Soil Moisture Dynamics Of Different Landscape Types In The Middle Reaches Of Heihe River

The Heihe River is the second largest inland river basin in China,carrying nearly 2million people’s daily lives.There are many types of landscapes in the middle reaches,and there are a large number of unique landscapes of farmland-forest land-oasis interlacing.However,due to the dry climate,scarce precipitation and scarce water resources,there are serious problems in local agricultural production activities and human survival.In particular,after the implementation of the "97" water plan,the state has increased the amount of water to be distributed to downstream areas,which has further exacerbated the shortage of water resources in the middle reaches.Therefore,it is of great significance to study the distribution characteristics of soil moisture and the change process of soil moisture with time for different landscape types for the reasonable allocation of water resources and sustainable development.In this paper,from May to October(in the rainy season),the soil moisture content of a variety of landscape types within a depth range of 0~100cm is monitored at fixed points,and the characteristics of soil moisture changes over time with different landscape types are simulated using Hydrus-1D software.The following conclusions were reached:(1)In the vertical direction,the soil moisture of each landscape type from May to October shows the following change characteristics with the deepening of soil depth: The riparian bank showed a decreasing-increasing-decreasing trend;The riparian forest at 5 Month,June,and September showed increasing-decreasing trends,while July,August,and October showed increasing-decreasing-increasing trends;The old Farmlands showed decreasing then increasing change trend;The farmland shelterbelt show a layer-by-layer increase trend;The new farmland shows a decreasing then increasing change trend;The desert-oasis ecotone shows a decreasing and increasing and decreasing then increasing change trend;The desert shows a decreasing then increasing trend.(2)From May to October,the coefficients of variation of soil moisture content in each landscape type are shallower than deeper,that is,the variability of soil moisture content in shallower soil is greater than that in deeper layers.In agricultural production activities,the management of shallow soil moisture should be strengthened to alleviate the reduction of crops caused by the deficit of shallow soil moisture.(3)From May to October,the soil moisture content of each landscape type was ranked as riparian beach>riparian forest>farmland shelterbelt>old farmland>new farmland>desert>desert-oasis ecotone.To some degree,the farther away from Heihe River,the smaller the soil moisture content is.In addition,the soil moisture of riparian beach and riparian forests is more responsive to the river inflow,while the soil moisture of farmland and farmland shelterbelt is more responsive to irrigation,and the soil moisture of desert-oasis ecotone and desert is more responsive to rainfall and vegetation.(4)On the time scale,the distribution characteristics of soil moisture content of each landscape type simulated by Hydurs-1D are as follows: the landscapes that increase daily from mid-May to mid-June are: old farmland,desert-oasis ecotone and new farmland,while the other landscape decreases day by day;the landscapes that increase daily from mid-June to mid-July are: riparian beaches,riparian forests,old farmland and new farmland;The landscapes that increase day by day from mid-July to mid-August are: old farmland,farmland shelterbelt and new farmland;the daily increase from mid-August to mid-September only there are new farmland;the landscapes that increase day by day from mid-September to mid-October are: riparian beaches and riparian fores.(5)The simulation accuracy of the Hydros-1D model in each landscape type is desert-oasis ecotone> desert> riparian beach> riparian forest> old farmland> new farmland>farmland shelterbelt.(6)In May to June and August and September,two periods,the farmland landscape decrease the type of soil moisture content change trends,and between May and June when the corn seedling stage,maize plants on the soil moisture content of the demand is higher,August and September in the filling stage of corn,corn grain yield effect is obvious,so in order to guarantee the high yield of maize,should be appropriate increase the two stages of irrigation water.However,October is the maturity period of corn,and the soil moisture content of farmland landscape type is larger than that of other months,so the irrigation water amount of farmland can be reduced appropriately at this time.In addition,from May to October,the soil moisture of farmland shelterbelt is higher than that of farmland landscape,so the leakage of irrigation water should be reduced in the future agricultural production practice,such as reducing the amount of single irrigation and increasing the times of irrigation.