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针对森林碳平衡再评估的重要性和区域尺度森林生态系统碳库量化分配的不确定性,该研究依据全国森林资源连续清查结果中甘肃省各森林类型分布的面积与蓄积比重以及林龄和起源等要素,在甘肃省布设212个样地,经野外调查与采样、室内分析,并对典型样地信息按照面积权重进行尺度扩展,估算了甘肃省森林生态系统碳储量及其分布特征。结果表明:甘肃省森林生态系统总碳储量为612.43 TgC,其中植被生物量碳为179.04 TgC,土壤碳为433.39 TgC。天然林是甘肃省碳储量的主要贡献者,其值为501.42 TgC,是人工林的4.52倍。天然林和人工林的植被碳密度均表现为随林龄的增加而增加的趋势,同一龄组天然林植被碳密度高于人工林。天然林土壤碳密度从幼龄林到过熟林逐渐增加,但人工林土壤碳密度最大值主要为近熟林。全省森林植被碳密度均值为72.43 Mg C·hm–2,天然林和人工林分别为90.52和33.79 Mg C·hm–2。基于森林清查资料和标准样地实测数据,估算出全省天然林和人工林在1996年的植被碳储量为132.47和12.81 TgC,2011年分别为152.41和26.63 TgC,平均固碳速率分别为1.33和0.92 TgC·a–1。甘肃省幼、中龄林面积比重较大,占全省的62.28%,根据碳密度随林龄的动态变化特征,预测这些低龄林将发挥巨大的碳汇潜力。
Based on the importance of the re-evaluation of forest carbon balance and the uncertainty of the quantitative allocation of carbon stocks in forest ecosystems at the regional scale, this study based on the area and accumulation proportion of each forest type in Gansu Province in the continuous national inventory of forest resources, 212 sites in Gansu Province were surveyed, sampled and analyzed in the field. The information of typical plots was expanded according to the area weights to estimate the carbon storage and its distribution in forest ecosystems of Gansu Province. The results showed that the total carbon storage of forest ecosystem in Gansu Province was 612.43 TgC, in which vegetation biomass carbon was 179.04 TgC and soil carbon was 433.39 TgC. Natural forest is the main contributor to carbon storage in Gansu Province, with a value of 501.42 TgC, which is 4.52 times that of plantation. The vegetation carbon density of natural forests and plantations all showed an increasing trend with the increase of forest age. The carbon density of natural forests in the same age group was higher than that of plantations. The soil carbon density of natural forests increased from young to over mature forests, but the maximum of soil carbon density in plantations was mainly near-mature forests. The average carbon density of forest in the province is 72.43 Mg C · hm-2, and natural forests and plantations are 90.52 and 33.79 Mg C · hm-2, respectively. Based on the data of forest inventory and the data of standard plots, the estimated carbon stocks of natural forests and plantations in the province in 1996 were 132.47 and 12.81 TgC, respectively, 152.41 and 26.63 TgC in 2011 with average carbon sequestration rates of 1.33 and 0.92 TgC · a-1. The proportion of young and middle-aged forest area in Gansu Province is larger, accounting for 62.28% of the province. According to the dynamic characteristics of carbon density with age, it is predicted that these young forests will exert great potential for carbon sinks.