Biological Survey of Ironwood Forest National MonumentRare Plant Inventory Rare plant distributions are detailed in a table.Federally Threatened/Endangered Species
The only Federally listed species in Ironwood Forest National Monument is the Endangered Nichol's Turk’s head cactus (Echinocactus horizonthalonius var. nicholii). This taxon occurs almost exclusively on certain types of limestone and is known from only three localities, one in Sonora, Mexico and two in the United States. One of the U.S. populations is in the Vekol Mountains in the Tohono O’odham Nation; the other is in the Waterman Mountains which are divided between the Tohono O’odham Nation and IFNM. A few plants can be found growing on quartzite outcrops within areas of limestone. Nichol's Turk’s head cacti are patchily distributed; we found plants on seven of the 15 flora plots that were done on limestone in this range. Where it did occur plants ranged from rare to locally abundant. Three major concentrations were documented. The nominate variety E. h. horizonthalonius is common and widespread in the Chihuahuan Desert. Arizona Protected Plants: The state of Arizona protects a number of native plant species in several categories. Species in the two most highly protected categories are listed here. Highly Safeguarded Protected Native Plants * Bursera fagaroides† † The Bursera in the Waterman Mountains is classified as B. microphylla but it is different from most other populations in leaf shape and vegetative phenology. It may be derived from a hybridization with B. fagaroides. Salvage Restricted Protected Native Plants (Sorted by genus) * Abutilon parishii Other rare species of concern or interest Many of these plants are illustrated in the plant galleries Although many common species are widespread, the floras of each distinct area support some species not found in other areas in the Monument. The numbers of restricted species ranges from one to 75, reflecting the floristic diversity of the areas. Species diversity is related to maximum elevation in the area, but are not necessarily correlated with the size of the area or its geographic location in the Monument. In part this is the result of special edaphic situations (limestone bedrock, sandy flats, artificial cattle tanks) or unique microhabitats (steep, deep shady canyons). Restricted distributions may also relate to biogeographic features (sandy desertscrub flats in the Lower Colorado River Valley, upland jojoba [Simmondsia chinensis] chaparral in the Silver Bell Mountains, etc.) or more random patterns related to the vagaries of seed dispersal. The packrat (Neotoma spp.) midden fossils on Wolcott Peak and in the Waterman Mountains present a unique opportunity to interpret some of the modern flora in IFNM. Ragged Top. The flora of Ragged Top (including Wolcott Peak) in 9.9 mi2 (Wiens 2000, this study) includes 401 taxa, 71.6% of the total IFNM flora. The steep rugged, shady canyons on Ragged Top support a remarkably diverse flora. A rocky wash on the northwest base of Ragged Top with 153 species is another diversity hotspot. A total of 76 IFNM taxa were found only on Ragged Top. Van Devender and Wiens (1993) reported plant macrofossils from three packrat middens from Wolcott Peak radiocarbon dated from 5020 to 14,550 yr B.P. (radiocarbon years before 1950). The late Wisconsin glacial vegetation on Wolcott Peak was a woodland/chaparral dominated by Pinus monophylla (singleleaf pinyon), Juniperus coahuilensis (redberry juniper), and Juniperus cf. osteosperma (Utah juniper; no longer in IFNM) in association with Ericameria cuneata, Opuntia chlorotica, Quercus turbinella, and Stipa speciosa (desert needlegrass; Ragged Top relicts), and Vauquelinia californica (Arizona rosewood). Pentagramma triangularis and Viguiera deltoidea (Parish goldeneye) found on Ragged To today were not identified in the midden assemblages but are probably ice age relicts as well. Ericameria cuneata (cuneate turpentine bush), Myosurus cupulatus, and Quercus turbinella (shrub live oak) were also found in ice age middens in the Waterman Mountains (Anderson and Van Devender 1991). Other Ragged Top isolates which are more common in more mesic woodlands and grasslands at higher elevations are Abutilon mollicomum (Sonoran Indian mallow), Asclepias linaria (pine needle milkweed), Cerastium texanum, Galium microphyllum (bedstraw), Ipomoea cristulata (scarlet morning glory), Ipomopsis multiflora, Muhlenbergia emersleyi (bullgrass), M. monticola (mesa muhly), M. rigens (deer grass), and Stachys coccinea (Texas betony). Chaenactis carphoclinia (pebble pincushion), Cryptantha decipiens, C. nevadensis (nievitas), Eriogonum thurberi (a wild buckwheat), and Rafinesquia californica (California chicory) are rare winter-rainfall annuals on the southeastern edges of their ranges. Justicia californica (chuparrosa is a widespread Sonoran Desert shrub with orange-red flowers near the northeastern edge of its range. It is an important nectar plant for migrating hummingbirds. The populations of Abutilon abutiloides, Argemone ochroleuca, Hibiscus biseptus (Sonoran rose mallow), Malvastrum bicuspidatum, Pisonia capitata, Plumbago scandens, and Waltheria indica on Ragged Top are isolates of plants that are common in more tropical areas in Sonora. In the Arizona Flora, Kearney and Peebles (1964) reported the Mexican prickly poppy Argemone ochroleuca (as A. mexicana) as occasional near Tucson, probably introduced from Tropical America. It is common on roadsides from north-central Sonora southward, mostly with cream-colored flowers. Individuals with canary yellow flowers are found south of Guaymas on the coastal plain of the Gulf of California. The single yellow-flowered plant collected in a wash near Ragged Top was probably introduced (Wiens 2000). Wiens (1990) reported the Ragged Top populations of Pisonia capitata as new for the flora of Arizona and the United States. Pisonia capitata (garambullo) is a spiny, woody shrub/vine in the Nyctaginaceae that is disjunct from the nearest Sonoran population by 285 miles. Abutilon parishii (Parish Indian mallow) was a candidate threatened species and Tumamoca macdougalii (Tumamoc globeberry) was listed as endangered; both were delisted because numerous new localities in Arizona and Sonora were discovered (Van Devender et al. 1994). (Since then Tumamoca has again become very rare; it can no longer be found in many documented localities.) Pisonia capitata was considered as potentially rare in Arizona by the Arizona Rare Plant Guide Committee (Richards, no date). Abutilon parishii and Tumamoca macdougalii are special plants for the BLM Tucson District (Richards, no date). Roskruge Mountains. Nineteen IFNM species were only found in the Roskruge Mountains. Dalea pulchra (indigo bush) and Sapindus drummondii (western soapberry) are more common in higher elevation desert grassland and oak woodland. Tobosa grass (Pleuraphis mutica) is a characteristic species in the Chihuahuan Desert Region to the east, where it forms distinctive swale communities within desert grassland. Ambrosia cordifolia (Sonoran bursage), Erigeron arisolius, and Tephrosia vicioides are common species in the more tropical portions of the Sonoran Desert in central Sonora. Although Cryptantha micrantha (bloodroot nievitas) was found only in the Roskruge Mountains, it was identified in a fossil packrat midden from the Waterman Mountains (Anderson and Van Devender 1991). A single massive organpipe cactus (Stenocereus thurberi) probably represents a chance dispersal by white-winged doves (Zenaida asiatica) or lesser long-nosed bats (Leptonycteris curasoae). This columnar cactus is common in Arizona Upland desertscrub from the western portion of the Tohono O’Odham Reservation west to Organpipe Cactus National Monument, and southward into tropical southern Sonora. Agave americana was planted at several road intersections on the Cocoraque Ranch, and is reproducing clonally. Other species were planted in the cattle tanks including Eucalyptus camaldulensis, Populus fremontii (Fremont cottonwood), Salix gooddingii (Goodding willow), or were established in them naturally (i.e., Lemna minor and Marsilea vestita). Sawtooth Mountains. Twenty IFNM taxa were found only in the Sawtooth Mountains. Most of them were previously reported by Mauz (1999). Many of them were found in the disturbed salt cedar (Tamarix aphylla) -dominated riparian habitats along Greene Wash and adjacent agricultural areas: e.g., Ambrosia monogyra (cheesebush), Asclepias subulata, Atriplex semibaccata, Datura wrightii, Eragrostis echinochloidea, Helianthus annuus (sunflower), Melilotus indicus (yellow sweet clover), Nicotiana glauca (tree tobacco), Rumex glomeratus, and Sorghum halepense (Johnson grass). Euphorbia trachysperma is an uncommon delicate annual that is endemic to the Sonoran Desert. Cheilanthes pringlei, a former U.S. Fish and Wildlife Service candidate species, is a rock-crevice fern that is locally common from the Tucson Mountains south into Sonora. Gutierrezia sarothrae is a common subshrub in disturbed habitats to the north, but is mostly replaced by G. microcephala in other areas in IFNM. Machaeranthera coulteri var. arida and Mammillaria tetrancistra (a fishhook pincushion cactus) are Lower Colorado River Valley plants reaching their eastern limits in the Sawtooths. Interestingly, Atriplex polycarpa (allscale) and Mammillaria tetrancistra were also found in middens in the Waterman Mountains well to the east of their present ranges (Anderson and Van Devender 1991). Waterman Mountains. Eighteen IFNM species were found only in the Waterman Mountains. Argyrochosma jonesii (Jones cloak fern), Bahia absinthifolia, Echinocactus horizonthalonius var. nicholii, Panicum hallii (Hall panicgrass), and Parthenium incanum (mariola) are species that typically are associated with limestone substrate and calcareous soils. Other limestone-loving plants in the Watermans that occur elsewhere in IFNM are Astrolepis cochisensis (Cochise cloak fern), Bouteloua trifida (red grama), Polygala macradenia, Tetraclea coulteri, Thymophylla pentachaeta, and Tiquilia canescens. Echinocactus horizonthalonius var. nicholii is a listed Federally Endangered cactus. Seeds of E. h. var. nicholii identified in a 22,380 yr B.P. woodland assemblage indicate that this isolated population of a typical Chihuahuan Desert species has been in the Waterman Mountains for a long time. Other species in the Watermans including Cheilanthes villosa (hairy lip fern), Euphorbia revoluta, Graptopetalum rusbyi, Hybanthus verticillatus, Mimulus rubellus, Panicum obtusum, and Talinum aurantiacum (flame flower) are more common in woodlands and grasslands in more mesic areas to the north and east. Euphorbia revoluta (a spurge) was also present on Wolcott Peak at 12,130 yr B.P. (Van Devender and Wiens 1993). Hermannia pauciflora is an uncommon suffrutescent herb in the Sterculiaceae that is endemic to the Sonoran Desert Region in Arizona and Sonora. Anderson and Van Devender (1991) reported plant macrofossils and pollen in 14 packrat midden samples radiocarbon dated from 1320 to 22,450 yr B.P. The well-preserved plant remains in the midden assemblages help understand the flora of the Watermans. In the late Wisconsin glacial period prior to 11,000 years ago, the vegetation was a woodland-chaparral dominated by Pinus monophylla, Juniperus coahuilensis, and J. osteosperma. These species plus Berberis sp. (barberry), Celtis reticulata (netleaf hackberry), Coryphantha vivipara, Krascheninnikovia lanata (winterfat), Salvia pinguifolia, and Yucca brevifolia (Joshua tree) no longer occur in IFNM. Other ice age plants including Agave deserti, Canotia holacantha, Monardella arizonica, Opuntia chlorotica (pancake prickly pear), and Vauquelinia californica (Arizona rosewood) no longer live near the midden sites but are still found as relictual populations at higher elevations in the Watermans. Canotia holacantha (crucifixion thorn), a small tree in the Celastraceae, is especially interesting because it is almost endemic to central Arizona except for two relict populations in Sonora Mexico (Turner et al. 1995). It was also reported from an 11,100 yr B.P. midden on Picacho Peak (Van Devender et al. 1991), 21 miles north of the Waterman Mountains. Agave cf. deserti was present on Wolcott Peak at 1230 yr B.P. (Van Devender and Wiens 1993) but is now restricted to the Watermans in IFNM. Sonoran desertscrub vegetation developed in the current postglacial period, the Holocene, with the disappearance of woodland plants and the arrival of modern dominants including saguaro (Carnegiea gigantea), desert ironwood (Olneya tesota), ocotillo (Fouquieria splendens), and palo verdes (Parkinsonia florida and P. microphylla). Saguaros were much more common than today at 8310 and 2600 yr B.P. Both Bursera microphylla and ironwood were first recorded in the Watermans at 8310 yr B.P. Bursera microphylla is in a tropical family (Burseraceae), which includes aromatic trees and shrubs variously called elephant tree, copal, palo mulato, or torote. B. microphylla is widespread in the Sonoran Desert from the Phoenix area south through the Sonoran Desert to coastal southern Sonora (Turner et al. 1995). It is interesting that the plants in the isolated Waterman population have unusually large leaflets reminiscent of Bursera fagaroides, a species only known in Arizona in Fresnal Canyon in the Baboquivari Mountains near the Sonora border. Either there has been evolution of new genetic variability through genetic drift or natural selection in the last 8000 years, or there has been hybridization with B. fagaroides. The Waterman Mountains Bursera population warrants a careful morphological, phenological, and molecular study to better understand its relationship with other populations. Hunter et al. (2001) determined the ploidy levels of Larrea divaricata (creosotebush) in from packrat middens from throughout the southwestern United States and northwestern Mexico by measuring the size of the guard cells around the stomates on leaves. Traditionally, it was thought that distributions of the three chromosomal races in L. divaricata closely correlated to the warm deserts of North America; i.e., diploid (Chihuahuan Desert), tetraploid (Sonoran Desert), and hexaploid (Mohave Desert). Subsequently, diploid populations were identified in the Verde Valley in central Arizona and in Baja California. Interestingly, L. divaricata in Waterman Mountains middens radiocarbon dated at 1320 and 6195 yr B.P. were diploid. It would be very interesting to check the ploidy level of L. divaricata in IFNM to see if the Watermans support a diploid population surrounded by tetraploids. Other areas. Creosotebush desertscrub typical of the Lower Colorado River Valley is best developed in fine-grained, often sandy, soils of the broad Aguirre and Avra Valleys and the Santa Cruz flats (Turner and Brown 1982). Ferocactus emoryi is a barrel cactus that is widespread from Central Sonora north into south-central Arizona. The single plant in the Aguirre Valley is near the northeastern limits for the species. Seven species of plants were found only in Avra Valley within the Monument. Petalonyx thurberi (sandpaper plant) is a Lower Colorado River Valley plant found from Baja California to Tucson. Anoda pentaschista, Eremalche exilis, Malacothrix fendleri, and Phacelia arizonica occur in areas with clayey soils that are seasonally flooded or with extensive sheet wash, often growing with the more-widespread Malvella sagittifolia, Oenothera arizonica (evening primrose), Physalis lobata, and Rhynchosida physocalyx. Some of these species (P. arizonica, Yucca elata, etc.) suggest an interesting ecological displacement of plants that are more common at higher elevations in the desert grasslands to the east into seasonally-watered valley bottoms in IFNM. The problematic exotic Malta starthistle (Centaurea melitensis) is potentially invasive in these areas (Richards, no date). Three IFNM plants were found only in both the Samaniego Hills and the Silver Bell Mountains, surprisingly few for the massive Silver Bells (Wiens 1991). Amaranthus graecizans and Portulaca oleracea (verdolaga) in the Samaniego Hills and Lepidium virginicum (peppergrass) and Machaeranthera tagetina in the Silver Bells are widespread annuals of disturbed soils. Artemisia ludoviciana (white sage) is a perennial herb that is widespread in higher, more mesic woodland habitats throughout the Southwest and northern Mexico. It is surprising that it is not more widespread in IFNM considering that it was present in the Waterman Mountains from 8,310 to 22,380 yr B. P. (Anderson and Van Devender 1991) and on Wolcott Peak 12130 yr B.P. (Van Devender and Wiens 1993). Brown (1978) reported Juniperus coahuilensis (as J. monosperma) and Vauquelinia californica from the Silver Bell Mountains. Apparently the J. coahuilensis was in error. Two species were recorded only on Pan Quemado. Boerhavia pterocarpa (spiderling) found with common B. erecta and B. megacarpa. Eriogonum polycladon was observed in a cattle tank at the south end of Pan Quemado in about 1994, but has not been found elsewhere in the Monument (Wiens 1996). Uncommon perennial plants. An additional 49 species of perennial plants were found in five or fewer of the major areas in IFNM discussed above. A number of them are relictual populations of species that were more widespread in the late Pleistocene: e.g., Encelia frutescens, Monardella arizonica, Opuntia chlorotica, and Vauquelinia californica. Plants that are common in more mesic grassland and oak woodlands at higher elevations to the east include Acacia angustissima (whiteball acacia), Bouteloua eriopoda (black grama), Cucurbita digitata (wild gourd), Hymenothrix wislizenii, Leptochloa dubia (sprangletop), and Maurandya antirrhiniflora (snapdragon vine). Cathestecum brevifolium (false grama or zacate borreguero) and Croton sonorae are common plants in the Sonoran Desert and tropical thornscrub in Sonora. Cathestecum brevifolium is a tufted, stoloniferous grass that was first reported for Arizona and the United States on Ragged Top, where there the population covers a substantial area (Wiens 1990). In the present inventory a second small population was discovered in the Silver Bell Mountains, 3 miles east-northeast of Ragged Top. Cathestecum brevifolium was considered as potentially rare in Arizona by the Arizona Rare Plant Guide Committee (Richards, no date). Mohave Desert or Lower Colorado River Valley plants reaching their eastern range limits in IFNM include Fagonia californica, Grusonia parishii (Parish cholla), Lycium macrodon (a wolfberry), and Pleuraphis rigida (big galleta grass). Grusonia parishii is found from southern Nevada and southeastern California to southern Arizona (Anderson 2001). In IFNM it forms dense mats on sandy flats or lower rocky bajadas in the Sawtooth Mountains. A patch in the Silver Bell Mountains near Malpais Hill is the southeastern most locality for the species. The crucifixion thorn (Castela emoryi), a spiny shrub/tree in the Simaroubaceae, is restricted to creosotebush desertscrub in the Aguirre Valley and the Santa Cruz flats. Both Mammillaria thornberi (Thornber fishhook pincushion) and Peniocereus greggii (Arizona night-blooming cereus) were candidate species considered for Threatened status by the U.S. Fish and Wildlife Service, but were delisted because numerous new localities in Arizona and Sonora were discovered. M. thornberi is typically found in desert flats underneath creosotebush bush. The numerous stems with strongly hooked spines are easily separated, suggesting that it might be dispersed on coyote or fox snouts. It is closely related to M. yaquensis in coastal thornscrub in southern Sonora. Peniocereus greggii is widespread in the Sonoran Desert but so cryptic that it gives a perception of rarity. Its gray-green stems are very similar to dead creosotebush stems. It would likely be encountered in most suitable habitats with concentrated surveys at night when it is flowering in June-July. It is no longer on any protection lists in the United States, although Mexico classifies it as Rara (Diario Oficial de la Federación 1994). Penstemon subulatus is endemic to Arizona from Mohave County south to Pima County (Kearney and Peebles 1964). It was found in the Silver Bell and Roskruge Mountains in the current inventory. It was considered as potentially rare in Arizona by the Arizona Rare Plant Guide Committee (Richards, no date). Uncommon annual plants. The significance of rare annual plants for conservation is difficult to assess. Abundances vary from year to year and seeds of most species can survive a decade or more in the soil, awaiting favorable rains. In the biseasonal northeastern Sonoran Desert annuals comprise 30 to 50% of local floras (Rondeau et al. 1996). In the Tucson Mountains, 46% of the flora are annuals with 62% of them winter-spring rainfall obligates. In IFNM, 238 species (42.5% of the flora) are annuals. Other species can be annual or perennial depending on microhabitats and rainfall or are perennial outside the desert: e.g., Bromus carinatus, Ditaxis neomexicana, Erigeron spp. (fleabanes), Erioneuron pulchellum (fluffgrass), Euphorbia spp., Glandularia gooddingii, Hedeoma nanum, Linum lewisii, Marina parryi, and Senecio flaccidus var. monoensis. In the obligate IFNM annuals, 134 of them rare or uncommon (found in 1 to 4 areas, 49.4% of the rare/uncommon IFNM taxa). Thirty-five of the annual are native species that would probably be common during periods with greater rainfall. Another 20 species (14.9%) are exotic species with little potential for causing ecological impact. The remaining 79 taxa of native annuals appear to genuinely be rare or uncommon in IFNM. Some of them were discussed in the individual area discussions above. Most of them are near the edges of their geographic distributions. Some like Antirrhinum cyathiferum, A. nuttallianum (wild snapdragons), Geraea canescens (desert sunflower), Lasthenia chrysostoma (goldfields), Linanthus aureus, and Loeflingia squarrosa are winter-spring annuals that are common in the Mohave Desert and/or the Lower Colorado River Valley to the northwest or west. Others such as Acalypha neomexicana and Gaillardia arizonica are more common in desert grassland or oak woodlands to the east or southeast. Gaillardia arizonica is interesting because it is a spring annual in the same genus as the blanket flowers (G. pinnatifida and G. pulchella), which are perennial summer herbs in grasslands from southeastern Arizona to Texas and the Great Plains. Additional species of annuals will presumably be found when a survey is conducted in a wet year. Amaranthus xtucsonensis (Tucson pigweed) is an occasional summer annual that was only recently described from the Tucson Mountains in Arizona and the Río Mayo Region of southern Sonora (Henrickson 1999). The type locality is Gates Pass in the Tucson Mountains. Wiens (2000) reported it for Ragged Top, and it was found on Pan Quemado and in the Roskruge and Waterman Mountains in the current survey. There is also a specimen from Organpipe Cactus National Monument in the University of Arizona Herbarium. Henrickson concluded that A. xtucsonensis was of hybrid origin with A. hybridus as one parent and an unknown species (not the local A. fimbriatus or A. palmeri). A. hybridus is no longer known from the Tucson area but is a common weed in agricultural areas near Sacaton on the Pima Indian Reservation (Kearney and Peebles 1964), possibly reflecting its use as a prehistoric cultivar. Setaria liebmanni is a summer annual bristlegrass that is found from Arizona to Nicaragua. In tropical southern Sonora, it is called cola de zorra, is abundant on roadside, and grows 5-6 ft tall in response to heavy monsoonal rains. Near its northern range in Arizona, it typically is a rare 6-inch tall annual. In the present inventory, it was found in the Roskruge and Sawtooth Mountains. The Sawtooth locality is the northernmost locality for the species and the first record for Pinal County. Trisetum interruptum is a summer annual grass that is found from Colorado and Texas west to southeastern Arizona, where it is uncommon. Wiens (2000) reported it on Ragged Top. It was also found in the Waterman Mountains in the present inventory. Disturbed xeroriparian areas. A total of 44 species were found only in disturbed xeroriparian habitats including cattle tanks, large arroyos, and seasonally-flooded valley bottoms. Twenty of these are exotics. Cattle tanks were surveyed in the Aguirre Valley (Gap Tank), Avra Valley (upper Blanco Wash), Pan Quemado (unnamed tank), Roskruge Mountains (Agua Dulce Ranch Tank, El Represo Lamita, and Indio Tank), Samaniego Hills (SASCO Tank and an unnamed tank), and the Waterman Mountains (unnamed dammed wash). The only aquatic plants in IFNM were Lemna minor (duckweed) in El Represo Lamita and Marsilea vestita (clover fern) in Agua Dulce Ranch tank. Cocío Wash in the Silver Bell Mountains and Greene Wash in the Sawtooth Mountains are highly disturbed athel tree (Tamarix chinensis) habitat. Valley bottom areas with clay soils that appeared to be seasonally flooded were surveyed in the Aguirre and Avra Valleys. The eastern edge of IFNM in Avra Valley accessed by the Manville and Reservation Roads entrances between Cocoraque Butte and Blanco Wash are especially muddy areas. The percentage of exotic plants found only in disturbed riparian areas in IFNM (47.7%) is very high. The total IFNM flora has 9.6% exotics and the Ragged Top flora has 6.5% exotics. Although most of the riparian exotics do not appear to be serious invasives, some of this suite of plants may potentially spread to other areas in the Monument. Tamarix chinensis is likely to establish in any area in the Monument that impounds runoff. Eragrostis echinochloidea was introduced as cattle forage by the Soil Conservation Service near Tucson in about 1936 (Kearney and Peebles 1964). Since then it has been collected in a few localities in Cochise, Pinal and Santa Cruz counties, Arizona (John R. Reeder, personal communication, 2003), and near Magdalena, Sonora (Van Devender, unpublished data), the first record for Mexico. Thus, this perennial African grass is expanding is slowly expanding its range, but apparently does not penetrate into natural habitats. Unlike areas in the Santa Catalina and Tucson Mountains (Rondeau et al. 1996), fountain grass (Pennisetum setaceum) is not yet invasive in IFNM. The only place it appears to be established is on the edge of Pan Quemado near houses on the very eastern border of the Monument. It was seen in Cocío Wash in mid-1990's, but was not found there in the current inventory.
|
|
