Abstract: A cascade ecological belt in the Horqin Sandy Land in Inner Mongolia was taken as the study area to lucubrate the variation of water and heat fluxes and the climatological footprints in vegetation growth season 2017,and their values were calculated and analyzed by using the large aperture scintillometer (LAS) and the “FELM” footprint model. The results showed that: ① On sunny days,the curves of the branches of surface energy were unimodal,and the latent heat flux curve fluctuated slightly; on cloudy days,the curves of daily variation of surface energy fluctuated irregularly;② The areas and locations of climatological footprints in the cascade ecological belt were different under different wind directions and different level of atmospheric stability,and the four source areas in the northeast,southeast,southwest and northwest of the study area in July 2017 were 0.265 km²,0.538 km²,0.239 km² and 0.524 km² respectively; ③ The source area under stable conditions was 0.599 km² and occupied 92% of that under unstable conditions; ④ On sunny days,the source area was reduced from 0.665 km² at 8:00 a.m. to 0.292 km² at 11:00 a.m. due to the strong turbulent exchange; in the afternoon,the turbulent exchange was weakened and the source area was enlarged from 0.283 km² at 14:00 to 0.479 km² at 17:00; ⑤ Affected by wind direction,atmospheric stability and other factors,the climatological footprints in early-,mid- and late-July were different. The source area was in an order of late->early->mid-July. The study results could provide a scientific basis and theoretical support for the sustainable utilization of hydrothermal resources and the environmental protection and regeneration in the Horqin Sandy Land under the complex conditions of underlying surface.

Key words: water and heat fluxes, climatological footprint, large aperture scintillometer, cascade ecological zone, source area, Horqin Sandy Land