Description:
Apacherian-Chihuahuan Semi-Desert Grassland and Steppe
The view SW, at 4900 feet, from the west side of the Dragoons near the Council Rocks, 30 August 2010. Lehman’s love grass flourishes after the summer rains, 0.8 meters tall, with 41-60% cover. Other common grasses include sprucetop and hairy grama, each with 1-4% cover. Agave palmeri also adds 1-4% cover, while 2 meter tall mesquite give 5-9% cover. Pinkthroat morning-glory (Ipomoea longifolia) sprawl under the grass.
Description
The Apacherian-Chihuahuan Semi-Desert Grassland and Steppe ecosystem ranges from 4000 feet at Zeits Canyon at the northern end of the Dos Cabezas, to 6500 feet on the south slope of Bowie Mountain. The latter is unusual, because this ecosystem is among the flattest, with 90% mapped on slopes of less than 10 degrees (18%). The majority of the lands are alluvial fans along the west side of the Dragoons and the west side of the Chiricahuas, especially between Whitewater Draw and Mesa Draw.
The ecosystem is characterized by less than 10-15% cover of shrubs and trees, and diverse perennial grasses, both native and exotic. After the abundant summer rains of 2010, many areas that otherwise might have been judged shrubby were suddenly grassy (see photo below); such places were mapped not as the semi-desert grassland, but the mesquite upland scrub.
The view NE from the plains of Halfmoon Valley, at the south end of the Chiricahuas, 5250 feet, 12 June 2010. Bunchgrasses give 15-25% cover, and include tobosa (Pleuraphis mutica), curly mesquite, sideoats, and cane bluestem, Bothriochloa barbinodis. Perennial shrubs include burroweed (Isocoma tenuisecta), wait-a-minute, and mesquite, giving 10-14% combined – the upper limit for ground cover of shrubs in this grass ecosystem.
The view south from foothills of the Dos Cabezas Mts., near Zeits Canyon, 4660 feet, 10 September 2010. Lehman’s lovegrass is the dominant ground cover (15-25%). Common associates include fairyduster (Calliandra eriophyllum), snakeweed, Agave parryi, catclaw, and a perennial Aristida grass. The hills in the background hold more shrubs, and are mapped as part of the Mesquite Upland Scrub.
The view north from the plain between Pinery and Pine Canyons, west side of Chiricahuas, 5300 feet, 13 September 2010. The grasses are mostly gramas, with associated plains love grass and spider grass. The 2 meter tall sunflowers are Helianthus annuus, and the large trees are 15 meter tall Emory oak.
Other Vegetation Classifications
The Apacherian-Chihuahuan Semi-Desert Grassland and Steppe ecosystem includes elements of several vegetation types mapped or described in other classification schemes. In each of the six schemes referred to below, the * symbol marks the vegetation type most similar to the Apacherian-Chihuahuan Semi-Desert Grassland and Steppe ecosystem.
And what is meant by ‘most similar’? For the USFS Plant “Habitat Type” (Potential Association), the USFS “Potential Natural Vegetation Type” (PNVT), and the Brown, Lowe, and Pase “Biome”, the * symbol denotes the best fit based on the description of the Habitat Type, PNVT, or Biome. For the Landfire, ReGap, and USFS mid-scale classifications, which are presently mapped at a 30 meter resolution and were used in creating the map, the * symbol denotes the classification that was most commonly attributed within the Apacherian-Chihuahuan Semi-Desert Grassland and Steppe, as mapped in this effort.
Landfire Existing Vegetation Type (EVT)
Apacherian-Chihuahuan Semi-Desert Grassland and Steppe*
Apacherian-Chihuahuan Mesquite Upland Scrub
Madrean Encinal
USFS Mid-scale Dominance Type
Grass Mix * (ERAGR, GAMX, GPMX)
Desert and Semi-desert Shrub Mix (ARPU5, FOSP2, OPUNT_PRVE, PRVE, SDMX, SEDX)
OakJP (JUDE2, JUDE2_QUAR, JUDE2_QUEM, JUDE2_QUERC, JUMO, JUNIP_QUERC, PICEB, PIMO, QUAR, QUAR_QUEM, QUEM, QUEM_QUOB, QUERC, QUOB)
USFS Plant Habitat Type (Potential Association)
Not identified
USFS Potential Natural Vegetation Type (PNVT)
Semi-desert Grassland *
(Note: the Provisional “Desert Communities – Upper” may, pending further research, describe much of this ecosystem. “Desert Communities – Lower”, does not, as the study area lacks species of lower desert communities.)
Brown, Lowe, and Pase Biome
Semi-desert Grassland *
Southwest Regional GAP Ecological System
Apacherian-Chihuahuan Semi-Desert Grassland and Steppe*
Apacherian-Chihuahuan Mesquite Upland Scrub
Madrean Encinal
