Soil organic carbon stocks in Laos: spatial variations and controlling factors
Soil organic carbon stocks in Laos: spatial variations and controlling factors
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DOI：
10.1111/j.1365-2486.2009.02013.x
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发表时间：
2010-04-01
影响因子：
11.6
通讯作者：
Valentin, Christian
中科院分区：
文献类型：
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作者：
Chaplot, Vincent;Bouahom, Bounthong;Valentin, Christian
表层土壤拥有最大的陆地有机碳(C)库，或许能够隔离大气中的碳，从而减缓气候变化。然而，这仍然存在争议，这主要是由于关于土壤中有机碳含量和储量及其控制的主要因素的数据和知识差距不足。到目前为止，尽管全世界对土壤有机碳(SOC)储量进行了无数次评估，但东南亚的坡地仍然没有得到调查，东南亚是世界上生物地球化学最活跃的地区之一。我们的主要目标是量化SOC存量，并评估各种环境因素的影响。因此，我们选择了面积230 566平方公里的老挝，那里大多是森林覆盖的陡坡，那里的耕作仍然主要是传统的，即不施肥或机械耕作的轮作耕作制度。3471个土壤剖面的分析数据表明，土壤表层1m处土壤有机碳含量约为46.4亿t，其中65%在0.3m以下，变异系数较大(CV=62%)，变异系数为1.8~771 mg C ha-1，平均值为129 mg C ha-1。主成分分析和t检验表明，这些蓄积量受土地利用的影响达到显著水平(P<；0.05)，林下蓄积量最大，轮作次之，连作最小。此外，SOC储量在区域上与年总降雨量和纬度相关，在山坡水平上与到河网的距离和坡度有关。据推测，这种相关性是通过矿物风化、土壤粘粒含量、土壤肥力和景观中有机碳再分布的作用来实现的。这些有机碳储量与环境因素之间的关系可进一步用于(1)预测全球变化对未来有机碳储量的影响；(2)确定土地利用规划的最佳策略，以最大限度地减少向大气排放的土壤碳，同时最大限度地增加土壤固碳。
Surface soils, which contain the largest pool of terrestrial organic carbon (C), may be able to sequester atmospheric C and thus mitigate climate change. However, this remains controversial, largely due to insufficient data and knowledge gaps in respect of organic C contents and stocks in soils and the main factors of their control. Up to now and despite numerous evaluations of soil organic carbon (SOC) stocks worldwide, the sloping lands of southeast Asia, one of the most biogeochemically active regions of the world, remain uninvestigated. Our main objective was to quantify SOC stocks and to evaluate the impact of various environmental factors. We, therefore, selected Laos with 230 566 km2 of mostly forested steep slopes, and where cultivation is still mainly traditional, i.e. a system of shifting cultivation without fertilization or mechanical tillage. Analytical data from 3471 soil profiles demonstrated that the top 1 m of soil depth holds an estimated 4.64 billion tons of SOC, 65% of which is in the first 0.3 m. SOC stocks to 0.3 m exhibit a high coefficient of variation (CV=62%) with values from 1.8 to 771 Mg C ha-1 and a mean at 129 Mg C ha-1. Furthermore, these stocks are significantly (at P < 0.05 level) affected by land use as shown by principal components analysis and t-tests with the largest amount being found under forest, less under shifting cultivation and the smallest under continuous cultivation. Moreover, SOC stocks correlated regionally to total annual rainfalls and latitude, and locally at the hill-slope level to the distance to the stream network and the slope angle. It is hypothesized that this correlation is through actions on mineral weathering, soil clay content, soil fertility and SOC redistributions in landscapes. These relationships between SOC stocks and environmental factors may be of further use in (1) predicting the impact of global changes on future SOC stocks; and (2) identifying optimal strategies for land use planning so as to minimize soil C emissions to the atmosphere while maximizing carbon sequestration in soils.