Research On Hydrological And Ecological Functions Of Forest Ecosystem In Upper Resch Of Ashi River Basin

The ecological function of the main water conservation forest stands in upstream of Ashi river basin were studied for scientific assessment on water conversation capacity and theoretical reference to forest planning and ecological construction. This experiment selected six forest stands in Maor Mountain experimental forestry station in2010-2011and set experimental sample plots and surface runoff field. The purpose was to study canopy layer, litterfall layer, soil layer, and surface runoff; construct evaluation index system; assess water conversation capacity of different stands by using analytic hierarchy process (AHP) and fuzzy math method; and forecast water conversation capacity of the optimized stands by Radial Basis Function (RBF) network and computer programming. Results showed that,(1) in the experimental zone, annual average rainfall was600-800mm, mainly focusing in June-August, maximum daily rainfall was mainly focused in July-August, which is considered as frequent occurrence period of heavy rain;(2) for the six forest stands, total penetration rainfall was listed in the decreasing order:Fraxinus mandshurica (524.29mm)> Larix gmelinii (455.72mm)> mixed coniferous and broad-leaved forest (494.48mm)> mongolian oak (513.51mm)> Pinus sylvestris (491.08mm)> Pinus koraiensis (469.35mm); total stem flow:mongolian oak (90.44mm)> Fraxinus mandshurica (74.79mm)> Pinus sylvestris (74.35mm)> mixed coniferous and broad-leaved forest (55.00mm)> Pinus koraiensis (36.23mm)> Larix gmelinii (32.18mm); canopy interception percentage at different rainfall degrees:Larix gmelinii> Pinus koraiensis> mixed coniferous and broad-leaved forest> Pinus sylvestris> Fraxinus mandshurica> mongolian oak;(3) litterfall layer thickness of the six stands ranged from2.8cm to5.5cm, total timber volume was9.27-39.81t-ha; maximum water holding capacity was192.56%-343.67%, with the decreasing order of Larix gmelinii> mongolian oak> mixed coniferous and broad-leaved forest> Fraxinus mandshurica> Pinus koraiensis> Pinus sylvestris; total efficient interception depths were Larix gmelinii of6.71mm, mixed coniferous and broad-leaved forest of4.87, Pinus koraiensis of3.02mm, Pinus sylvestris of1.98mm, mongolian oak of2.18mm, and Fraxinus mandshurica of1.72mm;(4) the averaged soil bulk density varied from0.97-1.26g/cm3, total porosity was in the range of50.16%-60.19%, maximum soil water-holding capacity was1949.51-2293.74t/ha; water conservation capacity of Fraxinus mandshurica (235.06mm), Larix gmelinii (243.36mm), mongolian oak (234.89mm), mixed coniferous and broad-leaved forest (233.70mm), Pinus sylvestris (219.73mm), Pinus koraiensis (205.39mm); efficient water-holding capacity ranging from234.66-438.56t/ha;(5) during the observation period, analysis on the surface rainoff data of28rainfalls showed that there were difference in surface rainoff between different forest stands, in the decreasing order of mongolian oak (1.2505mm)> Larix gmelinii (1.0912mm)> Fraxinus mandshurica (0.9246mm)> mixed coniferous and broad-leaved forest (0.7408mm)> Pinus sylvestris (0.7204mm)> Pinus koraiensis (0.6714mm); there were similar change trends of monthly surface rainoff and monthly rainfall between the forest stands, moreover, there was a good curve-fitting relation between the two parameters (p<0.05);(6) AHP analysis showed that water conservation capacity of Larix gmelinii stand was the best, followed by mixed coniferous and broad-leaved forest, and Fraxinus mandshurica stand is the worst;(7) RBF analysis indicated that the predicative surface rainoff was the largest for Larix gmelinii stand in August and the smallest for Pinus sylvestris stand; the averaged surface rainoff had the same results.