Abstract: To elucidate the mechanism of desertification in semi-arid area, the heat budget of desertificating grassland owing to over-grazing is analyzed using Bowen ratio method.The re.suits show that net radiation and latent heat flux are increased with grass growth. In daytime, net radiation is used for latent heat exchange, but at night,it is largely supplied by latent and soil heat fluxes.The net radiation and latent heat flux over the grassland are much larger than those above a sand dune.

Key words: Grassland, Heat budget, vegetation recovery, herbaceous plant, leaf, nutrient reabsorption efficiency, litter