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Tropical montane forests (TMF) are unique ecosystems with remarkable contributions to global diversity, nutrient, and carbon cycle regulation. In Central America as elevation increases, tree ectomycorrhizal (EM) associations become more common, to the extent that the EM-associated genus Quercus can be dominant. The nutrient acquisition pathways of EM fungi are associated with greater soil organic matter (SOM) accumulation and reduced inorganic nitrogen (N) availability. In the Volcán Barú National Park in western Panama, we used a transplant experiment to evaluate whether patches of Quercus forest affect soil nutrient availability and to measure its implications for seedling growth. We predicted that Quercus forest would have lower soil inorganic N and slower growth of non EM-associated seedlings due to plant–soil feedbacks (PSFs). We found Quercus forest had significantly lower N availability and the soil organic layer was deeper when compared to mixed, non-Quercus forest. Foliar N was lower for AM seedlings growing in Quercus forest than in mixed forest, but did not differ for Quercus seedlings. We found non-EM-associated seedlings grew slower in Quercus forest, consistent with lower foliar N concentration and low light availability. Our results suggest that changes in soil nitrogen availability have a limited effect on seedling growth. Under a global change scenario, studies predict future upslope migration of trees that may result in tree communities encountering unfavorable soil conditions generated by EM-dominated canopies. While longer-term experiments are needed, our results suggest that non-EM-associated seedlings may not be able to tolerate the low N conditions associated with EM-forests

Keywords:

arbuscular mycorrhizae, ecomycorrhizae, nitrogen, Panama, Quercus, seedling growth.

Cecilia Prada, Jim Dalling

Presentation within symposium:

S-29 Conservation of Oak-Dominated Ecosystems in the Tropics: Opportunities and Challenges

Role of Quercus species in biogeochemical cycles in western Panama

-Review-