Effects Of Diffetent Land Use Typys On Destributions Of Soil Moisture And Carbon In Loess Plateau Of Northern Shaanxi Province

Loess Plateau accounts for 70 % total area of Loess soil in the world.This region has unique climatic characteristics,vegetation resources and soil characteristics,and it is the focus area of the ecological construction.Since the implementation of conversion of cropland to forest(grassland)measures in the past 20 years,the land use types in this region has significant changed,and this change has also changed the soil hydrological conditions and soil carbon content.Therefore,more and more studies have focused on the study of soil moisture and carbon under different land use in recent years.However,most of these studies focused on surface soils,but less studies on soil moisture and carbon distribution in deep soils,especially soils below 10 m.In this study,the characteristics of soil water and carbon under different land use types were studied,including the distribution characteristics of soil physical and chemical properties,soil moisture and soil organic carbon and inorganic carbon.The main conclusions are as follows:(1)Soil particle compositions of four land use types were different.The sand content of the surface soil(0~2 m)were farmland>apple forest> Chinese Pine forest ? Chinese Arborvitae forest,and the sand content in deep soil showed no large difference.The content of silt in surface soil were Chinese Pine forest ? Chinese Arborvitae forest > farmland > apple forest,with the depth increasing the silt content of farmland increased,and the content was much higher than the forest.The changes of the clay content of the three forest were small,the value was Chinese Arborvitae forest > apple forest > Chinese Pine forest > farmland.The soil bulk density of four types increased with the increase of soil depth,and the change trend of farmland was higher,the soil bulk density was lower than that of the other three forest lands.With the increase of depth,the bulk density increased gradually.Soil pH did not change significantly,and there was no significant difference between farmland and forestlands.(2)Analysis of soil water characteristics of the four different land use types showed that the average soil water content in the 20 m soil layer were farmland > apple forest ? Chinese Pine forest ? Chinese Arborvitae forest.The values were 11.30 %,6.66 %,6.48 % and5.92 %,respectively.The soil water content of farmland showed that decrease firstly and then increase.The water content of three types of forest decreased at the level of 1~10 m.Below10 m,the soil water content increased gradually with the depth,but the trend was not obvious,and there was no significant difference among these three forest lands.(3)In this study,the SOC changes of different land use types were analyzed.SOC contents of the two land use types decreased with the soil depth.SOC of these two land use types changed greatly at the surface soil.The SOC contents of the forest lands were much higher than the farmland,and the SOC of the whole 20 m profile of the forest lands were about 1.74 times of the farmland.The change trend of SIC content was opposite to SOC.With the increasing depth the SIC increased,but the change was slow.The content of SIC was little different from that of farmland,but the total SIC contents were forest > farmland.The average SIC content of the farmland was 11.24 g·kg-1,which was about 86.6 % of the average content of SIC in forest land(12.98 g·kg-1).