山西吕梁山南段森林乔木层碳密度

Carbon densities of major tree species in forests in southern Lüliang Mountains of Shanxi Province,China

森林在区域和全球碳循环中起着关键作用,不同森林类型生物量和碳密度的精确估算是区域森林碳储量研究的重要基础。以2005和2010年吕梁山南段2期森林资源清查资料为基础,采用加权生物量回归模型法和转换因子连续函数法对森林乔木层的生物量进行估算,发现前者估算结果显著高于后者(P<0.01),加权生物量回归模型法更适宜于中小尺度生物量估算。依据回归模型法获得的28×112(物种×样方)碳密度矩阵,对森林群落进行TWINSPAN分类和DCA、CCA排序;采用单因素方差分析和相关分析对不同生境条件下乔木层的碳密度进行研究。结果表明:吕梁山南段森林群落可分为8个群系,不同群系间碳密度差异显著(P<0.01),其中辽东栎+色木槭群系和辽东栎+油松群系显著高于其他群系,白皮松+侧柏群系最低。2010年乔木层碳密度显著高于2005年,平均每年以1.54 t·hm-2的速度增加。乔木层碳密度与海拔或坡度呈显著相关,随海拔或坡度的增加碳密度呈先增后降的趋势。阴坡和半阴坡(北坡和东坡)碳密度大于阳坡和半阳坡(南坡与东南坡),山脊碳密度最小。因地制宜进行物种选择和抚育管理,可显著提高森林碳密度。

Forest plays an important role in regional and global carbon cycle. Accurate estimation of biomass and carbon densities of various forest types is important to assess their contributions to total carbon storage in a region. In this study, based on the national forest inventory data in 2005 and 2010, the biomass of main tree species of the forests in the southern Luiang Mountains was estimated by using both the weighted biomass regression model （WBRM） and the continuous function for biomass expansion factor （CFBEF）. The results showed that the estimates from the WBRM were significantly higher than those from the CFBEF （P〈0.01）, and the WBRM was better for biomass estimation at the medium to small scales compared with the CFBEF. On the basis of 28 x 112 （species x plots） carbon density matrix obtained by WBRM, the classification and ordination of forest communities were carried out using the methods of TWINSPAN, DCA and CCA, respectively. Meanwhile, one-way ANOVA was used to test the significance of difference in carbon density among different forest formations, and Pearson correlation analysis was used to assess the correlation of carbon density with the environmental factors （ elevation, slope, aspect and position）. The results showed that the forest communities in the southern Ltiliang Mountains were classified into 8 forest formations, and a significant difference in carbon density was found among these formations （ P〈0.O1 ）. Form. Quercus wutaishanica ＋ Acer mono and Form. Q. wutaishanica ＋ Pinus tabuliformis had significantly higher carbon densities than others, and the carbon density of Form. Pinus bungeana ＋ Platycladus orientalis was the lowest among the eight formations. Thecarbon density in 2010 was significantly higher than that in 2005. The total carbon density in- creased with an average value of 1.54 t ·hm-2· a-1. The impacts of the environmental factors on the formations were in order of elevation 〉 slope 〉 aspect 〉 position. There were significant correlations between the carbon density and elevation, and slope. The carbon density was first increased with the increase of elevation/slope, and then decreased. The forest carbon density was higher on shady and half-shady slopes （north and east） than on sunny and half-sunny slopes （ south and east-south）, and was lowest on steep slopes. In addition to tending management, tree species with stronger adaptability to environmental conditions should be selected for reforestation in order to enhance forest carbon density.