| The rocky mountain area of North China has always been a key area in the focus of forestry ecological construction,and it is also an important ecological barrier in North China Plain.Soil erosion and land degradation have become major problems plaguing the area of sustainable development.In order to reveal the effects of different vegetative restoration patterns on the soil biological characteristics and community population structure and provide the theoretical basis for better evaluating the ecological benefits of forestry ecological engineering and for establishing reasonable sustainable forest management measures to reduce soil erosion and land degradation,dynamic changes of soil physical and chemical properties,microbial quantity,microbial biomass carbon and nitrogen,enzyme activity and microbial community structure in soil planted with Robinia pseudoacacia 10 a(RP10)and 43 a(RP43)were studied systematically by using correlation analysis,principal component analysis and stepwise regression analysis,and compared to those of the farmland(FL)and the natural forest abandoned cropland(AC)in the rocky mountain of North China.The results showed that:(1)Vertical regularity were obvious in all lands's soil chemical properties,microbial quantity,microbial biomass carbon and nitrogen and normal enzyme activity(except catalase).They were sharply decreased with the deepening of the soil depth.Seasonal dynamic changes of their contents were different significantly in all lands.Their contents in the humus layer(0-5 cm)of RP43 were much higher than that of RP10;Soil microbial biomass carbon and nitrogen ratio from high to low were FL>AC>RP10>RP43;The contribution rates of soil microbial biomass nitrogen to soil total nitrogen in FL,AC,RP10 and RP43 were 1.21,5.44,3.55 and 2.26%,respectively,and that of soil microbial biomass nitrogen to soil total nitrogen were 1.21,5.44,3.55 and 2.26%,respectively.The contribution rates of soil microbial biomass nitrogen to soil total nitrogen in RP10 and RP43 were 2.93 and 1.86 times of that in soil of Farmland,respectively.Besides,the content of total nitrogen in RP10 and RP43 were 1.04 and 1.48 times of that in soil of Farmland,respectively.In summary,all these data were fully proved that Robinia pseudoacacia had a unique advantage in improving soil nitrogen content;(2)Analysis of the patterns similarity found that choosing different vegetation restoration after conversion of cropland to forest had great effect on the bacterial and fungal community structure,especially abandoned land.After analysis sequences obtained by BLAST alignments and phylogenetic analysis system,bacteria were composed of 8 genera,Acidobacteriabacterium and Alphaproteobacteria were dominant genera;fungi were composed of 15 genera,Agaricus,Cochliobolus,Fusarium and Ascomyceta were dominant genera;(3)The correlation analysis results showed that soil microbial biomass carbon and nitrogen and soil total nitrogen,organic matter,available potassium content were significantly correlation,enzyme activity and available potassium,available phosphoruscontent were significantly correlation.Further study on the each index was necessary for them.Stepwise regression equation indicated that the main factors affecting enzyme activitys were ammonium nitrogen and available potassium.With the increase of soil ammonium nitrogen and available phosphorus,the enzyme activities were increased.Principal component analysis results showed that the contribution of microbial quantity,soil microbial biomass carbon and nitrogen to the soil fertility was much higher,so they could be used to reflect the status of the soil fertility.In short,planted Robinia pseudoacacia in returning farmland to forest area could not only generate huge economic benefits,but also improve soil fertility,especially in terms of improving soil nitrogen content. |
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