模拟酸雨淋溶对缙云山针阔混交林与常绿阔叶林凋落物分解的影响

Effects of simulated acid rain leaching on the litter decomposition of coniferous broad-leaved mixed forest and evergreen broad-leaved forest in Mount Jinyun

【目的】探讨缙云山针阔混交林与常绿阔叶林凋落物分解在酸雨过程中的特点和规律,为优化缙云山森林管理,指导林分配置提供科学依据。【方法】以重庆缙云山2种典型林分为研究对象,进行4个不同酸碱度:pH 4.50(对照)、pH 4.00、pH 3.25和pH 2.50的酸雨模拟实验,结合Olson负指数衰减模型,分析针阔混交林与常绿阔叶林的凋落物分解速率并计算分解系数,定量分析模拟酸雨下2种典型林分的凋落物分解变化规律。【结果】①经过0.5 a的分解,对照、pH 4.00、pH 3.25和pH 2.50处理下针阔混交林质量残留率均高于常绿阔叶林,分别高4.60%、3.78%、4.22%和5.39%。其中,对照针阔混交林凋落物损失率达到半衰期与全衰期的时间为1.62、6.98 a,常绿阔叶林为1.29和5.56 a;不同酸碱度酸雨淋溶下针阔混交林凋落物损失率达50%和95%的时间分别为1.47~2.00和6.35~8.43 a,常绿阔叶林分别为1.23~1.50和5.33~6.48 a。②对照、pH 4.00、pH 3.25和pH 2.50各处理下针阔混交林的分解常数k值分别为0.43、0.47、0.40和0.35,常绿阔叶林则分别为0.54、0.56、0.51和0.46,k值随着处理pH的降低呈下降趋势。③研究区pH 4.00的模拟酸雨一定程度上对林内凋落物的分解有促进作用;pH 2.50和pH 3.25的模拟酸雨一定程度上抑制不同林下调落物的分解。【结论】重庆缙云山模拟不同酸碱度酸雨对2种典型林分的凋落物分解速率影响显著,常绿阔叶林分解速率总体高于针阔混交林,温度制约凋落物分解速率。

[Objective]This study,with an investigation of the characteristics and laws of litter decomposition in mixed coniferous and broad-leaved forest and evergreen broad-leaved forest during acid rain in Jinyun Mountain,is aimed to provide scientific basis for the optimization of forest management and the guidance in forest stand allocation.[Method]With two typical forests of Jinyun Mountain in Chongqing selected,four acid rain simulation experiments with different concentrations were conducted.Then,with the employment of the Olson negative exponential decay model,the decomposition rate of litter of two forest stands was assessed,and the laws of litter decomposition in two typical forest stands under simulated acid rain were analyzed.[Result](1)After a six-month decomposition,in comparison,the mass residue rate of the mixed coniferous and broad-leaved forest treated with acid rain of pH 4.50(ck),pH 4.00,pH 3.25,and pH 2.50 was higher than those of the evergreen broad-leaved forest under the same conditions by 4.60%,3.78%,4.22%and 5.39%.(2)The time for the control group to reach half-life and full-life of litter decomposition in the coniferous and broad-leaved mixed forest was 1.62 a and 6.98 a whereas that for evergreen broad-leaved forest was 1.29 and 5.56 a;the time for the material loss rate to reach 50%and 95%for the coniferous and broad-leaved mixed forest litter under different concentrations of acid rain is 1.47−2.00 a and 6.35−8.43 a whereas that for the evergreen broad-leaved forest is 1.23−1.50 a and 5.33−6.48 a.(3)The k values of the mixed coniferous and broad-leaved forests treated with ck,pH 4.0,pH 3.25,and pH 2.5 were 0.43,0.47,0.40,and 0.35,respectively while those of the evergreen broad-leaved forest were 0.54,0.56,0.51,and 0.46,respectively,and the overall k value shows a downward trend as the pH value of the treatment decreases.(4)The simulated acid rain with pH 4.00 in the study area promoted the decomposition of litter in the forest to a certain extent whereas the simulated acid rain with pH 2.50 and pH 3.25 inhibited the decomposition of falling objects in different forests to a certain extent.[Conclusion]In Jinyun Mountain of Chongqing,simulated acid rain of different concentrations had a significant effect on the decomposition rates of litters in the two typical stands and the decomposition rate of evergreen broad-leaved forest was higher than that of coniferous and broad-leaved mixed forest.