Study On Water Conservation Function Of Shrub In Qilian Mountains

Shrub is an important component of the forest vegetation types in Qilian Mountains and its distribution area covers 68% of the total forest area which plays an important role in water conservation. From the viewpoint of ecology, studied on the water-holding capacities of canopy,litter and soil of five main kinds of shrub types(Caragana jubata,Salix gilashanica,Dasiphora fruticosa,Berberis diaphana,Caragana tangutica ) in Pailugou watershed of Qilian mountains. Characteristics of shrubbery,s eco-hydrological functions were revealed through field investigation and samples analysis in the laboratory between May, 2007 to May, 2008, and comprehensively compared water conservation functions of the five shrub. So the study would provide the necessary theoretical supports for the management of the forest ecosystem in Qilian Mountains. The test results show that:1.During the whole rainy season, the average canopy interception rate is 22.46% for Berberis diaphana, 20.48% for Salix gilashanica, 16.76% for Caragana jubata, 10.42% for Potentilla fruticosa and 6.96% for Caragana tangutica.2.The litter standing crop of the five shrub is 35.44t/hm~2 for Salix gilasnanica,32.66t/hm~2 for Berberis diaphana,25.94t/hm~2 for Caragana jubata,18.53t/hm~2 for Potentilla fruticosa,14.38 t/hm~2 for Caragana tangutica;the litter maximum water-holding rate and the effective water-holding rate ranged from 165.69% to 402.80% and from 119.99% to 235.96%, respectively. Comprehensively compared litter of the five shrub, the order of their water-holding functions is Salix gilasnanica > Caragana jubata > Berberis diaphana > Potentilla fruticosa > Caragana tangutica.3.The soil maximum water-holding capacity and effective water-holding capacity of five different shrub ranged from 2354.50t/hm~2 to 3409.00t/hm~2 and from 518.50t/hm~2 to 1015.50t/hm~2, respectively. They decreased with the soil depth increasing, which is similar to the changes of the soil total porosity and non-capillary porosity. Comprehensively compared soil of the five shrub,the order of their water-holding functions is Salix gilasnanica > Berberis diaphana > Potentilla fruticosa > Caragana jubata > Caragana tangutica.4.The soil surface(0 to 20cm)steady infiltration rate ranged from 8.88 mm/min to 96.01 mm/min, the highest is in Salix gilasnanica stand for 96.01 mm/min, and then followed by the stand of Caragana jubata, Berberis dasystachya, Berberis diaphana and Caragana tangutica. Meanwhile, the cumulative infiltration capacity of the initial 30 minutes is from 338.25 mm to 4718.34 mm, which of Salix gilasnanica is still the highest, and then followed by that in Caragana jubata, Berberis diaphana, Potentilla fruticosa and Caragana tangutica.5.Comprehensively compared all indexes of the five shrub, the order of their water conservation capacity is Salix gilasnanica > Berberis diaphana > Caragana jubata > Potentilla fruticosa > Caragana tangutica.