Spatiotemporal Distribution of Fog Precipitation, Water-Use Efficiency, and Seedling Survivorship across Edges in Cloud Forest Fragments


Alexandra Ponette

Advisor: Lisa Curran


Tropical montane cloud forests (TMCF) in Mexico cover approximately one percent of the surface area. TMCF are adapted to cool temperatures, low precipitation, reduced radiation, sloping topography, wind stress, and persistent fog. These environmental conditions have affected the distribution, evolution, and ecology of cloud forest, which are restricted in spatial extent and are characterized by high rates of endemicity, species richness, and low productivity, but high rates of biomass accumulation. Susceptible to habitat fragmentation and climatic alterations, TMCF are sensitive indicator ecosystems to processes of change at multiple spatial and temporal scales. In Central Veracruz, Mexico, cloud forests are now small isolated remnants surrounded by cattle pasture, shade coffee plantations, urban areas, and secondary vegetation. The major objective of this research is to examine the effects of two agricultural land use systems on edge-related gradients in cloud forest microenvironments and the inter-specific responses of oak-laurel species to spatial and temporal changes in light and water availability. Comparison of cloud forest remnants surrounded by pasture and coffee farms will examine whether pastures and agroforests differ in the strengths and types of their edge effects and if coffee agroecosystems potentially buffer cloud forest trees against abiotic edge effects (i.e., desiccation) occurring within fragments.

I will use a 2003 Landsat ETM+ image, 2003-2004 high-resolution IKONOS images, 1995 digital orthophotos, ground surveys, and a geographic information system to conduct a supervised land use/land cover classification of the study region. Coupled with a recent classification of land use based on 1993 aerial photographs, I will use this information to map the size and location of forest fragments, as well as surrounding land uses within a 1-km and 5-km buffer zone of each remnant. From a set of 19 fragments in the southwestern region of Xalapa, I will select a subset of 6-8 fragments for study. Fragments range in size from 4 ha to 40 ha, with one large fragment of 900 hectares. One remnant is legally protected. An additional two remnants are owned by landowners interested in conservation. Understanding the potential adaptations and resilience of plants to environmental stress will be used to simulate population persistence and to inform rehabilitation efforts currently underway.

CEO Home Page

7 May 2004