Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
New Phytol. 2022 Jun;234(5):1654-1663. doi: 10.1111/nph.18047. Epub 2022 Mar 14.
The plume of hot gases rising above a wildfire can heat and kill the buds in tree crowns. This can reduce leaf area and rates of photosynthesis, growth, and reproduction, and may ultimately lead to mortality. These effects vary seasonally, but the mechanisms governing this seasonality are not well understood. A trait-based physical model combining buoyant plume and energy budget theories shows the seasonality of bud necrosis height may originate from temporal variation in climate, fire behaviour, and/or bud functional traits. To assess the relative importance of these drivers, we parameterized the model with time-series data for air temperature, fireline intensity, and bud traits from Pinus contorta, Picea glauca, and Populus tremuloides. Air temperature, fireline intensity, and bud traits all varied significantly through time, causing significant seasonal variation in predicted necrosis height. Bud traits and fireline intensity explained almost all the variation in necrosis height, with air temperature explaining relatively minor amounts of variation. The seasonality of fire effects on tree crowns appears to originate from seasonal variation in functional traits and fire behaviour. Our approach and results provide needed insight into the physical mechanisms linking environmental variation to plant performance via functional traits.
野火上方上升的热气体羽流会加热并杀死树冠中的芽。这会减少叶片面积和光合作用、生长和繁殖的速度，并最终导致死亡。这些影响随季节变化，但控制这种季节性的机制尚未得到很好的理解。一种基于特征的物理模型，结合了浮力羽流和能量预算理论，表明芽坏死高度的季节性可能源自气候、火灾行为和/或芽功能特征的时间变化。为了评估这些驱动因素的相对重要性，我们使用来自 Pinus contorta、Picea glauca 和 Populus tremuloides 的空气温度、火线强度和芽特征的时间序列数据对模型进行了参数化。空气温度、火线强度和芽特征随时间显著变化，导致预测的坏死高度出现显著的季节性变化。芽特征和火线强度几乎解释了坏死高度的所有变化，而空气温度则解释了相对较小的变化。火灾对树冠的影响的季节性似乎源自功能特征和火灾行为的季节性变化。我们的方法和结果为通过功能特征将环境变化与植物性能联系起来的物理机制提供了急需的见解。
