Root Distribution And The Effect On Soil Properties Of Typical Sand-fixing Afforestation In Gonghe Basin Of Qinghai Province

Desertification is one of the most serious environment problems in China,which has resulted in the land degeneration and affected local people life.Local economic development is also hindered by the desertification,and this situation may last for quite a long time.Gonghe Basin,located in Qinghai Province of China,is a typical desertification area.Artificial vegetation restoration,which performs well in desertification area of China,may immobilize moving dunes,control desertification and improve environment.Root is the most important plant organ of obtaining water and nutrients from soil1 and also plays a key role in plant growth and metabolism.Study of root system distribution patterns means significant for the selection of suitable afforestation tree species and survival rate enhancement.Six typical desertification control plants in local area:Caragana intermedia,Caragana korshinskii,Salix psammophila,Salix microstachya,Populus simonii and Salix cheilophilaand eight standing forests:Caragana intermedia pure forest,Caragana korshinskii pure forest,Salix psammophila pure forest,Salix cheilophila pure forest,Populus simonii pure forest,Cargana intermedia-Artemisia desertorum mixed forest,and Salix cheilophila-PopuIus simoniimixed forests were selected for this study.Thequadratswere set with the area of 20×20 m2.Plant height and crown diameter were measured and then type trees were chosen.The root samples of type tree were obtained by whole plant excavating method,and scanned by WinRhizo Pro 2500a Root Analysis System.Finally,root biomass density,root length density,specific root length,specific rootsurfacearea and root extinction coefficient were calculated and analyzed.The results are as follows:The root system of the plants selected in this study mainly concentrates in the depth range of 0?40 cm,the root biomass density and root length density decreased along the depth of the soil.The specific fine root length ofSalix microslachyawas significantly higher than that of other plant species,indicating that the root activity of the fine roots was the strongest and the adaptability to the environment was the best.The root extinction coefficient of Caragana intermedia and Salix psammophila was significantly higher than that of other plant species,and they have strong ability of holding soil.The biomass density of Caragana korshinskii was significantly higher than that of other plant species.In the Gonghe basin,artificial vegetation restoration should choose Salix microstacbyawith strongadaptabilityor Caragana intermediaand Salix psammophilawith strong soil capacity.Among the eight typical stands selected in this study,the root distribution of Salix cheilophila in the stand is the strongest adaptability to the environment,followed by Caragana intermedia,Caragana korshinskii and Salix psammophila^Artemisia desertorum can be planted as a pioneer plant.In the mixed planting mode,the utilization efficiency of Caragana intermedia and Artemisia desertorum was improved,the dependence of the plant on the surface soil was reduced,and the resistance and adaptability to the dry weather were enhanced.The distribution of root system of Salix cheilophila and Populus simoniiwas more uniform,which improved the utilization efficiency of s0il resources and helped to improve the adaptability.Therefore,we suggest that the region should set up Caragana intermedia.Artemisia desertorum mixed iortst,Salix cheilophila-Populus simonii mixed forest.Followed by Caragana intermedia pure forest,Caragana korshinskii pure forest and Salix psammophilaPure forest Butwe don,t recommend to plant Populus simoniipure forest.Caragana korshinskiipureforest,Caragana intermedia-Artemisia deserrorummixed forest and Salix psammophipureforesthavestrongerabilityto maintain soil and conserve water.Salix psammophila and Populus simoniipure forest were better able to improve soil permeability.In the mixed planting mode,the soil saturated water holding capacity increased,and the ability of soil water conservation was improved.The mixed planting of Caragana intermedia-Artemisia desertorum has a certain improvement effect on the soil,but should also pay attention to the timely management of loose land,if necessary,the application of fertilizer.