三江源国家公园不同草地土壤微生物功能基因的差异性分析

土壤微生物在陆地生物地球化学循环过程中起着非常重要的作用。为了探索青藏高原高寒草地类型地上植被特性和地下土壤环境与土壤微生物功能基因之间关系,以三江源国家公园高寒草原、高寒沼泽化草甸及高寒草甸3种典型草地类型为研究对象,利用基因芯片(GeoChip 5.0)技术测定其微生物功能基因丰度,并分析它们之间的差异及影响因素。结果表明:(1)3种草地类型地上群落结构和地下土壤环境存在差异性,其中高寒草原物种多样性指数、pH值较高,沼泽化草甸中土壤含水量、微生物量碳、地上生物量、土壤速效氮含量较高,高寒草甸中则是土壤微生物量氮含量较高;(2)3种高寒草地类型的碳循环、氮循环、磷循环、有机修复的土壤微生物功能基因丰度存在显著差异,其中这些功能基因的丰度在高寒沼泽化草甸最高,高寒草甸、高寒草原次之;(3)地上植物物种多样性虽对功能基因丰度变化的解释率(r2)在57.1%-61.2%之间,但统计学上不显著(P>0.05),而微生物基因丰度随地上生物量的增加而增加,且解释率(r2)为77.5%-80.0%(P<0.05)。在pH、土壤含水量、土壤微生物量等地下土壤环境因子中,pH对功能基因丰度存在显著影响(P<0.01)解释率在83.4%-87.5%间,且土壤微生物功能基因丰度随土壤pH的增加而降低;土壤含水量、土壤微生物量对土壤微生物功能基因丰度的解释率分别为81.9%-83.1%(P<0.05)和76.8%-86.2%(P<0.05),微生物功能基因丰度随这两者含量的增加呈上升趋势。进一步运用RDA分析发现,pH、土壤微生物量、地上生物量是影响微生物功能基因丰度的主要因子,其中土壤微生物量是土壤有机质的重要组成部分,土壤有机质又是通过地上植被凋落物沉积所得到的。因此,地上植被特性的自上而下控制因子影响了土壤环境中自下而上的控制因子,间接的影响了微生物功能基因丰度。由此得出,地上植被特性和地下土壤环境因子共同作用控制了微生物功能基因丰度使其出现差异性。

Analysis on the Difference of Microbial Function Gene in Different Grasslands of Sanjiangyuan National Park

Soil microorganisms play a very important role in the process of terrestrial biogeochemical cycling.In order to explore the aboveground vegetation characteristics,underground soil environment and soil microbial functional genes in alpine meadow of Qinghai-Tibet plateau,this study takes three typical grassland types of alpine steppe,alpine swamp meadow and alpine meadow of Sanjiangyuan National Park as research objects,to determine microbial functional gene abundance and further analyze the relationship between the three types of grasslands by Gene chip(Geochip 5.0)technique.According to the results,(1)According to the results,there exist great differences between the aboveground community structure and soil environment of three grassland types,among which the species diversity index and pH value of alpine steppe are higher,while the alpine swamp meadow contains greater proportion of soil water content,microbial biomass carbon,aboveground biomass and soil rapidly available nitrogen content.And the soil microbial biomass nitrogen content is higher in alpine meadow.(2)The abundance of soil microbial functional genes in carbon cycle,nitrogen cycle,phosphorus cycle and organic remediation also varies according to three grassland types,among which the abundance of functional genes in alpine swamp meadow was the highest,followed by alpine meadow and alpine steppe.And(3)even though the interpretation rate(r2)of aboveground plant species on functional gene abundance reaches 57.1%to 61.2%,it was not statistically significant(P>0.05),while microbial gene abundance increased in ahiger degree of biomass with an interpretation rate(r2)between 77.5%to 80.0%(P<0.05).Among the underground soil environmental factors including pH,soil water content and soil microbial biomass,pH had a significant effect on the functional gene abundance(P<0.01)with an interpretation rate between 83.4%to 87.5%,and the soil microbial functional gene abundance decreased with the increase of soil pH;In terms of soil water content and soil microbial biomass,their impacts on soil microbial functional gene abundance made the interpretation rates 81.9%?83.1%(P<0.05)and 76.8%?86.2%(P<0.05),respectively.Meanwhile,the soil microbial functional gene abundance increased with the growth of these two contents.Through further RDA analysis,it is found that pH,soil microbial biomass and aboveground biomass are the main factors affecting the abundance of microbial functional genes,among which soil microbial biomass is an important part of soil organic matter and the soil orgainc matter is generally obtained by litter deposition of aboveground vegetation.Therefore,the top-down control factors of aboveground vegetation characteristics influence the bottom-up control factors in soil environment,and indirectly affect the microbial functional gene abundance,thus being concluded that the aboveground vegetation characteristics and soil environmental factors together control the microbial functional gene abundance and make the difference.