疏伐抚育对大熊猫栖息地八月竹纯林土壤细菌群落多样性的影响

Thinning Effect on the Diversity of Soil Bacterial Communities in Dwarf Bamboo(Chimonobambusa szechuanensis)Pure Stands in Chinese Giant Panda Habitat

疏伐抚育可改善大熊猫栖息地土壤质量和森林生态系统功能、提升生物多样性。然而,现有研究主要以提升人工用材林木材产量为主,对以提升自然保护地栖息地功能属性为目的的森林疏伐抚育如何影响地下生态过程,特别是土壤微生物群落变化研究相对较少。本文以大熊猫国家公园大相岭片区八月竹(Chimonobambusa szechuanensis)纯林为研究对象开展疏伐抚育,分析两种处理对纯林土壤理化性质和细菌微生物组的影响,重点研究疏伐抚育一年后土壤细菌群落多样性变化。结果表明:(1)不同疏伐抚育模式对土壤细菌群落影响差异较大。以促进主食竹更新复壮为目的的疏伐抚育模式(处理A)显著提高了土壤细菌群落Sobs指数(P=0.024)和Chao指数(P=0.027),表现出更高的群落丰富度。而以促进纯竹林向大熊猫更为喜爱的竹阔混交林转变的疏伐抚育模式(处理B)对纯林保留带中地下生态系统的影响并不显著。(2)LEfSe分析(LDA score>3,P<0.05)发现,八月竹林土壤细菌群落核心菌门为酸杆菌门(Acidobacteria)、放线菌门(Actinobacteria)和变形菌门(Proteobacteria)。与八月竹纯林相比,处理A显著提高了土壤pH值(pH=5.05,P<0.001),但有机碳(50.2 g/kg,P<0.001)、全氮(5.04 g/kg,P<0.05)和微生物生物量碳(700.54 mg/kg,P<0.01)含量均显著降低。(3)RDA分析表明土壤细菌群落门丰度变化主要与pH值(r^(2)=0.45,P<0.05)和全氮含量(r^(2)=0.39,P<0.05)变化有关。上述研究结果可以为进一步研究与纯竹林疏伐抚育相关的土壤微生物功能菌群提供参考。

Thinning is a necessary means to improve the soil quality and forest ecosystem function of giant panda habitat and enhance biodiversity.However,past scientific attentions was paid more to improving the timber yield of artificial forest,but there were relatively few studies on how thinning for the purpose of improving the functional attributes of habitats in nature reserves affect underground ecological processes,especially the changes of soil microbial communities.In this study,it took pure bamboo(Chimonobambusa szechuanensis)stands in the Daxiangling district of the Giant Panda National Park of China as a case study for control-experiments of thinning.Two thinning patterns(A vs B)were designed to apply separately to two pure bamboo stands,a year later followed by a careful examination of the physical and chemical properties of the pure bamboo soils and the bacterial microbiome,particularly the changes of soil bacterial community diversity.We have the following facts:(1)Different thinning patterns had different effects on soil bacterial community.As for the pattern A with a purpose of promoting the prosperity of staple bamboo,it had marked positive effects on the soil bacterial communities.It significantly increased the Sobs index(P=0.024)and Chao index(P=0.027)of soil bacterial community,exhibiting higher community richness as compared to those in natural pure bamboo stands.In contrast,the effect of the pattern B,which intended to expedite a transition of pure bamboo stands to broad-leaved forest,which are popular with giant pandas,had no significant impact on the underground ecosystem in reserved zone of pure forest.(2)LEfSe analysis(LDA score>3,P<0.05)revealed that the core taxa of soil bacterial communities in the pure stands were Proteobacteria,Acidobacteria,and Actinobacteria.Furthermore,the contents of organic carbon(50.2 g/kg,P<0.001),total nitrogen(5.04 g/kg,P<0.05),and microbial biomass carbon(700.54 mg/kg,P<0.01)were significantly reduced in pattern A,while soil pH(pH=5.05,P<0.001)was significantly increased.(3)The variation in some bacterial phyla abundance was significantly correlated with soil pH(r^(2)=0.45,P<0.05)and total nitrogen content(r^(2)=0.39,P<0.05).In conclusion,this study provides insights into the soil functional microbes associated with thinning patterns in pure bamboo stands.