The evaluation of temporal stability in tree-growth/climate response in Wolong National Natural Reserve, western Sichuan, China

Background/Question/Methods It is generally assumed in dendroclimatological studies that the approximate relationship between tree growth and the limiting climate factor is stable over time. However, observed spatial and temporal instabilities in growth-climate relationships demonstrate the diverse growth responses triggered by the unprecedented climatic changes in the future, which may greatly complicate dendroclimatic reconstructions of past climate histories. Here, we test for the stability of the growth-climate relationship using the tree ring-width data of Abies faxoniana in Wolong Giant Panda Sanctuary of western Sichuan, China, and this study may provide qualitative verification for regional paleoclimatic studies and dynamic vegetation models for carbon uptake. 

Fifty two stands of A. faxonianawere sampled in a pristine forest site (2750 m a.s.l.) and increment cores were extracted for radial growth analyses. Several statistics were used to identify common patterns of interannual growth variability. A shift in climate facilitated comparison of climate–growth relationships during two distinct periods: 1956–1976 and 1977–2008. Tree radial growth was correlated against monthly total precipitation, mean temperature, minimum temperature, maximum temperature and sunshine duration from the nearby meteorological station. 

Results/Conclusions Tree radial growth showed time-dependent relationships to internnual climate variation. In the period of 1956-1976, tree growth showed a positive growth response to late winter to spring (prior December to current April) temperature variables, whereas high temperature in May of spring also have negative impact on tree growth. In the period of 1977-2008, growth of study site responded more strongly to the lower temperature in winter (negative) and high sunshine duration (positive). In addition, tree growth showed an internally consistent positive response to the precipitation in autumn to early winter (prior September to December) during the past 53 years. An anomalous reduction in growth indices was a noteworthy feature in the period of 1977-2008, which had resulted in increasing divergence between the trends in ring width and temperature. In the recent decades, the combination of the decline in sunshine duration and more cloud water effectively decreased the amount of solar radiation available for photosynthesis and plant growth, and this was therefore the most probable causes for the recent progressive fallen growth. The opposing growth trend with temperature in this study might contributed to the widely reported overall divergence phenomenon of high-latitude chronologies over recent decades, and the additional investigations on possible temporal instabilities of tree with climate are necessary before taking into account in dendroclimatic reconstructions, estimations of global warming impacts and carbon uptake projections.