• GENERAL BOTANICAL CHARACTERISTICS
• RAUNKIAER LIFE FORM
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS
• SEASONAL DEVELOPMENT

GENERAL BOTANICAL CHARACTERISTICS:

Indian ricegrass is a hardy, cool-season, densely tufted, native perennial bunchgrass that grows from 4 to 24 inches (10-61 cm) in height [18,23,83]. Plant spread is estimated at 8 to 12 inches (20-30 cm) [61]. When mature, seedstalks are open, loosely branched, or with lacy tops [60]. Spikes are erect and range from 0.8 to 2.8 inches (2-7 cm) in length [18]. Indian ricegrass has deep, fibrous, extensive roots and is one of the most drought tolerant of the native range grasses [61,83,123]. The common name is derived from seeds that resemble grains of rice [83,111].

RAUNKIAER LIFE FORM:

Chamaephyte

REGENERATION PROCESSES:

Plummer and others [93] report that Indian ricegrass naturally spreads aggressively from seed, but Valentine [115] describes seedling establishment as "poor" in comparison to that of other species. Plummer and Frischknecht [94] reported that numerous seedlings often develop in years with wet springs, while very few develop during dry springs. Therefore, years of good seedling establishment can be quite infrequent. A high degree of correlation between April precipitation and Indian ricegrass abundance has been reported [46].

Indian ricegrass is characterized by low seed germinability and variability in both length of dormancy and viability [15,36]. Some ecotypes require cool-moist stratification prior to germination [82]. Lack of uniformity in seed weight, size, and thickness can contribute to nonuniform germination and establishment [84]. Difficulties with seed shattering and seed dormancy often produce germination rates that are less than 85% [24]. Indian ricegrass is highly self-fertile [77].

Seed retains viability for at least 14 years when stored in a cool, dry warehouse. Approximately 38% of Indian ricegrass seed germinated after 20 years of storage [57]. Optimum germination temperatures are variable, but Toole [109] reports best success at 68 degrees Fahrenheit (20 ^oC). Detailed information on seed storage temperatures and germination is available [26,104,109].

Seed is dispersed by rodents, wind and water [68]. Seed caching by heteromyid rodents can produce favorable microenvironments that enhance seedling recruitment [15]. Seed dehulling by rodents as well as mechanical scarification can improve germination [52,82]. In captive studies, kangaroo rats ate approximately 75% of Indian ricegrass seed while caching 25% [82].

Rapid response suggests that Indian ricegrass may tiller after fire.

SITE CHARACTERISTICS:

Indian ricegrass grows on dry foothills, rocky valley or upper slopes, plains, and ridges [58,61,99]. It is moderately tolerant of both alkali and salt, and is adapted to soils of low fertility [29, 88]. This species is particularly well adapted to sand and attains greatest abundance on loose sandy soils where it forms almost pure stands [29,60,58]. Indian ricegrass dominates sandy soils throughout the sagebrush-grass zone [124]. Soils supporting Indian ricegrass range in texture from coarse sand to heavy clay [94]. It is also found on shallow shale soils [61].

Indian ricegrass grows in arid and semiarid climates throughout the Intermountain West [53]. It grows mostly in areas with mesic temperature regimes and arid moisture regimes [92].

Indian ricegrass is a dominant perennial grass at lower elevation sites throughout the salt desert ranges of western North America [15]. Elevational ranges of Indian ricegrass are as follows [28,77]:

4,000 to 9,500 feet (1220-2900 m) in Colorado
3,300 to 6,000 feet (1010-1830 m) in Montana
4,000 to 9,000 feet (1219-2743 m) in New Mexico
4,200 to 9,500 feet (1280-2900 m) in Utah
4,300 to 8,500 feet (1310-2590 m) in Wyoming

SUCCESSIONAL STATUS:

Koniak [73] reports that Indian ricegrass reaches greatest cover in early mid- to mid-seral stands following fire in pinyon-juniper communities of the Great Basin. Cover decreases by late succession [73]. In southeastern Idaho, Indian ricegrass increased during a 25-year disturbance-free period [22]. After approximately 20 more years, cover began to decline. In mixed-grass prairies of Colorado, Indian ricegrass plants commonly appear within the first 5 years after disturbance such as plowing [30]. Indian ricegrass is a pioneer on blowouts and loose sands of sand sage (Artemisia filifolia) communities of northeastern Colorado [97]. It is typically found on disturbed (but not undisturbed) sites in blackbrush (Coleogyne ramosissima) communities in parts of Nevada [47]. Indian ricegrass is present in several climax communities including climax bunchgrass communities of Oregon [1]. It forms part of a distinct sub-climax grassland community in parts of northern Utah [106].

SEASONAL DEVELOPMENT:

Indian ricegrass generally flowers early prior to summer drought [42]. In Nevada flower buds may form as early as February or March [2]. However, flowering is indeterminate and can continue through the spring and summer if growing conditions remain favorable [120]. Ackerman and others [2] reported that in the Nevada desert, Indian ricegrass flowered after spring rains, but not following summer rains. This suggests that lower temperatures may be required for flowering. Time of flowering varies as follows [28]:

      	earliest flowering      latest flowering
CO            May                      July
MT            May                      June
ND            June                     June
WY            May                      July

                      	Date  	Range (days)  Standard deviation

growth starts        	Apr 08       
flowerstalks appear 	May 22	27            7.9
heads fully out      	Jun 17	26            8.6
flowers in bloom     	Jun 20	20            6.5
seed ripe            	Jul 03	21            7.3
dissemination starts 	Jul 06
dissemination over   	Jul 29
plant drying         	Jul 03	48            7.8
plant dried          	Aug 06

Mean dates breaking dormancy     Mean days of active development
March 31                         72
April 2                          74
April 7                          74

Related categories for SPECIES: Achnatherum hymenoides | Indian Ricegrass