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Wildlife, Animals, and Plants |
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BOTANICAL AND ECOLOGICAL CHARACTERISTICS
GENERAL BOTANICAL CHARACTERISTICS:Shadscale is a densely clumped [19], rounded, compact native shrub [114,125]. It generally attains heights of 8 to 32 inches (20-81 cm) and widths of 12 to 68 inches (30-173 cm). Shadscale is considered an evergreen [28] to partially deciduous shrub [86], since a small percentage of leaves are dropped in the winter [136]. Branches are rigid, smooth when young [19], and spinescent with age [19,86,114,125]. The fruit is a small utricle (4-12 mm long and wide) that typically bears 1 seed. Seeds are from 0.06 to 0.08 inch (1.5-2 mm) broad [152]. Shadscale possesses a deep extensive rooting network [79,86]. Hodgkinson and others [79] report that the majority of roots from plants in northern Utah were fine roots (less than 0.02 inch (<0.5 mm) in width). Wallace and others [149] report a root:shoot ratio of less than 1, excluding fine roots. Hodgkinson and others [79] evaluated root distribution within northern Utah. No significant difference (p< 0.05) in fine shadscale root (<0.5 mm) density under and between shadscale plants was observed until 29.5 inches (75 cm) below the soil surface. Shadscale possesses wider ecological amplitude than most Atriplex species [48], and shows ploidy levels from diploid (2x) to decaploid (10x). Morphological subdivisions can be made in relation to environmental constraints. Plants of the Great Basin have relatively narrower leaves and darker spines, whereas plants of the Colorado Plateau generally have larger leaves and lighter colored spines [128]. Shadscale is relatively short lived [19,38].
RAUNKIAER [126] LIFE FORM:Phanerophyte Chamaephyte
REGENERATION PROCESSES:Shadscale is dioecious [114,152] and reproduces solely through seed [129]. Staminate flowers occur in clusters or in spikes [152], with pistillate flowers found near the end of smaller branches, at the base of leaves [114]. Flowers are wind pollinated resulting in "fairly" successful seed production [20,114]. The mechanisms behind shadscale germination are unclear. Laboratory germination experiments by Meyer and others [110] found a positive response to chilling that was enhanced further by dry storage. Seeds most responsive to chilling treatments were collected from warm desert fringe areas in northern Arizona and southern Utah. Freshly harvested seeds from these areas showed 20 to 50% germination after chilling and 3 years of storage. Chilling temperatures were 34 to 36 degrees Fahrenheit (1-2 °C). Seeds collected from cold desert areas were variable in their response to chilling. The pronounced seed bracts of shadscale provide a mechanical barrier to germination and must break down before seeds can germinate [55]. Vest [146] found fungal colonies reduced the hardness of shadscale bracteoles, facilitating germination. The slow breakdown of seed bracts may delay germination until favorable growing conditions exist [55]. The removal of dormancy in a fraction of the seed population each year spreads risk associated with germination over many years, increasing probability of establishment [110]. Within a blackbrush association of Nevada, Schultz and Ostler [131] observed little shadscale seedling recruitment until a large die-off of existing shadscale plants occurred. Seedling recruitment occurred most often under the skeleton of dead shadscale plants, after high mortality from prolonged drought. Gasto [67] observed no direct correlation between seedling emergence and location of mature plant. However, greater survival occurred when seedlings were adjacent to larger living shadscale individuals.
SITE CHARACTERISTICS:Shadscale occurs in arid climates [26,86] that receive 4 to 8 inches (100-200 mm) of precipitation annually. It occurs on dry slopes, flat areas, ridges, and valley bottoms [86]. Shadscale is a facultative halophyte [28,48,68,78,94]. Salts are concentrated in trichomes and deposited on leaf surfaces [28]. It is tolerant of arid conditions [28,102,130]. Plants remain photosynthetically active down to -11.5 mP [48] and from a temperature range of 23 degrees to 122 degrees Fahrenheit (5-50 °C). However, shadscale is less adapted to drought than many of its common associates [81,146], showing high mortality during periods of prolonged drought [130]. Tolerance to drought is achieved through partial shedding of leaves; this reduces water loss during severe moisture stress [102]. Soils: Shadscale prefers well-drained [43,59,68], moderately saline soils [19,43] where groundwater is below the rooting zone. In general shadscale inhabits a wide variety of soil types, possessing no comprehensive edaphic restrictions [78]. It may inhabit a wide variety of textural classes [21,24,152], from fine [19,86,152] to sandy [86] and gravelly soils [86,152]. Shadscale is considered an indicator of subsoil salinity [13]. Shadscale prefers saline soils where salt concentrations are greatest at deeper soil levels (36 to 60 inches (91-152 cm)) [43,68], with relatively lower salt concentrations in surface soil levels (0 to 18 inches (0-46 cm)) [68]. However, shadscale performs well under a variety of salt concentrations [68,78,94]. Kleinkopf and others [94] observed shadscale seedling growth under a wide salt gradient in the greenhouse. Moderate (50 ml/l) levels of salt were beneficial, whereas higher levels were detrimental to growth. Maximum yield occurred at 50 ml/l of sodium chloride. Shadscale does not require large amounts of soil nitrogen. Goodman [69] found nitrogen fertilization produced no significant increase (p<0.05) in biomass. Regional: In Arizona shadscale mainly occurs on dry plains and mesas [91]. In California shadscale is found east of the Sierra Nevada [77] in valley bottoms [6] and in the Mojave Desert [77]. The drainage bottoms of enclosed basins or marine shale outcrops are preferred sites within the Great Basin Desert [19]. In Nevada, Break and Jenkins [29] observed significantly greater (p<0.007) shadscale coverage in coarse rocky habitat (49% sand, 51% rock) compared to sandy habitat (64% sand, 33% rock). Shadscale also occurs on nonsaline slopes of western and central Nevada below big sagebrush communities [43]. In central Utah shadscale is found within arid valleys on relatively high saline soils [61]. Alkaline plains and hills are preferred in Wyoming [54]. Within the upper Snake River Plain of southeastern Idaho, shadscale communities occur in depressions and open areas on alkaline soils [5]. In the Trans-Pecos area of Texas, shadscale is found in eroded deserts, alkaline basins, flats, hills, and bluffs [125]. Elevation by state is as follows: Arizona 2,500 to 5,000 feet (762-1,524 m) [91] California less than 7,870 feet (< 2,400 m) [77] Colorado 4,500 to 7,500 feet (1,372-2,286 m) [76] New Mexico 5,000 to 6,500 feet (1,524-1,981 m) [105] Texas 4,000 to 6,000 feet (1,219-1,829 m) [148] Utah 2,790 to 7,020 feet (850-2,140 m) [152]
SUCCESSIONAL STATUS:The successional timeline of a shadscale community is generally slow in both grazed and ungrazed areas [27].
SEASONAL DEVELOPMENT:Shadscale growth is greatly related to seasonal precipitation. Shadscale is not fully deciduous, retaining the majority of its leaves through winter [1]. A small proportion of leaves are shed in the fall, with new leaves produced in March or April [114]. Within the Great Basin Desert, blooming season varies from late March in the southern portion of shadscale's range to about mid-June to the north. Shadscale generally flowers in spring [1] before the summer drought [58]. Fruits mature about 25 weeks after flowering and persist through winter [19]. West and Gasto [154] observed shadscale phenology in northwestern Utah for 7 years (1966-1973). Twenty individuals were observed every 2 weeks from March through October. The mean date for 1st observed occurrence of phenological stages is summarized below:
Everett and others [58] monitored the phenology of shadscale in a galleta-shadscale association within the Great Basin of Nevada. Over the course of 4 years (1969-1972), spring growth began most often at the end of March, with an average growing season of 126 to 130 days. Results are summarized below:
In western Colorado, shadscale begins vegetative growth early to mid-March, blooming in late March to mid-April. Late bloom occurs from mid-April to early May. Fruiting generally occurs in early May to mid-June with seed ripening in mid-June to early July [28]. Shadscale allocates considerable resources toward root growth. In northern Utah, root growth was observed a few days before shoot elongation and continued for several weeks after shoot elongation had ceased. The greatest root elongation was observed during June and July [62]. Seasonal root growth is linked to soil moisture depletion and soil temperature changes [35]. Root growth at various depths are summarized below [62]:
Related categories for SPECIES: Atriplex confertifolia | Shadscale |
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