Effects Of Bryophytes On Runoff Generation Between Exposed Bedrock On Rocky Desertification Slope

Karst rocky desertification slopes are exposed with broken terrain between bedrock,shallow soil layer,single vegetation type and serious water and soil loss.Bryophytes grow well between exposed bedrock,it is the main surface covering.A large number of bryophytes grow and cover the slope,resulting in the change of rainfall runoff and infiltration process on the slope,it has become one of the main influencing factors of rainfall runoff,infiltration and other hydrological processes between exposed bedrock and even the whole rocky desertification area.At present,there are many related studies on the microhabitat between exposed bedrock in rocky desertification slope land,and the research on bryophytes between exposed bedrock tends to be diversity and its impact on soil physical and chemical properties,water holding,soil conservation and other factors,while the research on the hydrological process of bryophyte coverage between exposed bedrock,rainfall yield,infiltration and so on is reported.Therefore,in this study,three dominant bryophytes,Bryum,Eurohypnum and Thuidium,were exposed in karst rocky desertification areas.Taking the bare soil as the reference object,using the simulated rainfall experimental method,this paper explores the effects of three bryophytes on the spatial distribution of rainfall runoff,runoff process,runoff and infiltration process under different rainfall intensity,slope and porosity among different exposed bedrock types.The research results can provide important scientific and theoretical basis for rocky desertification control and ecological restoration in karst area.The preliminary conclusions are as follows:(1)The runoff between exposed bedrock is mainly soil and underground,and the genus bryophyte significantly promotes the surface runoff.Under different environmental conditions,bryophytes have different effects on runoff and infiltration.Exposure type of bedrock is 20 cm(type a): With the increase of rainfall intensity and slope,bryophytes have an inhibitory effect on underground runoff;In the exposed bedrock with an opening of 40 cm(type b),With the increase of rainfall intensity,underground runoff increased,and bryophytes of bryophytes and feather mosses mainly inhibited soil runoff and promoted underground runoff;With the increase of slope,the underground runoff increases,and the soil runoff is restrained.The surface runoff increases except bryophyte.In different exposed bedrock types,with the increase of porosity,the underground flow increases significantly,and the soil flow decreases significantly.Under 5% porosity,the surface and soil flow ratio in exposed bedrock type B is less than 10%.With the increase of porosity,bryophytes significantly increased underground runoff.The variation trends of runoff yield,runoff yield ratio and runoff yield modulus in different spaces of surface,soil and underground are the same.(2)With the increase of rainfall intensity,the initial runoff increases and the stable time of runoff lags behind.The initial surface runoff under the cover of bryophytes is greater than that of the other two types of bryophytes and bare land under three rainfall intensities,and obviously lags behind the stability time of surface runoff.Slope has different effects on runoff yield in different soil layers covered by bryophytes.(1)Surface runoff generation process: with the increase of slope,the initial runoff and stable runoff increase;(2)Soil secondary flow process:with the increase of slope,the stability time of soil secondary flow increases;(3)Underground runoff generation process: there is no significant difference in the stability time of runoff generation under the two slopes,but in the exposed bedrock type A,the runoff decreases with the increase of slope,while in the exposed bedrock type B,the runoff increases with the increase of slope.Increasing underground porosity can reduce the stable time of flow production and increase the stability of flow production at the same time.(3)With the increase of rainfall intensity,the infiltration rate between exposed bedrock increases.In general,the infiltration rate of different soil layers is in the order of surface > soil >underground.Under different rainfall intensities and slopes,bryophytes generally inhibit surface infiltration and significantly promote underground infiltration.Under different porosity,the growth of the genus moss increased significantly with the increase of porosity.With the increase of rainfall intensity,slope and porosity,the underground runoff depth increases on the whole.On the whole,the runoff depth of different soil layers between exposed bedrock is underground > soil > surface.(4)Bryophytes can inhibit runoff production as a whole,slope has a negative correlation with runoff production,and rainfall intensity is the leading factor of slope runoff production.The underground porosity mainly increases the runoff yield on the slope by increasing the runoff coefficient,while the slope mainly inhibits the infiltration to reduce the underground runoff,and the rainfall intensity mainly promotes the runoff yield by increasing the runoff coefficient.(5)From the perspective of soil and water conservation,we should reduce the loss of underground precipitation and increase the water storage capacity of the surface and soil.Among the exposed bedrock with narrow opening,bryophytes can be selected to regulate the rainfall hydrological cycle mechanism,increase soil runoff and reduce underground leakage;The underground leakage between the exposed bedrock with wide opening is strong.Under the rainfall intensity of 90 mm / h,meihuimoss can reduce the flow production between the exposed bedrock.