Measurements of ozone, sensible heat, and latent heat fluxes and plant physiological parameters were made at a northern mixed hardwood forest located at the University of Michigan Biological Station in northern Michigan from June 27 to September 28, 2002. These measurements were used to calculate total ozone flux and partitioning between stomatal and non-stomatal sinks. Total ozone flux varied diurnally with maximum values reaching 100 Μmol m −2 h −1 at midday and minimums at or near zero at night. Mean daytime canopy conductance was 0.5 mol m −2 s −1 . During daytime, non-stomatal ozone conductance accounted for as much as 66% of canopy conductance, with the non-stomatal sink representing 63% of the ozone flux. Stomatal conductance showed expected patterns of behaviour with respect to photosynthetic photon flux density (PPFD) and vapour pressure defecit (VPD). Non-stomatal conductance for ozone increased monotonically with increasing PPFD, increased with temperature ( T ) before falling off again at high T , and behaved similarly for VPD. Day-time non-stomatal ozone sinks are large and vary with time and environmental drivers, particularly PPFD and T . This information is crucial to deriving mechanistic models that can simulate ozone uptake by different vegetation types.
展开▼
机译:在2002年6月27日至9月28日于密歇根州北部的密歇根大学生物站的北部混合硬木林中进行了臭氧,显热和潜热通量以及植物生理参数的测量。这些测量值用于计算总量臭氧通量以及在气孔和非气孔汇之间的分配。总臭氧通量每天都在变化,最大值在中午达到100 Mmol m -2 h -1,而最小值在晚上达到或接近零。白天的平均冠层电导为0.5 mol m -2 s -1。在白天,非气孔臭氧电导率占冠层电导率的66%,其中非气孔汇占臭氧通量的63%。气孔电导显示出预期的光合光子通量密度(PPFD)和蒸气压不足(VPD)行为模式。臭氧的非气孔电导率随PPFD的增加而单调增加,随温度(T)的增加而增加,然后在高T处再次下降,并且对VPD的表现类似。白天的非气孔臭氧汇很大,并且会随着时间和环境因素而变化,尤其是PPFD和T。该信息对于推导可模拟不同植被类型的臭氧吸收机制的模型至关重要。
展开▼