Between and Within-Site Comparisons of Structural and Physiological Characteristics and Foliar Nutrient Content of 14 Tree Species at a Wet, Fertile Site and a Dry, Infertile Site in Panama

background

This study seeks to analyze how stress resulting from different amounts of precipitation and soil nutrients affects tree growth. The study hypothesized that tree structure and physiology as well as foliar nutrient content would be significantly different between the sites, and trees at the wet, fertile sites would perform better. Secondly, the study hypothesized finding a greater variability of integrated tree growth at the drier site, as plant stress is expected to accentuate differences in performance. Lastly, it was hypothesized that leaf mass area and foliar N would predict photosynthetic capacity.

research goals & methods

13 native and one exotic tree species were planted in plots in two sites in Panama, one wet, fertile site and one dry, less fertile site.  The trees were planted at 3x3m spacing and Diameter at Breast Height (DBH), Leaf Area Index (LAI), gas exchange, Leaf Mass Area (LMA), and leaf nutrient measurements were taken.

conclusions & takeaways

Trees were more productive across all measurements at the wet site. Some species adapted to the dry sites by increasing water-use efficiency, especially the N-fixing species. LMA, foliar N, and LAI best predicted photosynthetic capacity at the wet site, while foliar N was the best predictor at the dry site. This research indicates that N-fixing species are best used for restoration projects at drier, infertile sites, while the category of “pioneer” species is best used at fertile sites.