Hydrological Dynamic Process Of Cover And Soil Layer

Forest litter layer is an important component of forest vertical structure,which has a tremendous impact on forest hydrological cycle process.Mulch organic cover is widely used in urban forestry construction,which is of great significance for roof greening and sponge city construction.Forest litter layer and Mulch organic cover layer are vertical structural layers which directly contact with soil.They all have the functions of eco-hydrology such as water conservation,delaying surface runoff,increasing soil infiltration and preventing soil erosion.In order to explore the water interception characteristics of the two kinds of mulches and their effects on the hydrological function of the soil layer.The litter layer of Quercus variabilis was selected as the typical representative litter layer of forest vegetation and the common organic Mulch cover layer as the experimental object.Variable factors of cover thickness,rainfall intensity and slope were set as variables to explore the response mechanism of cover interception and soil hydrology to these factors.The results can accurately describe the dynamic interception process of the mulch layer,explain the process of runoff generation and infiltration of the soil layer under the influence of the mulch layer,and provide experimental and data support for the runoff generation mechanism of the slope covered by organic matter.The main results of the experiment are as follows:1.In immersion experiment,the maximum water holding rate of undissolved layer and effective retention rate of semi-decomposed layer of Quercus variabilis litter were 312.8%and 265.9%,267.1%and 227.0%respectively.The maximum water holding rate of Mulch was 110.5%,and the effective storage rate was 93.9%.The water holding capacity of Mulch was lower than that of Quercus variabilis litter.The relationship between water holding capacity and soaking time of the two mulches satisfies logarithmic function,and the relationship between water absorption rate and soaking time is power function.2.The distribution of precipitation by the two mulches includes the lateral flow,the vertical flow and the water holding capacity of the mulch layer.Vertical flow accounts for the largest proportion,while lateral flow accounts for more than interception of Quercus variabilis litter.The size of Mulch overburden changes with the factors of conditions.The interception of Mulch with the same thickness was greater than that of Quercus variabilis litter,and the Mulch was also larger than that of Quercus variabilis mulch in the comparison of lateral flow.In the rainfall experiment,the effective water retention of Quercus variabilis litter layer ranged from 162%to 232%,and that of Mulch ranged from 42%to 101%.3.In the rainfall experiment,about 61.2%-75.8%of the interception water of Quercus variabilis litter flows from the layer as dripping rain or lateral flow,while 36%-62.4%of the interception water in Mulch cover drips from the Mulch cover or runs laterally as dripping rain.The interception capacity of Mulch is stronger than that of Quercus variabilis litter after rain.The difference between maximum water holding capacity and effective water holding capacity of Quercus variabilis litter is larger,and the elastic range of water holding capacity is larger than that of Mulch.4.The influence intensity of different factors on lateral flow in the litter layer of Quercus variabilis during rainfall process is slope>rainfall intensity>thickness.The mulch layer of Mulch is slope>rainfall intensity>thickness.The maximum water holding capacity(Hmax)of Quercus variabilis litter ranged from 3.10 mm to 7.10mm.The maximum water holding capacity(Hmax)of Mulch ranged from 3.38 mm to 15.37 mm.Effective water storage capacity(Hmin)of Quercus variabilis litter ranges from 1.07 mm to 1.72 mm.The main factors affecting its size are thickness and slope,and the relationship between Hmin and rainfall intensity is not significant.The effective water storage capacity(Hn,in)of Mulch ranged from 1.12 mm to 8.62 mm,and the influence intensity ranked from large to small as thickness>rainfall intensity>slope.Under the same rainfall conditions,the effective water storage capacity(Hmin)of Mulch was higher than that of Quercus variabilis,5.The distribution of precipitation under litter cover includes four parts:runoff,soil water holding capacity,soil water drainage capacity and water holding capacity of mulch layer.Soil drainage accounted for the highest proportion of water,followed by soil water holding capacity.runoff and water holding capacity of the cover changed with the thickness of the cover.Compared with bare soil and covered soil,the water holding capacity and drainage capacity of covered soil are higher than those of bare soil,and the runoff produced by covered soil is significantly smaller than that of bare soil.6.The runoff of soil layer covered with litter and Mulch of Quercus variabilis decreased significantly.The runoff generated follows the rule that it decreases with the increase of the litter thickness of Quercus variabilis,while the Mulch has the strongest ability to reduce runoff at the thickness of 2 cm.After that,the runoff generated with the increase of the litter thickness increases slightly.