Oak forest structure in the Sierra de Santa Rosa range, Guanajuato, Mexico

Abstract

THE STRUCTURE OF 4 OAK ASSOCIATIONS IN THE WESTERN PART OF THE SIERRA DE SANTA ROSA RANGE IN GUANAJUATO STATE IS DESCRIBED. OAK ASSOCIATIONS WERE SAMPLED USING THE POINT CENTERED QUARTER METHOD (21 SITES). WE CENSUSED 2 320 INDIVIDUALS OF TREES AND SHRUBS BELONGING TO 36 SPECIES, IN 22 GENERA AND 15 FAMILIES. OBSERVED SPECIES RICHNESS (29) WAS HIGHEST IN THE QUERCUS POTOSINA-Q. CASTANEA ASSOCIATION (QPC) BUT TREE DENSITY WAS THE LOWEST (650 INDIVIDUALS/HA). MEANWHILE, THE Q. LAURINA-Q. RUGOSA ASSOCIATION (QLR) HAD THE LEAST NUMBER OF OBSERVED SPECIES (12), BUT THE MAXIMUM SHRUB DENSITY (5 593 INDIVIDUAL/ HA). THE FISHER INDEX FOR ALPHA DIVERSITY AND THE RAREFACTION ANALYSIS CONFIRMED THE QPC AS THE MOST DIVERSE ASSOCIATION. ON THE OTHER HAND, THE Q. POTOSINA-Q. EDUARDII ASSOCIATION (QPE) HAD THE HIGHEST VALUE OF EQUITABILITY AMONG THE OAK-FOREST ASSOCIATIONS ANALYZED. BASED ON THE SIMPSON (PRESENCE-ABSENT) AND SØRENSEN ABUNDANCE INDEX VALUES, WE FIND THAT BETA DIVERSITY IS HIGH ACROSS THE Q. COCCOLOBIFOLIA AND QLR ASSOCIATIONS AND ALSO THE QLRQPE ONES. DUE TO THE HIGH DEGREE OF DISTURBANCE WITHIN THESE FORESTS, MOSTLY OF ANTHROPOGENIC ORIGIN, THE HETEROGENEITY IN OAK ASSOCIATIONS AS WELL AS THEIR STRUCTURE AND DIVERSITY OUGHT TO BE CONSIDERED IN FUTURE CONSERVATION AND RESTORATION MANAGEMENT PLANS.