Madrean Juniper Savannah

The view northeast towards the Santa Teresas, from 5400 feet (1646 m), above Deer Creek, 13 May 2011. Alligator juniper (Juniperus deppeana), typically 10 to 13 feet tall (3 to 4 m) provide about 20% cover along with scattered Emory oak (Quercus emoryi), prickly pear, and Agave. The oaks have suffered proportionately higher mortality than the junipers during recent years. Grasses, mostly gramas, add another 10-24% cover. Photo Point 679.

Description

The three most extensive Galiuro ecosystems – Madrean Juniper Savanna, Madrean Encinal, and Madrean Pinyon-Juniper – can be distinguished by two criteria: their dominant tree life-form, and the relative abundance of the herbaceous layer. The Madrean Juniper Savanna is usually the most open of the three ecosystems, for the conditions that favor its dominant tree – juniper – also support relatively abundant grasses. Juniper savanna differs from the oak encinal and pinyon-juniper in another way, too: 25% of the areas mapped as savanna were on relatively gentle slopes of less than 10 degrees (19 percent), while only 12% of the encinal is on similarly gentle slopes, and a mere 2% for the pinyon-juniper.

The typical total tree and shrub cover for the savanna was 15-40%, with higher cover values along alluvial terraces where watercourses exit the narrow canyons of the highlands and form braided channels. The majority of the juniper savanna skirts the base of the Galiuros, occupying a band above the grasslands and below the encinal (oaks) and the rocky ridges of pinyon and manzanita. Lowest elevations mapped within the National Forest were about 4000 feet along Rattlesnake Canyon in the NE study area, and at 4200 feet near the confluence of Redfield and Jackson Canyons in the SW study area. There were also 822 acres (333 ha) of scattered patches on higher slopes and ridgelines, surrounded by pinyon-juniper at up to 6600 ft, where beargrass (Nolina microcarpa) is a common associate.

The juniper savanna was distinguished from the encinal in large part by using imagery from June of 2010 and 2011, in which the junipers remained densely green, while the oak and manzanita were distinctly less so. Manzanita was often abundant and even co-dominant within the savanna (see Photo Points 217 and 824, below). Along alluvial terraces bordering larger watercourses, the juniper savanna would also pick up pinyon and oaks (Photo Point 812, below).

Because it was hard to distinguish between manzanita and small oak – actually, often impossible – it was equally hard to say if some of the alluvial fans along the toe of the mountain were mostly oak and juniper, or mostly manzanita and juniper. Oak was the indicator species for the encinal, so it is likely that some areas that are in fact encinal were wrongly mapped in this study as savanna. The converse is also true.

Photo Point 427

Looking south at 6540 feet (2000 m) along the West Divide Trail, 1.6 miles southeast of Rhodes Peak, 15 May 2011. This slope burned years earlier, and now supports a 5-9% cover of Juniperus deppeana averaging 20 feet tall (6 m) tall (out of view), and 5-9% cover of Cercocarpus montanus around 4 feet tall (1.2 m). More common are Guitierrezia sarothrae (snakeweed), 18 inches (0.4 m) and with 15-25% cover, and Nolina microcarpa, 4 feet (1.2 m), with 10-14% cover. Scattered oaks, 10 feet tall, with small leaves (25-40 mm, similar to Q. grisea), offered only 1-4 % cover. On very rocky exposures, shindagger (Agave schotti) was locally common. Bunchgrasses, especially sideoats (Bouteloua curtipendala), dominated, with 25-40% cover. See also below, PP 425, 426, for a nearby view of the same ecosystem.

Photo Point 422, on 15 May 2011. See description for PP 427, above.

Photo Point 425 on 15 May 2011. See description for PP 427, above.

At the southeast end of the study area, near Little Red Tank, about one mile north of Saddle Mountain. Looking north into relatively dense juniper savanna at 5100 feet (1550 m) The co-dominants are manzanita, typically 5 feet (1.5 m) and alligator juniper (several cohorts, from 7 to 20 feet tall (2-6 m), each with 15-25% cover – the same cover as bunchgrasses: Bouteloua curtipendala, B. hirsuta, Aristida ternipes, and, at the edge of its range, the annual Muhlenbergia microsperma. Also common were Quercus arizonica and Nolina microcarpa, each with 5-9% cover. Pinyon pine was uncommon, with less than 1% cover. Photo Point 824.

An uncharacteristic swath of dense manzanita, oak, pinyon, and juniper, along a small watercourse just south of Ash Canyon. Usually such vegetation was mapped as part of the encinal, but small incursions – the above amounted to about 12 acres – were mapped as part of the juniper savanna. 4900 feet, 2 October 2011, Photo Point 812

The view from FS road 691 to Jackson Cabin, looking NE into juniper savanna near the head of Swamp Springs Canyon, at 4700 feet, on 6 March 2010. Photo by Lon and Queta.

The view west from the West Divide Trail, in juniper savanna just south of Cedar Spring, at 5200 feet, on 10 June 2004. Photo by 'Raven Speaks', from Panaramio (Google Earth). The denser cover along the rocky ridge in the background was mapped as pinyon-juniper woodland.

Other Vegetation Classifications

The Madrean Juniper Savannah 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 Madrean Juniper Savannah ecological system.

And what is meant by ‘most similar’? For the USFS Plant “Habitat Type” (Potential Association) and the Brown, Lowe, and Pase “Biome”, 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 Madrean Juniper Savannah, as mapped in this effort. The actual percentage attributed is given in parenthesis (%).

For example, the Madrean Juniper Savannah 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 savanna ecosystem, 36% of the EVT pixels were attributed as Madrean Pinyon-Juniper, 34% as Mogollon Chaparral, and 13% were attributed as Madrean Juniper Savanna.

Landfire Existing Vegetation Type (EVT, version 1.0.5)

Madrean Pinyon-Juniper * (36%)

Mogollon Chaparral * (34%) (includes Quercus turbinella shrubland alliance)

Madrean Juniper Savanna (13%)

Apacherian-Chihuahuan Mesquite Upland Scrub (5%)

Apacherian-Chihuahuan Semi-Desert Grassland and Steppe (4%)

Madrean Encinal (3%)

North American Warm Desert Riparian (3%)

Note: The poor correspondence between this study and Landfire's EVT and BpS layers is due largely to the extent of land recognized as 'juniper savanna'. This study mapped almost 21,000 acres as juniper savanna, while Landfire mapped less than 6000 acres.

Landfire Biophysical Setting (BpS, version 1.0.0, which is older but judged by the author as locally more accurate)

Mogollon Chaparral * (40%)

Madrean Pinyon-Juniper (26%)

Madrean Juniper Savanna (12%)

Madrean Encinal (9%)

Apacherian-Chihuahuan Semi-Desert Grassland and Steppe (6%)

USFS Mid-scale Dominance Type

OakJuniperPinyon Mix * (70%) (JUDE2, JUDE2_QUAR, JUDE2_QUEM, JUDE2_QUERC, JUMO, JUNIP_QUERC, PICEB, PIMO, QUAR, QUAR_QUEM, QUEM, QUEM_QUOB, QUERC, QUOB)

Desert and Semi-desert Shrub Mix (20%) (ARPU5, FOSP2, OPUNT_PRVE, PRVE, SDMX, SEDX)

Grass Mix (8%) (ERAGR, GAMX, GPMX)

Upper Pine-Oak (2%) (PINUS_QUERC)

USFS Plant Habitat Type (Potential Association)

Juniperus deppeana/Bouteloua gracilis JUDE2/BOGR2

(Note: as described in the FS Handbook, 1997, herbaceous cover > 25%, and trees are typically 5-25% cover; however, the trees include Pinus edulis, which doesn't occur in the Galiuros, and leads me to believe that the habitat type is more typical of a bit further north and east.)

Juniperus deppeana/Arctostaphylos pungens JUDE2/ARPU5 (see PP 217)

(Note: according to the FS handbook (1997), the habitat type is only recorded from Bradshaw Mts, lacks pinyon, and the climate is Low Sun Mild. In contrast, the Galiuros often have border pinyon mixed with the juniper and manzanita, and the climate is High Sun Mild.)

The following habitat types may also be a part of the area mapped in this study as juniper savanna:

Quercus oblongifolia/Dasylirion wheeleri QUOB/DAWH2 (southwest Galiuros)

Quercus oblongifolia/Bouteloua (mixed) QUOB/mixed Bouteloua (southwest Galiuros)

Quercus emoryi/Dasylirion wheeleri QUEM/DAWH2

Pinus discolor/Piptochaetium fimbriatum PIDI3/PIFI (trees >25%, shrubs > 1%, herbaceous >5%. pinyon, juniper, gray oak/AZ oak hybrids)

USFS Potential Natural Vegetation Type (PNVT) based on 24 Oct 2011 draft map

Madrean Encinal * (52%)

Interior Chaparral (28%)

Semi-desert grassland (16%)

Madrean Pine-oak (3%)

NOTE: there is no direct PNVT equivalent of Madrean Juniper Savanna, although there is one proposed, called ‘Juniper Grassland” (Muldavin and Tripkie, in prep). Its closest relatives, meanwhile, are semi-desert grassland and Madrean Enicinal. The encinal is usually described as located between the grasslands and pine-oak, which fits; however, the description also says that junipers cannot co-dominate in the encinal. This is clearly the case in the juniper savanna as described in this study, so perhaps the encinal PNVT is not a good fit after all.

Brown, Lowe, and Pase Biome

Madrean Evergreen Forest and Woodland (Encinal Series)

Southwest Regional GAP Ecological System
Madrean Pinyon –Juniper * (43%)
Mogollon Chaparral (28%)
Apacherian-Chihuahuan Mesquite Upland Scrub (8%)
Apacherian-Chihuahuan Semi-Desert Grassland (6%)
Madrean Pine-oak (4%)
Madrean Encinal (4%)
Madrean Juniper Savanna (1%)
Note: The poor correspondence between this study and the GAP layer is due largely to the extent of land recognized as 'juniper savanna'. This study mapped almost 21,000 acres as savanna, while GAP mapped only 350 acres.

Area:

8390 ha

Area in acres:

20732 acres

Region:

Galiuro