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Convergence of morphological, biochemical, and physiological traits of upper and lower canopy of European beech leaves and Norway spruce needles within altitudinal gradients
Rajsnerová, Petra ; Klem, Karel ; Večeřová, Kristýna ; Veselá, Barbora ; Surá, Kateřina ; Rajsner, Lukáš ; Holub, Petr ; Urban, Otmar
Climatic variation along altitudinal gradients provides an excellent natural experimental set-up for investigating the possible impacts of climate change on terrestrial organisms and ecosystems. The present work has explored for the first time the acclimation of upper versus lower canopy leaves or needles in European beech (Fagus sylvatica) and Norway spruce (Picea abies) forests along an altitudinal gradient. We tested the hypothesis that restrictive climatic conditions associated with high altitudes reduce within-canopy variations of leaf traits. The investigated beech and spruce forests were located on the southern slope of the Hrubý Jeseník Mountains (Czech Republic). All measurements were taken on leaves from the upper and lower parts of the canopy of mature trees (>60 years old) growing at low (400 m a.s.l.), middle (720 m a.s.l.), and high (1,100 m a.s.l.) altitudes. Generally, we observed that with increasing altitude, which is associated with adverse microclimatic conditions, a convergence of CO2 assimilation rate and other physiological, morphological, and biochemical characteristics between the upper and lower canopy occurred. However, differences in altitudinal response among individual traits and species were found. Such plasticity in acclimation of leaves and needles has the potential to cause substantial change in the photosynthesis of individual parts of forest canopies within the vertical profile and their contribution to the overall carbon balance of vegetation.
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