[Differences of evapotranspiration on forest, grassland and farmland]

By using the 1990-2003 meteorological data gathered from 12 ecosystem stations of Chinese Ecosystem Research Network, the evapotranspiration rates of forest, grassland and farmland were estimated by soil-vegetation-atmosphere transfer model, with their change patterns under different climate conditions investigated. The results showed that the mean annual evapotranspiration from high to low ranked as tropical forestland, subtropical farmland, temperate forestland, temperate farmland and grassland. For farmland, rice field had the highest annual evapotranspiration, followed by wheat field, and maize field. There was an obvious monthly variation of evapotranspiration on forestland, grassland and farmland, but the inter-annual amplitude of the variation was steadier on forestland and grassland than on farmland.