PARENT SESSION
Oral Session #73: Applied Ecology and Ecological Economics. Presiding: J. Hof.
Friday, August 10, 2001. 8:00 AM to 12:00 PM. Hall of Ideas P&Q.
The effect of topography and microhabitat on the density and population structure of the harvested palm, Chamaedorea radicalis, in northeastern Mexico.
ENDRESS, BRYAN1, 1
ABSTRACT- Leaves of the understory palm, Chamaedorea radicalis , are harvested throughout northeastern Mexico for sale in the international cut foliage market. Palm densities and population structure were sampled along 15 transects (2915 m2 total), located on five hillsides in the El Cielo Biosphere Reserve, Tamaulipas, Mexico, to examine the effect of environmental variables on palm density and population structure. Transects were positioned perpendicular to the hillside's slope, and were classified in segments based on topographic position (valley, lower slope, mid slope, upper slope, ridge) and microhabitat (soil, rock, and rock outcrop). Two-way analysis of variance was used to test for the effect of topographic position and microhabitat on palm density. Chi-square goodness-of-fit was used to examine the effect of topography and microhabitat on population structure. Palm densities varied significantly depending on topographic position (p<0.001). Valley sites had the lowest mean density (0.07 palms/m2), while upper slopes had a mean density of 0.55 palms/m2. Microhabitat had no effect on palm densities. Population structure in valleys and lower slopes differed significantly from the pooled population structure (p<0.001); these areas had higher proportions of seedlings and juveniles, and fewer adults. The population structure on rock outcrops also differed (p<0.001); these areas were dominated by adults and had few seedlings. A low rate of adult survival in valleys and lower slopes due to livestock browsing or harvesting by palm collectors may account for the observed trends.
KEY WORDS: non-timber forest product, plant demography, palm ecology, Mexico