Study On Water Cycle Process And Plant Water Use Strategy In Karst Area Of Central Yunnan Based On Hydrogen And Oxygen Stable Isotope

The karst area in Central Yunnan is located in the subtropical monsoon humid climate area,with uneven temporal and spatial distribution of precipitation,broken terrain,fragile ecosystem and serious rocky desertification,which aggravates the shortage of water resources.How to effectively manage water resources and restore vegetation has become the key to the comprehensive control and sustainable development of rocky desertification in the area.This study takes Shilin County in Central Yunnan as the object,based on the analysis of the spatial and temporal changes of hydrogen and oxygen stable isotopes of atmosp Heric precipitation,lake water,reservoir water,soil water and plant water,the water cycle characteristics of different water bodies in the same habitat are determined through the transformation relationship of hydrogen and oxygen isotopes,and the water use proportion of typical karst plants is quantified by isosource model,combined with hydrogen and oxygen stable isotopes,the water use of plants is described qualitatively and quantitatively,and the water use strategies of plants in different habitats are revealed.The main conclusions are as follows:(1)The local meteoric water line(LMWL)in Shilin area is:?D=8.18?¹⁸O+9.71(R~2=0.988),atmosp Heric precipitation the variation range of?D value is-125?-7.1‰,The variation range of?¹⁸O value is-16.29?-1.4‰,which has obvious precipitation effect.The average value of?D value is 8.99‰,which generally shows the variation characteristics of high in dry season and low in wet season.In the dry season,the atmosp Heric precipitation mainly comes from the long-distance land water vapor.In the dry-rainy transition season,the water vapor is not only supplied by the mainland water vapor,but also transported by the ocean water vapor.In the rainy season,the water vapor is mainly from the bay of Bengal and the Arabian sea.In the rain-dry transition season,the water vapor is mainly from the short-distance land water vapor and the bay of Bengal.(2)Soil water in the study area is mainly supplied by atmosp Heric precipitation;Soil water of each layer the seasonal variation of?D and?¹⁸O value is different,and surface soil water The?D and?¹⁸O value is the most enriched in the dry-rainy transition season and the poorest in the rain-dry transition season,middle soil water the?D and?¹⁸O value shows a gradual dilution trend from dry season to rain-dry season,and the deep soil water the value of?D and?¹⁸O is the most enriched in rainy season and the poorest in rain-dry transition season.Soil water in vertical direction the?D and?¹⁸O value is enriched in the surface layer and depleted in the deep layer in the dry season,and the soil water in the wet season the?D and?¹⁸O value is depleted in the surface layer and enriched in the deep layer.(3)The LWL of Changhu water is:Y=0.79X-26.25(R~2=0.151);The RWL of Guanshan reservoir is:Y=6.36X-15.97(R~2=0.947),lake water?D is between-31.96‰?-21.04‰,?¹⁸O is between-2.21‰?-1.42‰,reservoir water?D is between-69.85‰?-58.55‰,?¹⁸O is between-8.41‰?-6.48‰;The evaporation of lake water is stronger than that of reservoir water.Lake?D and?¹⁸O value is the most enriched in the dry season and the most depleted in the rain-dry transition season?D and?¹⁸O value is the most enriched in the dry-rainy transition season and the most depleted in the rain-dry transition season.(4)Soil water,plant water and surface water in each habitat most of the?D and?¹⁸O values are located at the lower right of the local meteoric water line,and the difference of soil water,plant water and surface water?D and?¹⁸O values are all located in the variation range of the atmosp Heric precipitation?D and?¹⁸O value,atmosp Heric precipitation is the most direct and main supply source of all water bodies in the study area,and there is water evaporation in the process of water transport,and the variation range of plant water?D and?¹⁸O value is closer to soil water,soil water is the main water source for plant growth,and there is a water cycle relationship of atmosp Heric precipitation surface water soil water plant water.(5)Cyclobalanopsis glauca in dense branch forest,Quercus variabilis in secondary forest,Pinus yunnanensis in Yunnan pine forest and Pinus armandii in Lion Pavilion mainly use 20-50cm soil water to maintain growth in dry season,and a small part of it uses shallow soil water and atmosp Heric precipitation supplemented by precipitation.In the four habitats of dry rain transition season,rainy season and rain drought transition season,plants mainly use 0-10cm soil water.(6)There is a water competition relationship between symbiotic plants in Changhu scenic spot and Guanshan reservoir Cyclobalanopsis glauca and Quercus variabilis mainly use 0-20cm soil water in the dry season of Changhu Lake(near the water bank),Pinus yunnanensis and Pinus armandii mainly use 20-50cm soil water in the dry and rainy transition season,four plants mainly use atmosp Heric precipitation and 20-50cm soil water,and in the rainy season,except Pinus armandii mainly uses0-10cm soil water,the other three plants make balanced use of soil water at different depths,In the transitional season of rain and drought,except for the balanced utilization of atmosp Heric precipitation and soil water by Cyclobalanopsis glauca,the utilization of lake water is only 5%,and the utilization proportion of each water source by Quercus variabilis,Pinus yunnanensis and Pinus armandii is relatively balanced.Cyclobalanopsis glauca,Quercus variabilis and Pinus yunnanensis mainly use atmosp Heric precipitation and soil water at different depths in the dry season,rainy season and rain drought transition season on the far water bank,and make less use of lake water.The three plants mainly use lake water in the dry rain transition season.There are also obvious seasonal differences between Pinus yunnanensisand Pinus armandii growing in Guanshan reservoir.The two plants mainly use reservoir water in the dry season and rainy and dry transition season near the water bank.In the dry-rainy transition season,Pinus yunnanensis mainly uses atmosp Heric precipitation,Pinus armandii mainly uses atmosp Heric precipitation and 20-50cm soil water,and Pinus yunnanensis and Pinus armandii mainly use 20-50cm soil water in rainy season.The two plants on the far water bank mainly use 20-50cm soil water in the dry season.Pinus yunnanensis makes balanced use of all water sources in the dry-rainy transition season and rainy season.Pinus armandii mainly uses reservoir water and 0-10cm soil water in the dry-rainy transition season,atmosp Heric precipitation and reservoir water in the rainy season,and Pinus yunnanensis and Pinus armandii mainly use reservoir water in the rain-dry transition season.