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Flora of the Huachuca Mountains, Cochise County, Arizona

Janice E. Bowers and Steven P. Mclaughlin1

Abstract.-The Huachuca Mountains, Cochise County, Arizona, are one of about two dozen "sky islands" in southeastern Arizona. A herbarium search revealed that, prior to 1990, 849 species had been documented from the Huachuca Mountains. Field work conducted between 1990 and 1994 added another 144 species to the flora. Altogether, 993 species in 467 genera and 101 families are now known from the range. Of these, 65 are introduced. Madrean floristic elements dominate the flora, accounting for 69.9% of all native species. Sonoran elements (5.0% of all native species) are relatively poorly represented in the Huachuca Mountains compared to more arid mountain ranges in southeastern Arizona. The flora of the Huachuca Mountains is comparatively rich for an Arizona local flora, with 29-39% more species than expected based on its elevational range and collecting history. Substrate complexity and the presence of many well-watered canyon habitats and springs contribute to the high species diversity.

INTRODUCTION Our initial objective was, based on the work of these many collectors, to assemble a plant check­ The Huachuca Mountains (fig. 1), located in list for the entire range so that we could detemine southwestern Cochise County on the United if the flora was indeed, as Wallmo (1955) charac­ States-Mexico border, are one of two dozen moun­ terized it, "quite well known." Eventually, we also tain ranges in southeastern Arizona. Often becalne interested in how plant checklists grow referred to as "sky islands" (Heald 1951), these and shrink. In this paper, we compare the flora of ranges form a floristically diverse archipelago that the Huachuca Mountains with floras of other sky has been of keen interest to botanists for more islands in southeastern Arizona, and demonstrate than a century. The Huachuca Mountains in par­ that species composition of local floras is dy­ ticular have a long and illustrious botanical namic, subject to historical changes in climate, history. Plant collection dates back to the botanical land use, and other factors. The checklist will be explorations of John Gill Lemmon and Sara Plum­ published at a later date. mer Lemmon in 1882 (Crosswhite 1979) and has continued until the present day (fig. 2). Floristic work includes an enumeration of Timothy E. Wil­ STUDY AREA cox and Marcus E. Jones collections (Britton and Kearney 1894, Jones 1930) and checklists for Fort The north-south trending Huachuca Moun­ Huachuca, Ramsey Canyon, Garden Canyon and tains belong to the Basin and Range Province Coronado National Memorial (Goodding 1950a, (Hunt 1967). Maximum elevations are 9,466 feet 1950b; Pratt 1963; Toolin 1980; Yatskievych 1980- (2885 m) on Miller Peak, 9220 feet (2810 m) on 81; Ruffner and Johnson 1991; Parfitt and Christy Carr Peak, 8725 feet (2659 m) on Ramsey Peak, 1992). Altogether, 84 collectors have taken more and 8410 feet (2563 m) on Huachuca Peak. Several than 4000 specimens from the range. major canyons with perennial reaches drain the precipitous eastern slope and eventually flow into the San Pedro River. The western slope, part of the Santa Cruz River watershed, has only a few 1 University of Arizona, Tucson, AZ. streams with perennial reaches. Overall, the

135 I , I Mlle. N / I 2 , . I I i , , i J~f ,,' , 2 3 .. ~ Arizona 1:1 1/ Kilometer. J:a ~~/ I I // I if Sierra Vista

.-- " ., ", ...... -.... ,,"' .. , Fort . , ,I , ,, ...... ,- " " Military /" " ,..,f .:~ Aeservation,""': ~ ...... '' ''"''. , ,I " ...... ,'"

.--, .... -_ ... , Forest ~: C'o;~n.do " " National ~ ".morlal

Figure 1.-Huachuca Mountains and vicinity. The ....vy blllell line shows the study area boundary. A, Location of the Huachuca Mountains In Arizona; B, admlnlstrlltlw units In and near the Huachuca Mountains; C, major drainages and peaks of the Huachuca Mountains. Huachuca Mountains appear highly dissected,

500 with a large ratio of canyon to ridge habitat. Our study area had an elevational range of ! 400 4466 feet (1361 m) and covered about 122 square miles (31,600 ha). The northern and eastern t 300 boundaries roughly followed the base of the U) range, which varies from 5000-5200 feet (1524- ~ 200 J 1585 m) above sea level. The southern edge coincided with the International Boundary. The 1 100 5500-foot (1676 m) contour approximated the o western boundary. We excluded most private lands at the base of the range, with the exception

Vear of the Ramsey Canyon Nature Preserve, Peterson Ranch in Scotia Canyon, and aquatic habitats at Beatty's Miller Canyon Orchard in Miller Canyon. Figure 2.-Plant collection by YMr, Huachuca Mountain. The lower elevations of Fort Huachuca Military (omitting all years In which fewer tMn 10 apeclmen. we,. collected). Based on specimen. depo.... at the Reservation were also excluded from our study University of Arizona herbarium area.

136 Topography and Geology THE FLORA

The range is geologically diverse. Bolsa Plant Checklist Quartzite, the basal sedimentary unit, rests uncon­ formably on Precambrian granite. On the eastern In winter 1990 and spring 1991, we searched slope, Paleozoic sedimentary rocks, mainly lime­ the University of Arizona herbarium (ARIZ) and stone but also some shales and siltstones, top the the herbarium at Fort Huachuca for specimens Bolsa quartzite. On the western slope, sedimen­ from the Huachuca Mountains. We critically tary rocks of Cretaceous age, including evaluated all collections, and, if necessary, rede­ conglomerates and shales, interfinger with Trias­ termined them. Starting in August 1990 and sic-Jurassic volcanic and sedimentary rocks (Keith continuing through June 1994, we made 41 trips and Wilt 1978). into the range, mostly during the April-October growing season, and also in November and Janu­ ary. We attempted to sample every habitat throughout the growing season with special em­ phasis on discontinuous habitats such as cattle tanks, springs, peaks, and cliffs. Most of our effort was concentrated along trails and roads. Climate Between 1882 and 1989, collectors documented a total of 849 species in the Huachuca Mountains. Weather stations are maintained at Fort During the course of our project, we found 137 Huachuca at the northern end of the range and at species that were new to the flora. Another 7 spe­ Coronado National Memorial at the southern end. cies were added by other collectors between 1990 Annual precipitation at Fort Huachuca (4664 feet, and 1993. The total flora comprises 993 species 1422 m) is 14.6 inches (37.1 cm). About half falls in and infraspecific taxa in 467 genera and 101 fami­ July and August as high-intensity "monsoonal" lies. Of these, 65 species are introduced. The rains that originate as scattered convectional native flora comprises 906 species and 27 infras­ thunderstorms triggered and enhanced by surface pecific taxa. heating and orographic effects. Winters at Fort Huachuca are rather dry. December and January, the wettest winter months, average 1.7~ inches How Plant Checklists Grow (4.5 cm) of precipitation. About 10% of winter pre­ cipitation falls as snow, which seldom stays on the It is common for plant checklists to expand ground more than a day or two. At higher eleva­ over several decades of collecting. The Mount tions, annual rainfall exceeds 25 inches (63.5 cm), Shasta, California, flora grew from 425 species and snow can remain on the ground all winter. and infra specific taxa in 1940 to 525 in 1963 Winter storms result from cyclonic storms and (Cooke 1940, 1941, 1949, 1963), an increase of frontal systems associated with large-scale low about 1 percent per year. The flora of Tumamoc pressure systems that typically originate off the Hill, Tucson Mountains, Arizona, increased 0.6 coast of California and Baja California. They are percent per year between 1909 and 1985, from 238 less variable spatially and more variable tempo­ to 346 species (Thornber 1909, Bowers and Turner rally than summer storms (Sellers and Hill 1974). 1985). The flora of Organ Pipe Cactus National Summers and winters at Fort Huachuca are Monument grew from 522 species in 1980 (Bowers mild. The average January temperature is 46.3°F 1980) to 571 in 1992 (Pinkava et al. 1992), an in­ (7.9°C), with average daily maximum and mini­ crease of 0.8 percent per year. The flora of the mum temperatures of 58.4 and 34.2°F (14.7 and White Mountains, California, increased 3 percent 1.2°C). Summer temperatures are moderated by per year between 1973 and 1987, from 761 to 1078 afternoon cloud cover. The average July tempera­ species (Lloyd and Mitchell 1973, Morefield 1992). ture is 77.5°P (25.3°C), with daily maximum and The small yearly increment in each case suggests minimum temperatures of 88.6 and 66.4°P (31.4 that the initial floras were fairly complete. Linear and 19.1°C). At higher elevations, the average regression of percent increase against final size of January temperature is 400 P (4.4°C), and the aver­ the flora suggests that, not surprisingly, the larger age July temperature is 65°P (18.3°C) (Sellers and the flora, the more difficult it is to collect com­ Hill 1974)0 pletely (R2 = 0.95).

137 Most additions to local floras are probably had originally been collected before 1909. Ron­ plants that have been previously overlooked. On deau (1991) did not find 55 species that had been occasion, however, movement of species onto a collected in the Tucson Mountains between 1903 site increases the size of a local flora. New arrivals and 1988. In the Huachuca Mountains, 31 species may be natives or exotics. In either case, careful may no longer belong to the flora, despite con­ observation is needed to distinguish newly ar­ certed efforts to locate many of them. Inevitably, rived species from those that were simply collectors of local floras seldom if ever relocate all overlooked. Especially in recent years, introduc­ the plant species documented from an area. Some tion of exotics, either deliberately or accidentally, are simply overlooked. Mislabeled vouchers has expanded the size of many local floras. At might not have belonged to the flora in the first Glacier National Park, Montana, exotics increased place. This is a particular problem for collectors in at an accelerating rate between 1920 and 1993 (Le­ southeastern Arizona, where Lemmon's labels are sica et al. 1993). Over 76 years, the number of notoriously unreliable (Kearney and Peebles introduced species in the Tumamoc Hill flora in­ 1960). Matelea balbisii/ Spirodela polyrhiza/ creased by an order of magnitude, from 2 to 52 Woodsia scopulina and several other species re­ (Bowers and Turner 1985, Burgess et al. 1991). ported from the Huachuca Mountains might well Such examples could be multiplied many times. have been mislabeled as to location. Some species In the Huachuca Mountains flora, the 65 exotics are "lost" as a result of taxonomic recombination; include species seeded by the Forest Service to in our study area, Aquilegia longisissima/ Poly­ prevent erosion after fire (Dactylis glomerata/ gala piliophora and a few others might not prove Sanguisorba mino!; Melilotus spp.); escapes from to be good species. cultivation (Pyracantha koidzumii Hedera helix/ Of greater biological interest are species that Vinca majo!; Rubus procera); and naturalized ex- apparently no longer occur in an area. Some otics (Erodium cicutarium/ Bromus rubens/ plants lost from the Huachuca Mountains flora are Polypogon interruptus). About half of the exotic exotics that apparently failed to become estab­ flora was first documented after 1962. The rapid lished, including Coriandrum sativum/ Pastinaca vegetative growth and smothering habit of Rubus sativa/ Lonicera japonica, and several others. A procera and Vinca major represent serious threats few native species may have been eliminated by to the biodiversity of lower mesic canyons in the development of the lower reaches of Carr, Miller, Huachuca Mountains. and Ramsey canyons. Odontrichum decomposi­ The concentrated effort of compiling a plant tum, for example, was last seen at "James's resort" checklist is another reason local floras increase in near the mouth of Ramsey Canyon (Jones 1930), size. After 98 years of casual and infrequent col­ now an area of houses, gardens, and pastures. lecting in the Rincon Mountains, the documented Melica porteri "cannot exist in the presence of a flora was 517 species (Bowers, unpublished data). cow" (Goodding 1950a) and may have been elimi­ The final checklist of 986 species (Bowers and nated by grazing. Eventually, proliferation of McLaughlin 1987) represented an increase of 18 exotic grasses such as Eragrostis lehmanniana and percent per year. McLaughlin (1993) doubled the E curvula might have deleterious effects on the known size of the Pinalefto Mountains flora, from native flora. Both species dramatically decrease 406 in 1988 (Johnson 1988) to 824 in 1993. In the the diversity and productivity of native grasses Huachuca Mountains, collectors documented a to­ (Cable 1971, Bock et al. 1986). Eragrostis lehman­ tal of 849 species between 1882 and 1989. Between nianil was introduced into Cochise County in the 1990 and 1994, 144 species were added to the late 1940s; by 1951 it had spread onto Fort flora, an increase of about 5 percent per year. This Huachuca, apparently from nearby highways modest increment suggests that the flora was in­ (Goodding 1950a). Eragrostis curvula was intro­ deed comparatively well known at the start of our duced into the United States in 1928 (Crider 1945). project. These two exotics are now among the most com­ mon plants at low to moderate elevations in the Huachuca Mountains. How local Floras Shrink The fossil record demonstrates dramatic al­ teration of floras as a result of climatic change Loss of species from local floras has been (Betancourt et al. 1990). Historical climatic change noted infrequently in southeastern Arizona. Bow­ repeats this process on a briefer time-scale, espe­ ers and McLaughlin (1987) were unable to relocate cially among small, local populations. Extirpation 41 species in the Rincon Mountains; of these, 22 of 6 native perennials formerly found at high ele-

138 vations in the Rincon Mountains might have re­ Although our failure to relocate 31 species pro­ sulted from severe winter drought during vides only negative evidence, we find it 1920-1930 or 1942-1958 (Bowers and McLaughlin suggestive that distinct patterns such as fire, 1987). During the seasonally dry months of April, flood, drought and development can be identi­ May and June, such species depend on soil mois­ fied. Some apparently extirpated species might ture left by the winter snowpack. Severe winter well still occur in less accessible parts of the drought could have eliminated their presumably mountain range. small populations. A similar set of circumstances might have claimed some species in the Huachuca Mountains. High-elevation mesophytes not col­ FLORISTIC ANALYSIS lected there since 1913 include Adiantum pedatum, Achillea mil1elolium, Dugaldia All native species occurring in the Huachuca hoopesii, Macromeria viridillora, Sidalcea Mountains flora were classified into floristic ele­ neomexicana, and Veronica serpyl1ilolia. Cur-. ments based on the system of floristic areas for the rently, Vaccinium myrtillus, Pyrola chlorantha, western United States developed by McLaughlin Mertensia Iranciscana, Pedicularis grayi, Actaea (1992). Methods for assigning species to floristic rubra, Hypericum lormosllm, Senecio huachu­ elements are given in McLaughlin and Bowers canus and several others are known in the (1990) and McLaughlin (1994). For comparison, Huachuca Mountains only from small popula­ the floristic analysis of the Huachuca Mountains tions at high elevations and may be similarly flora is presented along with those from the Rin­ vulnerable. con and Pinalefto mountains (Bowers and Natural disasters, particular 1'fire and flood, McLaughlin 1987, McLaughlin 1993) (Table 1). may also have eliminated species from the flora. The system of floristic elements of McLaugh­ The Huachuca Mountains have experienced fre­ lin (1992) is hierarchical. Five floristic provinces quent severe fires in recent years (Taylor 1991, are recognized for the western United States: Cor­ Wohl and Pearthree 1991). The southern end of dilleran, Intermountain, Sonoran, Californian and the range has been particularly hard-hit, notably Madrean. These provinces are subdivided into in 1977, 1988, and 1991 (Taylor 1991). The disap­ subprovinces, which are in turn subdivided into pearance or retreat of several species can perhaps districts. Table 1 provides a breakdown of floristic be ascribed to these or earlier fires. Rosa woodsii, elements for the Madrean Floristic Province. collected in "moist draws" on Carr Peak in 1909, "Widespread" Madrean species are those that are is now known only from upper Bear Canyon; Hy­ (1) found in 20 or more of the local floras used by pericum lormosum, collected on "moist slopes" of McLaughlin (1992) to develop the classification, Carr Peak in 1909, is now known only from Bond and (2) centered on the Madrean Floristic Prov­ and Sawmill springs. Valeriana edulis, which is no ince. "Regional" Madrean species are ·those with longer known from the flora, may have been more restricted distributions (found in 10 to 19 of eliminated by fire. 101 local floras from the western United States) The most destructive fires may be followed by that are centered within the Madrean Floristic floods and debris flows, especially in steep drain­ Province. "Central Arizonan," "Chihuahuan," and ages (Wohl and Pearthree 1991), with dire "Apachian" species are narrowly distributed in consequences for riparian herbs (Gori 1992). The Table 1.-Florlstlc elements In the Huachuca, Rincon and small, scattered populations of Lilium parryi have Plnaleflo mountains. Values In the table are the experienced catastrophic declines in recent years percentage of the total native flora assigned to each as a result of flooding (Warren and Reichenbacher floristic element. 1991, Wood 1992). Riparian plants that might have Huachuca Rincon Pinalerio been eliminated from the Huachuca Mountains EIQri§li~ Elemeo§ MQ!.mt~i[)§ MQUOtAio§ MQUOtAilJ§ Madrean flora by floods or debris flows are Dryopteris Widespread 5.6 5.1 6;6 filix-mas, Aster coerulescens, Monarda fistulosa, Regional 17.8 19.0 20.5 Oenothera kunthiana, Rubus arizonensis and Central Arizonan 1.3 1.5 2.3 Glyceria borealis. Small populations of riparian Chihuahuan 6.4 4.3 2.4 Apachian ~ at.6 2.M plants might have been eliminated during Total Madrean 69.9 61.5 52.7 drought years, as well. Clearly, a variety of natural and man-made Sonoran 5.0 19.4 10.7 Cordilleran 18.0 10.6 27.2 disasters can eliminate species from local floras, Intermountain 3.5 2.9 4.6 particularly when populations are small and local. ~alifQ[[]ia[) 36 56 ~6

139 the western United States (found in 9 or fewer of Huachuca Mountains, where winters are neither the sample of 101 local floras) and are centered, as cold nor as wet, there is no spruce-fir forest, respectively, within the Central Arizona, Chihua­ and the mixed-conifer forest is of limited extent. huan and Apachian floristic districts. In the sky island region in general, and in the The Huachuca, Rincon and Pinaleno moun­ Huachuca Mountains in particular, the Cordille­ tains all lie within the Madrean Floristic Province, ran elements include both many widespread taxa since the majority of their species belong to Ma­ and many narrowly dis~ributed species with Mo­ drean elements. All three floras are placed within gollon affinities (centered in the Mogollon Rim of the Apachian district, since the Apachian element Arizona and the Mogollon highlands of New is the largest narrow-species element in their re­ Mexico). In the Huachuca Mountains, species spective floras. The Huachuca Mountains flora with Cordilleran and Mogollon affinities are has the highest percentage of Apachian species, found mostly at high elevations or in moist, and all species with Madrean affinities constitute shaded canyons. nearly 70% of the flora. The Cordilleran element accounts for 18% of the Huachuca Mountains flora; species with Sonoran and Californian affini­ SPECIES DIVERSITY ties are better represented in the flora of the Rincon Mountains, and those with Cordilleran The plant species diversity of the Huachuca and Intermountain affinities are better repre­ Mountains was evaluated in two ways. First, sented in the Pinaleno Mountains. The Chihuhuan based on the elevational range of the study area element is somewhat better represented in the and the collecting effort invested in compiling its Huachuca Mountains than in the Rincon or Pi­ flora, we compared the actual number of species naleno mountains. observed with the number expected to occur The importance of Madrean floristic elements (Bowers and McLaughlin 1982). The elevational in the Huachuca Mountains is not unexpected. range of our study area is 4466 feet (1361 m). For The Apachian element is particularly large. Gen­ collecting time, we estimated low and high values era notably rich in Apachian species (5 or more) in based on the number of years in which 50 or more our study area include Asclepias/ Bidens/ Brickel­ specimens were collected (22 years) and the lia/ lpomoea/ Dalea/ Desmodium/ Cyperus, and number of years in which 75 or more specimens Muhlenbergia. The Apachian element is most were collected (16 years). The results showed that, strongly associated with oak and pine-qak wood­ compared to other local floras from throughout lands, plant communities that are particularly Arizona, the Huachuca Mountains have 29-39% well represented in the Huachuca Mountains. more species than would be predicted based on The low percentage of Sonoran elements in the elevational range and collecting history. Huachuca Mountains contrasts with that of the We plotted number of species versus eleva­ Rincon Mountains. The base elevation of the Rin­ tional range for the Huachuca Mountains and 23 con Mountains is 2000 feet (610 m) lower than that other local floras from Arizona and New Mexico of the Huachuca Mountains, resulting in hotter (fig. 3). The regression line in figure 3 shows the summers, milder winters and lower rainfall, all relationship between elevational range and rich­ conducive to a higher representation of species ness in this sample of 24 floras [5 = 264 + with Sonoran affinities. Those Sonoran species 0.274(ilE), R2 = 0.502, P < .001)]. The flora for the within the flora of the Huachuca Mountains are Huachuca Mountains is the farthest above the re­ mostly species with widespread and regional dis­ gression line, that is, it has the highest residual tributions. Some are spring-flowering annuals, a value. Of the mountain ranges from the south­ group that is not well represented in the western United States whose floras have been Huachuca Mountains. investigated in detail, the Huachuca Mountains The Cordilleran elements are of much greater appear to be exceptional in their high species di­ importance in the Pinaleno Mountains, especially versity. above 9000 feet (2743 m) (McLaughlin 1993), than In local floras from the western United States, in the Huachuca Mountains (Table 1). Species elevational range is closely correlated with habitat with Cordilleran affinities are found mostly in the diversity, since both temperature and precipita­ mixed-conifer and spruce-fir forests in the Pi­ tion vary with elevation, often over short naleno Mountains, where moisture-loving, distances. Habitat diversity in turn is a major de­ cold-tolerant plants thrive under high winter pre­ terminant of species diversity. Thus local floras cipitation and low winter temperatures. In the from areas spanning a large elevational range

140 (such as the Huachuca Mountains) tend to have dry, spring-flowering species are not well repre­ higher species diversity (fig. 3). The Huachuca sented. Mountains also have many aquatic habitats and Groombridge (1992) lists the" Apachian/ Ma­ much variation in gelogical substrates, and these drean" region as one of 164 global centers of plant factors probably also contribute to high species diversity. Floras from the sky island region are diversity in the range. The complex topography of inherently richer than other floras from the west­ the range, with its numerous deep canyons cut­ ern United States (McLaughlin, this symposium). ting nearly to the ridge lines, makes a For example, the floras of the- Huachuca Moun­ topographically patchy landscape that may pro­ tains, Rincon Mountains, Sycamore Canyon, mote high species diversity. Bennett and Chiricahua National Monument and Buenos Aires Kunzmann (1992) attempted to quantify topo­ National Wildlife Refuge, all in the sky island re­ graphic "roughness" and found that their index gion, are farthest above the regression line in was correlated with species diversity among a Figure 3. Much of the high species diversity of the small set of floras from the sky island region. In Huachuca Mountains is due to the presence of a some sky island floras, a pronounced biseasonal large Apachian component. Although it is clear rainfall regime allows both a spring and a sum­ that certain floristic elements and floristic areas mer flora to flourish (Bowers and McLaughlin are richer than others, the environmental, histori­ 1987, McLaughlin and Bowers 1990). In the cal and ecological factors that determine these Huachuca Mountains, where winters are rather inherent differences are not yet well understood.

1200 CONCLUSIONS 1000 HUACHUCAS It RM wU'l . After 112 years of plant collection, the flora of U w Q 800 the fIuachuca Mountains is well known. Local flo­ U'l W PM > CNM NSR SA;R ras can never be completely collected. Additional ~ 600 SC" • AM"· z ". TM field work inevitably turns up species that had L>- a OA ~M. .OP been overlooked. Ornamental and crop plants in­ a::: " NHM w 400 " FB m CC ,,!M • AC vade from nearby settlements, sometimes ::l" • WT • CW becoming naturalized. Native plants, too, may oc­ z • PF • NM 200 cupy new territory. Natural disasters such as fire, flood, and drought may extirpate some species, 0 especially those with small populations in limited 0 500 1000 1500 2000 2500 habitats. Human-induced disasters such as graz­ ELEVATION RANGE (Meters) ing and plant introduction may also take a toll. figure 3.-Relationshlp between elevatlonal range (difference be­ Inevitably, some species will be overlooked by tween highest and lowest elevations) and species diversity collectors and mistakenly assumed to be extir­ among 24 local floras from Arizona and New Mexico. In addi­ pated. Between 1882 and 1994, additions (144) to tion to the Huachucas, the floras plotted are: AC, Aravalpa Canyon, AZ (Warren and Anderson 1980); AM, Animas Moun­ the Huachuca Mountains greatly exceeded sub­ tains, NM (Wagner 1973); BA, Buenos Aires National Wildlife tractions (31). Plant checklists serve as a baseline Refuge, AZ (McLaughlin 1992b); CC, Canyon de Chelly Na­ tional Monument, AZ (Halse 1973); CNM, Chirlcahua National for assessing floristic change in future decades. Monument, AZ (Reeves 1976); CR, Cooke's Range, NM (Co­ In a region known for its biological diversity, lumbus 1988); CW, Chiricahua Wilderness, AZ (Leith liter 1980); OM, Datil Mountains, NM (Fletcher 1972); FB, Fort the I-Iuachuca Mountains are exceptionally rich in Bowie National Historic Site, AZ (Warren et al. 1992); MM, plant species. Contributing factors include a large Mule Mountains, AZ (Wentworth 1982); NHM, Northern Huala­ Apachian floristic element, complex topography, a pai Mountains, AZ (Butterwick et al. 1991); NM, Navajo National Monument, AZ (Brotherson et al. 1978)j NSR, North­ wide elevational range, and a diversity of geologi­ ern Santa Rita Mountains, AZ (McLaughlin and Bowers 1990); cal substrates and aquatic habitats. Op, Organ Pipe Cactus National Monument, AZ (Bowers 1980); PF, Petrified Forest National Park, AZ (Petrified Forest National Park 1976); PM, Pinaleno Mountains, AZ (McLaughlin 1993); RM, Rincon Mountains, AZ (Bowers and McLaughlin LITERATURE CITED 1987); SC, Sycamore Canyon, AZ (Toolin et al. 1980); SA, Sierra Ancha, AZ (Pase and Johnson 1968); TM, Tucson Mountains, AZ (Rondeau 1991); WM, White Mountains, NM Benn(~tt, P. S. and M. R. Kunzmann.1992. Factors affecting (Hutchins 1974); WT, White Tank Mountain Regional Park, AZ plant species richness in the Madrean Archipelago (Keil1973); WU, Wupatki National Monument, AZ (McDougall 1962). north of Mexico. In A. M~ Barton and S. S. Sloane, Chiricahua Mountains Research Symposium, Proceed-

141 ings, Pine Canyon United Methodist Camp, Chirica­ Goodding, L. N. 1950a. Grasses on the Fort Huachuc" hua Mountains, Arizona, 16-17 March 1992, p. 23-26. Wildlife Area.InC.D. Wallmo, Fort Huachuca Wildlif Southwest Parks and Monuments Association, Tuc­ Area Surveys 1950-1951, p. 3-11. Arizona Game anc.. son, Arizona. Fish Commission, Phoenix. Betancourt,J. L., T.R. VanDevender, and P.S.Martin. 1990. Goodding, L. N. 1950b. Plants of the Huachuca Moun Packrat Middens: The Last 40,000 Years of Biotic tains. In C. O. Wallmo, Fort Huachuca Wildlife Are; Change. University of Arizona Press, Tucson. Surveys 1950-1951, p. 12-19. Arizona Game and Fish Bock, C. E.,J. H. Bock, K. L.Jepson, and J. C. Ortega. 1986. Commission, Phoenix. Ecological effects of planting African lovegrasses in Gori, D. 1992. Sensitive plant studies in the "sky island' Arizona. National Geographic Research 2:456-463. mountain ranges of s. e. Arizona. In A. M. Barton and S Bowers, J. E. 1980. 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