Abstract:

Forest ecosystems play an important role in water conservation.The ecosystems of subalpine coniferous forest zone in western Sichuan Province (SCFZ) play an important role in water conservation for China.In the last decades,the explosive hydropower exploitation of western Sichuan Province has been developed on the large rivers,and the 〖JP〗trend would be continued for a long time because of  the high electricity demand.However,fewer study focused on the ecosystem waterholding of SCFZ.After the devastating floods of 1998,China launched the Natural Forest Protection Project,and we also need to know whether it is conducive to enhancing ecosystem water conservation.Therefore,we evaluated the potential waterholding capacities of soils and ground covers of five typical restoration vegetation in Wanglang National Natural Reserve in the upstream of Shuiniujia Hydropower Station of Fujiang River,western Sichuan Province.Using the method of replacing space with time,five typical restoration ecosystems of grassland (dominated by Deyeuxia scabrescens),shrub (dominated by Salix paraqplesia),broadleaf forest (dominated by Betula platyphylla),mixed forest (dominated by Betula spp.and Abies faxoniana),and the climax forest (dominated by Abies faxoniana) were selected to quantify the waterholding capacity of soil and ground cover (litter and moss) in SCFZ.The results indicated as follows. (1) The soil bulk density increased with the depth and decreased with vegetation restoration,and the trend was mixed forestclimax forest>shrub>broadleaf forest>grassland.Furthermore,the drainability of broadleaf forest was stronger than else because of stronger grazing disturbance.(4) Following the vegetation restoration,the storage of ground cover increased from 800±146 t·hm-2 at the grass to 4528±772 t·hm-2 at the climax forest,the waterholding capacity of ground cover increased 〖JP+1〗from 2856±598 t·hm-2 at the grass to 19768±4383 t·hm-2 at the climax forest,and the composition of ground cover changed from the litter at the grass to moss at the climax forest,respectively.(5) As for the total waterholding capacity of soil and ground cover at the ecosystem scale,it increased largely with the vegetation restoration,and the trend was mixed forest > climax forest> shrub > broadleaf forest>grassland.The waterholding capacity of ground cover was far less than that of the soil in all the studied ecosystems.However,the ground cover could increase the soil water retention through improving soil physical characteristics,and such effect in mixed forest was significantly better than elsewhere.In conclusion,the present paper highlighted that vegetation restoration could significantly increase the waterholding capacity of soil and ground cover at both ecosystem and regional scales.Furthermore,this paper pointed out that moderately introduced broadleaf to the restoration vegetation and reducing human disturbance would be beneficial to the ecosystem water conservation of SCFZ