Mayr Stefan, Wolfschwenger Marion, Bauer Helmut
Institut f. Botanik, Universität Innsbruck, Sternwartestr. 15, A-6020 Innsbruck, Austria.
Physiol Plant. 2002 May;115(1):74-80. doi: 10.1034/j.1399-3054.2002.1150108.x.
At the timberline in the Central Alps, climatic conditions during winter frequently cause excessive drought stress (frost drought, 'Frosttrocknis'), which we hypothesized to induce cavitation in trees. We investigated the extent of winter-embolism in Norway spruce (Picea abies (L.) Karst.) growing near the timberline and analysed adaptations in vulnerability and anatomy. We found conductivity losses of up to 100% at the highest elevation (2020 m) correlated with low water potentials down to - 4.0 MPa. Vulnerability thresholds (50% loss in conductivity) decreased from - 3.39 MPa at 800 m to - 3.88 MPa at 1600 m corresponding to a decrease in tracheid cross-sectional area as well as pit and pit pore diameters. These thresholds were lower than potentials measured in embolized twigs near the timberline at the sampling dates probably due to lower potentials and/or a role of freeze-thaw events earlier in winter. Data indicated refilling processes, which may be of particular relevance for trees at the timberline, since adaptations in drought-induced vulnerability failed to prevent winter-embolism.
在阿尔卑斯山中部的树线地带，冬季的气候条件常常导致树木遭受过度干旱胁迫（冻旱，“Frosttrocknis”），我们推测这会引发树木的空穴化现象。我们研究了生长在树线附近的挪威云杉（Picea abies (L.) Karst.）冬季栓塞的程度，并分析了其在脆弱性和解剖结构方面的适应性。我们发现，在海拔最高处（2020米），导水率损失高达100%，这与低至-4.0兆帕的水势相关。脆弱性阈值（导水率损失50%）从800米处的-3.39兆帕降至1600米处的-3.88兆帕，这与管胞横截面积以及纹孔和纹孔孔径的减小相对应。这些阈值低于采样日期在树线附近栓塞小枝中测得的水势，这可能是由于较低的水势和/或冬季早期冻融事件的作用。数据表明存在再充盈过程，这对于树线地带的树木可能尤为重要，因为干旱诱导的脆弱性方面的适应性未能防止冬季栓塞。
