Study On The Change Of Soil Properties Of Multi-generation Robinia Pseudoacacia Plantation Renewed By Sprouting

The impact of forests on site quality is an important research direction for sustainable management of planted forests.Black locust(Robinia pseudoacacia L.)is one of the main afforestation species with a long history in the north of China,which has been localized.The characteristics of legumes and the regeneration way of sprouting regeneration make it different from other continuous plantation,and at present,there are few studies on the characteristics of different management generations of forest land.In this study,Robinia pseudoacacia forest of 10 years around age(aboveground part)in different generations and no forest land in the hilly area of western Henan Province were taken as the research object.The effects of robinia pseudoacacia multi-generation management on soil properties were analyzed from the perspectives of soil physical,chemical and biological characteristics.The effect of multi-generation management of Robinia pseudoacacia plantation on forest soil was clarified,which provided a theoretical basis for the formulation of soil fertility control measures under the management objectives of Robinia pseudoacacia plantation.The main results are as follows.1.In terms of soil structure,after the multi generation management of Robinia pseudoacacia plantation,the upper layer was superior to the deep layer,and the second and third-generation woodlands were superior to the first-generation woodlands.From the perspective of soil bulk density,porosity,and aggregate structure,the non-capillary porosity of the second-generation forest land and the third-generation forest land increased by 11.4% and 21.4%,respectively.The C1 layer also shows an upward trend with increasing generations.The deeper the soil layer was,the greater the change range of soil bulk density was among intergenerational forestland.The quantity and stability of soil surface water stable aggregates were in the order of control land> second and thirdgeneration woodlands > first-generation woodlands.2.The content of soil nutrients in the second-generation robinia pseudoacacia woodlands was significantly higher than that in the first-generation robinia pseudoacacia woodlands and remained relatively stable in the third-generation forest.There was no significant difference in soil nutrient content between the second and third-generation robinia pseudoacacia woodlands.The nutrient content in the upper layer of Robinia pseudoacacia forest soil is higher than that in the deep layer,and the increment of nutrient content in the upper layer is greater than that in the deep layer with the increase of generations,which shows that the ratio of nutrient content in the upper layer of the second and third generations of forest land to that in the first generation of forest land is greater than that in the deep layer.In the process of increasing generations of Robinia pseudoacacia forest,the accumulation of carbon is faster than that of nitrogen,and the supply capacity of carbon and nitrogen is less than that of phosphorus.3.The soil biological activity index(SAI)of the first generation Robinia pseudoacacia forest land,the second generation Robinia pseudoacacia forest land,the third generation Robinia pseudoacacia forest land and the control land are 0.22,0.77,0.75 and 0.09 respectively.Planting Robinia pseudoacacia in the hilly loess hilly area of western Henan can effectively enhance soil biological The biological activity of the soil is maintained at a high level after multi-generation management to the third generation.The activities of invertase,urease,neutral phosphatase,and polyphenol oxidase in the second and third generation woodlands were higher than those in the first and third generation woodlands.The content of bacteria,actinomycetes,total phospholipid fatty acids and diversity index of microbial community in Robinia pseudoacacia forest showed that the second and third generations of forest land were higher than the first generation of forest land and control land.The difference of PLFA content in different sites was smaller than that of other microbial groups,and was not consistent with the change trend of actinomycetes and bacteria,The content of fungi was higher in the first generation forest land.The results of principal component analysis of soil microbial PLFA showed that different generations of management resulted in significant differences in microbial community structure among the four sites.The results of redundancy analysis showed that bacteria were dominant in soil microorganisms,and the correlation between fungi and other microbial groups was relatively small.Soil environmental factors that have a greater impact on microbial PLFA include hydrolase,C / P,organic carbon content and so on.4.The main organic compounds in the rhizosphere soil of Robinia pseudoacacia are alkene,aromatic,alcohol,alkane,ester,ketone,amide,salt,acid and acetate,which are quite different from those in the control soil.The results showed that the allelopathic effect of rhizosphere soil extracts on the annual seedlings of Robinia pseudoacacia was not significant.