Influence of different detrending methods on climate signal in tree-ring chronologies in Wolong National Natural Reserve, western Sichuan, China

Abstract

Aims Tree rings are valuable for paleoenvironmental studies;however,the methods by which tree-ring series are processed are controversial.Our objective is to assess the impacts of different tree-ring detrending methods on climate-growth response patterns in Wolong National Natural Reserve,western Sichuan,China.Methods Fifty-four increment cores were taken from living trees of Abies faxoniana at a treeline site(3 450 m).We standardized tree-ring data with systematic growth forcing by five methods:conservative curve fits,67% of series length and fixed 30 years,60 years and 90 years cubic smoothing splines,and the resulted chronologies are abbreviated as CCF,CSS67%,CSS30,CSS60 and CSS90,respectively.We also composed the original tree-ring-width chronology(ORW) without standardization.Tree ring chronologies were correlated against(a) monthly climate data(mean,minimum and maximum temperatures,precipitation and relative humidity) from the nearby meteorological station and(b) monthly climate data(mean,minimum and maximum temperatures,pre-cipitation and frequency of frost) from a high resolution gridded climate dataset.Important findings In spite of differences in the strength of growth-climate correlations among the chronolo-gies,a similar linear response was the dominant mode.Radial growth was positively correlated with temperature in September of the prior year and March and July of the current year,as well as precipitation in Octo-ber-December of the prior year and April and July in the current year.In contrast,radial growth was negatively correlated with relative humidity in November of the prior year and March of the current year,as well as fre-quency of frost in February-March and July-August of the current year.Of the climatic response patterns for dif-ferent chronologies considered,CCF,CSS67%,CSS60 and CSS90 chronologies had average higher inter-cor-relations and the strongest climate signals.In contrast,CSS30 chronology exhibited weaker correlations with other chronologies,and showed a similar,albeit much lower sensitivity to climate.ORW chronology had the highest statistical values among the chronologies and could provide valuable climate information for tree-ring studies.