Short-term Effects of Thinning and Replanting Measures on Tree Growth and Stand Carbon Density of Low-efficiency Pinus massoniana Forest

Taking Pinus massoniana low-efficiency forest as the research object, 20% thinning intensity and replanting measures were adopted according to the characteristics of its stand characteristics and other factors. Data were obtained from plot surveys and sample measurements for four consecutive years from 2013 to 2017, and the short-term effects of thinning replanting measures on tree growth and forest carbon density were analyzed. Results show that the growth of individual tree in average DBH and average individual volume are significantly improved after thinning and replanting measures for 4 years（P<0.05）, and respectively increase by 77.78% and 109.68% to be compared with control plots. Carbon density of tree layer decreased significantly after thinning and replanting（P<0.05）. The carbon density of understory vegetation layer and litter layer shows a significant decrease （P<0.01）and significant increase（P<0.05）. The increase in carbon density in the soil layer is greater than that of the control plot, and the difference is significant（P<0.05）. The 4-year increase in total carbon density of the stand is significantly lower than that of the control plot（P<0.05）, and the increment of the plot is reduced by 4.91 t/hm² compared to the control plot. This study can provide a reference for the quality improvement of low-efficiency forests.