Decomposition Characteristics of Fresh Residues of Pleioblastus amarus in Different in-forest Environments
[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(T0.5)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 T0.5 of root in RB environment was significantly higher than that of CK.The decomposition period(T0.95)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 T0.95 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.
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