Effect Of Litter Input Of Artificial Robinia Pseudoacacia Forest On Soil Organic Carbon In Loess Hilly Area

Soil organic carbon is the basis of ecosystem services in terrestrial ecosystems,an important index for evaluating soil quality,and plays an important role in global warming.As the mainly important source of soil organic carbon,litter production is greatly affected by global changes?e.g.Nitrogen deposition,CO₂ concentration increases,global warming,drought frequency?.However,due to the complexity of the structure and function of the soil microbial community that drives the decomposition and transformation of litters,the effect of changing litters on soil organic carbon and its mechanism are still unclear.Therefore,the Detritus Input and Removal Treatment?DIRT?was conducted in Robinia Pseudoacacia forest including three treatments?control,CK;double litter,DL;no litter,NL?in Loess Hilly-Gully Region.Soil samples were collected in June,September,December of 2018 and March of 2019,respectively,to measure the soil temperature,moisture content?SMC?,p H,nutrient of N and P,organic carbon?SOC?,labial organic carbon?LOC?,resistant organic carbon?ROC?,microbial biomass C,N,P and its ratio,carbon-metabolism enzyme activity and microbial metabolism.The aim of the study is to reveal the effects of different litter inputs on soil carbon stocks and their mechanisms.The main results are as follow:From March to December of 2018,SOC,LOC and ROC were significantly increased over time in all litter treatment,and the variation range were 166.46%-283.20%,137.40%228.62%and 179.63%-307.96%,respectively.In addition,in December 2018 and March2019,SOC increased by 43.82%and 55.40%respectively in NL compared with the control,but there was no significant difference in DL.Compared with the CK,only MBC in DL significantly reduced in June 2018 and had no significant impact on the rest of the season;In NL,MBC significantly decreased by71.96%in June 2018,but increased by 101.59%and 120.27%in September and December2018,respectively,but had no significant difference in March 2019.In all seasons,DL had no significantly effect on HY:MBC,OX:MBC and soil temperature,but NL had significantly increased soil temperature by the range of 3.36%-18.68%.In June 2018,HY:MBC and OX:MBC increased significantly in NL,while in December 2018,OX:MBC decreased significantly in NL.In June 2018,there was a negative correlation between soil temperature and MBC?r=-0.644?,while in September,December and March 2019,there was a positive correlation between soil temperature and MBCThe results of variance partitioning showed that in all seasons,the total explanation rate of soil microbial biomass C,N,P and stoichiometric ratio,soil extracellular enzyme activity and soil microbial metabolism characteristics for variance variation of soil carbon components after litter treatment was more than 90%.Moreover,in June,December 2018,and March 2019,the explanation rate of soil microbial biomass was relatively higher.And in September,2018,the explanation rate of soil extracellular enzyme activity was relatively higher.The above results showed that in the artificial forest on the Loess Plateau,NL is more conducive to the accumulation of soil organic carbon,and compared with litter input,microbial driven litter decomposition and transformation process has a more important impact on soil organic carbon pool.In conclusion,this study emphasizes the important role of soil microorganisms in the process of soil carbon cycle,provides a scientific basis for predicting the change of soil carbon pool in the Loess Plateau under the background of global change.