长白山不同海拔树木生长对气候变化的响应差异

以长白落叶松和红松为例,探讨了长白山地区不同海拔树木生长对气候变化的响应。利用长白山北坡不同海拔4个长白落叶松样点和6个红松样点的树轮宽度资料建立差值年表,通过聚类分析、相关分析和响应分析等方法,研究树木生长特征及其气候响应。结果表明:两个树种年表的平均敏感度、树轮宽度指数的年际变率、信噪比等特征值较高,反映年表含有较强的环境信息。随海拔升高,长白落叶松年表特征值呈先下降后增加的趋势,红松年表特征值则呈先增加后下降的趋势。聚类分析将长白落叶松年表分成高、低海拔两类,红松年表分成高、中、低海拔三类。树木生长对气候响应存在海拔差异。高海拔长白落叶松生长受当年气温影响;低海拔长白落叶松生长对气候存在"滞后响应"。高海拔红松不仅受降水限制,且对气温有"滞后响应";中海拔红松不仅受气温限制,且对降水有"滞后响应";低海拔红松生长主要受气温限制。

Climate response of tree growth along an altitudinal gradient in the Changbai Mountains, Northeast China

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 mid-elevation 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. Hierarchical clustering 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.