Granite Hill 25-32 PZ

Description

This is the reference state for the Granite Hills ecological site. The information is derived from a range site description approved April 16, 1985.
The plant community is a post oak and live oak savannah. The understory is dominated by tall and mid grasses such as little bluestem, sand lovegrass, sideoats grama, and green sprangletop. The oak overstory shades about 20 percent of the ground. This site supports an abundance of forbs with some woody shrubs and vines. The north slopes grow a higher percent of little bluestem and oaks than south slopes.

The vegetation grows in the soil between the rock outcrops. In the Tall/Mid Grass Savannah State, the grasses soak up much of the sunlight and their fair share of the soil moisture as long as the woody canopy remains less than 15 percent. If no brush management is done, or if fire is not utilized, the woody canopy will continue to increase until a threshold is crossed at about 20 percent canopy. Once this happens, it will take mechanical or chemical intervention to restore the Tall/Mid Grass Savannah State community.

Submodel

Description

As retrogression occurs, juniper, Texas persimmon, whitebrush, and mesquite may form a dense canopy. Some common increasers or invaders on the are signalgrass, basin sneezeweed, pricklypear, tasajillo, mesquite and certain annuals.

Unless removed by prior mechanical or chemical treatment, the oaks and trees remain on the site at about a 15 percent canopy because of the relatively small amounts of soil on the site to support trees. The understory shrubs begin to increase in canopy and can be more than 15 percent. Once this condition exists, completion from woody species and an overstory reduces the herbaceous component of the plant community. The sun’s energy is captured by the woody species and most of the available soil moisture is utilized by the woody species.