Plant Invasions and Land Use in an Agricultural Frontier: The case of bracken fern invasion in southern Yucatan Peninsular region.
Laura
Schneider, Department of Geography,, Rutgers University, SYPR., laschnei@rci.rutgers.edu
(Presenting)
Plant invasions, affecting ecosystem recovery and household economics, are an important part of land-use change in the southern Yucatan peninsular region, Mexico, closely related to ecosystem function and homogenization of landscapes. Remote sensing analysis shows an increase of bracken fern from 60 km2 to almost 250 km2 in the region during the last 20 years (patch size up to 30 ha). The presence of bracken fern impedes regular succession of the vegetation and affects the amount of areas under forest opened for cultivation. The spatial distribution of bracken fern and its relation with land use suggests a complex process involving fire regimes, land management practices and environmental constraints. Biological strategies, such as a boom in bracken fern colonization just after fires and the increase in flammable biomass floor, show the dependency of bracken fern on continuous fires. In terms of land practices, results show low density of bracken in land-sparse areas characterized by intensive cultivation (swidden cultivation coupled with commercial chili production), and a high density in land-surplus areas characterized by less intensive cultivation (former large-scale agricultural and cattle projects). Large clearings of land promote the invasion, alternatively, where land is scarce and the household economy dependent largely on cultivation, the fern is attacked through labor. Finally, the invasion could have longer term ecological implications, analysis of soil nutrients show a decrease of Phosphorous in fields that have been invaded the longest. A nutrient that limits growth in the vegetation in the region is P, such decrease in P could make it more difficult for secondary vegetation to compete successfully with bracken fern. This understanding of the invasion dynamics is facilitated by linking biophysical, socio-economic, and remote sensing/GIS analysis and would not necessarily follow from a more specialized study.