Effect of Thinning Reserve Density on Carbon Storage in Middle-aged Chinese Fir Plantations

From 2017 to 2019, objected with 11-year-old Chinese fir plantations, a thinning experiment was carried out in Yangkou State-owned Forest Farm of Fujian Province, and the retention densities were 1200, 1500 and 2250 plants·hm^-2 respectively.The biomass model and carbon conversion coefficient of Chinese fir plantation were used to study the carbon storage of various organs and tree layers of Chinese fir 1~2 years after thinning.The results showed that after thinning, with the increase of growth time of Chinese fir stand, the smaller the thinning density, the larger diameter at breast height, tree height and individual volume of Chinese fir stand, and the opposite trend of stand volume.The carbon storage per plant increased with the decrease of thinning density, and the total carbon storage per plant was the largest when the density was 1200 plants·hm^-2.The carbon storage of tree layer increased with the increase of thinning density, and reached the maximum when the thinning density was 2250 plants·hm^-2.There was significant difference in the response of the carbon storage of each organ of Chinese fir and tree layer to different thinning retention density treatments.The increment of carbon storage per plant of Chinese fir increased with the growth time of Chinese fir stand after thinning treatment.The carbon storage increment of low thinning retention density treatment become more, while the carbon storage increment of high thinning retention density of Chinese fir tree layer.The lower the thinning density, the higher the carbon storage of Chinese fir forest.The comprehensive results showed that thinning measures significantly affected the carbon storage of Chinese fir plantation, and reasonable thinning intensity was conducive to the improvement of carbon sink capacity of Chinese fir plantations.