Modeling tree radial growth in a warming climate: where, when, and how much do potential evapotranspiration models matter?
Modeling tree radial growth in a warming climate: where, when, and how much do potential evapotranspiration models matter?
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DOI：
10.1088/1748-9326/ac1292
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发表时间：
2021
影响因子：
6.7
通讯作者：
M. Dannenberg
中科院分区：
文献类型：
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作者：
M. Dannenberg
基于过程的树木年轮宽度模型既用于重建过去的气候，也用于预测气候变化引起的生长变化。由于土壤水分观测在适当的空间和时间尺度上是不可用的，这些模型通常依赖于简单的水分收支驱动的部分基于温度的潜在蒸散量（PET）的估计，但PET模型的选择可能会有很大的影响模拟土壤水分，水分胁迫和径向生长。在这里，我使用四种不同的PET模型来驱动VS-Lite模型，并评估它们在复制观察到的生长变异性的能力以及对预计的21世纪变暖的模拟响应方面的差异程度。在1200多个树木年轮宽度年表在接壤的美国，有没有显着差异的四个PET模型在他们的能力，以复制观察到的径向生长，但模型不同，他们对21世纪变暖。与物理上更现实的PET模型（Priestley-Taylor和Penman-Monteith）相比，温度驱动的经验PET模型（Thornthwaite和Hargreaves）模拟了更大的变暖引起的PET增加和土壤水分减少。在较冷和更温和的地区，相对最小的水分限制的增长，模型模拟类似的小减少增长增加变暖。然而，在干旱地区，Thornthwaite和Hargregite驱动的VS-Lite模型模拟的水分应力增加大约是Priestley-Taylor和Penman-Monteith模型的两倍，这也转化为变暖下径向生长的较大模拟下降。虽然模型复制观测到的径向生长变异性的能力没有差异，这对某些应用来说是一个令人鼓舞的迹象（例如，将生长变化归因于特定的气候驱动因素），但模型对变暖的反应存在巨大差异，这表明，在将温度驱动的PET模型应用于温度趋势较大的气候条件时需要谨慎。
Process-based models of tree-ring width are used both for reconstructing past climates and for projecting changes in growth due to climate change. Since soil moisture observations are unavailable at appropriate spatial and temporal scales, these models generally rely on simple water budgets driven in part by temperature-based potential evapotranspiration (PET) estimates, but the choice of PET model could have large effects on simulated soil moisture, moisture stress, and radial growth. Here, I use four different PET models to drive the VS-Lite model and evaluate the extent to which they differ in both their ability to replicate observed growth variability and their simulated responses to projected 21st century warming. Across more than 1200 tree-ring width chronologies in the conterminous United States, there were no significant differences among the four PET models in their ability to replicate observed radial growth, but the models differed in their responses to 21st century warming. The temperature-driven empirical PET models (Thornthwaite and Hargreaves) simulated much larger warming-induced increases in PET and decreases in soil moisture than the more physically realistic PET models (Priestley–Taylor and Penman–Monteith). In cooler and more mesic regions with relatively minimal moisture constraints to growth, the models simulated similarly small reductions in growth with increased warming. However, in dry regions, the Thornthwaite- and Hargreaves-driven VS-Lite models simulated an increase in moisture stress roughly double that of the Priestley–Taylor and Penman–Monteith models, which also translated to larger simulated declines in radial growth under warming. While the lack of difference in the models’ ability to replicate observed radial growth variability is an encouraging sign for some applications (e.g. attributing changes in growth to specific climatic drivers), the large differences in model responses to warming suggest that caution is needed when applying the temperature-driven PET models to climatic conditions with large trends in temperature.