水土保持林生长过程及碳密度的动态变化

Growth process of soil and water conservation forest and dynamic change of its carbon intensity

刺槐是黄土高原主要的水土保持树种之一,对刺槐生长过程与碳密度动态变化的研究,是正确评价黄土高原水土保持林生态服务功能中亟待解决的关键问题。以山西吉县红旗林场马莲滩刺槐水土保持林为研究对象,采用样方(面积400 m2)调查和树干解析法,研究刺槐的生长过程,提出刺槐的树高生长模型、胸径生长模型、生物量与胸径的关系,并在此基础上模拟计算刺槐水土保持林生物量及碳密度的动态变化。结果表明:1)树龄12 a以前为刺槐树高和胸径的快速生长期,树高的平均生长速率可达0.63 m/a,胸径平均生长率为0.53 cm/a,树龄12 a时树高可达6.9 m、胸径5.19 cm、生物量10.18 t/hm2;2)利用建立的生物量预测模型得出,当树龄达到20 a时,刺槐水土保持林生物量的连年生长量最大,达2.99 t/hm2,树龄35 a时生物量的连年生长量曲线与平均生长量曲线相交,成为成熟林,总生物量达72.79 t/hm2,碳密度为35.52 t/hm2,对树龄35 a以上的刺槐水土保持林应该及时更新与改造。

Robinia pseudoacacia is one of the main tree species to conserve soil and water in China.There are large areas of Robinia pseudoacacia forests for soil and water conservation in the Loess Plateau.The growth and the dynamics of carbon storage of these plantations are the key to evaluate the ecosystem service function of soil and water conservation forests in this region.In this paper,taken the Robinia pseudoacacia forests for soil and water conservation constructed in Maliantan as object,simple investigation and stem analysis were employed to study its growth process.Height-age Models,Diameter at breast height（DBH） Increment Model and the relationship of biomass and DBH were determined.The growth process and the dynamic change of carbon intensity were simulated based on these models.The results showed that the tree height and DBH of Robinia pseudoacacia grew very fast during the first 12 years,and the average growth rate of tree height and DBH was 0.63 m/a and 0.53 cm/a,respectively.At the age of 20 year,the current annual increment of biomass of Robinia pseudoacacia forests reached the maximum,2.99 t/hm2.At the age of 35 year,the current annual increment curve intersects the average increment curve of biomass of Robinia pseudoacacia forest,which means the mature forest,and total biomass and the carbon density were 72.79 and 35.52 t/hm2,respectively.