2001. Merits of native and introduced Triticeae grasses on semi-arid rangelands. Can. J. Plant Sci. 81: 45-52. Experiments were conducted on four semiarid range sites to compare stand establishment , productivity, and persistence of several introduced perennial Triticeae grasses with that of their native counterparts. On Intermountain sites with severe water limitations (< 300 mm), native grasses were more difficult to establish, less productive, and less persistent than the introduced grasses. Stands of native grasses declined most rapidly under defoliation. At locations where moisture conditions were more favorable, particularly where more summer precipitation occurred, native Triticeae grasses established and persisted relatively well compared with the introduced entries. Although difficult to establish, stands of the rhizoma-tous native, western wheatgrass [Pascopyrum smithii (Rydb.) A. Löve] increased during the seasons after establishment. Choice of plant materials to be used in range seeding programs should be based on objective criteria. To do otherwise will perpetuate degradation of soil resources, especially on sites that are dominated by weedy annual species such as cheatgrass (Bromus tecto-rum) and medusahead rye (Taeniatherum asperum). It is proposed that adapted introduced grasses be equally considered along with native grasses as a component of seed mixtures on environmentally harsh sites that have been burned, infested with competitive weedy species, or otherwise degraded.. 2001. Attributs des Triticées indigènes et introduites dans les par-cours de pâturage semi-arides. Can. J. Plant Sci. 81: 45-52. Nous avons réalisé à quatre emplacements de parcours semi-arides des expériences visant à comparer l'installation, la productivité et la longévité de plusieurs Triticées vivaces d'introduction avec les propriétés d'espèces indigènes apparentées. Dans les vallée des montagne, exposées à de graves carences en précipitations (moins de 300 mm), les espèces indigènes étaient plus difficiles à installer et aussi moins productives et moins persistantes. En outre, leurs peuplements se dégarnissaient particulièrement vite sous l'effet du broutage. En revanche, dans les situations mieux arrosées, en particulier durant les mois d'été, leur installation et leur longévité se comparaient assez favorablement à celles des espèces d'introduction. Malgré des difficultés d'installation, les peuplements d'agropyre de l'Ouest [Pascopyrum metis (Rydb.) A. Löve], espèce indigène rhizomateuse gagnaient en densité dans les années suivantes. Le choix du matériel végétal à utiliser dans les programmes de ressemis en parcours devrait donc être fondé sur des critères objectifs, faute de quoi la dégradation du sol risque de se perpétuer, surtout aux emplacements dominés par des espèces annuelles envahissantes comme le brome des toits (Bromus tectorum et Taeniatherum asperum) (élyme tête-de-méduse). Les Triticées d'introduction adaptées aux conditions de parcours devraient donc être considérées tout autant que les espèces indigène...
Planting prostrate kochia in 'greenstrips' may be a viable option to decrease cheatgrass dominance.
Because of restrictions imposed by crossing barriers, crested wheatgrass breeders have usually limited themselves to selection and hybridization within ploidy levels i.e., diploid (Zn=14), tetraploid (2n=28), or hexaploid (2n=42) populations. Several procedures have now been devised and evaluated to transfer genetic traits among ploidy levels, and interploidy breeding appears to be a feasible approach in the crested wheatgrass complex. Plant scientists with the USDA-ARS at Utah State University have developed a superior breeding population by hybridizing induced tetraploid Agropyron cristatum (L.) Gaertn. with natural tetraploid A. desertorum (Fisch. ex Link) Schult. The cultivar 'Hycrest' was released from this germplasm base in 1984. Chromosome number of the Hycrest breeding population ranged from 2n=28 to 32 and averaged 30. Chromosome pairing relationships were similar to those observed in natural tetraploids and the cultivar was as fertile as the parental species. Hycrest produced significantly more seeds per spike than 'Nordan,' and ample genetic variability for seed set existed in the population to make additional improvement through selection. Hycrest produced significantly (p
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