Tree-ring δ~(18)O, a tool to crack the paleo-hydroclimatic code in subtropical China

摘要

Tree ring plays an important role in deciphering the paleoclimatic signals. Although tree-ring width (TRW) has obvious advantages in studying the hydroclimatic history in the middle-high latitudes, it has certain limitation in hydroclimatic signal extraction in the tropical to subtropical areas, which greatly limits our fully understanding about the hydroclimatic history in these areas. In this work, tree-ring delta O-18 (delta O-18(tree)) records from five independent tree-ring cores were measured and a composite delta O-18(tree) record (1939-2014) was developed in Guilin, subtropical southwest China. No "juvenile effect" existed in this delta O-18(tree) record and no relationship was found between delta O-18(tree) and TRW. Correlation analysis with the climatic parameters demonstrated that the delta(18)O(tree )record significantly (p 0.01) and negatively correlated with all the hydroclimatic parameters during the growing season (e.g. April-October precipitation, August-October relative humidity and April-November standardized precipitation -evapotranspiration index), while it only positively correlated with the August-September mean temperature (p 0.05). At high frequency, the above relationships were greatly strengthened. Compared with the temperature-limited TRW in Guilin and other areas of subtropical China, delta(18)O(tree )was a better choice for hydroclimatic reconstruction. Moreover, the delta O-18(tree) record in Guilin showed high consistency with other moisture-sensitive delta(18)O(tree )records in a large area of central-southeastern China. Analysis revealed that both large-scale circulation system (e.g. Indian summer monsoon, ENSO, westerlies) and local weather system significantly influenced the growing-season hydroclimatic variation in the study area. This study provides great potential for extracting hydroclimatic information from longer-living trees in subtropical China. (C) 2017 Elsevier Ltd and INQUA. All rights reserved.