长白山不同海拔树木生长对气候变化的响应差异

Abstract

Trees growing at the margins of their species' distributional ranges are considered to be the most sensitive to environmental factors. In tree species distributed across wide elevational gradients and playing vital roles in local ecosystems,altitudinal variation in growth conditions may be of great importance for sustainable forest management. The importance of altitudinal gradients is thus often emphasized. To investigate climate-growth relationships at different elevations,tree-ring width chronologies of Larix olgensis and Pinus koraiensis were developed from four and six sampling sites,respectively,at different elevations of a north-facing slope in the Changbai Mountains of northeastern China. Ten final residual chronologies were produced. Mean sensitivity( MS) and standard deviation( SD) were used to describe interannual variability in ring width as a proportion of local mean ring width. The signal-to-noise ratio( SNR) served as an expression of the strength of the observed common signal among trees. All chronologies had relatively high MS,SD,and SNR values, which reflected the sensitivities of trees to environmental conditions. There were no consistent trends in statistical characteristics of tree-ring chronologies along the elevational gradient. For L. olgensis,all values decreased with increasing elevation,reaching a minimum at the mid-elevation site; increases in these values were then observed above the midelevation site,which suggested that trees in the mid-elevation site had a complacent growth pattern. For P. koraiensis,all values increased with increasing elevation,reaching a maximum at the mid-elevation site,and then decreasing. Hierarchicalclustering analysis was used to highlight differences in radial growth among sites and to determine radial growth associations. For L. olgensis,chronologies were classified into two groups—low and high elevation—,while P. koraiensis chronologies at large were categorized into three groups—low,intermediate,and high elevation. Correlation and response functions were analyzed to determine primary climatic influences on growth. The bootstrap method was used to test significance. Monthly mean temperature and monthly total precipitation were used for the analysis. Our results suggest that along the elevational gradient,both species may respond in different ways to local climate change. March and June temperatures and previous November temperatures appeared to be the primary limitations to L. olgensis growth under either high or low elevation chronologies. Our data demonstrate that temperature is the dominant factor limiting growth at high elevations. At low elevations,no significant correlations with the current year' s climatic conditions were discerned. The previous year' s October temperatures and June precipitation affected P. koraiensis at high elevations. This lag in response suggests that a relatively warm autumn may favor the following year's growth. Precipitation in the previous year,temperature of the current year,and current spring temperatures had the greatest contributions to P. koraiensis growth at either intermediate or low elevations. In both species,lag effects were observed in growth responses to climate forces. Comparing the two species,L. olgensis is cold-tolerant,whereas P. koraiensis is warm-loving. The elevational differences in responses of L. olgensis and P. koraiensis to climate that were uncovered in this study should assist future regional dendroclimatological studies.