Effects Of Warming On Macro- And Meso- Soil Fauna Community And Greenhouse Gas Emissions In The Peatland,Great Hing'an Mountains

Peatland mainly distributes in the northern mid-high latitude region,it is very sensitive to global warming.As the main distribution area of peat land in China,the Great Hing'an Mountains has shown a trend of large-scale degradation of frozen soil in recent years under the background of climate warming.The pattern of freeze-thaw and freeze-thaw cycle have also undergone profound changes,which will inevitably lead to changes in the community structure and function of soil fauna.However,study on the effects of climate warming on the community structure and ecological function of soil fauan in this sensitive area is scare.Therefore,we first simulated the process of frozen soil degradation by using the method of space instead of time,and used the method of transect sampling to analyze the distribution of soil fauna community in wetlands and adjacent island forests in continuous permafrost region,discontinuous island permafrost region and seasonally frozen ground region,revealing the dynamics of soil invertebrate community under the change of freeze-thaw environment.And the relationships between soil fauna and environmental factors were analyzed as wel.Then a warming experiment using open-top chambers?OTC?in field and two microcosm experiments were established in a typical permafrost peatland in Great Hing'an Mountains,focusing on both the effects of warming and freeze-thaw action on the community structure and ecological function of soil fauna.The aim of this study were to explore the responses of soil fauna community structure and trophic relationships on warming and freeze-thaw action,discuss the effects of earthworms on greenhouse gas emissions?CO₂ and N₂O?under the interaction of temperature and moisture,and reveal the response mechanism of soil invertebrate communities to climate warming.Mainly draw the following conclusions:?a?Based on the transect investigation,a total of 918 soil macrofauna belonging to 8 orders,13 groups were captured;20,678 mites belonging to 3 orders,30 families,46 species were collected;8,037 Collembola belonging to 1 order,12 families,35species were identified.The individual numbers of soil macrofauna were not significantly different between discontinuous permafrost region and seasonally frozen ground region,but both were significantly higher than those in continuous permafrost region.The individual numbers of mites and Collembola?soil mesofauna?increased gradually from the continuous permafrost region to the seasonally frozen ground region,that was,from high latitude to low latitude.Temperature was the key factor that could affect soil fauna communities in the frozen soil region.In the same type of frozen soil area,mainly due to the vegetation type,the individual density,species number,Margalef index and Shannon-Wiener index of soil fauna in island forest were higher than that in wetland.Based on the corresponding analysis we found that Shannon-Wiener index and Pielou index of soil macrofauna were positively correlated with the soil total phosphorus content.Soil water content,soil organic carbon,soil total nitrogen content and soil total potassium content were significantly correlated with the diversity indices of soil mite and soil Collembola?soil mesofauna?.Redundancy analysis showed that soil temperature,soil organic carbon and soil total phosphorus content were the main factors affecting soil fauna distribution.?b?Based on a warming experiment using Open Top Chambers?OTC?in field,we detected the temperature and soil water content were both higher in warmed plots than the control plots.Warming and moistening significantly increased the number of individuals and species of soil macrofauna and soil Collembla,while the soil mite community did not change significantly.On the month scale,the number of individuals and species in August was significantly higher than that in May and September,because the rain and heat over the same period in August,which was characterized by lush vegetation and suitable soil temperature,providing a good habitat and abundant food for soil fauna.In warmed plots,the trophic level of Aphididae,Sminthuridae and Orchesellidae up to the third grade,and Tomoceridae and Lepidoptera larvae up to the fourth grade,while Aleyrodidae and Thripidae down to the second grade.The level of the other invertebrates did not change.The alteration in trophic levels was attributed to the impact of warming on light,heat,soil moisture,and vegetation in the peatland.?c?During the freeze-thaw incubation experiment,freeze-thaw action significantly reduced the individual number,species number and Shannon-Wiener index of invertebrate,and these index in large amplitude of FTC?-10?⁵??were the lowest.Meanwhile,the numbers of FTCs also significantly affected the individual number,species number and Shannon-Wiener index of invertebrate.These indices decreased when the number of FTCs increased.Different groups of invertebrate responded differently to freeze-thaw action,and the mites in this experiment were more tolerant to low temperature.?d?In the earthworm incubation experiment,we found the warming,moistening,earthworm and the interaction of these three factors significantly facilitate CO₂emission from peatland soil.In particular,earthworm significantly promote CO₂emission only in 80%WHC not in 60%WHC at identical temperature;When in the case of 80%WHC,temperature is the main factor that affect the soil CO₂ release.The interaction between moisture and earthworms had a significant impact on the formation and emission of N₂O from peatland soil.It means that in the case of 80%WHC,the addition of earthworms significantly improved the emission rate and cumulative emission of N₂O from soil.Soil DOC and MBC were closely related to CO₂ emissions,and we speculated that nitrous oxide is mainly produced by denitrification.