Abstract:The effects of five different ecosystems on surface runoff were studied through"watershed experiments" during 1993 to 1997 in Heshan Hilly Land Experiment Station.The results showed that the surface runoff coefficients of five ecosystems, viz. Acaciamangium forest, orchard, leguminous mixed forest, grassland, and forest-orchard-nurserysystem, were 2.3%, 6.97%, 13.30%, 17.90% and 22.16%, respectively, while thevariation rate difference of runoff modulus were in the order of A. mangium forest < leguminous mixed forest < forest-orchard—nursery system < grassland < orchard, being O.46，O.57，0.63，O.65 and 1.68 respectively The results showed that A .angium forest and legum inous mixed forest have better hydrological function on water conservation and adjustment than the others. Surface runoff coeffcients were different among the seasons showing that wet season > annual > dry season, but the seasonal change in variation rate diference of runoff modulus was in the order of dry season > annual > wet season. Between surface runoff （R）and precipitation (P)，there was a regressive relation equation，R=aP2+bP+c，and surface runoff had rio significant relationship with the rainfall intensity, and the surface runoff was often provided by some heavy rains The rainfall causing surface runof in A．mangium forest，orchard，leguminous mixed forest forest-orchard-nursery system and grassland were 15.9，13.28．8.1，6.71 and 5.21 mm，respectively The runof occurence and the flood peak was delayed by the five ecosystems for 10 to 30 minutes，and the maximum appeared in A． mangium forest．Some flows in hydrological function of orchard and forest-orchard-nursery system are discussed.
