Climate-tree growth relationships of Pinus sylvestris var. mongolica in the northern Daxing'an Mountains, China

Abstract

Aims Daxing'an Mountains, the northernmost and largest forest area in China, showed significant warming in the 20th century. Scots pine (Pinus sylvestris var. mongolica) is one of the two major conifer tree species in the boreal forests of these mountains. Our objective was to detect possible influence of climate change on boreal for- ests in this area through dendroclimatology. Methods We investigated climate-growth relationships of Scots pine using tree ring-width chronologies (total of 139 cores) developed from Mohe, Mengkeshan and Mangui in the northern Daxing'an Mountains. Four residual chronologies were developed from the cross-dated ring width series using the program ARSTAN. The relation- ships between climate and tree-ring index were analyzed using bootstrapped response functions analysis of the software DENDROCLIM2002. Redundancy analysis (RDA), a multivariate direct gradient analysis, and its or- dination axes are constrained to represent linear combinations of supplied environmental variables. It was carried out on the four Scots pine chronologies and 24 climate variables for 1973-2006 using the program CANOCO. STATISTICA for Windows, release 6.0 (StatSoft Inc., Tulsa, Oklahoma, USA) was used for other statistical analysis. Important findings Tree growth from the four sites showed different responses to local climates. Response analysis showed that the chronologies of Mohe I and Mohe II were negatively correlated with June temperature of the current year, while the chronologies of Mangui and Mengkeshan were positively correlated with October temperature of the previous year. The analysis indicated that temperature is the major limiting factor for the growth of Scots pine in the northern Daxing'an Mountains. Redundancy analysis between four Scots pine chro-