Testing the unifying theory of ozone sensitivity with mature trees of Fagus sylvatica and Picea abies.

摘要: The broad range in plant responses to chronic O 3 exposure compels a search for integrative, underlying principles. One such approach is the unifying theory proposed by Reich (1987), which combines response of contrasting physiognomic classes plants on basis their intrinsic leaf diffusive conductance and, hence, capacity uptake. Physiognomic differ proportional decline photosynthesis and growth when compared cumulative per unit time, but converge uptake time or O3 over entire lifetime leaf. based observations large number species, relying primarily studies juvenile trees subjected short-term exposure.To test applicability mature trees, broadleaf deciduous European beech (Fagus sylvatica L.) evergreen conifer Norway spruce (Picea abies (L.) Karst.) mixed stand were exposed either ambient air (control) with twice concentration delivered into canopy means free-air fumigation system. We accounted differences growing season length, longevity -related effects (gs) determining total On this basis, needles required 5 years take up as much did leaves one season. core sensitivity was substantiated relation However, contrary theory, formulated results natural more complex. increased complexity attributed additional environmental stressors, stress compensation at whole-tree level, differential sensitivities according age class position within canopy. Contrary no less sensitive than that beech, reduced twice-ambient regime first year exposure.