大兴安岭北端地形因子对针叶林土壤黑碳储量的影响

[目的]气候变化对人类社会发展产生的影响受到了世界各国的广泛关注,提高森林生态系统的固碳潜力被认为是经济可行且有效减缓大气二氧化碳(CO2)浓度的重要途径之一,大兴安岭地区森林生态系统的黑碳储量在全球碳循环和碳汇方面具有重要的作用.研究大兴安岭不同地形因子条件下土壤黑碳的储藏分布特征,为区域森林土壤黑碳储量准确估算和森...

Effects of topographic factors on soil black carbon storage in coniferous forests at the north end of Greater Khingan Mountains

【Objective】The impact of climate change on the development of human society has attracted extensive attention all over the world.Improving the carbon sequestration potential of forest ecosystems is considered to be one of the important ways to reduce atmospheric CO2 concentration economically and effectively.The black carbon(BC)reserves of forest ecosystems in the Greater Khingan Mountains area play an important role in the global carbon cycle and carbon sequestration.The storage and distribution characteristics of soil BC under different topographical factors were studied in order to provide basic parameters for the accurate estimation of BC storage in regional forest soil and for the quantitative evaluation of forest soil carbon sequestration.【Method】Based on differences in slope positions and slope aspects,20 sample plots were set up symmetrically in the cold temperate conifer forest area at the northern end of the Greater Khingan Mountains,and soil samples from different occurrence layers in 1 m sections were collected.Soil BC was separated by the oxidation of dichromate treated with HF/HCl.The effects of topographical factors(the position,aspect and gradient of slope)on the distribution of soil BC were investigated.The relative influence of each factor on the variation in soil BC density was quantified by the stepwise regression analysis.【Result】①The soil BC density in this area ranges from 0.02 to 3.64 kg/m2.The density of the humus layer was the highest,accounting for 50.3%of the total,which had an obvious surface agglomeration effect.The BC contributions ranged from 3.7%to 42.5%of the organic carbon.With increasing depth,there was an increasing trend(except for the litter layer).The results showed that the degree of decrease of the BC content in the soil layer was smaller than that of the organic carbon content,according to the soil layer.Compared with the non-BC composition,the downward migration of BC was greater,and its stability was stronger.The variation range of the BC content in each soil layer was 0.24 to 59.13 g/kg,and the spatial variability was large.②The soil BC content and density distribution were significantly affected by the slope position,and the BC content in the downslope position between different soil layers was higher than that in the upslope position.The density of BC in the humus layer of the downslope position was 2.21 times higher than that in the upslope position,and the BC density of the 1 m profile in the downslope position was 1.91 times than that of the upslope position.The ratio of BC to the organic carbon in different soil layers showed that the downslope ratio was higher than the upslope,but the difference did not reach a significant level.The stepwise regression showed that the slopes position had a great effect on the differentiation of soil BC.Slope could independently explain 42.1%of the spatial variation of BC density in the humus layer and 46.0%of the spatial variation of BC density in the 1 m profile.③The slope aspect affects the distribution of BC reserves through different illumination and temperatures.Overall,the BC content(except for the litter layer and the parent material layer)and BC density(except for the litter layer)showed that the sunny slope was slightly higher than the shady slope,but the difference was not significant.Thus,the slope aspect had little effect on BC.There was no significant correlation between the soil BC density and slope in the humus layer,compared with the 1 m profile and the illuvial horizon according to the upslope and downslope grouping.The trend of the point grouping was obvious:the BC density in the downslope was positively correlated with the slope,the BC density in the upslope was not significantly correlated with the slope,and the influence of the slope on BC distribution was not as great as that of the slope position.【Conclusion】The Greater Khingan Mountains forest region is rich in BC reserves.The black carbon mainly exists in the surface layer of soil and moves slowly.Its biochemical inertia can effectively promote carbon fixation and enhance the carbon sequestration capacity of forest soil.The slope position is the main control factor affecting the distribution of BC in forest soil in this region.In the same layer,there are great differences in the BC content and density among different soil profiles owing to different soil physical and chemical properties,vegetation types,surface runoff scour,and so on.The research results can partly explain the distribution of BC in the region and provide a reference for the selection and management of carbon sequestration forest sites.