Effects of Different Functional Groups of Dung Beetles on Greenhouse Gas Emissions from Cattle Dung Pats on Steppe Grassland

As an engineer in ecosystem, dung beetles play a vital role in decomposition and organic matter transfer of dung pats in pastoral systems. A dung pat decomposition experiment were conducted in the typical steppe area of Inner Mongolia by setting up isolated mesocosms containing dung pats only (control, T0), dung pats with a dweller dung beetle species Aphodius sordecens (T1), dung pats with a tunneller dung beetle speceis Onthophagus gibbulus (T2), dung pats with both beetle species (T3), and only soil treatment(CK). The fluxes of CH₄, CO₂, N₂O and totle(CO₂) were determined during decomposition of cow dung pats under these treatments, and the relationship of the GHG emission fluxes with environmental factors were analysed. The results show that the greenhouse gas produced by cattle dung pats was mainly CO₂(T0, CO₂ Flux=2 106 mg·m^-2·h^-1), while CH₄(T0, CH₄ Flux=2.769 mg·m^-2·h^-1) and N₂O(T0, N₂O Flux=0.019 mg·m^-2·h^-1) were less. The addition of A. sordecensT1, Totle(CO₂) Flux=2 657 mg·m^-2·h^-1 significantly increased the CO₂ fluxes (P < 0.05), while addition of O. gibbulusT2, Totle(CO₂) Flux=2 422 mg·m^-2·h^-1 or the addition of both beetle speciesT3, Totle(CO₂) Flux=2 398 mg·m^-2·h^-1 did not significantly alter the GHG fluxes (P>0.05). The two beetle species of different functional types showed different effects on GHG emissions in the process of dung pats decomposition, depending on the decomposition time and environmental conditions. The presence of O. gibbulus (T2) reduced GHG emissions (P < 0.05), but not for the presence of A. sordecens (T1) or both species (P>0.05) during the fresh dung pat period; while none of beetles had an impact on GHG emissions (P>0.05) during the dry dung pat period. The total GHG influx was positively correlated with soil temperature (P < 0.001), while the influxes of CH₄ and CO₂ was higher at a moderate soil moisture (P < 0.01). The results of the study suggest that under proper temperature and moisture conditions the GHG emissions could be promoted, and both dung beetle species, regardless of their functional types, could have influence on GHG emissions from dung pats in different time.