Tree-ring δ^(15)N of Qinghai spruce in the central Qilian Mountains of China:Is pre-treatment of wood samples necessary?  

作　　者：WANG Ziyi LIU Xiaohong WANG Keyi ZENG Xiaomin ZHANG Yu GE Wensen KANG Huhu LU Qiangqiang 

机构地区：[1]School of Geography and Tourism,Shaanxi Normal University,Xi'an 710119,China [2]State Key Laboratory of Cryospheric Science,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China [3]Qilian Mountain National Park Research Center(Qinghai),Xining 810008,China [4]School of Earth System Science,Tianjin University,Tianjin 300072,China

出　　处：《Journal of Arid Land》2022年第6期673-690,共18页干旱区科学（英文版）

基　　金：supported by the National Natural Science Foundation of China (41971104);the Open Foundation of the State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment;Chinese Academy of Sciences (CASSKLLQG1817);the Qilian Mountain National Park Research Center (Qinghai)(GKQ2019-01)。

摘　　要：A knowledge of the tree-ring stable nitrogen isotope ratio(δ^(15)N)can deepen our understanding of forest ecosystem dynamics by indicating the long-term availability,cycling and sources of nitrogen(N).However,the radial mobility of N blurs the interannual variations in the long-term N records.Previous studies of the chemical extraction of tree rings before analysis had produced inconsistent results and it is still unclear whether it is necessary to pre-treat wood samples from specific tree species to remove soluble N compounds before determining theδ^(15)N values.We compared the effects of pre-treatment with organic solvents and hot ultrapure water on the N concentration andδ^(15)N of tree rings from endemic Qinghai spruce(Picea crassifolia)growing in the interior of the central Qilian Mountains,China,during the last 60 a.We assessed the effects of different preparation protocols on the removal of the labile N compounds and investigated the need to pre-treat wood samples before determining theδ^(15)N values of tree rings.Increasing trends of the tree-ring N concentration were consistently observed in both the extracted and unextracted wood samples.The total N removed by extraction with organic solvents was about 17.60%,with a significantly higher amount in the sapwood section(P<0.01).Theδ^(15)N values of tree rings decreased consistently from 1960 to 2019 in both the extracted and unextracted wood samples.Extraction with organic solvents increased theδ^(15)N values markedly by about 5.2‰and reduced the variations in theδ^(15)N series.However,extraction with hot ultrapure water had little effect,with only a slight decrease in theδ^(15)N values of about 0.5‰.Our results showed that the radial pattern in the inter-ring movement of N in Qinghai spruce was not minimized by extraction with either organic solvents or hot ultrapure water.It is unnecessary to conduct hot ultrapure water extraction for the wood samples from Qinghai spruce because of its negligible effect on the removal of the labile N.Theδ^(15

关 键 词：tree rings stable nitrogen isotope ratio(δ^(15)N) nitrogen concentration solvent-extracted wood water-extracted wood wood pre-treatment Qinghai spruce Qilian Mountains 

分 类 号：S791.18[农业科学—林木遗传育种]