低效柏木林窗改造模式下香椿细根分解及其养分释放

Fine root decomposition and nutrient release in Toona sinensis plantation under the reconstruction mode of low-efficiency cypress forest gaps

细根分解是土壤生态系统养分归还的主要途径,为进一步掌握森林生态系统的物质循环特征,以川中丘陵区林窗改造补植阔叶树种5年生香椿人工林（Toona sinensis）为研究对象,应用埋袋法测定细根在50 m^2（L1）、10 0 m^2（L2）和150 m^2（L3）林窗内1年的分解速率,同时探讨细根分解自身养分释放动态.结果显示,香椿细根在前90 d分解最快,随着时间的推移,细根分解速率减缓,在分解365 d后,L1、L2和L3内香椿细根分解残留率分别为75.4 4%、73.92%和72.07%.香椿细根分解速率L3〉L2〉L1.并且在3种不同大小林窗内香椿1-3级、4级和5级细根1年的分解过程中碳、磷和钾浓度整体表现为下降趋势,氮、钙和镁整体表现为增加趋势.综上表明,林窗式改造对香椿细根分解和养分释放产生了一定影响,并且随林窗面积的不同而发生变化,有利于提高森林生态系统的服务功能.

Fine root decomposition is an important way in which nutrients are returned to plantation soil; thus, further study of this process will be helpful for understanding material cycling in forest ecosystems. We investigated a Toona sinensis plantation in the central Sichuan hilly region using litter bags containing T. sinensis fine roots to evaluate the dynamics of fine root decomposition and nutrient release for one year in forest gaps of 50 m^2（L1）, 100 m^2（L2）, and 150 m^2（L3）. The results showed that T. sinensis fine root decomposition was fastest in the first 90 days. As time passed, the decomposition rate slowed. One year later, the residue rate was 75.44%, 73.92%, and 72.07%, respectively. The fine root decomposition rate of L3 was greater than that of L2, which was greater than that of L1. During fine root decomposition, the dynamics of the fine root nutrient concentrations changed. C, P, and K concentrations of the fine roots declined in forest gaps, while N, Ca, and Mg concentrations increased overall in the fine roots. In conclusion, forest gaps had effects on the fine root decomposition and nutrient release of T. sinensis, and different sized forest gaps produced different results.