森林放牧对东北虎豹国家公园土壤理化性质和微生物群落组成的影响

Effects of forest grazing on soil properties and microbial community in the Northeast China Tiger and Leopard National Park

选取典型的放牧区和非放牧区,采用分层抽样设立了100个样方(放牧区47个、非放牧区53个),采用高通量测序数据并结合大数据分析的方法探讨了森林放牧对土壤理化性质和土壤微生物群落组成的影响.研究结果显示:放牧显著增加了土壤密度(P=0.005)和电导率(P=0.045),降低了土壤含水量(P=0.022),表明家畜的活动可能已经破坏土壤结构和降低土壤保水能力;放牧区的土壤可交换K+(P=0.015)与Ca2+(P=0.006)、全钙质量分数(P=0.004)显著高于非放牧区,表明放牧干扰加速了国家公园土壤养分积累.通过高通量测序技术,依据97%相似性原则,将细菌序列划分为9488个可操作分类单位(operational taxonomic units,OTUs),真菌序列划分为5676个OTUs.放牧区与非放牧区的土壤细菌和真菌群落组成差异显著,坡度、土壤电导率和植物丰富度是影响土壤细菌群落组成的主要因素,而真菌群落组成受到放牧强度、海拔、坡度、植物丰富度、土壤电导率、全氮和速效磷的显著影响.进一步分析表明:变形菌门的相对丰度与放牧强度、海拔、电导率显著正相关,而与植物丰富度显著负相关;放线菌门的相对丰度与电导率显著正相关;绿弯菌门的相对丰度与电导率、植物丰富度显著正相关;担子菌门的相对丰度与海拔、坡度显著正相关,而与电导率、速效磷质量分数、植物丰富度显著负相关;子囊菌门和孢霉菌门的相对丰度与电导率、速效磷质量分数、植物丰富度显著正相关,而与海拔、坡度显著负相关;罗兹菌门的相对丰度与全氮、速效磷质量分数、植物丰富度显著正相关,而与海拔、坡度显著负相关.本研究表明,长期林下放牧对东北虎豹国家公园土壤理化性质和土壤微生物群落结构产生了不同影响,考虑到土壤与其微生物之间的强相互作用,可以预计土壤微生物群落结构的变化将极大地改变土壤功能,这对指导野生动物栖息地的恢复具有重要意义.

Long-term forest grazing is a major anthropogenic disturbance in Northeast China Tiger and Leopard National Park,posing great threat to forest ecosystems due to heterogeneous and unpredictable changes in forest structure,function,and biodiversity.Understanding the responses of soil properties and microbial to grazing is useful for forest management and biodiversity conservation.The effects of long-term forest grazing on soil physicochemical properties and soil microbial community composition in the Northeast China Tiger and Leopard National Park were assessed in this study.Soil samples were collected in the summer in 2021,from 47 cattle-grazed forest plots and 53 un-grazed forest plots.High-throughput sequencing technique was used to analyze soil bacterial and fungal communities in two forest areas.Generalized linear mixed model and non-metric multidimensional scaling were used to assess effects of forest grazing on soil properties and microbiome.Continuous forest grazing was found to significantly increase soil bulk density(P=0.005),soil conductivity(P=0.045),but decrease soil water content(P=0.022);livestock grazing may therefore damage soil structure and reduce soil water retention capacity.Soil exchangeable K+(P=0.015)and Ca2+(P=0.006),soil total calcium(P=0.004)were significantly higher in grazed forests than un-grazed forests,grazing disturbance therefore accelerated soil nutrient accumulation in the National Park.A total of 9488 bacterial operational taxonomic units(OTUs)and 5676 fungal OTUs were obtained according to a 97%sequence similarity level.Non-metric multidimensional scaling revealed that composition of soil bacterial and fungal community differed significantly between grazed and un-grazed forests.Soil bacterial community composition was primarily influenced by slope,electrical conductivity,plant richness,whereas fungal community composition was significantly influenced by grazing intensity,elevation,slope,plant richness,electrical conductivity,total nitrogen and available phosphorus.The relative abundance of Proteobacteria was found significantly positively correlated with grazing intensity,elevation and electrical conductivity,but negatively correlated with plant richness.Relative abundance of Actinobacteriota was positively correlated with the electrical conductivity.Relative abundance of Chloroflexi was significantly correlated with electrical conductivity and plant richness.Relative abundance of Basidiomycota was significantly positively correlated with elevation and slope,but negatively correlated with electrical conductivity,available phosphorus and plant richness.Relative abundance of Ascomycota and Mortierellomycota were found significantly positively correlated with electrical conductivity,available phosphorus and plant richness,but negatively correlated with elevation and slope.Relative abundance of Rozellomycota was significantly positively correlated with total nitrogen,available phosphorus and plant richness,but negatively correlated with elevation and slope.These data suggest that forest grazing practices affect soil properties and microbes differently.Given the strong interaction between soil and microbiome,changes in soil microbial community structure can be expected to substantially alter soil function.This will have important ecological service implications,particularly for wildlife habitat and carbon storage in key regional priorities for biodiversity.