Importance of the limestone as a source of water for tree species in the karstic dry tropical environment of Yucatán, México.
Héctor Estrada Medina
Summary of project
Karst areas constitute about 10% of the land surface of the world (Ford and Williams, 1989). They are terrains with distinctive characteristics of relief and drainage formed over any kind of soluble rocks such as limestones, dolomites and evaporites. In Yucatán, México karst is developed on limestone with no surface streams and presenting different developmental stages. In northern Yucatán, where the youngest stage is present, shallow soils (less than 30 cm) overlying limestone bedrock are common. Bedrock is very hard immediately below the soil imposing serious restrictions on vertical root growth. Moreover, good drainage conditions along with high rates of evapotranspiration promote a decrease in water availability for the vegetation. Nevertheless, dissolution of limestone, a process that leads to the good drainage by producing hollows, openings and even small caverns is also the process that permits to tree species to penetrate more deeply. Thus, some roots are able to access the deeper, softer limestone layers and underground soil accumulations where they can find other sources of water and nutrients. We hypothesize that these two features, deeper soil materials contained along crevices and subsurface softer limestone layers, are the key factors for supporting forest vegetation in this environment. In this study, we will evaluate the role of the soil and rock layers as a source of water for tree species. Ultimately, the main goal is to understand the mechanisms and strategies that permit adult trees to succeed under karstic conditions. Our results will help to predict non-native tree species adaptation to this environment as well as helping to develop better agroforestry systems management practices. The sources of water will be identified by using a natural isotopes approach. The study area will be a limestone quarry located near to Mérida, Yucatán, México.