Water Utilization Characteristics Of Farmland Shelterbelt Under Oasis Water-saving Mode

With the popularization of urbanization and large-scale water-saving irrigation,the surface vegetation cover in the arid inland Oasis area of northwest China has changed greatly.Due to the uneven development of agriculture and forestry,coupled with the fact that the benefits of forestry lag behind the output of agriculture in the short term,forestry has always been placed at a disadvantage in the process of Agriculture-Forest-Pastoral water,often lagging behind agriculture in irrigated water quantity and irrigation system,especially after agricultural irrigation has achieved large-scale drip irrigation under larger film,The irrigation aqueduct of the original perennial shelterbelt disappeared,the irrigation quantity was not effectively guaranteed,which caused the large area of the original shelterbelt to decay and degenerate,Serious impact on the protective effect of shelterbelt,the comprehensive benefits are difficult to be guaranteed,this paper studied:?1?Using remote sensing technology,the TM/OLI image data of the Shihezi region of Xinjiang in 1998,2007 and 2017 were selected,and the vegetation cover and vegetation changes in three different time periods were analyzed based on the cell dichotomy model.?2?Use of stable oxygen isotopes(?¹⁸O)This paper studies the water utilization mechanism of common farmland shelterbelt Populus euphratica,Elaeagnus angustifolia and Ulmus pumila in arid Oasis area under the water-saving irrigation mode of farmland,according to the direct judgment method,The results are compared and analyzed by 3 methods of Isosource model and water absorption depth model.?1?The results showed that vegetation coverage was 52%,60%and 48%in 2007 and 2017,respectively,and decreased first and then decreasing,and the vegetation cover areas at the?and?levels increased at an average annual rate of 1.17%and 1.56%,respectively;?class,The vegetation cover areas at the?and?levels decreased at an average annual rate of 0.05%,0.26%and 0.75%,respectively,and in general,the area of vegetation degradation in the area was greater than that of the recovery area in the last 20 years.Combined with the analysis of land,meteorology,hydrology and other data,it is concluded that artificial causes such as excessive exploitation of groundwater and expansion of urbanization are the main causes of vegetation degradation in this area.?2?Different species of protective forest water use sources are different at different time.Among them,April Poplar mainly uses 10-20 cm shallow soil water,the contribution rate is83.3%,the average water absorption depth is 18cm,Elaeagnus angustifolia mainly uses 80-120 cm and 120-160 cm deep soil water,its contribution rate is 50.6%and 16.9%respectively,the average water absorption depth is 118 cm;The Ulmus pumila mainly uses 50-300 cm deep soil water and groundwater,the cumulative contribution rate is 82.5%,the average water absorption depth is 95cm.In May,poplar mainly used shallow 0-30 cm of soil water,the contribution rate of 57.1%of the average water absorption depth of 28cm,Elaeagnus angustifolia and Ulmus pumila instead of surface 0-10 cm soil water,its contribution rate of50.8%and 52.7%,the average water absorption depth of panax.June poplar using 0-20 cm shallow soil water and groundwater,the contribution rate is 38.7%and 10.5%respectively,the average water absorption depth is 25cm,sand jujube 76.9%of the water is derived from the shallow soil of 10-20 cm,the average water absorption depth is 34 cm,and 49.1%of the main water sources of Ulmus pumila are from 0-80 cm,the average water absorption depth is 29 cm,and another 12.3%comes from groundwater.In July,poplar mainly used 0-20 cm shallow soil water,its contribution rate was 50.4%,sand jujube for shallow 0-20 cm soil moisture utilization rate of 26.8%,significantly lower than June,Elaeagnus angustifolia for the rest of the soil layer water use is more average,about 10%maintenance,The utilization of groundwater is 16%,which indicates that the utilization rate of shallow soil water is reduced by sand jujube,which increases the utilization of groundwater.Ulmus pumila mainly use 0-10cm moisture,its contribution rate reached 63.6%,for other layers of water use is less than 5%,indicating that Ulmus pumila July mainly use 0-10 cm soil water,compared with June increased,9.2%of the water from groundwater,the use of groundwater slightly lower than last month.The water utilization rate of poplar to 0-20cm reached 56.8%in August,and in August Elaeagnus angustifolia the soil water use of surface 0-20cm was further reduced,0-10 cm:7.9%,10-20cm:7.7%,more stable use of intermediate layer and deep soil water,For 20-300 cm,the water and groundwater utilization rate of each layer is about 12%.The deep soil moisture utilization rate of 0-10 cm and 10-20 cm was 14.4%and 14.1%,respectively,and the moisture utilization rate of water and groundwater in other layered soils remained about 10%.The water utilization rate of poplar for each layer was about 10%in September.September Elaeagnus angustifolia mainly used 50-300cm deep soil water,of which the utilization rate of 160-200cm and 200-300cm was 25.5%and 27.7%,respectively,and the utilization rate of soil water in 0-10 cm and0-20 cm was reduced to 0.2%and 0.1%,and the utilization rate was almost zero.In September,the water utilization rate of elm for 0-10cm and 10-20 cm soil was 17.4%and 17.1%respectively,and the remaining water utilization rate was about 10%,which indicated that the use of water per layer in the elm was more uniform during the month.Farmland irrigation has an important influence on the water use mechanism of farmland shelterbelt,and this study provides reference for the optimal irrigation of farmland and farmland shelterbelt in this area.