Structure and woody species diversity of the Dasylirion cedrosanum (Nolinaceae) rosette Scrub of central and southern Coahuila state, Mexico

Abstract

The most prominent vegetation type in the state of Coahuila, in northern Mexico, is Chihuahuan Desert Scrub. This plant formation encompasses the little known Dasylirion cedrosanum (sotol) rosette scrub, a community that extends over more than one fourth of Coahuila and whose most distinctive species is subjected to intense extraction from its native communities for a variety of purposes. Based on a highly replicated sampling procedure that included 131 plots located in the state's central and southern portions, we analyzed vegetation structure, floristics, and species diversity of this plant community. A cluster analysis allowed us to differentiate five variants (associations) of the Dasylirion cedrosanum rosette scrub, which together host a richness of 97 species of vascular plants distributed in 61 genera and 28 families. These communities occurred across an elevational range of 850-2,550 m a.s.l. Dasylirion cedrosanum density varied between 193 and 705 ind./ha, with the highest value occurring in the Quercus intricata-Dasylirion cedrosanum association. Other prominent species in these scrublands were Agave lecheguilla and Euphorbia antisyphilitica. The Agave lecheguilla-Dasylirion cedrosanum association was the most broadly distributed and it hosted the highest richness species, while the largest Shannon diversity index value was recorded for the Dasylirion cedrosanum-Viguiera greggii association. The effects of human utilization of this species on the structure of those plant communities where it occurs are largely unknown; further studies are needed to better understand its dynamics and to be able to suggest more adequate regulations for its commercial harvesting.