秦岭中段南坡油松林生态系统碳密度

在秦岭中段南坡油松林分布较为广泛的不同区域,采用典型取样的方法设置油松林标准地50块。通过样地调查和室内分析,对本区油松林生态系统植被层、枯落物层及土壤层有机碳密度进行了研究与估算,分析了油松林生态系统各层次的有机碳密度在不同立地因子下的分布规律。结果表明:秦岭中段南坡油松林生态系统总有机碳密度为150.12 t/hm2,其中土壤碳分库的碳密度占油松林生态系统总碳密度的56.74%,是构成油松林生态系统碳的主体组成部分。植被层碳密度为62.29 t/hm2,占油松林生态系统总碳密度的41.49%,高于我国森林生态系统植被碳密度平均值,且仍有较大的固碳潜力。枯落物层碳密度为2.66 t/hm2,占油松林生态系统总碳密度的1.77%。在植被碳分库中,乔木层碳密度是其主体构成部分,为61.22 t/hm2,占植被层碳密度的98.30%;灌木层、草本层碳密度及其所占植被层碳密度的比例分别为:0.65 t/hm2(1.04%)、0.41 t/hm2(0.66%)。碳在乔木不同器官中的分配大小顺序为:树干(55.82%)、树枝(21.25%)、树根(10.28%)、树叶(7.35%)、树皮(5.30%)。灌木层碳密度和草本层碳密度受地形因子影响不显著。随海拔的升高,乔木层碳密度呈先增后减的变化趋势,在海拔1500—1700 m处达到最大值,枯落物层碳密度、土壤层碳密度及总碳密度变化不显著;随着坡度的增大,油松林生态系统枯落物层碳密度、土壤层碳密度及总碳密度显著减小,乔木层碳密度呈先增后减的变化趋势,在坡度为26—35°范围达到最大值;下坡位土壤层碳密度高于中坡位和上坡位,而中坡位乔木层碳密度和生态系统总碳密度高于下坡位和上坡位,枯落物层碳密度受坡位影响不明显;阳坡乔木层碳密度大于阴坡,枯落物层碳密度、土壤层碳密度及总碳密度受坡向影响不明显。

Organic carbon density in Pinus tabulaeformis forest ecosystem on the south slope of the middle Qinling Mountains, China

Organic carbon density (OCD) in different carbon pools of Pinus tabulaeformis forest ecosystem and its relationship with different geocentric factors are important for estimating forest carbon budgets, and helpful to understand forest carbon cycles.In this study, we established fifty sample plots at different site conditions using typical sampling method on the south slope of the Middle Qinling Mountains, where Pinus tabulaeformis is widely distributed. Organic carbon density in different carbon pools of Pinus tabulaeformis forest ecosystem and its relationship with different geocentric factors were estimated and analyzed. Our objective was to estimate OCD in different carbon pools of Pinus tabulaeformis forest ecosystem and its distribution on different geocentric factors, to understand the effects of geocentric factors on forest carbon budgets. The results showed that the total OCD of Pinus tabulaeformis forest ecosystem was 150.12 t/hm² in this region. The proportion of soil pool OCD was 56.74% and comprised the major part of the OCD of ecosystem. The OCD of litter pool was 2.66 t/hm², accounting for 1.77% of the ecosystem. Carbon density of vegetation pool was 62.29 t/hm²,taking up 41.49% of the OCD of ecosystem. The OCD of vegetation layer in this region was much higher than the average vegetation pool OCD of forest ecosystem in China, and mere carbon sequestrations are expected. The tree OCD was 61.22 t/hm², accounting 98.3% of the whole vegetation OCD. The OCD of shrub and herb were 0.65 t/hm² and 0.41 t/hm², accounting for 1.04% and 0.66% of the vegetation pool respectively. The OCD of different compositions of tree ranked as stem>branch>roots>leaf>bark. Effects of geocentric factors on the OCD of shrub and herb were insignificant. With the increase of elevation, the OCD of tree first increased and then decreased, peaking at 1500-1700 (a.s.l.). Variations of OCD in litter, soil and the ecosystem were insignificant. With the increase of slope gradient, the OCD of litter, soil and the ecosystem significantly decreased. In comparison, the OCD of tree first increased and then decreased, reaching its maximum on the slope gradient of 26-35°. The OCD of soil was higher in the lower slope compared with that of the middle and the upper slope, while the OCD of tree and the ecosystem was larger in the middle slope. Nevertheless, effects of slope position on the OCD of litter were slight. The OCD of tree at sun-facing slope appeared higher than that of back slope. While effects of slope aspect on the OCD of litter, soil layer and ecosystem were insignificant. It was concluded that effects of geocentric factors on the OCD of Pinus tabulaeformis forest ecosystem were mainly on the tree pool and soil pool on the south slope of the Middle Qinling Mountains. Effects of elevation, slope gradient, slope position, slope aspect were significant on tree pool, and effects of slope gradient, slope position were significant on soil pool. Geocentric factors should be considered in researches on forest ecosystem carbon cycles and estimation of carbon storage of forest ecosystem.