Decomposition Of The Litter Of Robinia Pseudocacacia With Different Ages And Its Effect On The Soil Environment In The Loess Plateau

In order to explore the effect of Robinia pseudoacacia(RP)plantation to the soil environment on the loess plateau,this study a four RP plantation litters from different ages(10,15,25,40 years)forest were dopted as the research object using the method of spatial sequence instead of time successional sequence.The nutrient nigration and transformation process between litter and soil was analyzed.The results showed as follows:(1)Litter organic carbon and total potassium were net released during the decomposition process.The total nitrogen content of litter in young plantations was firstly released and then enriched,while the mature plantation was firstly enriched and then released.Total phosphorus showed net enrichment on the whole decomposition.Studies have proved that the natural decomposition process of litter is mainly limited by P.The total litter stock under Robinia pseudoacacia plantation in the loess plateau was significantly different among different years and reached its maximum value in 25 years.The change rule of litter element reserves was TC >TN >TK > TP.The release rate of elements in mature forest was higher than that in the young age.(2)The content of soil C and N increased with the growth of forest age and decreased with the increase of depth.The change of soil total phosphorus was not significant.The soil total phosphorus increased with the increasing ages,but the change was no significant.The soil of Robinia pseudoacacia was mainly restricted by N in the vegetation restoration process.The un-decomposed litter layers and decomposed layers had significant effect on soil nutrient content.N and P were the main limiting factors affecting the litter-soil nutrient cycle.(3)With the increasing of forest age,Robinia pseudoacacia afforestation had significant effect on soil bacterial diversity,but the effect on fungal diversity is not significant.The dominant phylum(Proteobacteria and Actinobacteria)mutated in 25 years,and only Basidiomycetes showed significant difference in abundance in 40 years.Amino Acid Metabolism,Lipid Metabolism,Coenzyme and Vitamin Metabolism were the main sub-functional groups.The nutrient pattern of soil microorganisms in late mature RP forest changed from eutrophication to oligotrophication.N and P were the main soil elements affecting the change of microbial communities.What's more,the characteristics of litter can also significantly affect the change of soil microbial community and metabolic function.To sum up,we suggest that the management of the Robinia pseudoacacia plantation on the Loess Plateau should not only consider geographical conditions and climatic conditions,but also the changes of soil microbial communities.In order to maintain the sustainability of the vegetation,the plantation forest can be scientifically managed by rationally controlling the recovery period of the plantation.In this study,the restoration of Robinia pseudoacacia plantation can be considered for rational planning after 25 years of renovation.Therefore,establishing a complete evaluation mechanism of the Loess Plateau and upgrading the ecosystem function of the plantation forest are important contents for the future vegetation construction of the Loess Plateau.