降水季节性分配格局对亚热带灌木凋落物分解的影响

Effects of seasonal distribution pattern of precipitation on shrub litter decomposition in a subtropical forest

气候变化导致的降水季节性分配格局变化对水分可利用性、微生物活性及相关酶类活性的改变,可能对森林凋落物分解过程施加不同程度的影响,亟待深入研究。2020—2021年采用野外原位控制实验法和分解袋法,研究了我国亚热带常绿阔叶林中常见的灌木树种早竹(Phyllostachys violascens)和八角枫(Alangium chinense)凋落叶于1年内干季和湿季不同阶段的分解动态。共设置对照(CK),干季更干、湿季极端降水增加(DD)和干季更干、湿季降水等比例增加(EW)3种处理。结果表明:物种、降水处理和分解阶段均影响着凋落物分解率。试验期内,干季更干、湿季更湿的降水格局显著提升了两种凋落物的分解速率(早竹2.01%以上,八角枫4.69%以上),并以湿季降水等比例增加的影响最为显著。此外,干季更干、湿季更湿的降水格局提升了两种凋落物湿季对全年分解总量的贡献率,同样以湿季降水等比例增加的影响更为明显。这是因为干季更干、湿季更湿的降水格局可通过对酶活性和微生物生物量的正效应,降低凋落物中难降解物质和元素含量,间接提升凋落物分解率。因此,由气候变化带来的降水季节性分配格局改变不但会显著影响亚热带森林凋落物的分解过程,还会改变干季和湿季对全年分解总量的贡献率。

Changes in the seasonal distribution of precipitation induced by climate change affect water availability,microbial activity,and related enzyme activities,which may exert an influence on forest litter decomposition,deserving to be further studied.In this study,we examined decomposition dynamics of leaf litter of Phyllostachys violascens and Alangium chinense,two common shrub species in a subtropical evergreen broad-leaved forest in China in different stages of dry and wet seasons from 2020 to 2021 using field in-situ control experiment and litterbag methods.There were three precipitation treatments:control(CK),drier dry season,increased extreme precipitation in wet season(DD),and drier dry season,proportionally increased precipitation in wet season(EW).The results showed that species identity,precipitation treatment,and decomposition stage all affected litter decomposition rate.During the experimental period,the precipitation pattern of drier dry season and wetter wet season(DD and EW)significantly increased decomposition rates of the two types of litter(more than 2.01%for P.violascens and more than 4.69%for A.chinense),and the effect of the proportionally increased precipitation in wet season was the most significant.In addition,the precipitation pattern of drier dry season and wetter wet season increased the contribution rate of the two types of litter in the wet season to the total yearround decomposition,with the effect of proportionally increased precipitation in wet season being more obvious.This is contributed to the precipitation pattern of drier dry season and wetter wet season can indirectly improve litter decomposition by reducing the content of refractory substances and elements in litter through a positive effect on enzyme activity and microbial biomass.As a result of climate change,changes in precipitation distribution patterns will not only affect the decomposition of subtropical forest litter,but also change the contribution rate of dry season and wet season to the total annual decomposition.