Fire-induced tree mortality in a neotropical forest: the roles of bark traits, tree size, wood density and fire behavior
Fire-induced tree mortality in a neotropical forest: the roles of bark traits, tree size, wood density and fire behavior
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DOI：
10.1111/j.1365-2486.2011.02533.x
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发表时间：
2012-02-01
影响因子：
11.6
通讯作者：
Putz, Francis E.
中科院分区：
文献类型：
--
作者：
Brando, Paulo M.;Nepstad, Daniel C.;Putz, Francis E.
大规模的野火预计会加速亚马逊地区的森林枯死，但树种的火灾脆弱性仍然不确定，部分原因是缺乏将火灾引起的死亡率与火灾行为和植物特性联系起来的研究。为了解决这一差距，我们在亚马逊南部建立了两套实验。首先，我们测试了在实验孔加热过程中，哪些树皮性状最能预测树皮的传热率(R)。其次，使用大规模火灾实验的数据，我们测试了树木木材密度（WD），大小和估计的R（形成层绝缘的倒数）在一到五次火灾后对树木死亡率的影响。在第一个实验中，树皮厚度解释了82%的R方差，而树皮中存在的水减少了热源和维管形成层之间的温差，这可能是因为蒸发的高潜热。这一新发现为改进热带到温带地区火灾引起的形成层损伤的机制模型提供了重要的见解。在2007年干旱期间，当复火间隔为3年而不是1年时，树木死亡率随火灾强度的增加而增加（即由树孔上的树皮焦化高度表明），沿森林边缘的树木死亡率更高。与其他热带研究相反，死亡率和火灾强度之间的关系在火灾发生后的一年最为强烈，但在火灾发生后的3年里仍持续存在。中等烈度火灾下，厚树皮（=18 mm）的树木死亡率较低（=20%），随着树径、树高和木材密度的增加，树木死亡率显著降低。因此，火灾导致的树木死亡不仅受到形成层绝缘的影响，还受到其他减少火灾间接影响的性状的影响。这些结果可用于改进对热带森林火灾脆弱性的评估。
Large-scale wildfires are expected to accelerate forest dieback in Amazonia, but the fire vulnerability of tree species remains uncertain, in part due to the lack of studies relating fire-induced mortality to both fire behavior and plant traits. To address this gap, we established two sets of experiments in southern Amazonia. First, we tested which bark traits best predict heat transfer rates (R) through bark during experimental bole heating. Second, using data from a large-scale fire experiment, we tested the effects of tree wood density (WD), size, and estimated R (inverse of cambium insulation) on tree mortality after one to five fires. In the first experiment, bark thickness explained 82% of the variance in R, while the presence of water in the bark reduced the difference in temperature between the heat source and the vascular cambium, perhaps because of high latent heat of vaporization. This novel finding provides an important insight for improving mechanistic models of fire-induced cambium damage from tropical to temperate regions. In the second experiment, tree mortality increased with increasing fire intensity (i.e. as indicated by bark char height on tree boles), which was higher along the forest edge, during the 2007 drought, and when the fire return interval was 3 years instead of one. Contrary to other tropical studies, the relationship between mortality and fire intensity was strongest in the year following the fires, but continued for 3 years afterwards. Tree mortality was low (=20%) for thick-barked individuals (=18 mm) subjected to medium-intensity fires, and significantly decreased as a function of increasing tree diameter, height and wood density. Hence, fire-induced tree mortality was influenced not only by cambium insulation but also by other traits that reduce the indirect effects of fire. These results can be used to improve assessments of fire vulnerability of tropical forests.