黄土丘陵区退耕还林地刺槐人工林碳储量及分配规律

采用样地调查与生物量实测方法,研究了甘肃黄土丘陵区不同坡向(阳坡、阴坡)和退耕年限(退耕5a、8a和11a)刺槐人工林乔木不同器官、灌草层、枯落物层和土壤层的碳含量,以及刺槐人工林乔木层、灌草层、枯落物层和土壤层碳储量及其分配特征。结果表明:刺槐不同器官碳含量均值变化范围为43.02%—50.89%%,从高到低排列顺序为树干细枝中枝粗枝叶根桩大根粗根小根中根树皮细根;灌木层碳含量为35.76%—42.74%;草本层碳含量为35.83%—43.64%;枯落物层碳含量为39.55%—41.77%;土壤层(0—100 cm)碳含量均值变化范围0.22%—0.99%,随退耕年限增加而增大,土壤深度的增加而逐渐下降。刺槐人工林生态系统碳库空间分布序列为土壤层(0—100 cm)植被层枯落物层。阳坡和阴坡退耕5a、8a、11a刺槐林生态系统碳储量分别为52.52、58.93、73.72 t/hm2和49.95、61.83、79.03 t/hm2。退耕年限和坡向是影响刺槐人工林碳储量增加的主要因素。刺槐人工林具有良好的固碳效益,是黄土丘陵区的理想树种。

Characteristics of carbon storage and sequestration of Robinia pseudoacacia forest land converted by farmland in the Hilly Loess Plateau Region

The Grain for Green Project have played an important role in preventing soil erosion and restoring the regional ecological environment in the hilly Loess Plateau region, meanwhile it is important to research biomass and carbon pool of forest ecosystems. There is the close relationship between forest biomass and fixed carbon of forest ecosystems. Robinia pseudoacacia is a typical tree species for the Grain for Green Project in the hilly Loess Plateau region in Gansu Province. The amount of biomass directly affected the function of fixed carbon of Robinia pseudoacacia plantations ecosystems, so the plot investigation and biomass measurement were carried out in the Robinia pseudoacacia plantations afforested in three periods (5 years, 8 years and 11 years) and two slopes(sunny and shady slope). In different plot of Robinia pseudoacacia plantations, we investigated carbon content, carbon storage and allocation of the different tree organs, shrub layers, grass layers, litter layers and soil layers, respectively. The results showed that the average carbon content in different organs of Robinia pseudoacacia ranged from 43.02% to 50.89% and decreased in the order stem > fine-branch > medium-branch > thick-branch > leaf > stump > large-root > thick-root > small-root > medium-root > bark > fine-root. The average carbon content ranged from 35.76% to 42.74%, ranged from 35.83% to 43.64%, ranged from 39.55% to 41.77% in shrub, grass and litter layers, respectively. The average carbon in the soil layer (0-100cm)ranged from 0.22% to 0.99% and increased with conversion years but gradually decreased with the increase of soil depth.Carbon stocks in the different components of the studied forest ecosystems were in an order as: soil > vegetation > litter. Carbon storage on the sunny and shady slope of 5-,8-and 11-year plantations followed as:the ecosystem was 52.52 t/hm², 58.93 t/hm², 73.72 t/hm²and 49.95 t/hm², 61.83 t/hm², 79.03 t/hm². And the soil layer (0-100cm depth) was the largest carbon storage compont, which stored 39.5 t/hm², 42.08 t/hm², 49.68 t/hm²and 35.61 t/hm², 44.31 t/hm², 52.64 t/hm². And the vegetation layer component stored 12.88 t/hm², 17.29 t/hm², 24.69 t/hm²and 14.72 t/hm², 18.10 t/hm², 27.30 t/hm². And the tree layer stored 12.56 t/hm², 16.85 t/hm², 24.04 t/hm²and 14.34 t/hm², 17.52 t/hm², 26.39 t/hm². Of the tree layer, the stem was the highest carbon storage organ. The annual net primary productivity of sunny and shady slope were estimated to be 5.21 t·hm^-2·a^-1 and 6.57 t·hm^-2·a^-1 in the 5 years Robinia pseudoacacia plantation, and annual carbon storage were 2.54 t·hm^-2·a^-1 and 3.10 t·hm^-2·a^-1. Slop aspect and restoration years were the important factors affecting the carbon stock in Robinia pseudoacacia plantations. It was considered that Robinia pseudoacacia had a good carbon sequestration function, being able to be an ideal tree species in the hilly Loess Plateau of Gansu Province. And it may contributed to proper selection of Robinia pseudoacacia forest efficient management of young forest, offering great potential for future carbon sequestration, especially in the hilly Loess Plateau.