Characteristics Of Ephemeral Gully Morphological And Topsoil Particle Distribution Under Pine Massoniana Forest

The hilly red soil region in southern China is an important grain and oil base,which plays an important role in guaranteeing national food security and ecological security.However,due to large areas of artificial pure forests,especially the pure forests of Pinus massoniana,water and soil loss in the forests has become a serious problem,making soil erosion control in the southern red soil hilly region an urgent task.As the main form of erosion,ephemeral gullies contributes greatly to the soil erosion under the forest.The morphological characteristics of ephemeral gully and the features of topsoil particle distribution are the important reflection of soil erosion under the forest,meanwhile,it has an important influence on the erosion dynamics of the ephemeral gully,which in turn affects the process and development of soil erosion under the forest.Therefore,it is of great theoretical and practical significance to study the morphological characteristics of ephemeral gully and the distribution of topsoil particle under Pinus massoniana forest.The ephemeral gully under Pine massoniana forest in hilly red soil region was taken as the research object in this paper,using high-precision differential GPS?RTK-GPS?combined with ArcGIS technology,high-precision DEM?digital elevation model?was established in the study area;the classical statistics and geostatistics methods are applied to analyzing the morphological characteristics of the ephemeral gully and the distribution of the topsoil particle under the Pinus massoniana forest The topographic critical model of ephemeral gully erosion in Pinus massoniana forest was constructed.The results are expected to provide a theoretical basis for the establishment of prediction model of ephemeral gully erosion and the control of regional soil erosion under Pine massoniana forest in the hilly red soil region.The main conclusions are as follows:?1?The morphological characteristics of ephemeral gully.51 ephemeral gullies in the study area were analyzed,the basic morphological parameters were as follows:the drainage area was between 2.33¹24.86 m²,the length was between 2.04²5.03 m,the slope was between 6.28°⁴8.74°,the width was between 1.00⁵.52 m,the depth was between0.14¹.20 m,the width-depth radio was between 1.63¹0.25,the gradient was between0.06⁰.67,the cross-section area was between 0.07².03 m²,the gully density was between0.24².40 m/m².?2?Topographic critical model of ephemeral gully erosion.The morphological characteristics of ephemeral gully are mainly affected by the slope steepness and slope length,and there is a significant correlation between the morphological parameters of ephemeral gully;Then through the further analysis of the relationship between ephemeral gully slope?_e?and its drainage area?A?,the topographic critical model of ephemeral gully erosion under Pinus massoniana forest was constructed,which can be expressed as tan?_e?·^0.06=0.49.?3?Characteristics of topsoil particle distribution in ephemeral gully.Under the action of raindrop splash and surface runoff in the hilly red region,the topsoil particles in ephemeral gully consist mainly of gravels,which account for 71.34%,while the contents of clay and silt are the smallest,only 0.46%and 0.45%.The distribution contents of topsoil particles vary in different parts of ephemeral gully.Along the direction of the gully,from the upper slope of the ephemeral gully to the downhill position,the gravel content indicated a gradually decreasing trend;in contrast,the contents of very coarse sand,medium sand,fine sand,silt and clay indicated a gradually increasing trend;However,the change trends of soil particles content in the gully slope and gully edge are opposite to that in the gully bottom.In cross-slope direction,the content of gravel shows a trend of gully edge>gully slope>gully bottom,and the content of very coarse sand,medium sand,fine sand,silt and clay exhibits a trend of gully edge<gully slope<gully bottom.The distribution of topsoil particles is mainly affected by soil water erosion and soil weathering.