Abstract
Large-scale deforestation may affect the surface energy budget and consequently climate by changing the physical properties of the land surface, namely biophysical effects. This study presents the potential energy budget change caused by deforestation in Northeastern China and its climate implications, which was evaluated by quantifying the differences in MODIS-observed surface physical properties between cropland and forest. We used the MODIS land products for the period of 2001–2010 in 112 cells of 0.75° × 0.75° each, within which only best quality satellite pixels over the pure forest and cropland pixels are selected for comparison. It is estimated that cropland has a winter (summer) mean albedo of 0.38 (0.16), which is 0.15 (0.02) higher than that of forest. Due to the higher albedo, cropland absorbs 16.84 W∙m−2 (3.08 W∙m−2) less shortwave radiation than forest. Compared to forest, cropland also absorbs 8.79 W∙m−2 more longwave radiation in winter and 8.12 W∙m−2 less longwave radiation in summer. In total, the surface net radiation of cropland is 7.53 W∙m−2 (11.2 W∙m−2) less than that of forest in winter (summer). Along with these radiation changes, the latent heat flux through evapotranspiration over cropland is less than that over forest, especially in summer (−19.12 W∙m−2). Average sensible heat flux increases in summer (7.92 W∙m−2) and decreases in winter (−8.17 W∙m−2), suggesting that conversion of forest to cropland may lead to warming in summer and cooling in winter in Northeastern China. However, the annual net climate effect is not notable because of the opposite sign of the energy budget change in summer and winter.
Highlights
Land cover changes caused by human activities are important forcings of climate [1]
The objective of the present study is to investigate the energy budget change caused by deforestation and its climate implications in Northeastern China
Deforestation leads to a large increase in surface albedo, in areas where snow falls because short vegetation, like cropland, is buried by snow
Summary
Land cover changes caused by human activities are important forcings of climate [1]. Over the past300 years, 15%–30% of the global natural forest has been converted to pasture or cropland [2]. Land cover changes caused by human activities are important forcings of climate [1]. Over the same period in China, the forested area has decreased by 9.2% [3]. During the past two decades, this area has decreased by 8.52 × 105 hectare (hm2) because of cropland expansion, in Northeastern China [4]. Such large-scale deforestation can affect climate through both biogeochemical and biophysical processes. Biogeochemical effects of land cover change (e.g., changes in carbon sinks) can alter the concentration of atmospheric greenhouse gases and affect global climate [5,6,7]. Previous studies have reported that, unlike biogeochemical effects, which affect climate on a global scale, biophysical effects usually act at regional or local scales and may counteract or enhance biogeochemical processes [12,13]
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