作 者 ：曹广民,龙瑞军*,张法伟,李以康,林丽,郭小伟,韩道瑞,李婧
期 刊 ：生态学报 2010年 30卷 23期 页码：6591~6597
Keywords:carbon sequestration, alpine meadow, mattic epipedon, succession,
摘 要 ：以广布于青藏高原的高寒矮嵩草草甸为研究对象，研究了草甸碳储存的场所、碳库容量随草甸演替的变化过程及其碳增汇潜力的空间分布格局，同时探讨了高寒草甸碳增汇潜力估测的困惑与解决方法。结果表明，高寒草甸生态系统碳增汇潜力空间分布格局差异极大，主要受到土层厚度和草地演化进程的影响。高寒草甸碳主要贮存于草毡表层，其增汇潜力在于退化草地草毡表层的恢复与重建。保持适宜厚度的草毡表层是协调高寒草甸生产与碳生态服务功能的关键。随着退化高寒草甸的恢复，土壤容重呈现下降趋势，计算其系统碳增汇潜力，需要用根土体积比进行土层深度的校正。高寒草甸具有较大的固碳潜力，但其潜力的发挥受到气候和草地恢复与管理措施的影响，比较漫长。
Abstract:Alpine meadows widely distribute on the Qinghai-Tibetan Plateau and store a large amount of carbon (C) in soil. Since 70ths last century, a large area of alpine meadows have been suffering from degradation with increasing human activities (e.g. increasing grazing intensity) under climate change. There is a great potential of C storage for these large area of degenerated grassland if they are recovered in future. However, it is difficult to estimate the potential because of many uncertain factors. Base on our understanding about C processes occurred in the Kobresia meadows on the Plateau, this paper here used a time-space substitution method to investigate the location of C storage, the capacity of C storage at different stages during grassland succession and its spatial variability. And also assessed the method used for estimating the potential of C storage in alpine meadows. Mattic epipedon (M.E) is a main storage horizon in soils, which is mainly consisted of dead roots and clay. Its thickness strongly controls the capacity of C storage in alpine meadows because of high C content in M.E.. The thickness of M.E. increases normally with grassland degeneration succession. The degeneration succession of alpine meadows can be divided into seven stages: (1) graminoid-Kobresia community, (2) K. humilis community, (3) K. pygmaea community, (4) M.E. thickening of K. pygmaea community, (5) M.E. cracking of K. pygmaea community, (6) M.E denuding of K. pygmaea community, and (7) Forb- black soil land. Organic C storage in roots and clay of M.E. reaches a saturated level at the M.E denuding stage, but its collapse at this stage leads to a break of ecosystem stability. A half amount of stored C can be lost due to the loss of M.E. at the black-soil type stage. Alpine meadows on the Qinghai-Tibetan Plateau are observed to be at different stages, i.e. M.E. thickening of K. pygmaea community in the northern part of the Plateau, M.E denuding of K. pygmaea community and black-soil type in the three river region and graminoid-Kobresia community in the Qilian Mountain region. The thickness of M.E. is greater in both the three river region and the northern part of the Plateau than in the Qilian Mountain region. Therefore, the potential of C storage is in an order as follows: the three river region> the Qilian Mountain region> the Sorthern Tibetan plateau. This clearly indicates that the capacity of C storage depends on M. E. thickness and grassland succession stage, with significant spatial variability across the whole plateau. Soil bulk density as an important factor in estimating the potential to store C shows a continuous decrease and thus leads to a feint of C loss with restoration of degraded grasslands because of raised soil depth by roots. This indicates that it should be corrected by the soil/root (volume) ratio when estimate C sequestration in soils. Considering both biomass production and C ecological service, alpine meadows should be maintained at the stage of graminoid-Kobresia community or K. humilis community. A suitable thickness of M.E. is about 2.0-3.1cm.
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