Temporal and spatial variations in soil organic carbon sequestration following revegetation in the hilly Loess Plateau, China
Temporal and spatial variations in soil organic carbon sequestration following revegetation in the hilly Loess Plateau, China
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DOI：
10.1016/j.catena.2012.07.003
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发表时间：
2012-12
期刊：
影响因子：
6.2
通讯作者：
Z. Wang;Guo-bin Liu;Mingxiang Xu;Jin Zhang;Yang Wang;Li Tang
中科院分区：
文献类型：
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作者：
Z. Wang;Guo-bin Liu;Mingxiang Xu;Jin Zhang;Yang Wang;Li Tang
土地利用变化是影响土壤有机碳（SOC）变化和全球碳平衡的主要因素之一。自20世纪70年代末以来，黄土高原丘陵地区在几次植被恢复计划中发生了重大的土地利用变化，特别是在退耕还林工程中。然而，目前尚未对该地区植被恢复引起的有机碳时空变化进行全面研究，这不利于准确预测土壤有机碳固存潜力和土地利用变化的影响。本研究以黄土丘陵丘陵区坡耕地和5种典型植被类型为研究对象，根据不同的植被恢复年限和不同的地貌特征，将其划分为36个类群，研究植被恢复后土壤有机碳的时空变化特征及相关因子的影响。结果表明：土壤有机碳浓度在表层（0 ~ 5cm）随着植被的恢复而显著增加，随着土壤深度的增加，土壤有机碳浓度的增加速度减慢，但不同土壤深度的变化系数表明，植被恢复对土壤有机碳浓度的影响可达30cm。土壤有机碳的时间变化主要表现在两个阶段：前10年和15年，土壤有机碳剖面质量（SOC密度，SOCD）略有增加；在此阶段之后，SOCD显著增加，造林林地、灌丛林地和撂荒农田的固碳率分别为0.69、0.55和0.24t·ha−1·yr−1（造林10 ~ 35年）。野生草地的固碳速率为0.23t·ha−1·yr−1（植被恢复10 ~ 35年），与撂荒地相似。野生灌丛林地SOCD在前10年快速增加，增幅为0.93t·ha−1·yr−1，之后25年的增幅为0.56t·ha−1·yr−1。不同地形土壤有机碳的空间差异已达到年SOCD增量的数倍，植被恢复后呈现出新的趋势：阴坡区土壤有机碳固存量显著高于阳坡区，缓坡与陡坡区土壤有机碳固存量差异不显著。采用一般线性模型确定与土壤有机碳变化最相关的因子。恢复年限对土壤有机碳变化的贡献占总贡献的近一半（42%），土地利用类型对土壤有机碳变化的贡献占33%。流域土壤有机碳分布证实了土地利用和复盖年限对土壤有机碳变化的主导作用。在区域尺度上，地形对土壤有机碳的影响较小，但坡向对土壤有机碳的影响较大。黄土丘陵丘陵区土壤有机碳固存速率为0.21 ~ 0.64t·ha - 1·yr - 1，其中以野生灌丛植被固存速率最高，其次为人工林地、人工灌丛植被、撂荒耕地和野生草地。考虑到该地区植被面积大，固碳率较高，固碳对降低大气碳浓度的贡献较大。
Land use change is one of the major factors that affect soil organic carbon (SOC) variation and global carbon balance. Since the late 1970s, a significant area of the hilly Loess Plateau has undergone major land use changes during several revegetation programs, especially in the Grain for Green Project. However, so far there has not been a comprehensive study to determine temporal and spatial variations in SOC due to revegetation in this region, which hampers accurate predictions of the SOC sequestration potential and the land use change impacts. In this study, slope cropland and five typical revegetation types in the hilly Loess Plateau were selected, and then classified into 36 groups according to different revegetation years and landforms to investigate temporal and spatial variations of SOC and the impacts of relevant factors following revegetation. The results showed that the SOC concentration in the top soil horizon (0–5cm) increased most significantly with revegetation and that increases in SOC slowed with increasing soil depth, but coefficient of variations in different soil horizons indicated that revegetation could cause SOC concentration differences at up to a 30cm depth. Temporal variation in SOC occurred in two main phases in replanted cropland: in the first 10 or 15yr, the profile mass of SOC (SOC density, SOCD) increased slightly; after this phase, SOCD increased significantly, with sequestration rates of 0.69, 0.55 and 0.24t·ha−1·yr−1(revegetation 10 to 35yr) for planted woodland, planted shrubland and abandoned cropland, respectively. The SOC sequestration rate in wild grassland was 0.23t·ha−1·yr−1(revegetation 10 to 35yr), which was similar to that in abandoned cropland. In contrast, the SOCD in wild shrubland increased rapidly in the first 10yr, with a rate of 0.93t·ha−1·yr−1, and then by 0.56t·ha−1·yr−1over the next 25years. SOCD spatial differences in different landforms had reached several times the annual SOCD increment and followed a new trend after revegetation: SOC sequestration in shady slope areas was significantly higher than in sunny slope areas, but no significant difference was found between gentle slopes and steep slopes after revegetation. A general linear model was used to identify the factors that were most relevant to SOC variation. Revegetation years accounted for nearly half of the total contribution to SOC variation (42%), and land use type was responsible for 33% of SOC variation. SOCD distribution in a watershed confirmed that variables of land use and years after revegetation dominated SOC variation. Landforms had a small influence on SOC variation at the regional scale, but the influence of the slope aspect was still large. The SOC sequestration rate was about 0.21 to 0.64t·ha−1·yr−1with revegetation in the hilly Loess Plateau, which was highest in wild shrubland, followed by planted woodland, planted shrubland, abandoned cropland and wild grassland. Considering the large area of revegetation and relatively high SOC sequestration rate, SOC sequestration in this region should contribute significantly to decreasing the carbon concentration in atmosphere.