Getting to the roots: exploring root traits in tropical forests

Abstract

Roots are a fundamental part of every forest ecosystem, but they are severely understudied due to their invisibility and complexity. Recent studies propose the Root Economic Space (RES) framework, which explains resource acquisition strategies through two key trade-offs: the conservation gradient (fast vs. slow strategies) and the collaboration gradient (interaction with mycorrhizal fungi). Although this framework appears to explain many underground processes, root research is dominated by trees from temperate regions. Tropical ecosystems remain understudied, despite the importance of these ecosystems for global biodiversity and their vulnerability to climate change. This study examined the variation and universality of root traits across the globe, with a focus on tropical regions. Fine roots of 20 tree species were sampled in a dry tropical forest in Costa Rica and compared with existing fine root data from tropical rainforests and forests worldwide. Findings suggest that there are significant differences between tropical forests, but that this variation is not directly explained by wet and dry forest types. On the global root economic space, results indicate that tropical tree species have on average, thicker and denser roots than species from colder regions. Tropical forests show more variation along a conservation gradient, while colder regions show slightly more variation along the collaboration gradient. This could be explained by the longer growing season in the tropics, and more collaboration with (arbuscular) mycorrhizae. Overall, this research provides insight into the universality and differences of tree roots across biomes worldwide.