Characteristics Of Soil Microbial Carbon,nitrogen,phosphorus And Soil Enzyme Activities In Dongting Lake Wetlands In Response To Reforestation And Wetland Restoration Projects

Wetland soil enzyme activity and microbial carbon,nitrogen and phosphorus are important components of wetland ecosystem function,and can directly reflect the active degree and metabolic level of soil microbial communities.In this paper,the 3-year poplar clearing site(D3)and the 6-year poplar clearing site(D6)in Dongting Lake were used as research objects,and the 9-year poplar woodland(P9)and the native reed site were used as controls(CK).By analyzing the characteristics of changes in soil enzyme activities,microbial carbon(MBC),microbial nitrogen(MBN),microbial phosphorus(MBP)contents and stoichiometric ratios in wetlands with different harvesting years after poplar clearing,we To elucidate the effects of human activities on the soil ecosystem of Dongting Lake wetlands,the results are as follows:(1)Except for Acid phosphatase(ACP),the activities of different enzymes differed significantly(p<0.05)among the different sample sites.β-glucosidase(BG),N-acetylglucosaminidase(NAG),Leucine Aminopeptidase(LAP),and Polyphenol oxidase(PPO)were significantly lower in D6 than in the other sample sites,while P9 was higher than in the other sample sites.However,the stoichiometric ratios of different source enzymes were not significantly different among the sample plots(p>0.05).(2)Microbial carbon,nitrogen and phosphorus were significantly different(p<0.05)among the sample plots,while MBC,MBN and MBP contents of D6 were significantly lower than other sample plots.In contrast,P9 was higher than the other sample sites.In addition to C/P ratio,C/N ratio and N/P ratio were significantly different among different plots(p<0.05).Vector analysis showed that CK,P9 and D3 were mainly limited by nitrogen nutrients,while D6 was mainly limited by phosphorus nutrients.(3)Redundancy analysis and Monte Carlo test results showed significant correlations(p<0.05)between different enzyme activities and Total nitrogen(TN),pH,Soil organic carbon(SOC),Available phosphorus(AP),Bulk density(BD),Silt,and Ammonium nitrogen(NH4+),and with SOC,TN,Clay,Silt,Available potassium(AK),and No significant correlation(p>0.05)was found between Nitrate nitrogen(NO3-).Microbial carbon,nitrogen and phosphorus were significantly correlated with BD,TP,pH,AP and NH4+,but not with soil SOC,TN,Clay,Silt,AK and NO3-.(4)Pearson correlation results showed that BG was significantly positively correlated with SOC,TN,and AP,and negatively correlated with BD.NAG was significantly positively correlated with TN,NH4+,SOC,TP,and AP,and negatively correlated with BD and pH.LAP was significantly negatively correlated with BD and pH,and significantly positively correlated with TN,NH4+,SOC,TP,and AP.ACP was significantly correlated with TN,NH4+,SOC,TP,and AP,SOC,TP and NO3-were significantly positively correlated.Urease was significantly and negatively correlated with NH4+ only.PPO was significantly and positively correlated with Silt,SOC,and AP,and negatively correlated with BD and pH.The above results showed that poplar clearing significantly reduced enzyme activity and microbial carbon,nitrogen and phosphorus content compared with poplar plantations and native reedbeds,and continued to decrease with the increase of clearing years.This indicates that poplar clearing alone is not sufficient to achieve wetland restoration goals in the short term,and long-term monitoring of the restoration process of the Dongting Lake wetland ecosystem needs to be strengthened.The results of the study can provide important theoretical support and scientific reference for the ecological protection and restoration of Dongting Lake wetlands.