Brown & Lowe (1994): Biotic Communities Near Cascabel

Sources: Brown, David & Charles Lowe, 1980, Biotic Communities of the Southwest, Republished by University of Utah Press, 1994; Brown, David, ed., 1994, Biotic Communities: Southwestern United States and Northwestern Mexico, Salt Lake City: University of Utah Press

Note: the material presented below closely follows the above sources. Any commentary on this is presented in brackets.

153.2: Chihuahuan Desert Scrub

154.12: Arizona Uplands

143.1: Semidesert Grassland

123.3: Madrean Evergreen Woodland

142.1: Plains & Great Basin Grassland

122.3: Petran & Madrean Montane Conifer Forest

(Pale Green: 133.3 Interior Chaparral)

Wetlands (no number)

Biomes of our area:

153.2: Chihuahuan Desert Scrub

Hot in summer, cold in winter -- freezing temperatures: in the NW reaches, these appear more than 100 nights a year, and some days do not get above freezing (p. 170). CDS is expanding into areas that historically were semidesert grassland, and these areas are the ones receiving more than 300 mm (12") of rain annually. (Otherwise, less.) However, well over half of this is summer rain (May through Sep). Creosotebush is a dominant plant (but note: a distinctive "diploid form", see p. 172-3), in some places sharing or relinquishing dominance to Tarbush or Whitethorn Acacia. Upslope, Agave Lecheguilla is one of the most prevalent among the leaf and and stem succulents. Sandpaperbush may be locally dominant in SE Arizona, for example in the Tombstone Hills. CDS is "essentially a shrub dominated biome in which leaf and stem succulents sometimes heavily participate." (177) Small cacti are common.

Because of its recent origin, few warm-blooded vertebrates are centered here (it's mostly a SE extension for more general desert-adapted species). Herpetofauna are more distinctive: Greater Earless, the spiny lizards, other lizards listed. Some species are in fact relict grassland species, e.g. Bolson Tortoise.

154.12: Sonoran Desert Scrub: Arizona Uplands Series

"Truly spectacular, it is the best watered and least desert-like desertscrub in North America." (Turner, in Brown, p 200) The arboreal nature of this desert subdividsion is often very similar to Sinaloan thornscrub, and indeed could be considered "a depauperate northern form of that tropic-subtropic biome." (ibid.) Cacti are so important here that Shreve called it the "stem succulent desert". Rainfall averages between 200 mm (8") in Sonoita, Sonora to 425 mm (18") at Reno Ranger Station Arizona. Proportion of summer rainfall (June - August) varies from 30 to 60%, higher to the south and lower to the north. For all stations, winter rainfall averages 75 mm (3"); that for the Mohave and other desert subdivisions [of the Sonoran, I think] is 30-50 mm (1-2").

Main dominant vegetation: Foothills Palo Verde and Saguaro series-- a community best developed away from valley floors on bajadas and mountain sides. Desert Ironwood -- another tree legume -- sometimes plays a secondary role to PV. (Ironwood is more frost sensitive.) Boundaries between this series and the Creosotebush-White Bursage series -- White Bursage & Creosotebush appear at lower elevations (valley floors), then going up the bajada, Triangle leaf Bursage at higher elevations everywhere, along with Saguaro and Palo Verde. Locally, Jojoba attains high abundance where there is 300-450 mm (12-18") annual rain with more than 100 mm (4") during the winter. So it's best developed at the desert's upper limits and where a transition to Interior Chaparral occurs. (But its occurrence is almost entirely within the Sonoran Desert, so there is a jojoba-mixed scrub series here.)

Creosotebush-Crucifixion-thorn series is also found at upper elevation ecotones, especially on limestone substrates at the northern and eastern edges of the Sonoran Desert: on marginal, cold alluvium sites.

The structural density and adequate winter precipitation support moderate densities of Mule Deer, Javelina, Black-tailed Jackrabbit, Gray Fox, Harris Antelope Squirrel (latter an endemic). Rich birdlife is especially associated with Paloverde-cacti-mixed scrub series -- Harris Hawk, White-winged and Inca Doves, Pyrrhuloxia -- these are in fact thornscrub species extending northward in suitable habitats. (p. 203)

This also the distribution center for some limited range reptiles: Regal Horned Lizard, Western Whiptail, Gila Monster (esp reticulated), Coral Snake, Tiger Rattlesnake.

143.1: Semidesert Grassland

Shreve called these "desert-grassland transition". (Brown, p. 123) This is potentially a perennial grass-scrub dominated landscape positioned between desertscrub below and evergreen woodland, chaparral, or plains grassland above. This grassland largely adjoins and surrounds the Chihuahuan Desert, and is closely linked with it. At its NE limits, its lower elevation limits are about 1,100 meters (3,600'), but more typically the lower range is between 1100 and 1400 m (4,600'); its upper limits are usually between 1,500 (5,000') and 1,700 m (5,600'), and bounded usually with Madrean evergreen Woodland or with Plains grassland.

Average rainfall mostly between 250 and 450 mm (10-18"), with more than 50% from April to September -- usually 150 mm (6") or more. Perennial grass production depends mainly on predictability of this rain. Unlike Plains Grassland, winters are mild -- freezing temperatures usually occur less than 100 days a year. Originally, the grasses were perennial bunch grasses (clump bases separated by intervening bare ground), but in areas heavy grazing decreased these, increase in low growing sod grasses -- Curly Mesquite Grass eg.

Black Grama grass, with Tobosa grass, are the two most diagnostic grasses dominant in semidesert grassland -- the former on gravelly upland sites, the latter on heavier, flood-subject soils. In some places, Plains grassland grasses -- Sideoats Grama, Hairy Grama, Plains Bristlegrass, Plains Lovegrass may be prominent. Lehmann Lovegrass -- invasive from South Africa -- now occupies extensive areas in some western parts of this region.

123.3: Madrean Evergreen Woodland

Part of the Warm-temperate Forests and Woodlands, this mild winter-wet summer woodland centers in the Mexican Sierra Madre (hence its name), reaching northward into the mountains of southeastern Arizona and southwestern New Mexico. At its lower elevation, this woodland may be very open, with evergreen oaks, junipers, and Mexican Pinyon. Higher up, it gives way to pine forest. In our area, the most prevalent oaks are Bellota Oak, Arizona White Oak, and others. In Cochise County, the lower contact of this Biome is usually with grassland, more rarely with Chihuahuan desertscrub or Interior Chaparral [how about Sonoran desertscrub? see map above!], usually below 1,500 to 1,800 m (5,000-5,900') on thin-soiled habitats. Where the major contact is with grassland, the muhlys and the gramas are common. Many cacti and leaf succulents also extend well into the Madrean Evergreen Woodland.

Mean annual precipitation in this zone usually exceeds 400 mm (16"), with more than half falling during the summer. Freezing temperatures are considerable in our area. Whitetail Deer have their main habitat here in the Soutwest, along with the Coatimundi. Mexican Jay, Acorn Woodpecker, and numerous other birds.

142.1: Plains & Great Basin Grassland

Part of the Cold-Temperate Grasslands, these reach their southernmost ends in our area. Formerly open, grass-dominated landscapes with grasses forming almost continuous covers, they are now much altered. Situated on open, exposed plains, they are naturally subject to high solar heat and winds, with lightning-set grass fires repeatedly renewing the form. With intensive grazing, fire incidence declined, and shrub invasions have occurred. In Arizona this Biome is present mainly in the Sonoita-Elgin and San Rafael vallleys, but it also occurs in the Sulfur Springs Valley and in an isolated form in The Mesas (directly east of Redington in the saddle between the Galiuros and the Winchesters -- see the map showing an isolate of 142.1, above).

In our area, these grasslands are mostly restricted to elevations above 1,500 m (4900') -- the Mesas lie at 5,300' and above), reaching to the higher contacs with Woodlands -- juniper-pinyon or encinal. Rainfall ranges between 300 mm and 460 mm (12-18") per year, mostly during summer thunderstorms.

122.3: Petran (Rocky Mountain) and Madrean Montane Conifer Forest

These are pine-to-fir forests, in our area reaching their best development between 2,300 and 2,650 m (7,500-8,700'). Average rainfall ranges from just above 460 mm to 760 mm (18-30") or more. Nightime freezing usually begins by mid-Spetember and ends in May. Both of these forest types can be divided into Ponderosa Pine Forest (generally at lower elevations) and Douglas-Fir-and-Aspen Forest at higher elevations, in canyons, and on north-facing slopes. Gambel Oak is an important factor for some wildlife.Various grasses and forbs are common. Aspen stands are rich wildlife communities (for varieties of mammals and birds)

133.3 Interior Chaparral

This vegetation type occurs at mid-elevations of the drier mountains of southeastern Arizona, mainly beween 1,050 m and 1,850 m (3,450-6,100') elevation, its upper limits bordering on Ponderosa Pine or pinyon-juniper woodlands. Its lower contacts may be with Arizona Uplands or semidesert grasslands. Rainfall varies from 380 to 635 mm (15-25") per annum, mostly as rain, and the typical feature is spring drought (April to June, the early growing season, being the driest time of the year). Shrub Live Oak and Manzanita are species which produce prolific seed crops that may be stored in the soil for decades, germinating only after fire. It links with Madrean Evergreen Woodland in higher, wetter reaches. Hollyleaf Buckthorn is one plant to watch for.