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深入了解干旱缺水地区森林植被碳密度的空间分布特征是定量评价森林固碳能力、合理协调林水矛盾的重要基础。然而,目前有关干旱缺水地区的植被碳密度的研究仅限于典型样地上的碳储量、碳密度的比较,对区域尺度上森林植被碳密度的空间分布特征了解较少。为此,利用宁夏六盘山自然保护区2005年森林资源一类清查数据,计算了森林植被碳密度,并分析了其与林分结构特征和环境因子的关系。结果表明,六盘山的森林植被碳密度(t/hm2)平均为26.17(0.67—120.63),其中天然次生林为30.2(7.6—120.6),显著高于人工林的15.7(0.67—66.7)。森林植被碳密度随林龄增加而线性增大,天然林和人工林的平均增速分别为1.11和2.48 t hm-2a-1,而且,部分未成熟林的林分植被碳密度已接近甚至超过全国同类森林类型成熟林的植被碳密度平均值。随林分密度增加,森林植被碳密度增大,但在林分密度>1000株/hm2后,森林植被碳密度不再增大,达到其最大值,其中,天然林为75.4 t/hm2,人工林为34.6 t/hm2;林冠郁闭度对森林植被碳密度的影响与林分密度相似,森林植被碳密度增长的郁闭度拐点为0.5。水分条件是影响六盘山森林植被碳密度的重要因素,森林植被碳密度(t/hm2)由700 mm以上地点的32.5(7.6—120.6)下降至年降水量500—600 mm地点的10.9(0.67—42.9),而且随年降水量减少,最大森林植被碳密度所对应的海拔高度呈增加趋势,如在年降水量为>700、600—700和<600 mm的地区,最大碳密度所在海拔高度分别为1900—2100、2100—2300和2300—2500 m。综上所述,研究区森林植被还有较大的固碳潜力,从提高森林固碳功能角度来看,林分郁闭度不宜超过0.5。
A deep understanding of the spatial distribution characteristics of carbon density of forest vegetation in arid and dry areas is an important basis for quantitative evaluation of forest carbon sequestration and reasonable coordination of forest and water conflicts. However, the current research on vegetation carbon density in arid and water-scarce regions is limited to the comparison of typical carbon storage and carbon density in typical plots, and little is known about the spatial distribution of vegetation carbon density at the regional scale. Therefore, based on the inventory data of forest resources in Liupan Mountain Nature Reserve in Ningxia in 2005, the carbon density of forest vegetation was calculated, and the relationship between the vegetation density and environmental factors was analyzed. The results showed that the average carbon density of forest vegetation (t / hm2) in Liupan Mountains was 26.17 (0.67-120.63), of which natural secondary forest was 30.2 (7.6-120.6), which was significantly higher than that of plantation (15.7%, 0.67-66.7). The carbon density of forest vegetation increased linearly with age, and the average growth rate of natural forest and plantation was 1.11 and 2.48 t hm-2a-1, respectively. Moreover, the carbon density of some immature forest stands near or even exceeded The average of vegetation carbon density in the mature forest of the same type of forest in China. With the increase of stand density, the carbon density of forest vegetation increased, but after the stand density> 1000 plants / hm2, the carbon density of forest vegetation no longer increased, reaching its maximum value, of which, the natural forest was 75.4 t / hm2, The forest density was 34.6 t / hm2. The influence of canopy crown density on forest vegetation carbon density was similar to that of stand density. The inflection point of canopy density of forest vegetation was 0.5. Water condition is an important factor affecting the carbon density of forest vegetation in Liupan Mountains. The carbon density of forest vegetation (t / hm2) decreased from 32.5 (7.6-120.6) at the point above 700 mm to 10.9 (0.67- 42.9). And with the decrease of annual precipitation, the altitude corresponding to the maximum carbon density of forest vegetation tends to increase. For example, in the areas with annual precipitation> 700, 600-700 and <600 mm, the maximum carbon density is at the altitude 1900-2100, 2100-2300 and 2300-2500 m. In summary, there is still greater potential for carbon sequestration in forest vegetation in the study area. From the perspective of enhancing the carbon sequestration of forests, the stand density should not exceed 0.5.