不同林内环境下苦竹新鲜残体的分解特征

Decomposition Characteristics of Fresh Residues of Pleioblastus amarus in Different in-forest Environments

[目的]研究苦竹新鲜残体的分解过程及影响因素可以预测苦竹林在受到极端气候事件导致的机械损伤后生态系统物质循环变化过程,评估灾害对森林碳汇功能的影响,为灾后森林科学管理提供依据。[方法]以广东南岭地区皆伐后苦竹大量扩张的次生林为对象,设置对照(CK)和移除林下竹子(RB)两种林内环境,采用分解袋法研究了苦竹各器官新鲜残体的分解特征。[结果]苦竹各器官新鲜残体的分解过程可以分为两个阶段,即前期阶段(前2个月)质量快速损失,后期阶段(后24个月)缓慢分解。前期阶段各器官平均质量损失率依次为竹叶(51.2%)>竹枝(31.7%)>竹根(24.4%)>竹秆(16.6%),各器官间均存在显著差异(P<0.05),RB环境下竹叶的质量损失率显著低于CK。后期阶段各器官平均质量损失率依次为竹枝(40.3%)>竹叶(29.1%)>竹秆(28.1%)>竹根(19.6%),各器官间除竹叶与竹秆外均存在显著差异,RB环境下竹枝的质量损失率显著高于CK,竹根的质量损失率显著低于CK。Olson分解模型能够较好地模拟各器官的分解过程,平均分解系数(k)依次为竹叶(0.891)>竹枝(0.554)>竹秆(0.249)>竹根(0.242),各器官间除竹秆和竹根外均存在显著差异,RB环境下竹叶的k显著低于CK。各器官分解50%的周期(T_(0.5))依次为竹秆(2.48 a)>竹根(2.44 a)>竹枝(0.97 a)>竹叶(0.51 a),其中竹根和竹秆显著高于竹枝和竹叶,RB环境下竹根的T_(0.5)显著高于CK。各器官分解周期(T_(0.95))依次为竹根(12.81a)>竹秆(12.12 a)>竹枝(5.22 a)>竹叶(3.22 a),其中竹根和竹秆显著高于竹枝和竹叶,RB环境下竹秆的T0.95显著低于CK,竹根的T_(0.95)显著高于CK。各器官基质质量与分解指标间的相关系数总体上表现为前期阶段高于后期阶段,CK环境下高于RB环境下,其中碳(C)、钾(K)、C/氮(N)、C/磷(P)与分解指标间相关系数较小,N、P、N/P与分解速率呈正相关,木质素/N与分解速率呈负相关。[结论]苦竹新鲜残体的分解过程表现为前期快速失重后期缓慢分解;竹叶分解速率最快,其次为竹枝,竹秆和竹根最慢;各器官基质质量中,N、P、N/P、木质素/N对分解速率影响较大,且主要影响分解前期阶段;清除林下竹子能减缓竹叶和竹根的分解,加快竹秆和竹枝的分解,减弱基质质量对分解速率的影响。

[Objective]To study the decomposition process of fresh residues of Pleioblastus amarus(Keng)keng and its influential factors,predict the changes in processes of ecosystem material cycling in bamboo forests after being mechanically damaged by extreme climatic events,and assess the impacts of the dis-aster on the function of forest carbon sinks for providing a basis for the scientific management of forests after the disaster.[Methods]Based on the secondary forests,where P.amarus expanded greatly after clearcutting,in the Nanling area of Guangdong Province,two treatments including removal of understory bamboos(RB)and control(CK)were set uo to generate distinct in-forest environments,and the decom-position characteristics of fresh residues from various organs of P.amarus were studied using the decom-position bag method.[Results]The decomposition process of fresh residues of each organ of P.amarus could be divided into two stages,rapid mass loss in the early stage(first 2 months)and slow decomposi-tion in the later stage(last 24 months).The average mass loss rate of each organ in the early stage was in the order of leaves(51.2%)>twigs(31.7%)>roots(24.4%)>culms(16.6%),and there were significant differences(P<0.05)among all organs,with a significantly lower mass loss rate of leaves in RB environ-ment than that of CK.The average mass loss rate of each organ at the later stage was in the order of twigs(40.3%)>leaves(29.1%)>culms(28.1%)>roots(19.6%),and there were significant differences among the organs except for leaf and culm.The mass loss rate of branches in RB environment was significantly higher than that of CK,while the mass loss rate of roots was significantly lower than that of CK.The Olson decomposition model could well fit the decomposition processes of various organs.The average decom-position coefficient(k)of leaves(0.891)was the largest,followed by the twigs(0.554),culms(0.249),and roots(0.242).There were significant differences of the k among all organs except for culms and roots,and the k of leaves in RB environment was significantly lower than that of CK.The period of 50%decomposi-tion(T_(0.5))of each organ was in the order of culms(2.48 a)>root(2.44 a)>twigs(0.97 a)>leaves(0.51 a),with roots and culms significantly higher than twigs and leaves,and the T_(0.5) of root in RB environment was significantly higher than that of CK.The decomposition period(T_(0.95))of each organ was in the order of roots(12.81 a)>culms(12.12 a)>twigs(5.22 a)>leaves(3.22 a),with roots and culms significantly high-er than twigs and bamboo leaves.Under RB environment,the T_(0.95) of culms and roots was significantly lower and higher than that of CK,respectively.The correlation coefficient between the substrate quality of various organ and decomposition indexes was generally higher in the early stage than in the later stage,and higher in the CK than in the RB environment.Among them,the correlation coefficients between car-bon(C),potassium(K),C/nitrogen(N),C/phosphorus(P)and the decomposition indexes were relatively small;N,P,and N/P were positively correlated with decomposition rate,and lignin/N was negatively correl-ated with decomposition rate.[Conclusion]Decomposition of fresh residues of P.amarus is characterized by a rapid weight loss in the early stage and a slow decomposition in the later stage.Leaves have the fast-est decomposition rate,followed by twigs and culms,and roots are the slowest.Among the substrate qual-ities of various organ,N,P,N/P,and lignin/N have significant impacts on the decomposition rate,in partic-ular in the early stage of decomposition.Removal of understory bamboo can slow down the decomposi-tion of leaves and roots,accelerate decomposition of culms and twigs,and attenuate the effects of sub-strate quality on decomposition rates.