An experimental assessment of soil-based habitat partitioning in understory palms

Soil nutrient and water availability can shape plant communities by influencing species composition and the functional traits that allow species to regenerate, grow and reproduce. My dissertation research established patterns of understory palm community assembly and functional traits in relation to soil gradients in lower montane forests in western Panama and then examined the mechanistic basis of these patterns using seedling transplant experiments. My research showed that while spatially limited seed dispersal may influence palm species distribution patterns, soil nitrogen and base cation availability and soil texture were also important in influencing species composition at the mesoscale level. I examined trade-offs between growth and morphological, physiological, and defense traits in determining seedling performance along these soil gradients. Functional traits of both adults and transplanted seedlings of palms indicated that soil nutrient availability was important in determining foliar N and nutrient conservation strategies, whereas soil texture may be important in determining water conservation strategies. Furthermore, susceptibility to herbivore attack influenced seedling functional traits that were important in determining growth at low and high nutrient sites. These results suggest that niche partitioning along soil nutrient and water availability gradients along with the influence of pathogens and herbivores may promote the high palm species diversity documented for montane forests of Panama.