| This study takes Zejiashan as an example,the world’s most typical subtropical dolomite karst zone in the world’s most typical subtropical dolomite karst zone in the world natural heritage buffer zone,Zejiashan,located in Shibing County,Guizhou Province.Runoff and sediment yield simulation experiments.Study the soil formation rate and soil erosion characteristics and their influencing factors under different land uses,and explore the coupling relationship between soil formation rate,soil erosion characteristics and rocky desertification under different land uses in the dolomite karst area.It will provide a theoretical reference for the rate of soil formation and the characteristics of soil erosion in the dolomite karst area of southwest my country,as well as the development trend and prevention of rocky desertification.Among them,the monitoring period of the test piece and runoff plot is from October 2019 to October 2020,for a complete hydrological year.The results of the study are as follows:（1）The average soil formation rate of the soil parent material layer（raw soil layer）under different land uses is economic fruit forest land(3.71 t·km-2·a-1)>grain land(2.64 t·km-2·a-1)>Abandoned land(2.23t·km-2·a-1)>Economic fruit forest-grassland(1.86 t·km-2·a-1)>Economic fruit forest-grain land(1.48 t·km-2·a-1)>grassland(0.16 t·km-2·a-1)>woodland(0.14 t·km-2·a-1).The physical and chemical properties of the soil parent material layer（raw soil layer）under different land uses are different.Soil depth significantly negatively affects soil p H,significantly positively affects soil water content,and significantly negatively affects soil organic matter.There is a negative significance between soil water content and soil p H,and between soil bulk density and soil porosity Very significant negative correlation（p<0.05）.There is a significant positive correlation between soil depth and soil water content and the amount of dissolution,dissolution rate,and soil formation rate.Soil organic matter and soil p H are significantly negatively correlated with the amount of dissolution,dissolution rate,and soil formation rate（p<0.05）.The dissolution rate and dissolution rate of flakes have a significant positive effect on the soil formation rate,which plays a decisive role.Therefore,sampling depth and soil water content promote the dissolution rate,dissolution rate,and soil formation rate,and soil organic matter and soil p H have an inhibitory effect on the dissolution rate,dissolution rate,and soil formation rate.（2）The total amount of soil erosion under different land uses is abandoned land（749.467 L）>grain land（556.613 L）>woodland（418.2L）>grassland（403.748 L）>economic fruit forest land（381.65 L）>economic fruit forest-grain Land（294.229 L）>Economic Fruit Forest-Grassland（258.068 L）.The maximum loss is 2.9 times the minimum loss,and the difference is not very large,but relatively concentrated.The main climatic factor affecting soil erosion is rainfall and temperature,humidity has almost no effect on soil erosion.The amount of rainfall affects the total amount of soil erosion,while the intensity of rainfall affects the formation of effective runoff,which in turn affects whether soil erosion occurs.The level of temperature mainly affects the activity of plant roots and soil animals in the soil,which in turn affects the response of the soil to changes in the external environment.Different types of land use also have a greater impact on the total amount of soil erosion.The total amount of soil erosion in the economic fruit forest-grassland and economic fruit forest-grain land is less.Compared to woodland,grassland,economic fruit forest-grassland,economic fruit forest-grass land,the vegetation coverage of the land planted with corn alone is smaller,the gap between plants is larger,and the degree of interception of rainwater by plants is relatively smaller.That is to say,under the same rainfall and rainfall intensity,more rainwater will directly act on the soil on the surface,exerting a greater force on the soil,and then forming the phenomenon of soil erosion.In order to obtain greater economic benefits,humans will loosen the soil and fertilize the forest land every year,and take certain measures to keep the rainfall in the soil to ensure the growth of the forest trees.That is,due to human activities,the total amount of water and soil loss in the economic fruit forest land is small.Abandoned land has the largest amount of soil erosion.Abandoned land is the land that has been abandoned recently.It used to be agricultural land and the soil is relatively soft.After the annual herb plants wither in winter,rainfall directly affects the ground,resulting in greater soil erosion,which in turn produces greater soil erosion.In summer,only some herbaceous plants grow sporadically in abandoned land.However,because it is an annual herbaceous plant,its plants are small,and the ability to absorb and intercept rainfall is limited.Rainfall mainly falls to the ground and forms an effective overland flow.Produce erosive power,which in turn produces a larger amount of soil loss.（3）The annual amount of soil formed is economic fruit forest land(3.71 t·km-2·a-1)>grain land(2.64 t·km-2·a-1)>abandoned land(2.23t·km-2·a-1)>Economic Fruit Forest-Grassland(1.86 t·km-2·a-1)>Economic Fruit Forest-Grain Land(1.48 t·km-2·a-1)>Grassland(0.16t·km-2·a-1)>Woodland(0.14 t·km-2·a-1).The amount of soil loss is abandoned land(274.628 t·km-2·a-1)>economic fruit forest land(178.461 t·km-2·a-1)>grain land(48.419 t·km-2·a-1)>Economic fruit forest-grain land(10.488 t·km-2·a-1)>economic fruit forest-grassland(6.291 t·km-2·a-1)>woodland(1.883 t·km-2·a-1)>grassland(1.745 t·km-2·a-1).（4）Using the amount of annual soil loss minus the amount of annual soil formation,the annual net loss of soil for each land use is abandoned land(272.398 t·km-2·a-1)>Jingguo forest land(174.751 t·km-2·a-1)>grain land(45.779 t·km-2·a-1)>economic fruit forest-grain land(9.008 t·km-2·a-1)>economic fruit forest-grassland(4.431 t·km-2·a-1)>Forestland(1.743 t·km-2·a-1)>Grassland(1.585 t·km-2·a-1),which is exactly the same as the change trend of annual soil loss under different land use.That is to say,the amount of soil formed under different land use types did not change the trend of soil loss,but only slowed the amount of soil loss.Moreover,the amount of mitigation is small compared with the amount of soil loss,and the mitigation effect is not large,and it does not fundamentally solve the problem of soil loss.According to the minimum grading intensity of the soil erosion intensity grading standard in the southwest karst area,the soil erosion intensity under different land use types in the dolomite karst area discussed in this article is:woodland,grassland,economic fruit forest-grassland and economic fruit forest-grain land.The intensity of soil erosion is slight,the intensity of soil erosion of grain land is mild,the intensity of soil erosion of economic fruit forest land is moderate,and the intensity of soil erosion of abandoned land is intensity,limitless and severe.（5）Forest land,grassland,economic fruit forest-grassland,economic fruit forest-grain land are the least prone to rocky desertification.Grain land,economic fruit forest land,and abandoned land have higher and higher levels of rocky desertification.That is,the lower the forest and grass vegetation coverage,the greater the probability of rocky desertification.It is recommended that the slopes and mountain tops engaged in planting industry should be closed as far as possible to cultivate forests,and return farmland to forests and grasses to prevent soil erosion.For agricultural land with a gentle slope,interplanting production methods should be adopted to plant crops as much as possible,and single-planting models can be reduced.Only in this way can we better maintain water and soil,increase productivity,and maintain soil fertility. |
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