Effects Of Successive Monoculture On Carbon Storage And Soil Labile Carbon In Chinese Fir Plantations

Forest ecosystem are considered to have a large potential for temporary andlong-term carbon (C) storage. Enhancing C sequestration by increasing plantationforests has been suggested as an effective measure to mitigate elevated atmosphericcarbon dioxide (CO₂) concentrations and hence contribute to the prevention of globalwarming. Chinese fir (Cunninghamia lanceolata) is one of the most importantplantation tree species in China in terms of planting area, yield and timber usage. But,there is little research on how successive monoculture impacts on carbon storage inChinese fir escosystem, and we can't compile accurate carbon budget of Chinese firplantations. A relative few studies were carried out in forests of southern China, animportant area of Chinese fir. We choose different generation plantations of Chinese fir,viz. 40-year-old first generation, 39-year-old second generation and 87-year-old firstgeneration to compare their carbon pools. The results are as follows.The total carbon stocks of the second generation Chinese fir plantation is 20.06%lower than that in the first generation Chinese fir plantation. Also, lower carbon storagesof 20.17%, 24.71%, 34.78% and 22.89% in tree layer, forest floor, coarse woodydebris and soil layer are found in the second generation in comparison with the firstgeneration. But the second generation Chinese fir forest has 33.70% higher carbonstorage in understory than the first generation. Total carbon storage in the first and secondgeneration Chinese fir plantations are 82.45% and 65.91% of the old-growth Chinese firforest (319.21t·hm^-2) respectively. Carbon storage in tree layer of the first and secondgenerations occupied 74.47% and 59.45% of the old-growth Chinese fir, respectively. Inaddition, soil carbon concentration in 0-20cm and 20-40 cm layers is lower in the first andsecond generation Chinese fir plantations compared with the shaw. The first generationChinese fir plantation has higher concentrations of dossolved organic carbon andmicrobial biomass carbon in soils than the second generation Chinese fir plantation, whilethere is no significant difference in light fraction organic carbon between the twogeneration plantations (P＞0.05). These results show that carbon storage decreases withincreased generation. Successive monoculture of Chinese fir is disadvantage for increasing carbon sequestration in plantations.