School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7000, Australia.
Glob Chang Biol. 2014 Sep;20(9):2793-9. doi: 10.1111/gcb.12540. Epub 2014 Apr 25.
Large trees are critical components of forest ecosystems, but are declining in many forests worldwide. We predicted that growth of large trees is more vulnerable than that of small trees to high temperatures, because respiration and tissue maintenance costs increase with temperature more rapidly than does photosynthesis and these costs may be disproportionately greater in large trees. Using 5 00 000 measurements of eucalypt growth across temperate Australia, we found that high temperatures do appear to impose a larger growth penalty on large trees than on small ones. Average stem diameter growth rates at 21 °C compared with 11 °C mean annual temperature were 57% lower for large trees (58 cm stem diameter), but only 29% lower for small trees (18 cm diameter). While our results are consistent with an impaired carbon budget for large trees at warmer sites, we cannot discount causes such as hydraulic stress. We conclude that slower growth rates will impede recovery from extreme events, exacerbating the effects of higher temperatures, increased drought stress and more frequent fire on the tall eucalypt forests of southern Australia.
大树是森林生态系统的重要组成部分，但在世界上许多森林中都在减少。我们预测，大树的生长比小树更容易受到高温的影响，因为呼吸和组织维持成本随温度的增加比光合作用增加得更快，而这些成本在大树中可能不成比例地更大。利用澳大利亚温带地区 500 万次桉树生长的测量数据，我们发现高温似乎确实对大树的生长造成了比小树更大的惩罚。与 11°C 的年平均温度相比，21°C 时的平均茎直径生长速度，大树（58 厘米直径）低 57%，而小树（18 厘米直径）仅低 29%。虽然我们的结果与温暖地区大树碳预算受损一致，但我们不能排除水力压力等原因。我们的结论是，生长速度较慢将阻碍大树从极端事件中恢复，从而加剧高温、干旱胁迫增加以及更频繁的火灾对澳大利亚南部高大桉树森林的影响。
