Sul Ross State University

A Vegetation Classification for Amistad National Recreation Area,
Val Verde County, Texas, 2001

by Chris Casaday, Bonnie Warnock and Louis A. Harveson

Currently, a range inventory is recognized as the highest natural resource priority for Amistad NRA to protect native vegetation and to start proper management of livestock.

Objectives of this project were:

1. inventory Amistad lands and vegetation therein, to establish a baseline for long term monitoring and management of range resources;
2. complete a vegetation reconnaissance and vegetation inventory of Amistad lands;
3. conduct data collection on identified vegetation transects; and
4. map and analyze grazing lands to determine grazing levels and carrying capacities on Amistad lands.

The line intercept and belt transects methods and a 0.25-m² quadrat was used to collect data. Mapping was done with the aid of Arcview software. The PC-ORD program aided in the analysis of the data.

Photopoints were taken at each transect and the transect locations were georeferenced with a GPS unit.

Ten communities were found following the naming structure of Bezanson (2000). These communities were a netleaf hackberry-Plateau liveoak floodplain woodland, cenizo-blackbrush xerophytic brush, blackbrush xerophytic brush, guajillo xerophytic brush, mesquite thicket, Chihuahuan desert scrub, huisache xerophytic brush, oreganillo xerophytic brush, lower elevation desert grassland and a wetland brush communities.

Six similar communities were found from this study and Labus (1989). Six similar communities were also found from this study and Hedges and Poole (1999).

Labus (1989) found four different communities, Hedges and Poole (1999) found five different communities, and this study found four different communities.

Stocking rates were set to a light grazing plan to improve or maintain current conditions. Stocking rates were calculated by community as follows: netleaf hackberry-Plateau liveoak floodplain woodland (79.50 ha/AU), mesquite thicket (159.84 ha/AU), cenizo-blackbrush xerophytic brush (58.44 ha/AU), huisache xerophytic brush (25.11 ha/AU), Chihuahuan desert scrub (422.58 ha/AU), oreganillo xerophytic brush (81.65 ha/AU), blackbrush xerophytic brush (41.14 ha/AU), lower elevation desert grassland (13.76 ha/AU), wetland brush (8.24 ha/AU), and guajillo xerophytic brush (8.77 ha/AU).

Four management alternatives were suggested. With the baseline data and the vegetation map, Amistad NRA can begin to implement a long term grazing management program.

Cooperative funding provided by the National Park Service and Sul Ross State University.