Sonoran Paloverde-Mixed Cacti Desert Scrub

On the west side of the Galiuros, looking WSW down Kielberg Canyon on 26 March 2011, at 4000 feet. Photo by Lon and Queta.


 On the west side of the Galiuros, looking ESE up Kielberg Canyon on 30 September 2010, at 3700 feet. Photo by Lon and Queta.
The Sonoran Paloverde-Mixed Cacti Desert Scrub ecosystem ranges from the lower limit of the study area at 3700 feet near the mouth of Kielberg Canyon on the west slope, to just about 4500, just upslope. This is the main population of saguaros in the study site; there are two smaller sites just to the north, at Cienaga Canyon and YLE Canyon (with the latter deemed too small to map).  The author has not visited these sites recently, and can offer no more than the photo documentation above. However, it should be mentioned that creosote and brittlebush are apparently absent from this ecosystem in the Galiuros, while mesquite, prickly pear, and blue palo verde appear common in the photographs – as well as perennial grasses. Overall shrub cover likely exceeds 40%.
Because the saguaro is the indicator species for this ecosystem (the imagery is good enough to detect their shadows), it is no surprise that 84% of the ecosystems was found on hot steep slopes with over 10 degree slope (19%).
Other Vegetation Classifications
The Sonoran Paloverde-Mixed Cacti Desert Scrub ecosystem includes elements of several vegetation types mapped or described in other classification schemes. In each of the seven schemes referred to below, the * symbol marks the vegetation type most similar to the Sonoran Paloverde-Mixed Cacti Desert Scrub ecosystem.
And what is meant by ‘most similar’? For the USFS Plant “Habitat Type” (Potential Association) and the Brown, Lowe, and PaseBiome”, the * symbol denotes the best fit based on the description of the Habitat Type or Biome. For the Landfire, ReGap, and USFS PNVT and mid-scale dominance classifications, which are presently mapped as 30 meter pixels, the * symbol denotes the classification that was most commonly attributed within the Mesquite Upland Scrub, as mapped in this effort. The actual percentage attributed is given in parenthesis (%).
For example, the Paloverde-Mixed Cacti polygons created by this study were used as a 'cookie-cutter' on the Landfire Existing Vegetation Type (EVT) layer (see methods). Within this study’s Paloverde-Mixed Cacti, 38% of the EVT pixels were attributed as Mesquite Upland Scrub Mogollon Chaparral, 34% were Paloverde-Mixed Cacti, and 10% were Madrean Pinyon-Juniper.
Landfire Existing Vegetation Type (EVT, version 1.0.5)
Apacherian-Chihuahuan Mesquite Upland Scrub * (38%)
Sonoran Paloverde-Mixed Cacti Desert Scrub (34%)
Madrean Pinyon-Juniper Woodland (10%)
Mogollon Chaparral (8%)
Landfire Biophysical Setting (BpS, version 1.0.0, older but judged by the author as locally more accurate)
Sonoran Paloverde-Mixed Cacti Desert Scrub* (37%)
Apacherian-Chihuahuan Semi-Desert Grassland and Steppe (31%)
Mogollon Chaparral (14%)
Madrean Pinyon-Juniper Woodland (9%)
USFS Mid-scale Dominance Type
Desert and Semi-desert Shrub Mix * (61%) (ARPU5, FOSP2, OPUNT_PRVE, PRVE, SDMX, SEDX)
USFS Plant Habitat Type (Potential Association)
Not identified
USFS Potential Natural Vegetation Type (PNVT, based on 24 Oct 2011 draft map)
Mohave-Sonoran Desert Scrub * (82%)
Madrean Encinal Woodland (7%)
Semi-desert Grassland (6%)
Brown, Lowe, and Pase Biome
Sonoran Desertscrub (Arizona Upland subdivision)
Southwest Regional Gap Ecological System (The top three were equally common attributions in the Gap map)
Apacherian-Chihuahuan Mesquite Upland Scrub*
Chihuahuan Creosotebush, Mixed Desert and Thorn Scrub
283 ha
Area in acres: 
699 acres