Ecological Stoichiometry Of Soil-Microbial-Extracellular Enzyme Under Different Abandoned Years In The Arid Area Of Northern Weihe River Basin

Clarifying the characteristic of soil enzymatic activity and stoichiometry variations and their driving factors during vegetation restoration in abandoned land have important implications for understanding changes of soil nutrients with abandoned years and maintaining the stability of ecosystems.In recent years,soil extracellular enzymes have been widely used as the direct medium for decomposition of organic matter by microorganisms,which can directly characterize the nutrient restriction of soil microorganisms.This study takes the abandoned land of different years（5,10,20,25,33 years）in the Arid Area of Northern Weihe River Basin as the research object.By measuring soil nutrients,soil microbial biomass,and the activities of five extracellular enzymes involved in soil C,N,and P cycles,the effects of abandoned years on soil,microorganisms,and extracellular enzymes and their ecological stoichiometric characteristics were discussed.And combined with the vector model of extracellular enzyme counting,we explored the nutrient limitation of microbial communities and its driving factors in the process of abandonment succession in the Arid Area of Northern Weihe River Basin,revealing the nutrient dynamics in the process of abandonment,and providing a theoretical basis for improving the management of soil resources after abandonment.The results show that:（1）Abandonment significantly increase the contents of soil C and N（P<0.05）.With the increase of abandoned years,SOC and TN contents increased first and then decreased,and both reached the peak after 20 years of abandonment,but the total amount still increased significantly.The contents of Soil P decreased significantly with the increase of abandoned years.With the increase of years of abandonment,soil C:N did not change significantly in each soil layer.Soil C:P increased significantly with the increase of abandoned years in surface soil,showed an increase trend with the increase of abandoned years.Soil N:P did not change significantly with the different abandoned years,but showed a trend of first increasing and then decreasing.（2）Abandonment significantly changed the contents of C,N and P and their stoichiometric ratios of soil microbial biomass（P<0.05）.Generally speaking,with the increase of abandoned years,the contents of MBC and MBN in soil increased first and then decreased,while the contents of MBP decreased significantly.But,MBC:MBN and MBC:MBP showed a trend of first increasing and then decreasing.（3）Abandonment significantly changed soil enzyme activities and their stoichiometric ratio（P<0.05）.With the increase of abandonment years,the activities of soil C enzyme（BG,CBH）and N enzyme（NAG,LAP）decreased significantly,and the activity of P enzyme（AKP）increased significantly in the 0-10 cm soil layer,but in deeper soil Significant reduction between layers（10-20 cm,20-40 cm）.Soil extracellular enzyme stoichiometric carbon/nitrogen ratio(C:N_EEA),carbon/phosphorus ratio(C:P_EEA)and nitrogen/phosphorus ratio(N:P_EEA)all showed a significantly decreased trend with the increase of abandoned years,which was basically consistent with the change trend of various extracellular enzyme activities in soil.（4）According to the enzyme vector econometric model,abandonment significantly affected soil microbial nutrient limitation characteristics.With the increase of the years of abandonment,the length of the vector generally showed a decreasing trend among different soil layers,indicating that the degree of microbial limitation by C decreased with the increase of the years of abandonment.The vector angles of soil enzyme stoichiometry between different soil layers under different abandonment years were all greater than 45°,and increased with the increase of abandonment years,which indicated that microorganisms were strongly limited by P,and the degree of restriction showed a similar pattern with the increase of abandonment years.increasing trend.Among them,TP,AN,AP and DOC were the main driving factors regulating the soil enzyme activity and enzyme stoichiometric ratio in the abandoned land in the hilly area of the Loess Plateau.