趋于平缓,而N、Ca的养分释放率增加整体比较平缓,元素分解速率均以P最快,其次是K、Mg,而N、Ca最慢;而草根分解过程中N、P、K、Ca、Mg的养分释放率初期增加都比较快,随后趋于平缓,并且元素分解速率呈现不规则变化,其中Ca分解率最慢,其他元素的分解率相近。由于细根和草根在垂直分布上的差异,整个生态系统中,土壤上下层地下凋落物的主要种类也有所不同,因而有利于三倍体毛白杨+黑麦草生态系统的可持续发展。

This study aims to investigate the rate of mass loss and release of nutrient elements of fine root and grass root in plantation of Triploid Populus tomentosa and Lolium multiflorum established on an abandoned farmland at Tianquan County in Sichuan Province. Fine root decay is influenced by an array of factors, of which the two most important are probably climate and the chemical composition of fine root. Rate of mass loss showed logarithmic relationship with time for fine root and grass root, with annual dry mass loss of 73.9% , 69.8% , 73.44 and 79.53% for fine root Ф0 - 1 mm,Ф1 - 2 mm,Ф0 - 2 mm and grass root respectively. Nutrient dynamics during decomposition showed the following tendency： 1 ）The content of N and Ca increased in the course of fine root decomposition, but the content of P, K and Mg declined; 2）The nutrient content of grass root was irregular during the decomposition ; 3） The percentages of P, K and Mg releasing and mass loss during decomposition of fine root following the similar trend, but the percentages of N and Ca has a gently releasing; 4）The percentages of nutrient releasing have a same trend during decomposition of grass root. It＇ s beneficial to the artificial ecosystem for the divergence of vertical distribution of fine root and grass root.