Thursday, August 9, 2007

PS 56-1: The future of trees in La Sepultura Biosphere Reserve buffer zone, Chiapas, Mexico: Woody cover and sapling recruitment in a silvo-pastoral landscape

Colibrí Sanfiorenzo-Barnhard1, Luis García-Barrios Sr.2, Neptalí Ramírez-Marcial2, Romeo J. Trujillo-Vázquez2, and Elvia Meléndez-Ackerman3. (1) University of Puerto Rico- Río Piedras, (2) El Colegio de la Frontera Sur, (3) Organization for Tropical Studies (OTS)

The integration of conservation and agriculture has become an important topic in Ecology. Buffer zones around reserves are among the areas where such integration is crucial.  La Sepultura Biosphere Reserve- created in 1993 in Chiapas, Mexico - is notorious for its biodiversity. One of its most important buffer zones - the upper “Tablón” river basin - has been intensively managed by peasants for 46 years. Commercial maize production on steep slopes under slash and burn was the norm. In 1994 –after NAFTA- maize prices crashed and peasants shifted to cattle grazing. The recent transition from fallows to grasslands has produced a complex mosaic of rangelands with different levels of woody plant cover. 91% out of 23 cattle producers interviewed at Los Angeles Ejido own open pastures with hardly any trees; 65% own a patch of mature forest (oak and tropical deciduous forests) where animals browse and 50% own grasslands with intermediate tree, shrub and/or regrowth cover. To promote tree conservation and restoration in this landscape it is important to first understand where natural sapling recruitment is still successful along this woody cover gradient.  Using the Point Intercept Sampling Method in 5 silvopastoral landscape units (5790 linear meters) we found a strong and positive linear relation between the presence of saplings and the tree cover in their immediate linear neighborhood (+- 1.5 m).  In contrast, sapling presence was strongly but negatively related to shrub and re-growth cover. Consequences for tree conservation, for management and for further studies will be discussed.