Comparison Of Soil Nematode Communities Structure And Diversity Across The Main Grasslands In Northern China

Soil nematodes play many key roles in soil ecosystem, such as predator, competitor and commensal, occupy many levels of soil food web, and directly participate in the process of nutrient cycling and energy flow. Thus, soil nematode community structure and diversity can directly affect the function and stability of the entire ecosystems in some ways. Previous studies of soil nematode were focused on small research scale, little is known about the research on the large regional scale. This study sets a research transect in the east part of Eurasian grassland zone to investigate the change rules of soil nematode diversity and community structure. In addition, our research not only has a good understanding of driving factors of soil nematode change rules, but also can provide a certain theoretical basis for grassland reasonable utilization and sustainable development.In this study, four research sites of Eurasian grassland were established, they were meadow steppe, typical steppe, desert steppe and alpine meadow. We used Behrman funnel method to extract soil nematode, stereomicroscope to count the number of nematode, and microscope to identify. Finally calculate the relevant ecological index and analyze the correlation with soil physicochemical properties. The results are as follows:(1) There were 79 genera identified in this experiment. The dominant genus among different grassland types are Acrobeloides and Acrobeles in meadow steppe, Cervidellus in typical steppe, Chiloplacus and Cervidellus in desert steppe, Filenchus, Acrobeloides and Chiloplacus in alpine meadow, respectively. All dominant genera are bacteria except one genera is plant feeding which is belong to alpine meadow.(2) Significant differences of soil nematode density are through these grassland types. The meadow grassland has the highest nematode abundance(518/100 g dry soil),the desert grassland has the lowest one(113/100 g dry soil). Soil nematodes abundance is mainly affected by soil moisture contents, soil electrical conductivity and soil C:N. In particular, soil nematode abundance increases with the increase of soil water contents first, and reaches a highest number it decreases with the increase of soil water contents. At the same time, soil nematode abundance exhibits a negative correlation with soil electrical conductivity, but a positive correlation with soil C:N.(3) The soil nematodes community composition of four grassland types are different, in addition to typical steppe and desert steppe have some similar to some extent. From the nutritional groups, bacteria have the highest percentage among all the grassland types. However, predatory/omnivorous nematodes are the lowest group, the percentage of fungivorous and plant feeding nematode is different among four grassland types. From c-p groups, four grasslands all have the highest percentage of c-p2 group and the lowest percentage of c-p1. The second low percentage that all the four grasslands have is c-p5, c-p3 and c-p4 groups exhibit different percentages among four grassland types.(4) Meadow steppe has the highest soil nematode diversity. Redundancy analysis(RDA) result shows that soil electric conductivity is the driving factor of soil nematode diversity, and they are negative correlation. Soil electric conductivity mainly changes the stability of soil nematode community structure to influence its diversity.(5) From the perspective of soil nematode’s channel index, four grassland types have different matter decomposition way, meadow steppe and typical steppe are given priority to with bacteria way(NCR﹥0.75), while, desert grassland and alpine meadow is predominantly fungi way(NCR﹤0.75). From the perspective of soil nematode’s wasilewska index, all grassland have good soil quality, among them, typical steppe is the best(WI=9.40) and meadow steppe is the worst(WI=4.09).In conclusion, soil nematode abundance, diversity and community structure are highly distinct across four grassland types at a regional scale. Soil nematode abundance is mainly driven by soil C:N and soil nematode diversity is mainly driven by soil electrical conductivity. This study not only exhibits a good understanding of the driving factors of soil nematode change rules, but also provides a certain theoretical basis for reasonable grassland utilization and sustainable development.