Effects Of Mixed Pinus Massoniana And Schima Superba On Soil Microbial Residue Carbon In Surface Soil Of Degraded Pinus Massoniana Forest

Soil organic matter(SOM)is the core of soil fertility and the material basis for maintaining soil productivity,which is of great significance to vegetation restoration in the red soil erosion area of South China.More and more researches have shown that microbial residues play an important role in soil organic matter.Therefore,it is of great significance to study the contribution of soil microbial sources of Pinus massoniana Plantation and its mixed forest to soil organic matter in red soil erosion area.In this study,the authors selected the pure Pinus massoniana and Masson Pine-wood lotus mixed forest which were located in the erosion degraded land of Hetian Town,Changting County,Fujian Province,and used the paired experiment design to compare the differences of organic carbon,amino sugar and microbial residual carbon in the surface soil,and discussed the influence of soil microbial community structure,soil physical and chemical properties on soil microbial residual carbon,It provides scientific basis for further understanding the mechanism of soil organic matter recovery from microorganisms in the red soil erosion area of South China.The results are as follows:(1)The total amount of soil amino sugars in the 39-year-old Pinus massoniana and Schima superba mixed forest is 1.9 times that of the pure forest,the Glu N mixed forest is 58% higher than the pure forest,and the Galactosamine(Gal N)mixed forest It is 42% higher than the pure forest,and the microbial residue carbon(MRC)mixed forest is 55% higher than the pure forest.Soil organic carbon(SOC),soil total nitrogen(TN),bacterial residue carbon(BRC)and muramic acid(Mur A)in the39-year-old Pinus massoniana mixed forest were also significantly higher than those of pure Pinus massoniana forests,and these indicators are recovering.19 years are not significant.This shows that the effect of mixed conifer and broadleaf on the masson pine forest takes a long time to show up.With the increase of restoration years,pure masson pine forest soil nitrogen content,total amino sugar,glucosamine,galactosamine,and microbial residue carbon all showed a significant decrease;while mixed forest soil amino sugar,microbial residue carbon and other indicators both are significantly higher than the restoration of mixed forests for 19 years.This shows that as the restoration period increases,the restoration of soil organic matter in the pure forest of Pinus massoniana will be hindered or even degraded,and the mixing of Pinus massoniana and Schima superba can effectively increase the amount of microbial source organic matter,thereby enhancing the formation and accumulation of soil organic matter in eroded and degraded lands.(2)The soil microbial biomass carbon and nitrogen increased with the increase of recovery period,and the mixed of Pinus massoniana and woody lotus also increased the biomass carbon and nitrogen in degraded land.The total amount of soil microorganism and bacteria in the mixed forest in the recovery of 39 years was significantly higher than that of the pure forest in the recovery period(P < 0.05).The results showed that the number of gram negative bacteria,Gram-positive bacteria,arbuscular mycorrhizal fungi and actinomycetes were significantly increased after 39 years of restoration of Pinus massoniana and xylem,and the ratio of fungi to bacteria was decreased(P < 0.05),but the number of fungi was not significantly affected.(3)The redundancy analysis showed that TN,Doc,litter c/n,PLFA and pH were the main factors affecting the carbon of microbial residues.TN and litter c/n account for 44.9% and 9.4% of the variation of carbon in microbial residues.Therefore,it was suggested that the improvement of soil nitrogen efficiency and litter quality could significantly promote the formation of organic matter from microbial sources.Therefore,the bottleneck of further improvement of soil organic matter in single Pinus massoniana forest is mainly affected by the low nitrogen level and low litter quality(c/n).The key to improve soil organic matter in erosive degraded land in the future is to introduce a certain number of litter quality trees through forest transformation,and appropriate fertilization,which can improve the accumulation of soil organic matter in erosive degraded land to a certain extent.