毛竹凋落叶组成对叶凋落物分解的影响

Effects of different proportion mixed Phyllostachys pubescens leaf litter on litter decomposition in P.pubescens forest

毛竹混交林具有较高的生产力和较好的生态功能,可能与混合凋落物的养分归还特征有关。本研究采用凋落物分解袋法对不同混合比例毛竹凋落叶分解特征进行了为期1年的研究,共设置5个处理,分别为Ⅰ(毛竹纯叶)、Ⅱ(毛竹、楠木叶比例为8:2);Ⅲ(毛竹、杉木叶比例8:2)、Ⅳ(毛竹、楠木叶比例5:5)和Ⅴ(毛竹、杉木叶比例5:5)。结果表明,不同处理凋落物分解速率符合Olson指数分解模型,R2均高于0.92。5个处理分解系数的排列顺序为Ⅱ>Ⅰ>Ⅲ>Ⅴ>Ⅳ,分别为0.68、0.66、0.58、0.55和0.49。处理Ⅰ和Ⅱ的分解速度显著高于其他处理,说明并非所有类型毛竹混合凋落叶均会促进凋落物分解,只有合适的比例和树种会促进凋落物分解。其中,竹阔混合凋落叶的分解速度高于竹针混合凋落叶的分解速度,竹阔混交可能更有利于竹林持续生产力的维持。N、P、K3种元素养分释放模式不同,N元素表现为净富集与净释放交替出现;P元素在经过4个月的快速富集后,4—5个月有短暂的净释放过程,其后呈富集状态;K元素浓度先升高后降低,在放置的前3个月净释放,随后呈富集状态。竹林凋落叶的养分含量对凋落物养分归还有重要影响,尤其是C/N和P可能作为竹林凋落物分解的指示者。

Mixed Phyllostachys pubescens forest has high productivity and good ecological functions,which is possibly related to the nutrient return characteristics of mixed litter.By using litterbag method,a one-year experiment was conducted to study the decomposition characteristics of different proportion mixed P.pubescens leaf litters in P.pubescens forest in the Yangkou National Forest Farm,Fujian Province of Southeast China.Five treatments were installed,i.e.,pure P.pubescens leaf litters（Ⅰ）,P.pubescens＋Phoebe bournei litters（mass ratio 8：2,Ⅱ）,P.pubescens＋Cunninghamia lanceolata litters（8：2,Ⅲ）,P.pubescens ＋P.bournei litters（5：5,Ⅳ）,and P.pubescens＋C.lanceolata litters（5：5,Ⅴ）.The litter decomposition rates of different treatments were all compatible with the exponential decomposition model of Olson（R20.92,P0.01）.The decomposition rate in treatments Ⅰ and Ⅱ was significantly higher than that in other treatments,and the coefficient of decomposition was in the order of Ⅱ Ⅰ Ⅲ Ⅴ Ⅳ,being 0.68,0.66,0.58,0.55,and 0.49,respectively,which illustrated that only appropriate proportions of mixed tree species leaf litters could promote the litter decomposition.The litter of mixed bamboo-broadleaved forest had higher decomposition rate than that of mixed bambooconifer forest.Therefore,the mixed bamboo-broadleaved forest could benefit the persistent productivity of bamboo forest.During decomposition,the N,P,and K in the litters had different release patterns.The N followed the pattern of alternate enrichment and release;the P was rapidly enriched in the first four month,released from the fourth month to fifth month,and then enriched;the K was released in the first three months,and then enriched.The nutrient return of the litters was closely related to the nutrient contents of the litters.The litter C /N ratio and P content could be the key indices for the litter decomposition.