APPLICATION AND CHALLENGES OF TREE-RING STABLE OXYGEN ISOTOPE IN SOIL MOISTURE RECONSTRUCTIONS
Soil moisture stands as a pivotal metric for evaluating agroecological drought conditions.The scarcity of long-term soil moisture records significantly hampers the accuracy and reliability of soil moisture simulations and forecasts,leading to imprecise and low-confidence assessments of agroecological drought across various global regions.In light of this,recent advancements have seen the implementation of soil moisture reconstructions derived from tree rings,offering insights into the historical dryness or wetness of soils and the driving factors behind agro-ecological droughts in both arid and humid locales.This review begins by highlighting the superiority of the tree-ring δ18O index over traditional tree-ring width index for soil moisture reconstruction.We proceed to establish a comprehensive global database of tree-ring δ18O,consisting of 237 chronologies,to explore its utility in soil moisture reconstruction efforts.Notably,over 20％of these chronologies show a significant correlation with soil moisture during summer months(p＜0.05),with no significant difference in the correlation coefficients between arid and humid areas.This finding underscores the substantial potential of tree-ring δ18O as a tool for reconstructing soil moisture across diverse climatic regions.Furthermore,we identify and discuss two primary challenges in the selection of soil moisture products and the depth of soil moisture reconstruction.Looking forward,in the quest to reconstruct soil water dynamics,it is crucial to focus on several key areas:the trends,variability,and range of soil moisture changes over centennial to millennial scales in both arid and humid zones;the principal factors driving changes in soil moisture;and the proxy-model comparison of soil moisture data.
soil moisturetree ring δ18Oclimate reconstructionagroecological drought
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