| dc.description.abstract | Deep rooting is an advantageous plant strategy because it expands a tree’s available water sources to reliable deep pools and is predicted to be more common in ecosystems with seasonal precipitation regimes, allowing trees to maintain positive water status throughout dry periods. Studying deep roots without disturbance is difficult, yet, caves existing close to the surface present such an opportunity. In the Yucatán Peninsula, Mexico, caves have formed in the limestone bedrock. Overlying thin soils appear unable to retain enough water to support dense subtropical forests. In the state of Quintana Roo, deep roots emerge from ceilings and walls of shallow caves, some directly contacting water. Despite their prevalence, it is unknown which species provide these roots and how they impact surface processes. Therefore, above and below ground diversity and biomass was evaluated at caves to investigate deep rooting specialization as well as patterns in water use and water use efficiency among co-occurring species. Through DNA barcoding, 38 species were identified with roots in the caves, though root diversity was dominated by Ficus spp. While deep rooting specialization was apparent, root abundance was not predicted by tree size or functional groups. Overlapping root systems, seemingly the result of local bedrock characteristics, suggest competition for space and resources. Tree and root abundance decreased with site distance inland, showing increased depth to groundwater alters water access and community composition in Quintana Roo. Stable isotope data from stem water and leaves revealed significant variation in water use and water use efficiency among species. However, this was not explained by root abundance or functional groups. Tree size was informative, with larger trees utilizing more deep water while small trees were successfully supported by shallow water sources. Further, natural history, morphological, and physiological differences provided insight into water use strategies, suggesting inter- and intraspecific variation may explain plant responses to water limitation and help predict impacts of disturbance and climate change. This novel research describes a holistic view of deep rooting by trees in a seasonally dry karst landscape, unraveling the complexity of these biological structures and their importance in water-limited ecosystems around the world. | en |
