Index of Species Information

SPECIES:  Pinus cembroides


Introductory

SPECIES: Pinus cembroides
AUTHORSHIP AND CITATION : Pavek, Diane S. 1994. Pinus cembroides. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].

ABBREVIATION : PINCEM SYNONYMS : Pinus discolor Bailey & Hawksworth [20,76,77] Pinus lagunae Passini [3] Pinus orizabensis Bailey & Hawksworth [3] Pinus remota (Little) Bailey & Hawksworth [28,88,94] SCS PLANT CODE : PICE COMMON NAMES : Mexican pinyon border pinyon papershell pinyon TAXONOMY : The currently accepted scientific name of Mexican pinyon is Pinus cembroides Zucc. It is a member of the pine family (Pinaceae) [16,41,98]. Two varieties in addition to the typical variety are recognized: papershell pinyon (P. c. var. remota Little) and Mexican pinyon (P. c. var. bicolor Little) [44,79,88]. There is taxonomic disagreement about P. cembroides in the strict sense. Bailey and Hawksworth and others have split P. cembroides infrataxa and raised them to specific status [3,20,30,77,70,94]. Two subspecies (P. c. ssp. lagunae D. K. Bailey and P. c. ssp. orizabensis D. K. Bailey) beside the typical subspecies of P. cembroides were recognized; however, recently each was raised to specific status [3,70]. The two varieties, P. c. var. remota and P. c. var. bicolor, were synonomized to P. remota (Little) Bailey & Hawksworth and P. discolor Bailey & Hawksworth (border pinyon), respectively [20,30,47,77,94]. All names are currently used in the literature. Bailey and Hawksworth relegated P. c. var. bicolor to synonomy with P. discolor based on differences in flowering times, bark color, needle color and number, and two monoterpene compounds [70]. Variation in flowering time and needle number throughout the revised range of P. cembroides is inclusive of P. discolor characters [1,16]. Therefore, this writeup considers P. cembroides in the broad sense. For readers who support the realignment, studies concerning United States populations of P. cembroides may be interpreted as P. discolor [29,57,76]. Hybrids occur between Mexican pinyon and true pinyon (P. edulis) where their ranges overlap [29]. LIFE FORM : Tree FEDERAL LEGAL STATUS : No special status OTHER STATUS :


DISTRIBUTION AND OCCURRENCE

SPECIES: Pinus cembroides
GENERAL DISTRIBUTION : Mexican pinyon is distributed in the mountains of western Texas, southwestern New Mexico, and southeastern Arizona [16,41,46,74,75,92]. A large part of its range occurs in Mexico, extending from the United States border southward along the Sierra Madre Occidental and Sierra Madre Oriental into northern Puebla [23,28,29,38,60]. Mexican pinyon also occurs in Baja California Sur [18,50,85,90]. Papershell pinyon occurs on the Balcones escarpment of central and western Texas and extends into northern Mexico [1,16,52,66,79]. ECOSYSTEMS : FRES20 Douglas-fir FRES21 Ponderosa pine FRES28 Western hardwoods FRES32 Texas savanna FRES34 Chaparral - mountain shrub FRES35 Pinyon - juniper STATES : AZ NM TX MEXICO BLM PHYSIOGRAPHIC REGIONS : 7 Lower Basin and Range 12 Colorado Plateau 13 Rocky Mountain Piedmont KUCHLER PLANT ASSOCIATIONS : K019 Arizona pine forest K023 Juniper - pinyon woodland K031 Oak - juniper woodlands SAF COVER TYPES : 66 Ashe juniper - redberry (Pinchot) juniper 67 Mohrs (shin) oak 210 Interior Douglas-fir 211 White fir 237 Interior ponderosa pine 239 Pinyon - juniper 240 Arizona cypress 241 Western live oak SRM (RANGELAND) COVER TYPES : NO-ENTRY HABITAT TYPES AND PLANT COMMUNITIES : Mexican pinyon occurs as individual scattered trees in interior chaparral [11,56,61,74,82] and as occasional to frequent trees in the Madrean evergreen and encinal woodlands [10,20,36,54,55,67,86]. Mexican pinyon becomes dominant in the pygmy conifer (Pinus spp.)-oak (Quercus spp.) scrub [67,84,95,97], pinyon (Pinus spp.)-juniper (Juniperus spp.) woodlands [14,19,51,58,61,72], and pine (Pinus spp.)-oak woodlands [11,32,50]. Mexican pinyon is an important species in Douglas-fir (Pseudotsuga menziesii), Chihuahua pine (Pinus leiophylla var. chihuahuana), and ponderosa pine (P. ponderosa) series [20,37]. Mexican pinyon is one of the dominant trees in pinyon series [27,49,64]. It is minor in geographical range compared to true pinyon and is included in the true pinyon series, since Mexican pinyon replaces true pinyon across limited areas in Arizona and New Mexico [30,63,84] Mexican pinyon occurs as a minor species in some of the relict Arizona cypress (Cupressus arizonica) forests that are in upland positions [29,62,67,68,74]. Some of the publications that list Mexican pinyon as a dominant or indicator species are: (1) Preliminary classification for the coniferous forest and woodland series of Arizona and New Mexico [49] (2) A series vegetation classification for Region 3 [63] (3) Plant communities of Texas (Series level): February 1992 [84]. Woody species associated with Mexican pinyon but not previously mentioned in Distribution and Occurrence include Arizona madrone (Arbutus arizonica), Texas madrone (Arbutus texana), western white honeysuckle (Lonicera albiflora), and Madrean mockorange (Philadelphus madrensis) [11,19,49,74].

MANAGEMENT CONSIDERATIONS

SPECIES: Pinus cembroides
WOOD PRODUCTS VALUE : Mexican pinyon is used for fuel, fenceposts, and small construction timbers, but rarely for lumber [23,33,70,90]. The wood is soft, heavy, and varies from fine- to coarse-grained [51,69,70]. IMPORTANCE TO LIVESTOCK AND WILDLIFE : Mexican pinyon seeds are utilized by wildlife including Merriam's turkey, thick-billed parrot, black bear, porcupine, squirrels, chipmunks, and other small mammals and birds [9,23,29,46,69,90]. Collared peccary infrequently consume Mexican pinyon seeds from July to September [22]. Cattle, goats, and mule deer browse Mexican pinyon [90,99]. In oak-juniper-pinyon woodland of southeastern Arizona, 36 breeding bird species foraged for insects more on Mexican pinyon and Chihuahua pine needles than would have been expected from random foraging patterns [4]. PALATABILITY : NO-ENTRY NUTRITIONAL VALUE : Mexican pinyon seeds have the highest amounts of protein of the pinyons. Its seeds are approximately 19 percent protein, 60 percent fat, and 14 percent carbohydrates [47]. COVER VALUE : Mexican pinyon groves and pinyon-juniper associations furnish cover for wildlife such as white-tailed deer, pronghorn, rock squirrel, mountain cottontail, mice, ringtail, and common hog-nosed skunk [19,39,46,47]. VALUE FOR REHABILITATION OF DISTURBED SITES : Mexican pinyon was 1 of 38 pine species tested in planting trials on sandhills in northwestern Florida. Mexican pinyon did not survive [12]. OTHER USES AND VALUES : The oily and edible Mexican pinyon seeds are an important food source in the southwestern United States and in Mexico [23,40,43, 51,53,69]. Seeds are harvested by native Americans and commercial pickers in the fall after the cones open [43,53]. Mexican pinyon and other pinyons have been harvested commercially for about 50 years; Mexican pinyon seeds are primarily marketed in Mexico [28,51]. Mexican pinyon seeds are less preferred than those of other pinyons due to the hard seedcoat [47]. Mexican pinyon has been used as an ornamental in the United States since 1830 [44,53,101]. It is cultivated for Christmas trees [28,40,53]. Mexican pinyon resin is used to waterproof and cement pots, baskets, and jewelery [47,90]. OTHER MANAGEMENT CONSIDERATIONS : Mexican pinyon and the woodlands it occurs in have been examined for production potential, silvicultural practices, utilization, and alternative products [2,25,28,60,76]. Seed-tree and shelterwood cutting do not usually work well for Mexican pinyon due to harsh site conditions [34,78]. Individual tree and group selection cutting has been successful in some pinyon-juniper woodlands [78]. Volume equations have been derived for Mexican pinyon assessment [15]. Grazing occurs in most pinyon-juniper woodlands [47]. Grazing removes young Mexican pinyon leader shoots; Mexican pinyon recovers by growing from lateral buds [29]. Conversion of natural pinyon-juniper woodlands in which Mexican pinyon occurs to grasslands has resulted in the destruction of mature trees on a few hundred thousand acres [53]. Despite the report by Little [53] that he had never seen evidence of pinyons invading grasslands, the pinyon-juniper type is reported to have invaded surrounding communities, including grasslands, for the past 50 to 80 years [8]. In Arroyo Ancho of Chihuahua, Mexico, 5- to 7-year-old Mexican pinyon had invaded an area dominated by oaks and grasses [29]. Mexican pinyon should be considered for reforestation projects in arid and semiarid areas. It normally produces useful products such as fuel and food under these climate conditions [70]. Mexican pinyon is susceptible to pinyon blister rust (Cronartium occidentale) and pinyon dwarf mistletoe (Arceuthobium divaricatum). Mexican pinyon infected by pinyon dwarf mistletoe has reduced growth rates, reduced seed production, increased mortality, and is predisposed to infection by other pests [35,91].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Pinus cembroides
GENERAL BOTANICAL CHARACTERISTICS : Mexican pinyon is a native, monoecious small tree. It averages 23 feet (7 m) tall with a trunk diameter of 7 to 12 inches (17.8-30.5 cm), but in protected areas it can reach up to 50 feet (15 m) high and have a trunk diameter of 14 inches (35 cm) [16,33,41,69,75]. Stout, spreading branches make a compact to spreading, rounded crown [16,75]. The bark is thin, 0.5 inch (1.3 cm) or less [33,57,70]. Evergreen needles are in bundles of three or infrequently in bundles of two or four. The needles are 0.8 to 2 inches (2-5 cm) long [16,33,75,90]. Cones are 0.8 to 2 inches (2-5 cm) long [25,51]. The seeds are thick walled, wingless, and 0.5 to 0.75 inch (1.3-1.9 cm) long [16,33,69]. RAUNKIAER LIFE FORM : Phanerophyte REGENERATION PROCESSES : Mexican pinyon regenerates by seed; reports of vegetative reproduction were not found in the literature. Mexican pinyon begins bearing seeds at about 25 years, although trees on dry sites have delayed maturity [57]. Seed production increases with age [28,33]. Cones require 3 years to mature. In Arroyo Ancho, Chihuahua, Mexico, Mexican pinyon produced about 110 to 125 cones per tree during 1978 [29]. Large crops are produced at intervals of 3 to 8 years [28,33,44]. Synchrony of cone crops has not been found [29]. Rainfall is positively correlated with the production of the cone buds. Summer moisture stress at the time of cone bud production occasionally may promote an above-average crop of strobili the following spring, indicating that reproductive growth is favored over vegetative growth when trees are stressed. Temperatures in late August and early September are negatively correlated with cone production; maximum production occurred when the mean maximum weekly temperature was below 75 degrees Fahrenheit (24 deg C) [28]. Cones can experience heavy predation by invertebrates; up to 90 percent of the seed crop may be lost to insect predation [29,33]. Insects destroy a higher percentage of the cones from small than large cone crops [53]. Mexican pinyon and other pinyons produce only a few seeds per cone. Seed viability is initially high (85-95%) but decreases within 1 year [25,33]. The heavy, wingless seeds fall and germinate beneath the relatively open seed tree canopies [80]. The seeds are adapted to dispersal and burial by rodents, other mammals, and birds such as Clark's nutcrackers and jays [48,53,57,85]. Clumped seedlings may reflect animal facilitation and/or microsite differences. Conditions for cone and seed collection and seed germination are discussed in the literature [29,44,89]. Seeds are thick walled, but stratification is not necessary for germination [25,29,44]. Establishment of Mexican pinyon seedlings depends on the availability of adequate water during the first dry seasons. Mexican pinyon establishment is facilitated by nurse plants such as low shrubs and trees [5,29,53]. In a transplant study, Mexican pinyon seedlings without cover died within 8 weeks, and seedlings planted beneath adjacent oak canopies survived [29]. Four-month-old seedlings of Mexican pinyon and other pines were subjected to drought tolerance experiments in a greenhouse study. Mexican pinyon was the most drought resistant species; its seedlings survived 60 days without water [6]. Tree growth rates vary widely [17,33,57]. Mexican pinyon stand structure and regeneration patterns are strongly influenced by disturbances such as fire [80]. SITE CHARACTERISTICS : Mexican pinyon occurs in semiarid climates with relatively high temperatures and evaporation rates. Precipitation is bimodal with wet winters and summers [53,66,82]. Mexican pinyon is found on nearly level to steep slopes, foothills and ridgetops, and in mid- to upper slope draws, ravines, and washes [23,36,61,68,80]. It belongs to woodlands that are very dense on north-facing slopes but open on south- and east-facing slopes [14]. Mexican pinyon typically occurs from 4,000 to 7,000 feet (1,219-2,188 m) in elevation [14,19,33,84]. The maximum elevation of Mexican pinyon changes with latitude, extending from as low as 2,000 feet (610 m) in the northeastern part of its range to as high as 8,203 feet (2,500 m) in southern Mexico [13,80,93]. Mexican pinyon occurs on soils that vary in texture and depth [29,70]. Soils may be shallow and eroded with textures ranging from sandy loam to loamy sand [29,80]. However, soils also can be more than 60 inches (152 cm) deep with moderately fine to very fine textures or with alluvial layers of stratified sands, gravels and cobbles [19,23,61,86]. Mexican pinyon occupies soils derived from a broad range of parent materials including granite, basalt, limestone, sandstone, and mixed alluvium [17,59]. Along a moisture gradient from mesic to xeric sites in Arizona, Mexican pinyon was not present on the mesic end of the gradient. It had 124 stems per acre (306 stems/ha) at the midmesic point and increased to 618 stems per acre (1526 stems/ha) at the most xeric end of the gradient. The increase in Mexican pinyon stem number may have been due to a release from competition with other less drought-tolerant conifers such as Chihuahua pine [96]. SUCCESSIONAL STATUS : Facultative Seral Species Mexican pinyon does well as an understory tree when canopies are relatively open. Most Mexican pinyon seedlings establish beneath open canopies in partial shade. Mexican pinyon becomes less shade tolerant as a sapling [20,25,33,80]. Mexican pinyon woodlands vary in community structure; succession is not well defined for these systems. The pine-oak woodlands and forests in which Mexican pinyon occurs are considered both as ecotones that are not well developed and as climax vegetation that is extensive and well developed [11,30]. Since pinyons will invade dry rocky sites, Little [53] suggested that Mexican pinyon could be considered a pioneer species. However, most authors identify it as a late successional or climax species, especially since nurse plants facilitate Mexican pinyon establishment [20,24,25, 100]. Mexican pinyon is climax in pinyon, evergreen oak, and Chihuahuan pine woodlands [49]. Mexican pinyon is an infrequent and minor seral species in white fir (Abies concolor) and Douglas-fir forests [21,49]. SEASONAL DEVELOPMENT : New leaves are formed annually in the spring and persist for 3 to 4 years [33]. Seed production requires 3 years. Female cone buds are formed from August to September [28]. Pollination occurs the following spring during March and April [98]. Cones mature from August through October of the third year [28,90]. Seeds begin to drop by mid- to late October [33].

FIRE ECOLOGY

SPECIES: Pinus cembroides
FIRE ECOLOGY OR ADAPTATIONS : Community composition and the spatial distribution of intermixed woody species and understory species influence the effect fire has on Mexican pinyon. Despite its thin bark, mature Mexican pinyon is relatively resistant to low- to moderate-severity fires. Mexican pinyon more than 80 years old have survived at least four fires, including one of moderate severity, in Big Bend National Park, Texas [62]. Seedlings probably establish from bird and rodent caches following fire. Mexican pinyon belongs to diverse communities with varying fire regimes. Historically, fires probably occurred every 10 to 30 years in pinyon-juniper woodlands. Fire is the primary cause of secondary succession in pinyon-juniper woodlands [42]. Pygmy conifer-oak scrub on steep, rocky slopes and crests develops in response to fire and drought [67]. It is fire adapted and its structure is maintained by periodic fires [95]. Madrean oak-pine woodlands probably are fire-tolerant, fire-maintained communites. The fire regime is not well understood for these associations [21,82]. Mexican pinyon occurs in a Madrean oak-pine woodland in Rhyolite Canyon in Chiricahua National Monument, Arizona. Historically, surface fires occurred here in 1- to 38-year intervals. The fire regime has become longer here and elsewhere since livestock grazing has reduced surface fuels [21,83]. In a Madrean evergreen woodland in Boot Canyon in Big Bend National Park, Texas, ring counts from fire scarred Mexican pinyon indicated that at least 10 fires occurred between 1770 and 1940, an average of about 1 every 20 years. Low-severity surface fires do not always produce scars on Mexican pinyon. Additionally, cross dating with other species is necessary due to missing growth rings in Mexican pinyon [62]. Average intervals between scar-producing fires were estimated at possibly 70 years for seven sites in the Chisos Mountains in Big Bend National Park [62,82]. POSTFIRE REGENERATION STRATEGY : Tree without adventitious-bud root crown Initial-offsite colonizer (off-site, initial community) Secondary colonizer - off-site seed

FIRE EFFECTS

SPECIES: Pinus cembroides
IMMEDIATE FIRE EFFECT ON PLANT : Low-severity fires kill Mexican pinyon seedlings and young trees; severe fires kill even mature trees [17,62]. Fire probably kills seeds unless they are covered with an insulating layer of soil. DISCUSSION AND QUALIFICATION OF FIRE EFFECT : NO-ENTRY PLANT RESPONSE TO FIRE : Mexican pinyon probably establishes from seed cached by birds and small mammals following fire. A proposed sere for the pinyon-juniper woodlands in which Mexican pinyon occurs suggests that tree seedlings establish within approximately 30 years following fire [25]. In narrow canyons in the highlands between Puebla and Veracruz, Mexico, Mexican pinyon forests reach crown closure 20 years following fire [80]. DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : NO-ENTRY FIRE MANAGEMENT CONSIDERATIONS : Although varying with microsite differences or canopy closure, fuel loads in pinyon pine habitats where Mexican pinyon is the principal tree are usually discontinuous and light, resulting in low fire frequencies [57,62,100]. Fuel in uncut stands is mostly on the surface beneath tree canopies, which limits fire spread between trees. With open canopies, the understory can vary from sparse to dense herbaceous and shrubby vegetation [17,80]. Surface fuel build up is slow in low productivity pinyon-juniper savannas [62]. Fire effects in this vegetation type are not well understood [17]. Fire suppression and reduction of surface fuels by grazing have resulted in the invasion of grasslands and chaparral by pinyon [17,65,82,100]. Prescribed burning can kill invading seedlings and young trees less than 4 feet (1.2 m) tall [9,17]. A single fire can reduce Mexican pinyon sapling density tenfold. Mexican pinyon 80 years or older are more resistant to fire [62]. If fires do not kill mature trees, follow up with mechanical control methods can be used to eliminate pinyon [17,100]. Low-severity surface fires at 50 or 60 year intervals will thin Mexican pinyon, preventing development of thickets. Fire intervals greater than 80 years result in dense stands of Mexican pinyon and a build up of fuel. There is also a larger risk of severe fires and crowning [62]. In narrow canyons, Mexican pinyon crowns can overlap both with one another and with herbaceous vegetation on slopes. Small fires can easily become crown fires. Fire hazard can be reduced by thinning stands [80]. Dwarf mistletoe infection in Mexican pinyon stands may affect fire hazard conditions by increasing flammability within crowns and increasing downed woody fuels [35].

REFERENCES

SPECIES: Pinus cembroides
REFERENCES : 1. Adams, Robert P. 1977. Chemosystematics--analyses of populational differentiation & variability of ancestral & recent populations of Juniperus ashei. Annals of the Missouri Botanical Garden. 64(2): 184-209. [19845] 2. Aldon, Earl F.; Loring, Thomas J., tech. coord. 1977. Ecology, uses, and management of pinyon-juniper woodlands: Proceedings of the workshop; 1977 March 24-25; Albuquerque, NM. Gen. Tech. Rep. RM-39. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 48 p. [17260] 3. Bailey, D. K.; Hawksworth, Frank G. 1992. Change in status of Pinus cembroides subsp. orizabensis (Pinaceae) from central Mexico. Novon. 2(4): 306-307. [21301] 4. Balda, Russell P.; Masters, Nancy. 1980. Avian communities in the pinyon-juniper woodland: a descriptive analysis. In: DeGraaf, Richard M., technical coordinator. Management of western forests and grasslands for nongame birds: Workshop proceedings; 1980 February 11-14; Salt Lake City, UT. Gen. Tech. Rep. INT-86. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station: 146-169. [17903] 5. Barton, Andrew M. 1992. Factors controlling lower elevational limits of plants: responses of pines to drought in the Chiricahua Mountains, Arizona. In: Ffolliott, Peter F.; Gottfried, Gerald J.; Bennett, Duane A.; [and others], technical coordinators. Ecology and management of oak and associated woodlands: perspectives in the sw United States & n Mexico: Proceedings; 1992 April 27-30; Sierra Vista, AZ. Gen. Tech. Rep. RM-218. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 191-194. [19764] 6. Barton, Andrew M.; Teeri, James A. 1993. The ecology of elevational positions in plants: drought resistance in five montane pine species in southwestern Arizona. American Journal of Botany. 80(1): 15-25. [20527] 7. Bernard, Stephen R.; Brown, Kenneth F. 1977. Distribution of mammals, reptiles, and amphibians by BLM physiographic regions and A.W. Kuchler's associations for the eleven western states. Tech. Note 301. Denver, CO: U.S. Department of the Interior, Bureau of Land Management. 169 p. [434] 8. Blackburn, Wilbert H.; Bruner, Allen D. 1975. Use of fire in manipulation of the pinyon-juniper ecosystem. In: The pinyon-juniper ecosystem: a symposium; 1975 May; Logan, UT. Logan, UT: Utah State University, College of Natural Resources, Utah Agricultural Experiment Station; 1975: 91-96. [454] 9. Block, William M.; Ganey, Joseph L.; Severson, Kieth E.; Morrison, Michael L. 1992. Use of oaks by neotropical migratory birds in the Southwest. In: Ffolliott, Peter F.; Gottfried, Gerald J.; Bennett, Duane A.; [and others], technical coordinators. Ecology and management of oak and associated woodlands: perspectives in the sw United States & n Mexico: Proceedings; 1992 April 27-30; Sierra Vista, AZ. Gen. Tech. Rep. RM-218. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 65-70. [19744] 10. Bock, Carl E.; Bock, Jane H. 1990. Effects of fire on wildlife in southwestern lowland habitats. In: Krammes, J. S., technical coordinator. Effects of fire management of Southwestern natural resources: Proceedings of the symposium; 1988 November 15-17; Tucson, AZ. Gen. Tech. Rep. RM-191. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 50-64. [11273] 11. Bowers, Janice E.; McLaughlin, Steven P. 1987. Flora and vegetation of the Rincon Mountains, Pima County, Arizona. Desert Plants. 8(2): 50-94. [495] 12. Brendemuehl, R. H. 1981. Options for management of sandhill forest land. Southern Journal of Applied Forestry. 5: 216-222. [9305] 13. Bryant, Vaughn B., Jr. 1974. Late quaternary pollen records from the east-central periphery of the Chihuahuan Desert. In: Wauer, Roland H.; Riskind, David H., eds. Transactions of the symposium on the biological resources of the Chihuahuan Desert region, United States and Mexico; 1974 October 17-18; Alpine, TX. Transactions and Proceedings Series No. 3. Washington, DC: U.S. Department of the Interior, National Park Service: 3-21. [16055] 14. Buechner, Helmut K. 1950. Life history, ecology, and range use of the pronghorn antelope in Trans-Pecos Texas. American Midland Naturalist. 43(2): 257-354. [4084] 15. Chojnacky, David C. 1988. Juniper, pinyon, oak, and mesquite volume equations for Arizona. Res. Pap. INT-391. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 11 p. [3373] 16. Correll, Donovan S.; Johnston, Marshall C. 1970. Manual of the vascular plants of Texas. Renner, TX: Texas Research Foundation. 1881 p. [4003] 17. Covington, W. Wallace; DeBano, Leonard F. 1990. Effects of fire on pinyon-juniper soils. In: Krammes, J. S., technical coordinator. Effects of fire management of Southwestern natural resources: Proceedings of the symposium; 1988 November 15-17; Tucson, AZ. Gen. Tech. Rep. RM-191. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 78-86. [11275] 18. Critchfield, William B.; Little, Elbert L., Jr. 1966. Geographic distribution of the pines of the world. Misc. Publ. 991. Washington, DC: U.S. Department of Agriculture, Forest Service. 97 p. [20314] 19. Denyes, H. Arliss. 1956. Natural terrestrial communities of Brewster County, Texas, with special reference to the distribution of the mammals. American Midland Naturalist. 55(2): 289-320. [10862] 20. Dick-Peddie, William A. 1993. New Mexico vegetation: past, present, and future. Albuquerque, NM: University of New Mexico Press. 244 p. [21097] 21. Dick-Peddie, William A.; Alberico, Michael S. 1977. Fire ecology study of the Chisos Mountains, Big Bend National Park, Texas: Phase I. CDRI Contribution No. 35. Alpine, TX: The Chihuahuan Desert Research Institute. 47 p. [5002] 22. Eddy, Thomas A. 1961. Foods and feeding patterns of the collared peccary in southern Arizona. Journal of Wildlife Management. 25: 248-257. [9888] 23. Elias, Thomas S. 1980. The complete trees of North America: field guide and natural history. New York: Times Mirror Magazines, Inc. 948 p. [21987] 24. Erdman, James A. 1970. Pinyon-juniper succession after natural fires on residual soils of Mesa Verde, Colorado. Brigham Young University Science Bulletin. Biological Series. 11(2): 1-26. [11987] 25. Evans, Raymond A. 1988. Management of pinyon-juniper woodlands. Gen. Tech. Rep. INT-249. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 34 p. [4541] 26. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [905] 27. Ffolliott, Peter F.; Thorud, David B. 1974. Vegetation for increased water yield in Arizona. Tech. Bull. 215. Tucson, AZ: University of Arizona, Agricultural Experiment Station. 38 p. [4448] 28. Fisher, James T.; Mexal, John G.; Phillips, Gregory C. 1988. High value crops from New Mexico pinyon pines. I. Crop improvement through woodland stand management. In: Fisher, James T.; Mexal, John G.; Pieper, Rex D., technical coordinators. Pinyon-juniper woodlands of New Mexico: a biological and economic appraisal. Special Report 73. Las Cruces, NM: New Mexico State University, College of Agriculture and Home Economics: 13-23. [5259] 29. Floyd, Mary Elizabeth. 1981. 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