Water-use Strategy Of Caragana Microphylla At Different Ages In Horqin Sandy Land

In this paper,we select 3-,5-and 9-year-old Caragana microphylla living in the Korqin sandy land naturely to study their soil water dynamics under the shrub,the distribution of root biomass and analyse isotopic characteristics of xylem water of C.microphylla and potential water sources.The water source and water use mechanism of C.microphylla were analyzed qualitatively and quantitatively in two means:direct method,and multiple linear mixed model method.These studies can provide reference for reasonablely distrubuting water resources,improving cultivation method to artificial forest of C.microphylla and offer maintaining local ecological environment balance.?1?The soil moisture dynamics and the distribution of root biomass under different-age shrubs were analyzed.The water requiement of 3-and5-year-old C.microphylla was higher than that of 9-year-old C.microphylla,but which is on the contrary in vigorous growth period.Root distribution has influence on soil moisture distribution under the shrub after rain.With the age increasing,it is more difficult that soil water is supplied under the shrub.?2?The characteristics of hydrogen and oxygen stable isotopes in different periods of different sorts of water?precipitation,soil water,xylem water and groundwater?in the study area were analyzed.The result includes the local meteoric water line belong to study area(?D=6.44?^{1 8}O-6.88),whose slope and intercept are less than the global meteoric water line.And the precipitation in the region is affected by twice evaporation and evaporation under the cloud layer.There is no obvious rainfall effection and temperature effection on stable isotopic characters of rain?3?Direct method was used to analyze the water source of C.microphylla at 1/3 point,2/3 point and edge under the shurbs.The main water absorbing areas and strategy of 3 species of C.microphylla have different characteristics in different periods.?4?Quantitative analysis of contribution rate of water from all soil layer under shrub of Caragana microphylla at different ages by multivariate mixed model method shows that 30⁸0 cm is an important water source for 3-year-old Caragana microphylla,and 60¹00 cm is an important water source for 5-year-old C.microphylla.0⁶0cm is an important water source for the9-year-old.?5?Through the comparison of soil water content,rate of contribution from Soil water of every layer and root biomass,it was found that the main water sources of C.microphylla are mainly influenced by soil water content.The distribution of soil moisture after rainfall can be influenced by the distribution of root under the shrubs.The 3-year-old C.microphylla's roots activity may be inhibited during successively rain.The 5-year-old C.microphylla'root is autonomous in water uptake.The 9-year-old often uses water from different soil layer without distinguish.With tree age increasing,C.microphylla has stronger ability of resistance against drought.