Using Endemic Plant Species to Establish Critical Habitats in the Sierra de La Laguna Biosphere Reserve, Baja California Sur, Mexico

Abstract

The Sierra de La Laguna, in the southern part of the state of Baja California Sur, Mexico, was decreed a biosphere reserve in 1994. It harbors relict plant communities with a high level of endemism. Floristic research has established that the two main communities, the oak-pine woodland (OPW) and the dry tropical forest (TDF), harbor 43 and 33 endemic species, respectively. We segregate the reserve surface into seven major habitats and each endemic species were assigned a hierarchic value into an abundance-distribution scale, useful as dominance ranking. Using such scale, we found that almost half of the species are in the lowest rank (low abundance and aggregate distribution). Using GIS, we obtain the surface for each habitat, where mountainsides represent the largest in the reserve area. We obtained an index of importance from the proportion of endemic species by habitat and its surface occupied, founding that, in spite of the small and fragmented nature of the upland riparian habitats, they have the greatest index value. Consequently, for future conservation plans in the reserve, these habitats should be considered remarkable sites, meriting better attention to ensure endemic plant preservation. Also, since 86% of the endemic species appear in one, two or three habitats, a high dependency on particular environmental conditions is suggested for them.

Linajes de angiospermas endémicas en México: zonas de alto endemismo para la conservación

“…The notable endemism in the Sierra La Laguna, Baja California, had also been pointed out (León de la Luz & Breceda, 2006) and resulted in the Sierra La Laguna reserve being decreed one of Mexico's biosphere reserves (Arriaga-Cabrera et al, 2000).…”

Occurrence of landslides during the approach of tropical cyclone Juliette (2001) to Baja California Sur, Mexico

“…The original composition of the rocks forming the substrate might also reinforce this differential weathering style; in this case, metamorphic rocks provide a structurally complex system with numerous fractures for roots to deepen and extract more water, but also enabling slopes to develop failure under increased pore pressure in the upper portions of the continuum bedrockregolith-colluvium. A mixed forest structure along the ecotone (León-de la Luz and Breceda, 2006) is also more conducive to heterogeneous concentration of runoff. Combination of upland and lowland tree associations has edge effects on soil moisture and runoff (Joffre and Rambal, 1993;Breshears et al, 1997;Asbjornsen et al, 2004).…”

Phenotypic variation of flowering and vegetative morphological traits along the distribution for the endemic species Yucca capensis (Agavaceae)

“…Despite Yucca capensis not being a dominant element in terms of abundance throughout its geographic range (León de la Luz and Breceda, 2006), its ecological function as part of the close mutualistic interaction with the pollinating moth is fundamental, as the permanence of one species depends on the reproductive success of the other. However, part of the range of Y. capensis is suffering from a conversion of land use for touristic and agricultural developments as well as the general expansion of the human population, which could imply a risk for the permanence of both species.…”