标题：Community structure and floristic composition of Quercus fusiformis and Carya illinoinensis forests of the Northeastern Coastal Plain, Coahuila, Mexico
摘要：In order to describe community structure and richness in oak and walnut forests occurring along the SanRodrigo, 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 treeheights. Tree regeneration and herb and shrub stratum were assessed in 5 2-m2 quadrats per site. A total of 48 speciesdistributed 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, whereasfor the walnut forest the corresponding values were 302 stems/ha and 21.26 m2/ha. The species with the highest relativeimportance values were Quercus fusiformis (59.48%) and Carya illinoinensis (57.58%). Total tree richness was 14species, the most common ones being Celtis reticulata and Diospyros texana, followed closely by C. illinoinensis andQ. fusiformis. Anthropogenic impact appears to result in a poor regeneration reflected as a low sapling density, as wellas in the reduction and fragmentation of these communities; in turn, this process has led to intrusions of species typicalof the xerophytic Tamaulipan Thorn Scrub. Further studies are needed on the regeneration of the dominant species ofthese forests in order to describe their dynamics and to promote their preservation.
关键词：Biología;Botánica; Ecología;basal area; forest regeneration; oak forest; species invasions; tree density; walnut forest
