长白山红松和鱼鳞云杉在分布上限的径向生长对气候变暖的不同响应

用树木年代学方法研究了近50年来气候变化对长白山自然保护区两种广泛分布的重要乔木树种红松(Pinus koraiensis)和鱼鳞云杉(Picea jezoensis var. komarovii)分布上限树木径向生长的影响, 发现红松年轮宽度具有与温度升高相一致的趋势, 而鱼鳞云杉年轮宽度则出现随温度升高而下降的“分离现象”。对水热条件的正响应是分布上限红松年表与温度保持一致的关键: 生长季的温度和降水的增加对上限红松的生长有促进作用, 且二者对树木生长的有利效应有相互促进的现象; 生长季的延长也有利于红松的生长。升温导致的水分胁迫是造成上限分布的鱼鳞云杉年轮宽度与温度变化趋势相反的重要因素: 分布上限的鱼鳞云杉年表与大多数温度指标均呈负相关关系; 随着温度升高, 年表与年降水量尤其是春季降水量的相关性逐渐由负转正; 各月的高温以及生长季中后期的少雨是形成上限鱼鳞云杉窄轮的主要气候因素, 而较低的各月温度以及生长季后期充足的降水则有利于上限鱼鳞云杉的生长; 此外, 生长季长度没有变化也可能是造成鱼鳞云杉年表序列对温度变化敏感性下降的重要因素。

Different responses of radial growth to climate warming in Pinus koraiensis and Picea jezoensis var.komarovii at their upper elevational limits in Changbai Mountain,China

Aims Temperature is generally considered the limiting factor for tree growth at species’ upper elevational limits. Our objectives were to determine the upper elevational limit response of radial growth in Pinus koraiensis and Picea jezoensis var. komarovii to climate warming in Changbai Mountain Nature Reserve of China and to elucidate temperature sensitivity of radial growth.
Methods We selected typical trees at each species’ upper limit for increment coring and established ring-width chronologies for both species. We compared the general trend of the chronologies with temperatures during 1958–2006. To determine species’ response to rising temperature, we analyzed the relationship between chronology and important meteorological factors (temperature, precipitation, growing season length, effective accumulative temperature, etc.) using correlation, response function, moving correlation and pointing year analyses.
Important findings As temperature rose, ring widths in Pinus koraiensis exhibited the same increasing trend as temperature, while ring widths in Picea jezoensis var. komarovii exhibited decreasing sensitivity to temperature. The increase of temperature and precipitation in the growing season mutually enhance Pinus koraiensis growth. Prolongation of the growing season and rising temperature during the growing season also can accelerate the growth of Pinus koraiensis. For Picea jezoensis var. komarovii, water stress caused by increasing temperature is the main reason for its relationship between ring width and temperature. Correlations between Picea jezoensis var. komarovii ring width and almost all temperature indices are significantly negative. As temperature rose, correlations between ring width and precipitation, especially spring precipitation, changed from negative to positive. High temperature in each month and inadequate precipitation in the middle and late growing season are the important meteorology conditions for narrow rings. Also, the insignificant extension of the growing season may relate to reduced temperature sensitivity in tree ring growth.