Madrean Pinyon-Juniper Woodland

The view north over the East Divide of the Galiuros, from 7660 feet (2330 m) on Bassett Peak. Virtually the entire rocky habitat within view is home to the Madrean Pinyon-Juniper Woodland, featuring border pinyon (Pinus discolor), alligator juniper (Juniperus deppeana) silverleaf and netleaf oak (Quercus hypoleucoides, Q. rugosa), and manzanita (Arctostaphylos pungens). Mountain mahogany and beargrass were common associates. October 3, 2011.

 

 

The Madrean Pinyon-Juniper Woodland is the second largest ecosystem in the study area (after Madrean Encinal), and with the greatest elevation range, from 4500 feet near Kielberg Canyon, to 7763 feet atop Bassett Peak. It is also the steepest ecosystem, with 98% on slopes of excess of 10 degrees (19%). The Madrean Pinyon-Juniper is also strongly correlated with the massive rhyolitic rocks that characterize much of the skyline of the Galiuros, except in the northern study area. There, in the watershed of Four Mile Canyon, this ecosystem is replaced by encinal and by Great Basin Pinyon-Juniper, with the latter characterized by the single-needle pinyon.

 

In contrast, the Madrean Pinyon-Juniper ecosystem is dominated by the three-needle border pinyon, Pinus discolor. The trees are typically 10 to 25 feet tall, and can form nearly mono-specific stands with cover values exceeding 60%. More common, however, is a mix of pinyon with manzanita, silverleaf and netleaf oak. In mature stands, there is a thin understory of pinyon and oak recruits, usually with less than 10% cover. Patches of beargrass and agave can add another 10-20%. Bunchgrasses can add up to 20% cover in sunny patches, yet generally did not. Surface fuels were mostly limited to downed wood, which could be heavy.

 

South facing slopes hold smaller pinyon, while the shrubby manzanita, silverleaf and netleaf oak increase in cover, often to 40-80% (e.g., Photo Points 505 and 566) and could be described as Mogollon chaparral, but occurred in patches that were deemed too small (< 25 acres, or 10 ha) to map for this project.

 

At the opposite extreme, north slopes within the Madrean Pinyon –Juniper often held stringers of 30 to 50 feet tall Douglas fir reaching up from the Madrean Pine-Oak ecosystem in the canyons. If the big trees were widely scattered – say, one every 50 meters – the area was mapped as part of the Pinyon-Juniper. The emergent firs indicate a lack of fire for several decades, at least.

 

The landforms that support the Madrean Pinyon-Juniper Woodland – steep and with plenty of bedrock - appears to be intimately connected to the Madrean Pine-Oak in the Galiuros. The pine-oak is the land of tall conifers, which in the Galiuros is mostly in the canyons bounded by the rocky habitat of the Madrean Pinyon-Juniper. This could be because of the enhanced runoff from the rocks. Further north in the study site, where the Great Basin Pinyon-Juniper ecosystem was mapped (single-needle pinyon) on a distinctly less-rocky landform, there were no Douglas fir, Ponderosa pine, or Chihuahuan pine.

 

NOTE: The Madrean Pinyon-Juniper, as mapped in this study, would be comparable to the "Madrean Oak-Conifer-Manzanita on Rocks" ecosystem mapped previously in the Rincons, Catalinas, Chiricahuas, Dos Cabezas, and Dragoons. However, it is not an exact fit, because the "Madrean Oak-Conifer-Manzanita on Rocks" ecosystem ranged both higher and lower in elevation, and included species not found in the Galiuros.

 

 

The view southeast to Rhodes Peak (right) and Kennedy Peak (left, distant), at 6500 feet (2000 m), along the West Divide Trail, 15 May 2011. Border pinyon (Pinus discolor), averaging 10 feet tall (3m), is the clear dominant, typically with 40-60% cover. Also common are silverleaf oak (Q. hypoleucoides, 10 feet, 10-40%) and manzanita (Arctostaphylos pungens, 5 feet, 10-15%). As seen in Photo Point 382, below, there is an understory of young pinyon, netleaf and silverleaf oak, beargrass, agave, and Arizona orange (Choisya dumosa var arizonica). The pinyon ecosystem along this stretch of the West Divide is similarly dense all the way from the saddle at the head of Pipestem Canyon to the ramparts guarding Rhodes Peak, but further south and north the vegetation along the ridge switches to encinal and juniper savanna (see Photo Point 349 below).

 

 

 

Along the West Divide Trail, 15 May 2011, at 6900 feet (2100 m), about one-third mile north of Rhodes Peak. Beneath tall (7 m) border pinyon with a cover exceeding 60% is an understory of beargrass (1.5 m tall, 10-14%) and Agave sp. (0.5 m, 5-9 %), along with scattered young pinyon, netleaf and silverleaf oak (Q. rugosa, Q. hypoleucoides), all with less than 1% cover at this site.

 

 

 

 

Looking SE along a slope above Rattlesnake Canyon, at 5200 feet (1600 m), about 2 miles south of Powers Garden, on 16 May 2011. Pinus discolor, averaging 20 feet tall (6 m), with 15-25% cover, is dominant at this photo station, but barely. Common associates include a small leafed oak, possibly gray oak (Q. grisea, 7 feet, 10-15% cover), manzanita (Arctostaphylos pungens, 4 ft, 10-15%), mountain mahogany (Cercocarpus montanus, 7 ft, 5-9%), and beargrass (Nolina microcarpa, 3 ft, 5-9%). Bunchgrasses, especially Muhlenbergia spp and spidergrass, added another 5-9% cover. The slope to the left rear is Madrean Encinal, dominated by oaks rather than pinyons.

 

 

The view NE up a steep slope above Rattlesnake Canyon, 5400 feet (1650 m), about a quarter mile east of Rattlesnake Spring, 16 May 2011. Pinus discolor is common, with 25-40% cover, but manzanita is even more abundant, with 40-60% cover. Small oaks (2-3 m) and beargrass add another 20% cover. Bunchgrasses, such as Muhlenbergia in the foreground, add no more than 5-9% cover.

 

Upper Rattlesnake Canyon catching the morning sun on 17 May 2011, 6300 feet (1900 m). The hill on the right faces east and is mostly oak and alligator juniper towards its base (the shadow line), but Pinus discolor increases steadily towards the top, eventually dominating with 25-40% cover. Bunch-grasses were common in gaps, and added 10-15% cover.

 

 

 

Typical mix of understory vegetation on steep (60%) slope facing east at 6500 feet (2000 m) on Upper Rattlesnake Trail near jct. with East Divide Trail, 17 May 2011. Beneath border pinyon (30 feet tall, 25-40% cover) and alligator juniper (25 ft, 15-25%) are Quercus rugosa, Q. hypoleucoides, Q. arizonica, Garrya wrightii (silktassel), Arctostaphylos pungens, Muhlenbergia (bullgrass) and beargrass (Nolina).

 

Manzanita of unusual height (10 feet tall!) add 10-15% cover to this south-facing slope at 6500 feet (2000 m) near the jct of the Upper Rattlesnake trail and the East Divide Trail, on 17 May 2011. The slope holds a 60-80% cover of 12-15 foot Pinus discolor and silverleaf oak.

 

 

A ridgeline along the East Divide Trail, 1.5 miles south of Kennedy Peak, at 7000 feet (2150 m), on 17 May 2011. Pinus discolor, typically 20 feet tall (6 m) form a breezy overstory with 40-60% cover, with alligator juniper adding another 5-9%. Together they shelter Agave parryi and Nolina microcarpa (10-14% cover). Sunny spots harbor pinyon rice grass, Piptochaetium fimbriatum, with 15-25% cover.

 

The view SW up the East Divide Trail, above Ash Creek at 6500 feet (2000 m). This steep and stony slope was dominated by 4-foot tall manzanita with over 60% cover, while Pinus discolor contributed only 10-14% and Quercus hypoleucoides added 5-9%. Still, this was mapped as part of the Madrean Pinyon-Juniper woodland, not chaparral, because the patch was too small.

 

 

The Madrean Pinyon-Juniper Woodland 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 Pinyon-Juniper Woodland 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 Pinyon-Juniper Woodland, as mapped in this effort. The actual percentage attributed is given in parenthesis (%).

 

For example, the Madrean Pinyon-Juniper Woodland 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 Madrean Pinyon-Juniper ecosystem, 42% of the EVT pixels were attributed as Madrean Pinyon-Juniper, 27% as Mogollon Chaparral, and 10% were attributed as Madrean Lower Pine-Oak Forest and Woodland.

 

Landfire Existing Vegetation Type (EVT, version 1.0.5)

Landfire Existing Vegetation Type (EVT)

Madrean Encinal * (29%)

Madrean Pinyon-Juniper Woodland * (28%)

Madrean Lower Montane Pine-Oak Forest and Woodland (22%)

Rocky Mountain Warm Desert Riparian Systems (12%)

Mogollon Chaparral (includes (Q. turbinella alliance) (6%)

Southern Rocky Mountain Ponderosa Pine (1%)

 

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

Madrean Pinyon-Juniper * (54%)

Madrean Lower Montane Pine-Oak Forest and Woodland (16%)

Madrean Encinal (15%)

Mogollon Chaparral (10%)

 

OakJuniperPinyon Mix * (45%) (JUDE2, JUDE2_QUAR, JUDE2_QUEM, JUDE2_QUERC, JUMO, JUNIP_QUERC, PICEB, PIMO, QUAR, QUAR_QUEM, QUEM, QUEM_QUOB, QUERC, QUOB)

Upper Pine-Oak (43%) * (PINUS_QUERC)

Desert and Semi-desert Shrub Mix (5%) (ARPU5, FOSP2, OPUNT_PRVE, PRVE, SDMX, SEDX)

Sparsely vegetated (5%)

Ponderosa Pine (1%)

Pinus discolor/Quercus hypoleucoides * PIDI3/QUHY (shrubs, including QUHY, over 25%, while PIDI is >5%)

Pinus discolor/Piptochaetium fimbriatum PIDI3/PIFI * (pinyon, juniper, gray oak/AZ oak hybrids  >25% cover; shrubs – silktassel, manzanita > 1%; herbaceous layer >5% )

Pinus discolor/Muhlenbergia emersleyi PIDI3/MUEM (savanna-like, with >5% pinyon and alligator juniper)

Pinus discolor/Rhus virens var. choriopylla PIDI3/RHVIC (uncommon, e.g., switchbacks along Tortillta Trail above Horse Canyon)

Pinus discolor/Choisya dumosa var arizonica PIDI3/CHDUA (described in FS handbook as a limestone type, which it is, in the Dragoons, but also found on rhyolite in Galiuros).

Cupressus arizonica/Quercus hypoleucoides CUAR/QUHY (part of the Madrean Pine-Oak, actually, but stringers of this habitat type can be found in the Madrean Pinyon-Juniper as mapped in this study)

 

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

Madrean Pine-oak Woodland * (50%)

Madrean Encinal (18%)

Mixed conifer – Frequent Fire (16%)

Interior Chaparral (16%)

Brown, Lowe, and Pase Biome

Madrean Evergreen Forest and Woodland (Encinal Series)

 

Southwest Regional GAP Ecological System

Madrean Pine-oak * (47%)

Mogollon Chaparral (17%)

Rocky Mountain Ponderosa Pine (16%)

Madrean Pinyon–Juniper (13%)

Colorado Plateau Mixed Bedrock Canyon and Tableland (5 %)