The vegetation cover of the Loess Plateau in China has been markedly restored through implementation of land management measures and ecological engineering. Previous studies of the effects of vegetation restoration on climate focused primarily on carbon sequestration and ignored biogeophysical effects. In this study, we used remote sensing data from 2001–2017 to quantify land cover change, vegetation restoration, and the corresponding differences in radiative forcing (RF). Furthermore, we derived the carbon dioxide (CO 2) equivalent for vegetation restoration from the 100-year global warming potential (GWP). Our results showed that cropland and forestland areas increased continuously from 2001–2017, with positive average rates of 13.76% and 33.24% per year, respectively. Vegetation greenness (expressed as the Normalized Difference Vegetation Index) also showed an increasing trend, indicating a gradual increase in vegetation activity. Conversely, surface albedo showed a decreasing trend closely related to the vegetation greenness increase. During the whole study period, both RF and GWP showed an increasing trend, with average annual rates of 0.13 W/m 2/yr and 0.19 kgCO 2/m 2/yr, respectively. The global average RF was 1.58 W/m 2 and the global average GWP was 3.7 kgCO 2/m 2. Vegetation restoration on the Loess Plateau induced an overall decrease in surface albedo, thus an increase in surface energy, or warming effect, equivalent to an emission of 3.7 kgCO 2/m 2. We concluded that it is essential to consider the biogeophysical effect of vegetation restoration when quantifying the global effect of vegetation on climate.

Effects of permafrost degradation on carbon (C) and nitrogen (N) cycling on the Qinghai-Tibetan Plateau (QTP) have rarely been analyzed. This study used a revised process-based biogeochemical model to quantify the effects in the region during the 21st century. We found that permafrost degradation would expose 0.98±0.49 (mean±SD) and 2.17±0.38 Pg C of soil organic carbon under the representative concentration pathway (RCP) 4.5 and the RCP 8.5, respectively. Among them about 60% will be decomposed, enhancing heterotrophic respiration by 9.54±5.20 (RCP 4.5) and 38.72±17.49 (RCP 8.5) Tg C/yr in 2099. Deep soil N supply due to thawing permafrost is not accessible to plants, providing limited benefits to plant growth and only stimulating net primary production by 6.95±5.28 (RCP 4.5) and 27.97±12.82 (RCP 8.5) Tg C/yr in 2099. As a result, permafrost degradation would weaken the regional C sink (net ecosystem production) by 303.55±254.80 (RCP 4.5) and 518.43±234.04 (RCP 8.5) Tg C cumulatively during 2020–2099. Permafrost degradation has a higher influence on C balance of alpine meadow than alpine steppe ecosystems on the QTP. The shallower active layer, higher soil C and N stocks, and wetter environment in alpine meadow are responsible for its stronger response of C balance to permafrost thaw. This study highlights that permafrost degradation could continue to release large amounts of C to the atmosphere irrespective of potentially more nitrogen available from deep soils.