| The typical black soil region of Northeast China is the main grain production area of China. This region has suitable climate and superior soil condition, soil erosion is week if without human disturbance. However, the long term cultivation has caused serious soil erosion in this region. According to Integrated Scientific Investigation of Soil and Water Loss and Ecological Security in China:Subsection of Black Soil region of Northeast China, the soil erosion area of black soil region has increased to 183 thousands km2 from 88.2 thousands km2 in 1950s. Soil thickness has decreased to 20-30cm from 60-70cm in 1950s. However, soil erosion researches on black soil region started relatively late. Although the hydrological monitoring data is comparatively complete, it can not express the characteristics of soil erosion because a little part of eroded soil can be carried to rivers due to the gentle and long slopes in this region. In this paper, 10 hydrologic station controlled areas from natural forest region (Daxinganling Mountains), hilly and gully regionâ… , hilly and gully regionâ…¡and rolling hills are selected. RUSLE was chosen to calculate soil erosion modulus of these 10 areas, combining with the sediment monitoring data, sediment delivery ratio (SDR) was estimated. This study could provide important scientific basis for the policy making and measures configuration of soil and water conservation. Main results were as follows:(1) The calculation method of soil erosion facters in RUSLE have been selected, the map of rainfall erosivity factor, soil erodibility factor, slope length and steepness factors and cover-management factor of the 10 hydrologic station controlled areas were acquired.(2) Sediment delivery ratio (SDR) of different soil erosion regions in the Songhua River Basion were calculated based on soil erosion modulus and sediment monitoring data. The annual average SDR of natural forest region (Daxinganling Mountains) was 0.0073, the annual average SDR of hilly and gully regionâ… was 0.0139, the annual average SDR of hilly and gully regionâ…¡was 0.0539, and the annual average SDR of rolling hills was 0.1453.(3) Trend analysis showed that erosion modulus in the same trends with rainfall erosivity, but sediment modulus and SDR was irrelevant to rainfall erosivity. Abrupt change analysis showed that erosion modulus, sediment modulus and SDR had abrupt change while rainfall erosivity did not show abrupt change. It indicated that there maight be other factors driving the trend and abrupt change. (4) The relationship between land use change and erosion modulus, sediment modulus, and SDR in Nianzishan, Dashizhai and Dashanjuzi hydrologic station controlled areas were analyzed. The results showed that in Nianzishan hydrologic station controlled area, sediment modulus and SDR had same trend with bare land ratio, but had opposite trend with grassland coverage ratio. In Dashizhai hydrologic station controlled area, sediment modulus and SDR had dramatic increase since 1984, it may drived by the decreasing of forest coverage and the increasing of dry land ratio and bare land ratio. In Dashanjuzi hydrologic station controlled area, sediment modulus showed increasing trend, it may drived by the increasing of dry land ratio and the decreasing of forest coverage; while the SDR of Dashanjuzi hydrologic station controlled area showed no trend change in the study period. In brief, the decrease of forest coverage, grassland coverage and the increase of dry land ratio, bare land ratio would drive the increasing or even dramatic change of sediment modulus and SDR of hydrologic station controlled areas. |
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