Tall fescue or creeping foxtail suppresses foxtail barley

Foxtail barley (Hordeum jubatum L.) is a troublesome weed in irrigated pastures. Several grass species seeded on two irrigated pastures at Lethbridge to test their ability to compete with foxtail barley. Tall fescue (Festuca arundinacea Schreb.) and creeping foxtail (Alopecurus arundinaceus Poir) reduced foxtail barley groundcover significantly compared to orchardgrass (Dactylis glomerata L.), pubescent wheatgrass (Agropyron trichophorum (Link) Richt.) and western wheatgrass (Agropyron smithii Rydb.); therefore, seeding of these grasses in areas subject to foxtail barley invasion should be encouraged. Key words: Foxtail barley, tall fescue, creeping foxtail, wet soils, salinity, weed suppression

Impacts of seeding depth on emergence and seedling structure in eight perennial grasses

The effects of seeding depth (1.5, 3, or 6 cm) on seedling emergence, morphology, and anatomy were examined in cool-season (Agropyron dasystachyum, Agropyron desertorwn, Agropyron smithii, Elymus angustus, and Elymus junceus) and warm-season (Andropogon scoparius, Bouteloua curtipendula, and Bouteloua gracilis) perennial grasses. Caryopsis weights ranged from 0.5 mg in Bouteloua spp. to 4.7 mg in E. angustus. Prominent elongation of the subcoleoptile internode at greater seeding depths and short coleoptiles were observed in And. scoparius, B. curtipendula, and B. gracilis (type A seedlings). The remaining species had relatively long coleoptiles and no subcoleoptile internode elongation (type B seedlings). Up to 40% of the seedlings in the Agropyron species had intracoleoptile internode elongation when seeded at 3- and 6-cm depths. Relative emergence from 6 cm compared with 1.5 cm was best in Agr. dasystachyum and Agr. smithii and poorest in the type A species and in E. junceus. Diameters of xylem vessels in the subcoleoptile and intracoleoptile internodes remained relatively constant, but numbers of vesels decreased with depth of seeding, especially in the type A species. Decreases in hydraulic conductance with depth of seeding were greater in type A than in type B seedlings, mainly because of longer subcoleoptile internodes and smaller effective vessel radii in the former. Key words: grass seedling emergence, hydraulic conductance, morphology, seeding depth, seed weight, xylem dimensions.

HABITAT CHARACTERISTICS AND GRASSHOPPER COMMUNITY DYNAMICS ON MIXED-GRASS RANGELAND

A study was conducted in Butte County of western South Dakota to determine the relationships between habitat characteristics and spatial and temporal changes in community structure of grasshoppers on mixed-grass rangeland. Detrended correspondence analysis (DCA) of 29 undisturbed grasshopper communities and correlation analysis of DCA axis values and habitat variables denned specific spatial gradients underlying the community structure of grasshoppers. Results indicated that grasshopper communities changed along a primary gradient of percentage of coverage of grasses, particularly Buchloe dactyloides (Nutt.) Engelm., and a secondary gradient of percentage composition of clay and sand in the soil.DCA of 24 grasshopper communities sampled in 1986 and 1987, multiple regression analysis, and factor analysis were used to determine the relationships between specific habitat characteristics and changes in communities of grasshoppers treated with either a nonselective insecticidal spray (malathion) or a selective insecticidal bait (bran bait with carbaryl). Results indicated that between-year change in community composition, or the difference between post-treatment communities in 1986 and 1987, was positively correlated with percentage of coverage of total grasses and forbs. Community malleability, defined as the tendency of a community to return to its predisturbed state, was greater in habitats with high coverages of Agropyron smithii Rydb. and Carex spp., low coverage of Bouteloua gracilis (H.B.K.) Lag. ex Steud., and low species richness of grasses. Our results emphasize the importance of habitat characteristics in structuring undisturbed grasshopper communities and in community change after perturbation with insecticides.

Vegetation patterns within southern Alberta coulees

Native grassland communities located in coulees near Lethbridge, Alberta, were studied to identify the associations present and the environmental factors influencing them. The vegetation along 16 transects was described using point quadrants, with additional study sites analyzed for soil and environmental variables. The data were analyzed using detrended correspondence analysis and indicator species analysis (TWINSPAN) and the results are discussed in relation to recognized plant associations. The primary environmental factor affecting the distribution of these associations is a xeric–mesic gradient, which is discussed in terms of site topography and the physiological requirements of Agropyron smithii and Bouteloua gracilis. A disjunct Festuca scabrella community is recognized and implications of this are discussed.