Effects Of Replanting Schima Superba On Stand Quality Of Pinus Elliottii Plantations

Taking the disaster-affected Pinus elliottii plantations in Jishui County,Jiangxi Province was taken as the research object.The paired fixed sample plots of operation(replanting one-year-old seedlings of Schima superba)and control(pure plantations)were set up in 2013,and the fixed sample plots were investigated and determined in 2013 and2021.Through sample survey and sample determination.The effects of replanting Schima superba on the quality of Pinus elliottii plantations were analyzed from three aspects of vegetation,soil and carbon density by means of paired sample T test.The results can provide reference for improving the stability and function of Pinus elliottii plantations.The main results and conclusions are as follows:(1)After 8 years of replanting Schima superba,the average DBH of Pinus elliottii in the operation plot was significantly higher than the control plot(P<0.05).The average coverage of shrub layer was significantly lower than the control plot(P>0.05),while the average coverage of herb layer was significantly higher than the control plot.but there was no significant difference in the average height of shrub layer and herb layer.There was no significant difference in Patrick richness index,Shannon-Wiener index and Pielou evenness index of understory vegetation between the operating plots and the control plots.(2)After 8 years of replanting Schima superba,the soil bulk density in the 0-10 cm soil layer of the operation plots was significantly smaller than that of the control plots(P<0.05),and the maximum water holding capacity,field water holding capacity and total porosity were significantly larger than those of the control plots,while all physical indexes in the 10-20 cm and 20-30 cm soil layers were not significantly different from those of the control plots(P>0.05).The contents of soil organic matter and available potassium in 0-10 cm soil layer were significantly higher than those in control plots,while the contents of available nitrogen and available phosphorus in each soil layer were significantly higher than those in control plots.(3)Using principal component analysis combined with norm value in 16 soil physical and chemical indicators,capillary water holding capacity,total phosphorus,total porosity,organic matter,field capacity and total nitrogen were selected to form the minimum data set for evaluating soil quality.After 8 years of replanting Schima superba,the soil quality comprehensive index of 0-10 cm,10-20 cm and 20-30 cm soil layers in the operation plots was higher than that in the control plots.The soil quality index of 0-10 cm soil layer was significantly higher than that of the control plots(P<0.05).(4)After 8 years of replanting Schima superba,the carbon density of tree layer,litter layer,soil layer and total carbon density of stand in the operation plots increased by 62.01%,108.66%,40.09% and 41.31%,respectively,compared with the control plots,while the carbon density of understory vegetation layer decreased by 12.75%,among which the carbon density of litter layer and total carbon density of stand increased significantly(P<0.05).The carbon density of tree layer,vegetation(tree layer+understory vegetation layer+litter layer)and the total carbon density of the plantations in the 8 years were significantly higher than those in the control plots(P<0.05);The proportion of vegetation layer carbon density in the total carbon density of the stand increased more obviously than that of the control plots.