Comparison of the Methods Using Stable Hydrogen and Oxygen Isotope to Distinguish the Water Source of Quercus variabilis in Dry Season
DENG Wenping,YU Xinxiao,JIA Guodong,LI Yajun,LIU Yujie,BAI Yanjing(Key Laboratory of Soil and Water Conservation and Desertification Combating of Ministry Education,School of Soil and Water Conservation,Beijing Forestry University,Beijing 100083,China)
Plant water source depends on the distribution of available water in the environment,and the capability of plants in capturing water.The study of plant water source will help to understand the vegetation variation(type and distribution)under the context of global change,as well as the selection of suitable plant species in the process of degraded ecosystem restoration.Stable isotope of hydrogen and oxygen were considered to be a good tool and have been used to identify the source of water,because different water sources possess different hydrogen or oxygen isotope signatures.In this study,we used three different methods to estimate the sources of water used by Quercus variabilis,the dominant species in the rocky mountain areas of Northern China.Furthermore,the advantages and disadvantages of the three methods were compared.The three methods are as follows:the method of direct reference,a two-three compartment linear mixing model,a multiple sources linear mixing model.Results displayed that:Quercus variabilis extracted different water sources in different season during dry season,the main water source concentrated in surface soil layer(0—30cm)in spring,and sublayers(30cm)in fall.The three methods we used in this study have their own range of application and limitations.The method of direct reference could rapidly distinguish the seasonal differences of main water sources,but could not get the contribution rates of different sources.The method of integrating the direct reference with two-three compartment linear mixing model could quickly calculated the contributed proportions of the main water sources,however,could use only in the situation that only less than three water sources were available,and more suitable to operate in the condition that the soil layer is shallow,and homogeneous isotopic characteristics of some soil layer after the rainfall.The multiple sources mixed-linear model can remedy the defects of two-three compartment linear mixing model,therefore it can be used to quantify more than three water sources as well as the range of each source,whereas did not work on the soil layers that was after rainfall exceeding a certain threshold,in rocky mountain of northern China.
【CateGory Index】： S792.189
【CateGory Index】： S792.189