黄土高原淤地坝对陆地碳贮存的贡献

Variations of Sediment and Organic Carbon Storage by Check-Dams of Chinese Loess Plateau

我国黄土高原地区广泛分布的以防洪拦沙、淤地为目的的淤地坝工程可能在增加陆地碳贮存方面起一定作用。为验证这一假设,利用碾庄沟流域淤地坝普查资料,结合土壤侵蚀野外调查,研究了1957～2000年碾庄沟流域淤地坝控制区土壤侵蚀产沙时间空间变化与淤地坝库泥沙有机碳储存关系,并估算了黄土高原地区淤地坝拦泥对全球陆地生态系统碳收支的贡献。在研究的12个淤地坝小流域内,流域土壤侵蚀产沙平均速率为25800t/(km2·a),变异系数为42%。土壤侵蚀产沙速率的大小序列为50年代>60年代>70年代>80年代。坡地土壤侵蚀向淤地坝输沙速率(S,t/km2·a)随流域面积(A,km2)的增大呈线性函数减小(R2=0.46,p<0.05)。1957～2000年碾庄沟流域淤地坝共储存有机碳173,133t,提高流域碳储存强度在0.13～5.03t/(hm2·a)之间,平均为1.28t/(hm2·a)。到2002年底,黄土高原地区淤地坝工程共增加有机碳贮量为0.123Gt,占1994～1998年全国大面积人工造林工程增加碳贮量的17.08%,是美国年沉积泥沙有机碳储量(0.04Gt/a)的3.08倍。我们的结果表明,黄土高原地区淤地坝拦蓄泥沙及淤成的坝地是陆地生态系统重要的碳吸收汇之一。

Checkdams, intensively distributed in the hilly areas of the Chinese Loess Plateau, may have large potential for increasing carbon storage in terrestrial ecosystems. To confirm this hypothesis, we examined the spatial and temporal variations of sediment yields and organic carbon trapped by checkdams in the Nianzhuanggou watershed with a area of 54.2 km2 and total of 181 dams constructed duration of 1957~2000 based on the field survey and China dam inventory. Our results suggest that eroded sediment rate calculated on the trapped sediments in thewelldefined dam catchments spatially ranged from 4 140 to 50 267 t/(km2·a) among 12 dam catchments within the Nianzhuanggou watershed. Eroded sediment rates are negatively correlated with the catchemnt size through a linear regression relationship with R2 value of 0.46 for the selected 12 dam catchments. Temporal patterns in eroded sediment rates increased in the following order: 50s>60s>70s>80s, which closely depend on the reforestation on steep slopes. Since 1 957, checkdams in the Nianzhuanggou watershed have stored 173,133 t of carbon, and their average carbon storage rate ranged from 0.13~5.03 t/(hm2·a) with an average of 1.28 t/(hm2·a). Applying this estimation to the Chinese Loess Plateau, checkdam constructions for the 1957~2002 period increased about 0.123 Gt ofcarbon. This estimation is 3.08 times higher than annual amount of soil carbon (0.04 Gt/a) eroded and deposited across the U.S., and accounts for 17.08% of total amount of carbon uptake (0.72 Gt C) by Chinese forests for the period from 1994 to1998. 