Study On Different Forest Types Of Litter And Soil Characteristics And Water Conservation Function In The Water Source Of Chemu River Reservoir In Kunming City

As the main forest species cultivated and managed in urban water source area,water source conservation forest plays an important role in water source conservation,water and soil conservation and water quality purification.Based on the water source of Chemu river reservoir in Kunming—Shuanghe Monande Water-source forest nature reserve in yunnan province was taken as the research area,with the main vegetation types in the area--semi-humid evergreen broad-leaved forest,Pinus yunnanensis forest,Pinus armandi forest,mixed forest and Alnus nepalensis forest,Acacia dealbata forest as the research object,and select the slope dryland as control,adopt the method of combining the field investigation and indoor test,the different vegetation types in the study area of the litter and soil characteristics and water-holding ability were analyzed,and the physical and chemical properties,and using the TOPSIS method,the comprehensive index evaluation system,to evaluate the water conservation function of various vegetation types.The main conclusions are as follows:?1?There were significant differences in soil nutrient content between different vegetation types 0⁶0cm.The content of organic matter was highest in evergreen broad-leaved forest(65.11g·kg^-1)and lowest in young Pinus yunnanensis forest(23.44g·kg^-1).With the increase of soil depth,the vertical decline of soil organic matter content was obvious,and the contents of soil total nitrogen,total phosphorus and available nutrients also had similar change characteristics,while the total potassium increased with the increase of soil depth.The order of soil fertility of different vegetation types was mixed forest?1.80?>evergreen broad-leaved forest?1.74?>Alnus nepalensis forest?1.51?>Pinus armandi forest?0.58?>mature Pinus yunnanensis forest?-0.44?>Acacia dealbata forest?-0.86?>young Pinus yunnanensis forest?-1.75?>slope dryland?-2.46?.The general performance was that the soil fertility of broad-leaved forest and coniferous mixed forest was better than that of coniferous forest,and the soil fertility of woodland was better than that of slope dry land.?2?The soil sand content ranged from 50.34%to 69.74%,and the clay content ranged from 7.54%to 26.76%.The soil texture types were mainly sandy clay loam and sandy loam,with good permeability and water retention.The soil bulk density of forest land was between 1.22g·cm^-3 and 1.41g·cm^-3,which was significantly lower than that of slope dry land(1.52g·cm^-3).The ranking was mature Pinus yunnanensis forest>young Pinus yunnanensis forest>Acacia dealbata forest>Alnus nepalensis forest>Pinus armandi forest>mixed forest>evergreen broad-leaved forest,which increased with the increase of soil depth.The soil total porosity ranged from 42.52%to 53.86%,and the order was opposite to the bulk density.The fractal dimension of soil in different forest types ranged from 2.611 to 2.802,which was positively correlated with bulk density and structural failure rate.The content of water stable large aggregate in forest land from 71.61%to 78.20%,which is significantly higher than that in slope dry land?55.40%?,indicating that forest land has obvious effect on soil improvement,good porosity,and strong ability to store water and precipitation.?3?The natural water content at the end of the dry season ranges from 11.79%to18.65%,and the order of size was Alnus nepalensis forest>Pinus armandi forest>evergreen broadleaved forest>mature Pinus yunnanensis forest>mixed forest>young Pinus yunnanensis forest>Acacia dealbata forest>Slope dryland,which increased with the increase of soil depth.The maximum soil water holding capacity,capillary water holding capacity and non-capillary water holding capacity range from 2550.89 to 3231.47t·hm^-2,1811.07 to 2283.93t·hm^-2,739.83 to 1093.13t·hm^-2,the water-holding capacity of the soil was shown as evergreen broad-leaved forest>mixed forest>Pinus armandi forest>Alnus nepalensis forest>Acacia dealbata forest>young Pinus yunnanensis forest>mature Pinus yunnanensis forest>slope dryland,and the water-holding capacity of the soil in the upper layer was higher than that in the lower layer.The soil precipitation range from 184.35 to 239.02mm,and it was ranked as mixed forest>Alnus nepalensis forest>evergreen broad-leaved forest>young Pinus yunnanensis forest>Pinus armandi forest>Acacia dealbata forest>mature Pinus yunnanensis forest>slope dryland slope.The effective soil storage was between 82.79 mm and 138.17 mm,and it was ranked as mixed forest>Acacia dealbata forest>Pinus armandi forest>evergreen broad-leaved forest>mature Pinus yunnanensis forest>slope dryland slope>young Pinus yunnanensis forest>Alnus nepalensis forest.The change of soil storage precipitation and effective storage quantity is not consistent,but both of them are mixed forest with needle and broad,both of them show a decreasing trend with the increase of soil depth,and the surface soil storage capacity is better than that of the subsoil.?4?The range of litter accumulation in different forest vegetation types ranged from 4.75 to 17.45t·hm^-2,and the range of total thickness ranged from 2.06 to 7.57cm.Mixed forest were the highest,while young Pinus yunnanensis forest were the smallest.Except for coniferous forests such as Pinus armandi forest and Pinus yunnanensis forest,the semi-decomposed layer?Oe?accumulation of other vegetation types is greater than the undecomposed layer?Oi?.The natural water content ranged from 0.34 to 2.28t·hm^-2,and it was ranked as evergreen broad-leaved forest>mixed forest>Pinus armandi forest>Alnus nepalensis forest>Acacia dealbata forest>mature Pinus yunnanensis forest>young Pinus yunnanensis forest.The maximum water capacity content ranged from 7.05 to 32.19t·hm^-2,and it was ranked as Pinus armandi forest>mixed forest>evergreen broad-leaved forest>mature Pinus yunnanensis forest>Alnus nepalensis forest>Acacia dealbata forest>young Pinus yunnanensis forest.The effective storage capacity content ranged from 5.45 to25.34t·hm^-2,and it was ranked as mixed forest>Pinus armandi forest>evergreen broad-leaved forest>mature Pinus yunnanensis forest>Alnus nepalensis forest>Acacia dealbata forest>young Pinus yunnanensis forest.According to the order of the three sizes,the coniferous mixed forest,evergreen broad-leaved forest and Pinus armandi forest had better water holding capacity.The maximum water holdup of litters was between 148.47%and 210.88%,and the effective retention rate was between 119.06%and 165.43%,both of which showed that broad-leaved forest was higher than coniferous forest,and semi-decomposed layer was higher than undecomposed layer.There is an obvious logarithmic function relationship between the water holding capacity and water holding capacity of litters of different vegetation types and the water loss,water loss rate and experimental time:W=alnt+b,R²>0.93.There was an obvious power function relationship between the water holding rate and water loss rate of litter and experimental time:V=k t ⁿ,R²>0.99.?5?The comprehensive water conservation functions of litter and soil in different forest vegetation types were as follows:evergreen broadleaved forest?0.373?>mixed forest?0.409?>Alnus nepalensis forest?0.485?>Pinus armandi forest?0.499?>Acacia dealbata forest?0.594?>mature Pinus yunnanensis forest?0.685?>young Pinus yunnanensis forest?0.739?>slope dryland?0.973?.According to the hydrological characteristics of litter and soil of 7 forest vegetation types,the evergreen broadleaved forest was the most capable of water and soil conservation and water conservation,followed by mixed forest and Alnus nepalensis forest,and the youngest yunnan pine forest was the worst.The maintenance and management of existing evergreen broad-leaved forest can be strengthened,and the mixed needle-width forest with reasonable structure can be constructed,so that the hydrological and ecological benefits of the water source area of Chemu river reservoir can be brought into play stably.