Temporal-spatial Variation And Hydrological Effects Of Litter Of Larix Principis-rupprechtii Plantation In Liupan Mountain

Forest litter layer is an important part of forest ecosystem,which connects vegetation and soil,plays an key role in nutrient circulation,material and energy flow,soil and water conservation.However,there is not much research on this subject at present,especially the influence of litter characteristic changes on hydrological processes and soil physical properties.In this paper,the forest littter of Larix principis-rupprechiii plantation in the Xiangshuihe small watershed of Liupan Mountain,Ningxia were taken as the research object.To analyse the change of litter amount with stand density,forest age and slope grade,and study the characteristics and process of litterfall,hydrological features and the influence of the soil physical property when covering the forest litter in the 2017 and 2018 growing season,the research will provide the theoretical and technical support on the ecological construction and forest management in this area.The main research results are as follows:(1)With the increase of stand density,forest litter amount of Larix principis-rupprechtii showed an increasing trend and then gradually decreased.When the stand density was about 1400?1500 trees/hm~2,the litter amount was the largest.Litter amount of Larix principis-rupprechtii increased with the increase of age of the forest.When the age of the forest was young,litter amount increased rapidly,and litter amount growth began to slow down when the forest age was more than 40a.The litter amount of Larix principis-rupprechtii increased slowly first and then decreased with the increase of slope.(2)With the increase of stand density,the total amount of litterfall of Larix principis-rupprechtii showed an increasing trend,with the total litterfall amount ranging from 2.601 to 3.169t/hm~2,and the amount of litterfall with the density of 1600 plants/hm~2 was the largest.Among them,leaf litter was the main component.The monthly leaf litter in stands with different densities presented "single-peak" in the growing season,and the maximum value appeared in October,accounting for 63.63%?70.50%of total amount.Branches,cones and other litter accounted for a small amount of litter,and the change rule was "irregular".The relationship between cumulative monthly dynamic changes of litters and the time fitted cubic polynomial equation(R~2>0.89).There was a correlation between the leaf litter amount and the change value of leaf area index in Larix principis-rupprechtii plantation during the litterfall period,which showed a significant correlation with the linear equation(R~2>0.79).(3)The maximum water holding capacity of litter with different densities ranged from 34.81 to 71.50 t/hm~2.and the maximum water holding capacity was the highest when the density was 1200 trees/hm~2.The relationship between the cumulative water holdup of litte and the immersion time showed a logarithmic function(R~2>0.93),and the instantaneous water absorption rate and the immersion time showed a power function relationship(R~2>0.89).The daily evaporation rate of litter increased with the increase of moisture content of litter,which is logarithmic,showing a good fitting effect(R~2>0.70).(4)The response of soil hydrological and physical properties to the removal of litter was studied,and the result indicated that in the 0?100cm soil layer,the average bulk density of the removal of surface litter(LR)and the retention of litter(CK)were 1.38g/cm~3 and 1.30g/cm~3.The average total porosity of LR and CK were 44.88%and 49.74%.Capillary porosity was 36.33%and 42.56%.The non-capillary porosity was 8.55%and 7.19%respectively.The soil infiltration rates of LR and CK were 6.25 and 7.98mm/min respectively.The range of soil steady infiltration rate was 3.81 mm/min and 5.22 mm/min.The average soil infiltration rates of LR and CK were 4.38 and 5.64 mm/min.The results of the study on the effect of thickness of litter coverage on soil evaporation showed that the litter thickness could effectively reduce soil evaporation and reduce soil evaporation capacity of the thickiness was 10cm>8cm>6cm>4cm>2cm>0cm respectively.