Evaluation Of Soil Fertility Quality Of Paulownia Plantation At Different Ages In Subtropical Region

In order to reveal the influence of different age Paulownia plantation on the main soil fertility factors,and provide scientific basis for the selection of afforestation and logging age and the sustainable management of soil in this region.Taking four forest-age Paulownia plantations in Wutang,Yuanjiapu and Xinnongcun of Xiangyin County as the research objects,15 plots were set up to investigate the topography,climate,soil and vegetation in the study area.The vegetation,slope,slope direction and elevation under the forest in the test area were measured.A total of 29 physical,chemical and biological indicators were determined.The minimum data set was screened out by principal component analysis,and the soil fertility quality evaluation system of Paulownia plantation at different forest ages was established.The soil fertility quality of four forest-age Paulownia plantations and the control were evaluated by weighted summation method,fuzzy comprehensive evaluation method and DEA model method.The main conclusions are as follows:(1)The water content,total porosity,capillary porosity,non-capillary porosity,maximum water holding capacity and minimum water holding capacity of Paulownia plantation and control soils with different forest ages were significantly different in 0-20 cm soil layer(p>0.05),in 20-40 cm soil layer there were significant differences in water holding capacity(p>0.05),and in 40-60 cm soil there were significant differences in capillary water holding capacity(p>0.05),while the other soil physical indexes were significant differences(p>0.05).There was no significant difference in the standard among different forest ages(p<0.05).(2)There were significant differences in soil pH value,organic matter,total nitrogen,total phosphorus,available phosphorus,available magnesium and iron content in 0-20 cm soil layer between different forest age Paulownia plantation and control soil(p>0.05);soil pH value,organic matter,total nitrogen,total phosphorus,available iron,manganese,copper and zinc content in 20-40 cm soil layer.There were significant differences in soil pH,total nitrogen and available iron,manganese and zinc contents between 40-60 cm soil layers and 60-1000 cm soil layers(p>0.05),total potassium and soil available calcium,magnesium,iron and manganese contents in 60-1000 cm soil layers in Paulownia Plantation Soils of different forest ages(p>0.05).There were significant differences(p>0.05).There was no significant difference in other soil chemical indexes among different forest ages(p<0.05).(3)There were significant differences in urease activity and catalase activity in 0-20 cm soil layer between Paulownia plantation and control at different forest ages(p<0.05),urease activity and invertase activity in 40-60 cm soil layer(p<0.05),and phosphatase activity in 60-100 cm soil layer(p<0.05),while there were no significant differences in other soil biological indicators among different forest ages.Sex difference(p>0.05).(4)The correlation analysis of 29 soil physical,chemical and biological indicators showed that there were many significant or extremely significant correlations.The minimum data set(MDS)for soil fertility quality evaluation of Paulownia plantation at different forest ages was established,and the 12 most representative indicators were selected as follows:bulk density,maximum water holding capacity,organic matter,total phosphorus,available phosphorus,available potassium,available calcium,available iron,available copper,urease activity,catalase activity and microbial biomass P.(5)Three kinds of soil fertility quality evaluation scores of Paulownia forest land of different forest agesSoil fertility quality evaluation score based on weighted summation method,ranked from big to small as:12-year-old Paulownia plantation>1-year-old Paulownia plantation>9-year-old Paulownia plantation>control>3-year-old Paulownia plantation;Soil fertility quality evaluation score based on fuzzy comprehensive evaluation method,ranked from big to small as follows:12-year-old Paulownia plantation>1-year-old Paulownia plantation>9-year-old Paulownia plantation>3-year-old Paulownia plantation>control.Soil fertility quality evaluation score based on DEA model was ranked from large to small as follows:3-year-old Paulownia plantation>1-year-old Paulownia plantation>9-year-old Paulownia plantation>12-year-old Paulownia plantation>control.