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Vegetation patterns of Pine Canyon, Big Bend National Park, Texas, in relation to elevation and slope aspect
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Data on the woody vegetation of Pine Canyon, Big Bend National Park, Texas was gathered on an elevational gradient from 1250 m to 2000 m elevation using the point-centered quarter method. Sampling was conducted at 12 sites at 1250 m, 1500 m, 1625 m, 1750 m, 1875 m, and 2000 m on the south-facing and north-facing slope. The data is used in a qualitative analysis of communities, species composition, and lifeform distribution. Direct gradient analysis of species' importance values, diversity and richness, and stem density are also analyzed. Communities encountered on the south-facing slope, from low to high elevation, are: Chihuahuan Desert shrubland, sotol grassland, open oak shrubland, mixed shrubland, and oak-pinyon-juniper woodland. Communities encountered on the north-facing slope, from low to high elevation, are: Chihuahuan Desert shrubland, sotol grassland, open oak-pinyon woodland, oak-pinyon-juniper woodland, oak-pine woodland, and mixed woodland. Shrubs are equally important on both slope aspects. Succulents are more important on the south-facing slope, while trees are more important on the north-facing slope. A direct gradient analysis of importance values, of prevalent species, on the elevational gradient of both slope aspects support the idea that plant species do not always peak in importance at a single position on the elevational (environmental) gradient. Diversity of woody plants at each sampling site was calculated using the Shannon-Weiner Index, while richness was the number of species at each site. Diversity and richness are consistently higher on the north-facing slope at each sampling level. On the more mesic south-facing slope, diversity and richness are highest in the oak-pinyon-juniper woodland at 2000 m elevation, and decline as elevation decreases into the sotol grassland and Chihuahuan Desert shrubland. On the more mesic north-facing slope, diversity and richness are highest in the Chihuahuan Desert shrubland at the lowest elevation sampling level, and the mixed woodland at the highest elevation sampling level. Diversity and richness are lowest in the middle elevations on the north-facing slope, especially in the sotol grassland. Stem density is consistently higher on the south-facing slope at each sampling level, and at the lower elevations on both slope aspects.
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Harris, Bryan Joseph (1997). Vegetation patterns of Pine Canyon, Big Bend National Park, Texas, in relation to elevation and slope aspect. Master's thesis, Texas A&M University. Available electronically from
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