Description:
North American Warm Desert Riparian System
The view west up Cutoff Canyon at its confluence with Siphon Canyon, near Fort Bowie National Historic Site, Apache Pass, 4500 feet, 12 September 2010. To the right, a large hackberry tree obscures several walnut trees. To the left, a thicket of desert willow dominate the terrace behind the large gum bumelia tree (Sideroxylon lanuginosum spp rigidum), an uncommon species more typical of Texas. The watercourse is dry, but scoured by occasional floods.
Description
The North American Warm Desert Riparian ecosystem is the smallest ecosystem in this study area – only 656 acres. These relatively open watercourses below 5000-5500 feet are also relatively flat: 93% are on slopes of less than 10 degrees (18% slope), where the canyons leave the mountain bedrock and open onto alluvial fans.
The ecosystem is limited to four watercourses – Leslie, Siphon, Rucker/Whitewater, and Pinery – and is characterized by many of the same trees found in the higher elevation Rocky Mountain Montane Riparian ecosystem, especially sycamore and velvet ash. However, this lower elevation ecosystem typically holds a higher proportion of ash, with significant contributions from hackberry and/or desert willow. Adjacent terraces are usually home to sideoats and spider grass and very large Quercus emoryi, averaging 15 meters tall. Very cobbly soils may support stands of 2 meter tall Apache plume. At Leslie Canyon, abundant perennial water has created a jungle of ash, willow, and in places the exotic Johnson grass.
In the scheme of the National Vegetation Classification System (NVCS), the area mapped is part of the North American Warm Desert Lower Montane Riparian Woodland and Shrubland. The similarly named North American Warm Desert Riparian Woodland and Shrubland is restricted to elevations below 1200 meters (3900 feet).
The view east up Pinery Canyon at the Riggs Ranch, Chiricahua Mts., 5300 feet, 13 September 2010. A galley forest of sycamore, amid large oak and ash.
The canyons mapped in this ecosystem include:
Pedregosa Mountains
Leslie Canyon
Chiricahua Mountains
Lower Pinery
Lower Rucker/Whitewater Draw
Dos Cabezas Mountains
Siphon Canyon/Cutoff Canyon
Other Vegetation Classifications
The Rocky Mountain Montane Riparian ecosystem, as mapped in this study, is similar if not identical to the NVCS Rocky Mountain Lower Montane-Foothill Riparian Woodland and Shrubland. The shorter name was adopted because that’s what appears in the Landfire (see crosswalk below).
The observed 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 Rocky Mountain Montane Riparian ecological system.
And what is meant by ‘most similar’? For the USFS Plant “Habitat Type” (Potential Association), theUSFS “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 my map, the * symbol denotes the classification that was most commonly attributed Rocky Mountain Montane Riparian ecosystem, as mapped in this effort.
Landfire Existing Vegetation Type (EVT)
Rocky Mountain Montane Riparian *
North American Warm Desert Riparian
(Note: Landfire attributed Rucker/Whitewater and Pinery as Rocky Mt. Montane, while Leslie and Siphon were attributed as North American Warm Desert. These are reasonable if arbitrary decisions).
USFS Mid-scale Dominance Type
(Note: the Coronado Mid-scale map did not map riparian habitat, and hence had no riparian vegetation type)
USFS Plant Habitat Type (Potential Association)
Arizona sycamore series (PLWR2 series)
USFS Potential Natural Vegetation Type (PNVT)
Cottonwood Willow Riparian Forest
Brown, Lowe, and Pase Biome
Interior Southwestern Riparian Deciduous Forest and Woodland
Southwest Regional GAP Ecological System
(Note: ReGAP did not map montane riparian habitat, and hence had no appropriate vegetation type)
