More than a century of Grain for Green Program is expected to restore soil carbon stock on alpine grassland revealed by field 13C pulse labeling

Anthropogenic changes in land use/cover have altered the vegetation, soil, and carbon (C) cycling on the Qinghai-Tibetan Plateau (QTP) over the last similar to 50 years. As a result, the Grain for Green Program (GfGP) has been widely implemented over the last 10 years to mitigate the impacts of cultivation. To quantify the effects of the GfGP on C partitioning and turnover rates at the ecosystem scale, an in situ C-13 pulse labeling experiment was conducted on natural and GfGP grasslands in an agro-pastoral ecotone in the LakeQinghai region on the QTP. Wefound that there were significant differences in the C stocks of all the considered pools in both the natural and GfGP grasslands, with higher CO2 uptake rates in the GfGP grassland than that in the natural grassland. Partitioning of photoassimilate (% of recovered C-13) in C pools of both grasslands was similar 25 days after labeling, except in the roots of the 0-15 and 5-15 cm soil layer. Soil organic C (SOC) sequestration rate in the GfGP grasslandwas 11.59 +/- 1.89 g C m(-2) yr(-1) significantly greater than that in the natural grassland. The results confirmed that the GfGP is an efficient approach for grassland restoration and C sequestration. However, it will take more than a century (119.19 +/- 20.26 yr) to restore the SOC stock from the current cropland baseline level to the approximate level of natural grassland. We suggest that additional measures are needed in the selection of suitable plant species for vegetation restoration, and in reasonable grazing management. (C) 2016 Elsevier B.V. All rights reserved.