掌握旅游干扰对土壤微生物多样性及群落结构的影响, 有助于旅游区环境资源的恢复和管理。该研究在北京松山国家级自然保护区油松(Pinus tabuliformis)林内设置了不同旅游干扰强度(高干扰、低干扰和无干扰)的样地, 调查样地内微生境状况, 测量土壤理化性质, 利用第二代高通量测序技术测定土壤微生物多样性和群落结构, 以评价不同旅游干扰强度对油松林土壤微生物的影响机制。结果显示: 1)高强度干扰显著降低了土壤真菌α多样性, 低强度干扰显著降低了土壤真菌系统发育多样性。干扰强度越大, 土壤真菌多样性越低, 而土壤细菌多样性越高。2)在土壤真菌群落方面, 3类样地的土壤优势真菌门均为担子菌门(Basidiomycota)和子囊菌门(Ascomycota); 高强度干扰显著降低了子囊菌门相对多度, 对担子菌门相对多度无显著影响, 而低强度干扰均对担子菌门和子囊菌门无显著影响。LEfSe分析表明无干扰区的差异类群为真菌Pseudogymnoascus属和3个真菌物种(Oidiodendron griseum、Acrodontium hydnicola、Metacordyceps chlamydosporia); 低干扰区内未能检测到差异类群; 高干扰区差异类群为真菌Clavariaceae科。3)在土壤细菌群落方面, 3类样地的土壤优势细菌门均为变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和酸杆菌门(Acidobacteria); 高强度干扰和低强度干扰对它们的多度无显著影响。LEfSe分析表明无干扰区的差异类群占总差异类群的82.05%, 指示性最强的为细菌Gaiellales和Solirubrobacterales目; 低干扰区未发现差异类群; 高干扰区的差异类群占总差异类群的17.95%, 主要表现为病原指示菌和与人类活动相关的菌群, 指示性最强的为细菌Flavobacteriia纲和疣微菌门(Verrucomicrobia)下一属。4)偏最小二乘法路径模型(PLS-PM)发现干扰强度显著影响微生境指标和土壤真菌多样性; 冗余分析显示, 土壤状况和微生境指标分别解释了不同干扰强度下真菌和细菌群落结构变化的71.35%和74.47%, 乔木胸径、草本盖度和凋落物盖度是不同干扰强度下真菌和细菌群落差异的主要因子。由上可见, 旅游干扰显著降低了油松林土壤微生物α多样性, 并显著影响了其群落结构, 影响效果的不同与干扰强度和微生物种类有关, 并且受到土壤理化性质和微生境状况调控。因此未来应注意旅游区内微生境和土壤状况的修复。

Aims Understanding the effect of tourism disturbances on soil microbial diversity and community structure is necessary for the restoration and management of environmental resources in tourist areas. Therefore, we conducted a field survey in Beijing Songshan National Nature Reserve, to reveal the effect of different tourism disturbance intensity on soil microorganisms in a Pinus tabuliformis forest.

Methods Three intensity groups, high disturbance (HD), low disturbance (LD) and no disturbance (ND), were conducted in the P. tabuliformis forest. We investigated microhabitat conditions and measured soil physicochemical properties. Next generation sequencing technique was used to determine the diversity and community structure of soil microorganisms. Then, we evaluated the impact of tourism disturbance intensity on soil microorganisms.

Important findings 1) HD significantly reduced soil fungal alpha diversity, and LD significantly reduced soil fungal phylogenetic diversity. Soil fungal diversity showed a decreasing trend, and soil bacterial diversity showed an increasing trend with increasing disturbance intensity. 2) For soil fungal community structure, the dominant phylum of three intensity groups were Basidiomycota and Ascomycota. HD disturbance significantly affected the relative abundance of Ascomycota, but had no effect on Basidiomycota, LD had no effect on both of them. LEfSe analysis showed that indicators of ND were Pseudogymnoascus and three species (Oidiodendron griseum, Acrodontium hydnicola, Metacordyceps chlamydosporia); indicator of HD was Clavariaceae; there was no indicator in LD. 3) For bacterial community structure, the dominant phylum of three intensity groups were Proteobacteria, Actinobacteria and Acidobacteria, but HD and LD had no effect on them. LEfSe showed that indicators of ND accounted for 82.05% of total indicators, and the most indicative ones were Gaiellales and Solirubrobacterales; indicators of HD accounted for 17.95% of total indicators, they mainly manifested as pathogenic indicator bacteria and bacterial groups related to human activities, the most indicative ones were Flavobacteriia and one genus of Verrucomicrobia; there was no indicator in LD. 4) Partial Least Squares Path Modeling (PLS-PM) found disturbance intensity significantly impacted microhabitat and alpha diversity of soil fungi. Redundancy analysis showed that soil and microhabitat condition explained 71.35% and 74.47% of variations in community structure of fungi and bacteria under different intensity group, respectively. Tree diameter at breast height, herb cover and litter cover were the main factors that altered fungal and bacterial community structure. In conclusion, tourism disturbance significantly reduced alpha diversity and impacted community structure of soil microbiota in the P. tabuliformis forest, and the degree of influence associated with disturbance intensity and the kind of microorganisms. Moreover, the impact was also controlled by microhabitat and soil physical and chemical properties. Therefore, future attentions should be paid to the restoration of microhabitats and soil conditions in tourism areas.