Emberson Lisa D, Büker Patrick, Ashmore Mike R
Stockholm Environment Institute, University of York, York, UK.
Environ Pollut. 2007 Jun;147(3):454-66. doi: 10.1016/j.envpol.2006.10.026. Epub 2007 Apr 6.
Two different indices have been proposed for estimation of the risk caused to forest trees across Europe by ground-level ozone, (i) the concentration based AOT40 index (Accumulated Over a Threshold of 40 ppb) and (ii) the recently developed flux based AFstY index (Accumulated stomatal Flux above a flux threshold Y). This paper compares the AOT40 and AFstY indices for three forest trees species at different locations in Europe. The AFstY index is estimated using the DO(3)SE (Deposition of Ozone and Stomatal Exchange) model parameterized for Scots pine (Pinus sylvestris), beech (Fagus sylvatica) and holm oak (Quercus ilex). The results show a large difference in the perceived O(3) risk when using AOT40 and AFstY indices both between species and regions. The AOT40 index shows a strong north-south gradient across Europe, whereas there is little difference between regions in the modelled values of AFstY. There are significant differences in modelled AFstY between species, which are predominantly determined by differences in the timing and length of the growing season, the periods during which soil moisture deficit limits stomatal conductance, and adaptation to soil moisture stress. This emphasizes the importance of defining species-specific flux response variables to obtain a more accurate quantification of O(3) risk.
为估算地面臭氧对欧洲森林树木造成的风险，已提出了两种不同的指标，（i）基于浓度的AOT40指标（累积超过40 ppb阈值）和（ii）最近开发的基于通量的AFstY指标（高于通量阈值Y的累积气孔通量）。本文比较了欧洲不同地点三种森林树种的AOT40和AFstY指标。AFstY指标是使用针对苏格兰松（Pinus sylvestris）、山毛榉（Fagus sylvatica）和圣栎（Quercus ilex）参数化的DO(3)SE（臭氧沉积与气孔交换）模型估算的。结果表明，在物种和区域之间使用AOT40和AFstY指标时，所感知到的O(3)风险存在很大差异。AOT40指标在欧洲呈现出强烈的南北梯度，而AFstY的模拟值在各区域之间差异不大。不同物种之间模拟的AFstY存在显著差异，这主要由生长季节的时间和长度、土壤水分亏缺限制气孔导度的时期以及对土壤水分胁迫的适应性差异所决定。这强调了定义物种特异性通量响应变量以更准确量化O(3)风险的重要性。
