米槠天然林树木根系分解和化学组分变化

运用网袋法，在福建建瓯万木林自然保护区米槠天然林内,将米槠根系按直径大小分成0～1、1～2和2～4 mm 3个级别进行分解研究.结果表明:在为期2年(720 d)的分解试验过程中，网袋内所有米槠根系的分解速率均呈现前期较快、后期较慢的变化特征，主要是可萃取物的淋溶损失使根系的前期分解较快，而酸不溶性物质浓度的上升抑制了其后期分解.根系分解1年(360 d)后，不同径级根系的分解速率由其初始可萃取物和N浓度控制;而分解2年(720 d)后，其根系底物中初始C/N、初始酸不溶物质与N、P浓度共同决定分解速率.在分解过程中，米槠3个径级根系都表现为N浓度不断上升、P浓度不断下降的趋势,其中N的释放呈现富集-释放格局，而P则为直接释放.

Root decomposition characteristics of Castanopsis carlesii stand in Wanmulin Natural Reserve of Fujian Province.

By using litter-bag method, the root decomposition characteristics of Castanopsis carlesii stand in Jian’ou Wanmulin Natural Reserve of Fujian P rovince were studied over two years. Three classes of roots, i.e., 0〖KG-*2〗-〖 KG-*7〗1 mm, 1〖KG-*2〗-〖KG-*7〗2 mm, and 2〖KG-*2〗-〖KG-*7〗4 mm in diameter, were tested. During the 2-year period of decomposition, all classes roots show ed a bi-phase pattern, being decomposed faster in prophase and slower in anapha se. The leaching loss of extractable substances in roots made root decomposition faster in prophase, while the increase of the acid-insoluble substances conce ntration in roots restrained the decomposition in anaphase. In the first year, t he decomposition rate of all classes roots was controlled by the initial concent rations of their extractive substances and N; while in the second year, the deco mposition rate was controlled by the initial C/N and the initial concentrations of acid-insoluble substances, N and P of the roots. During decomposition, all c lasses roots showed an increasing N concentration and a decreasing P concentrati on, and the N showed an enrichment-release pattern, while the P showed a direct release pattern.