Water Sources And Use Strategies Of Plants In Daihai Lake Wetland

Daihai is a key strategic node in the construction of ecological barrier in the north of China.However,with the shrinking of lake surface area,the problems of lake water ecological environment are prominent and need to be solved comprehensively.The ecological restoration and restoration of the degraded wetland ecosystem in the lakeshore zone of Daihai Lake is one of the key links in the comprehensive management of lake water ecology.However,the lack of water resources in the lake is important for wetland restoration and restoration in the land water ecotones of Daihai Lake,and it is of practical significance to explore the water use strategies of the lakeside wetland plants for the protection and restoration of the wetland vegetation.Based on the stable isotopes of hydrogen and oxygen(?¹⁸O??D)tracer technology,through comparative analysis of the isotopic composition of plant xylem water and soil water in different depths in wetland plant community,and then determine the utilization ratio of plants to soil water in different soil layers,combined with potential plant water sources?precipitation,soil,lake water,groundwater?,use Isosource model to quantify the water source of wetland plants in the lakeside zone.The conclusion is as follows:1)The?¹⁸O??D of precipitation in Daihai Lake ranges from-7.8‰^-6.6‰and-53.4‰^-43.8‰,the?¹⁸O??D of groundwater ranges from-10.11‰^-9.23‰and-70.95‰^-66.30‰.the?¹⁸O??D of Lake waters ranges from are-2.05‰to 2.25‰and-24.53‰to-2.39‰;the?¹⁸O??D of soil water ranges from-12.06‰to 2.13‰and-92.13‰to-4.81‰;the?¹⁸O??D of plant xylem water ranges from-10.14‰^-2.26‰and-82.87‰^-39.11‰.The slope and intercept of the precipitation line are smaller than the global atmospheric precipitation line,and there is an unbalanced secondary evaporation of precipitation.The?¹⁸O??D values of groundwater are relatively stable,far exceeding the multi-year weighted average range of northern precipitation,indicating that groundwater is not replenished by precipitation.The values of lake water?¹⁸O??D between the groundwater evaporation line and the local atmospheric precipitation line.The evaporation enrichment is obvious,and it is jointly replenished by precipitation and groundwater.2)With the increase of the distance from the lake water surface,the average soil moisture content of each soil layer gradually decreases.The soil water content in the profile of the bare land of the backwater lake bed first increased and then decreased.Under the influence of vegetation coverage and plant water absorption,the soil water content in the profile first decreased and then increased.3)The variation of soil water?¹⁸Owith the depth of profile is more obvious than that of water content.The?¹⁸Ovalue of 0¹00cm soil water decreases with the increase of depth.The?¹⁸Ovalue of 0³0cm surface soil is enriched and fluctuates greatly.The fluctuation decreases with the increase of depth and tends to be stable and close to the?¹⁸Ovalue of groundwater.The soil water near the lake is mainly affected by the lake water and precipitation,while the soil water far away from the lake is mainly affected by precipitation and groundwater.4)Reed and Tamarix,as the dominant species of wetland plant community in Daihai lakeside zone,have developed root system,strong plasticity and adaptability for water use,and can transform between shallow and deep soil water.When it is close to the lake and the soil moisture content is high,it mainly absorbs 0-30cm of shallow soil moisture.When it is far away from the lake and the soil moisture content is low,and it competes with other herbaceous plants in the absorption of surface soil moisture,the niche separation of water use appears,and gradually turns to use deeper soil water.5)The main herbaceous plants in the lakeside wetland?Leymus secalinus,Scirpus triqueter,cryptolepis strigos,Agrostis alba,Potentilla anserina,Calamagrostis epigeios,Elymus dahuricus,Artemisia argyi?mainly use 0³0cm of surface soil water,which contributes 62.1%¹00%of water Fierce competition.However,when the soil moisture content is low and the competition is fierce,the plants with larger plants and longer roots,such as Leymus secalinus,Scirpus triqueter,cryptolepis strigos and Artemisia annua,will absorb water to the deeper soil,showing the niche separation of water use of wetland plant community.