Effects Of Precipitation Intensity On The Structure Of Soil Micro-Food Web And Ecosystem Multifunctionality

Precipitation regime changed under the background of global change.The precipitation regime in arid and semi-arid areas showed a trend of increasing precipitation intensity and decreasing precipitation frequency without changing precipitation mounts.Soil microorganisms and nematodes play important roles in terrestrial ecosystems,constituting soil micro-food webs and participating in various subsurface ecological processes.Ecosystems are multi-dimensional,providing multiple ecological functions and services simultaneously(i.e.,ecosystem multifunctionality).The change of precipitation pattern can exert profound influence on the structure and function of ecosystem by influencing soil micro-food web.However,most of the previous studies focused on the effects of precipitation changes on soil microorganisms or soil nematodes alone,there were few studies on the response of soil micro-food web to precipitation change.Therefore,this study conducted field experiments on precipitation addition in arid and semi-arid steppe to reveal the response rules of soil micro-food web and ecosystem versatility to changes in precipitation regime,providing scientific basis for future sustainable development of Inner Mongolia steppe and its surrounding areas.This precipitation addition field experiment was carried out in Inner Mongolia temperate grassland for 8 consecutive years(total precipitation remained unchanged,precipitation frequency and precipitation intensity changed),including 5 precipitation intensity treatments(2 mm,5 mm,10 mm,20 mm and 40 mm).The microbial biomass and diversity were determined by phospholipid fatty acid method(PFLA)and high-throughput sequencing method,and morphological identification was used to determine the composition and structure of nematode community.The results show that:(1)The change of precipitation intensity significantly affected the concentration of soil fungal PLFA,which reached the maximum value under 20 mm treatment,while had no significant effect on the concentration of bacterial PLFA.The diversity of fungi was significantly responsive to the change of precipitation intensity,and Shannon diversity index,ACE index and Chao diversity index were all the highest under the treatment of 10 mm precipitation intensity.The response of bacterial diversity index to precipitation intensity was not significant.Soil microbial community composition was not significantly affected by precipitation intensity.Except for extreme precipitation intensity,soil microbial community composition was different under different precipitation intensity treatments.(2)The soil nematodes extracted in this study belonged to 26 families and 33 genera.The total abundance increased with the increase of precipitation intensity,and the maximum was 1,458 individuals per 100 g dry soil under the treatment of 40 mm precipitation intensity.The lowest precipitation intensity of 2 mm was 401 individuals/100 g dry soil.The abundance of bacterivores increased monotonically with the increase of precipitation intensity.The abundance of fungivores and predatory/omnivorous was significantly higher in medium-high precipitation(10 mm,20 mm and 40 mm)than in low precipitation(40 mm).The abundance of plant parasites was highest under extreme precipitation(40 mm).Shannon diversity index,evenness index and richness index were significantly affected by precipitation intensity.The composition of soil nematode community was scattered among different precipitation intensities.(3)Soil water content,fungivores abundance and nematode diversity were significant factors that directly affected ecosystem multifunctionality.