PhD Student University of California Merced, United States
Background/Question/Methods
Leaf veins supply water and nutrients which are required for growth and photosynthesis. In general, variation in leaf traits correlate to differences in growth rates between leaves at the top of the canopy that experience full sunlight compared to those in the basal interior of the canopy. We hypothesized that climate variation across latitudinal gradients might affect both leaf growth rates and the relationship between this and leaf traits. Understanding these relationships may help us better predict climate change responses in trees. Our study species was Fagus sylvatica, which occurs across a broad latitudinal gradient in Europe that correlates with differences in precipitation and temperature. Leaves were examined from the top, basal interior, and basal exterior of the tree canopy. We quantified the growth rate of the leaves, and measured the major veins, minor veins, stomatal densities, and stomatal size to observe any correlation with growth rate. There is expected to be a different relationship at different latitudes due to temperature and precipitation variations across the gradient having a stronger correlation between growth rate and vein sizes.
Results/Conclusions
We found that leaves on the top of the canopy where leaves grew faster in warmer southern regions compared to leaves in the colder, wetter north part. Canopy leaves in the south showed a 25% more vein structure and 50% larger stomata relative to the lower leaves in the canopy, as well as higher stomatal densities. Growth rate shows to be higher in southern Europe due to variations in leaf traits and arid conditions. In the north, there was not much variations in leaf traits within species. The lower leaves did not show much variations across traits or latitudes compared to the canopy leaves. We concluded that there is a stronger correlation between growth rate and anatomical and morphological traits in Fagus sylvatica growing in the hotter and dryer regions of southern Europe compared to the northern regions. This implies that there are patterns in leaf traits within species allowing them to be more suitable for growth in arid condition.
