杉木人工林细根分解和养分释放及化学组成变化

在福建建瓯万木林自然保护区杉木人工林里采用网袋法进行杉木细根（按直径大小分成0～1mm、1～2mm、2～4mm3个级别）分解研究．在为期720天的时间里，网袋中所有细根分解均表现出2个快慢不同的阶段：细根在前期分解速度较快，3个径级干重年（360天）损失率分别达54．8％、41．2％和38．2％；后期分解速率显著下降．3个径级细根分解过程中，皆呈现N浓度上升、P浓度变化平缓、K浓度下降趋势．细根化学组成分析显示：0～1mm、1～2mm径级可萃取物浓度呈下降趋势，酸溶性物质浓度变化平缓，酸不溶性物质浓度呈上升趋势；2～4mm径级可萃取物、酸溶性物质浓度呈下降趋势，酸不溶性物质浓度呈上升趋势．相关分析表明：不同径级细根分解速率与其底物中初始的P、K、可萃取物浓度呈极显著正相关，而与C／P比、酸不溶性物质／N、酸不溶性物质／P显著负相关．

Decomposition Dynamics of Fine Roots of Cunninghamia lanceolata in Mid-subtropics

Decomposition of fine roots （divided into 041 mm, 142 mm, 244 mm in diameter） was studied by litter bag method in natural reserve of Jian＇ou, Fujian. In a 720 d period of decay, fine roots in all litter bags decomposed in a bi phase manner： in the first stage, all fine roots showed faster decomposition, with their mass loss rate added up to 54.8%, 41.2%, 38.2% in 360 d, respectively; whereas, decomposition of all fine roots slowed down significantly in the second stage. Consistent increase in concentration of N and decrease in concentration of K and no significant variation of P concentration were observed. Chemical composition analysis of the fine roots showed that concentration of extractives declined, while acid insoluble carbon fraction increased and acid soluble carbon fraction remained stable in the ,a process of decomposition. Statistical analysis indicated that decomposition of fine roots were positively correlated with initial P, K and extractive concentration, but negatively correlated with initial ratio of C/P, acid insoluble/N and acid insoluble/P.