Community structure and floristic composition of Quercus fusiformis and Carya illinoinensis forests of the Northeastern Coastal Plain, Coahuila, Mexico

Resumen

In order to describe community structure and richness in oak and walnut forests occurring along the San
Rodrigo, San Diego, Escondido and Arroyo de las Vacas rivers on the Northeastern Coastal Plain (NE Coahuila,
Mexico), we established 30 1 000-m2 circular plots, where we measured diameter at breast height (DBH) and tree
heights. Tree regeneration and herb and shrub stratum were assessed in 5 2-m2 quadrats per site. A total of 48 species
distributed in 29 families were recorded. Families with the largest richness were Poaceae, Asteraceae, and Malvaceae.
For the oak forest, tree stratum density and basal area values were 386 stems/ha and 24.36 m2/ha, respectively, whereas
for the walnut forest the corresponding values were 302 stems/ha and 21.26 m2/ha. The species with the highest relative
importance values were Quercus fusiformis (59.48%) and Carya illinoinensis (57.58%). Total tree richness was 14
species, the most common ones being Celtis reticulata and Diospyros texana, followed closely by C. illinoinensis and
Q. fusiformis. Anthropogenic impact appears to result in a poor regeneration reflected as a low sapling density, as well
as in the reduction and fragmentation of these communities; in turn, this process has led to intrusions of species typical
of the xerophytic Tamaulipan Thorn Scrub. Further studies are needed on the regeneration of the dominant species of
these forests in order to describe their dynamics and to promote their preservation.