| Afforestation in northern Shaanxi has played an important role in improving the ecological environment and soil quality in the loess hilly region.At the same time,the main driving factors of ecological restoration were the interaction of plant,microorganism and soil nutrient to promote the material and energy flow after returning to cultivated land.Alternative methods of this study is based on space-time,choose to restore life to 17,27,42 years of Robinia pseudoacacia(RP),restore age 27,42 years of Caragana korshinskii(CK),restore fixed number of year for 42 years of Abundond farmland(AF),a total of six vegetation restoration sample area,and adjacent no fertilizer farmland(FL)as the control,studies the conversion of forest land in the process of vegetation restoration in different vegetation types,different length of recovery and under the interaction between soil nutrient and plant nutrient and its ratio of measurement,the soil enzyme activity and soil bacterial diversity and abundance and other factors change and differentiation characteristics,The effects of soil nutrient and its measurement ratio on plant carbon and nitrogen phosphorus and its measurement ratio,soil bacterial abundance and soil enzyme activity were explained.The main conclusions are as follows:(1)Characteristics of soil nutrient characteristics in converted forest landCompared with FL,the content of soil SOC,TN,TP increased significantly in the depth of 0~30cm profile,and the total nutrient content decreased with the increase of soil profile depth in thethree soil layers.Compared with 10~20 cm,20 ~30 cm soil layer,the variation of SOC,TN,TP content were much more significant(P < 0.05).(2)Characteristics of soil biological characteristics in converted forest landThe activity of urease,sucrase,catalase and alkaline phosphatase in all vegetation types was higher than that in FL,except for RP17 a forest land,the activity of enzyme in each vegetation type was significantly higher than that in FL(P < 0.05).The highest level of activity was in 0~10cm and the lowest was in 20~30cm.And the difference of sucrase activity was the most significant among different soil layers,but the difference was not significant among different soil layers compared with other vegetation types.The difference of enzyme activity between 10~20cm soil layer and 20~30 cm soil layer was significantly lower than that between 0~10 cm and 10~20 cm or between 0~10 cm and 20~30 cm soil layer.The highest soil bacteria relative abundance of phyla,class,and order in different vegetation restoration type was Proteobacteriae,Alphaproteobacteriae,and Acidimicrobiales,respectively.The ?-diversity of bacteria in different vegetation types is significantly different from that in FL,and the variation of ?-diversity is not obvious.(3)Variation characteristics of soil plant nutrients in forest landThere was no significant difference in the contents of C,N,P among leaves of different vegetation types,undergrowth herbaceous plants and litter,and the general trend of C,N,P content in the same vegetation type was higher in leaves than in undergrowth herbaceous plants,and higher in understory herbaceous plants than in litter,and the ratio of C/N was the highest in undergrowth herbaceous plants.The ratio of litter to litter was higher than that of leaf,and the change trend of C/ P ratio was the same as that of undergrowth herbaceous grass.(4)The effect of plant-soil-microorganism interaction in forest landAt the same time,plant nutrients and their metrological characteristics and soil nutrients and their metrological characteristics,soil nutrients and their metrological characteristics and soil enzyme activity,soil bacterial microbes and soil nutrients and their metrological characteristics all showed the most obvious interaction effect of 0~10cm soil layer.Environmental factors such as slope,recovery years,altitude,slope direction were positively correlated with the total nutrient content,and the surface layer had the strongest correlation.Relative to other indexes,the interpretation rate of litter N/ P and soil nutrient variation in three layers of soil was the highest.Among the soil nutrients and their metrological characteristics,the three factors SOC,C/ P,TN had the greatest influence on soil enzyme activity,while floatula,acidobacterium,Planctomycetes,Acidobacterium and N1423 WL had the strongest correlation on soil nutrients and their metrological characteristics of 0~10cm.In summary,the soil nutrient content and enzyme activity are increased during the process of vegetation restoration;the limitation of phosphorus and nitrogen is alleviated during the vegetation growth process;at the same time,the bacterial community structure and abundance are improved,the soil carbon cycle is regulated,and the plant-microbe-soil carbon Nitrogen and phosphorus nutrient pool interactions have significant effects. |
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