Abstract: Weighing method was adopted to study the formation time and the amount
 of soil condensation water in four habitats (mobile sandy land, fixed sandy lan
d, farmland, and Mongolian pine forest land) in Horqin Sandy Land in August 2007
. The soil condensation water began to form at 20:00〖KG-*2〗-〖KG-*7〗22:00, in
creased gradually at 22:00〖KG-*2〗-〖KG-*7〗4:00, and began to evaporate after
4:00. In the four habitats, soil c
ondensation water was mainly formed in 0〖KG-*2〗-〖KG-*7〗9 cm layer, and the a
mount was the greatest in 0〖KG-*2〗-〖KG-*7〗3 cm layer, accounting for 40% of
the total. The soil condensation water also formed in 9〖KG-*2〗-〖KG-*7〗30 cm layer, but in ver
y small amount. There was a greater difference in the mean daily amount of soil condensation wate
r in 0〖KG-*2〗-〖KG-*7〗3 cm layer in the four habitats, with the sequence of f
ixed sandy land > mobile sandy land > farmland > Mongolian pine forest land, which indicated that
 the habitat with better vegetation condition was not benefit the formation of s
oil condensation water. The mean daily amount of soil condensation water in 0〖KG-*2〗-〖KG-*7〗3
0 cm layer was 0172 mm in fixed sandy land, 0128 mm in Mongolian pine forest
 land, 0120 mm in mobile sandy land, and 0110 mm in farmland.

Key words: Horqin sandy land, habitat, condensation water, condensation amount, Biome-BGC model, ensemble Kalman filter, data assimilation, leaf area index, carbon flux, evapotranspiration.