Root-plowed rangeland in southern Texas is often dominated by fabaceous shrubs. We tested the hypothesis that the shrub community present 40 years after rootplowing does not exhibit successional trends toward the mixed-brush species community that existed before rootplowing. Twenty shrub clusters, each organized around a central honey mesquite individual, were selected within a control site and a root-plowed (35-40 years ago) site at each of 3 locations. Number of all woody plants species including cacti Opuntia spp. and Yucca spp. beneath the nuclear honey mesquite was determined. Shrub species richness within clusters increased with increasing central honey mesquite basal diameter on control and root-plowed sites. Species richness/honey mesquite in root-plowed (2 +/- 0.5 species, +/- SE) sites was lower than species richness/honey mesquite > 200 mm in diameter on control sites (7 +/- 0.4 species/honey mesquite). Honey mesquite seedlings (1-60 mm basal stem diameter) composed 39 +/- 14% of the shrubs beneath honey mesquite canopies on root-plowed sites compared to less than or equal to 3% of the woody plants present on untreated sites. Honey mesquite may continue to dominate root-plowed sites for some time, since honey mesquite was the major subordinate shrub species on root-plowed sites.

Increases in fringed sagebrush (Artemisia frigida Willd.) following disturbance on Northern Mixed Prairie are due to enhanced growth of established plants and seedling recruitment. The roles of seed production and the soil seedbank in population dynamics of fringed sagebrush following disturbance are, however, unknown. Furthermore, seed rain has not been documented for this species. The objectives of this study were to determine: 1) the effect of disturbances in the sward on seed production; 2) relationships between the soil seedbank and current seed production; and 3) seed rain over time for fringed sagebrush. Disturbances of clipping, litter removal, tillage, and a combination of clipping and litter removal were imposed on a sandy range site in central Saskatchewan. Following disturbance seed production plant-1 either increased or was unchanged compared to the undisturbed control. Greater seed production resulted from increased production of seeds head-1, heads inflorescence-1 and inflorescences plant-1. The timing of seed rain varied considerably among individual plants. Five temporal patterns of seed rain were identified for individual fringed sagebrush plants: 1) 5.2% of the plants began and completed dispersing seeds within 6 to 8 weeks of flowering; 2) 20.8% began dispersing within 6 to 8 weeks of flowering and completed dispersal before snow was received in autumn; 3) 37.7% began dispersing seeds within 6 to 8 weeks of flowering and continued over the winter; 4) 29.9% delayed dispersal of seeds more than 8 weeks after flowering and continued over the winter; and 5) 6.5% began and completed seed dispersal during the winter. The number of fringed sagebrush seeds in the soil was correlated with seed production only when many seeds were produced (r=0.76), indicating that annual seed production is of limited importance for maintaining a seedbank. A persistent seedbank is important in maintaining fringed sagebrush populations when seed production is limited. Diverse rates and times of seed rain along with a persistent seedbank may enable fringed sagebrush to occupy safe sites that develop in time.

Knowing that sheep or goats can be used to control brush we quantified pasture changes during and after brush control. Over an 8-year period we measured the effects of control (no soil amendment), medium soil amendment (4,500 kg lime and 40 kg P ha-1), and high soil amendment (9,000 kg lime and 117 kg P ha-1) on soil fertility, pasture botanical composition and production of brushy pasture grazed by sheep or goats. Botanical composition was estimated from clipped samples. Soil pH was 4.8 in the control, 6.5 in the medium and 7.0 in the high amendment plots. Medium and high amendment increased legume dry matter in the pasture from 2 in the check to 8%. More animal grazing days were obtained on paddocks treated with lime and P. Grazing with sheep or goats and lime and application of P resulted, after 4 years, in pastures with a grass, legume, and other broadleaf plant composition similar to that of brush-free, natural pasture.

Assessing nutritive value of key grass species in relation to plant development is essential for producers to efficiently manage livestock enterprises. Changes in nutritive value for tiller populations of 2 common Nebraska Sandhills grasses, prairie sandreed [Calamovilfa longifolia (Hook.) Scribn.] and sand bluestem [Andropogon gerardii var. paucipilus (Nash) Fern], in response to morphological development was evaluated at the Gudmundsen Sandhills Laboratory (GSL) during the 1990 and 1991 growing seasons. Morphological development was determined on a 40 to 60-tiller sample from each block (12 blocks in 1990 and 8 blocks in 1991) at ten-day intervals using a comprehensive staging system. In vitro dry matter digestibility (IVDMD), crude protein (CP), neutral detergent fiber (NDF) and lignin were determined for leaves and correlated with the morphological index (Mean Stage by Count), growing degree days and day of the year. Leaf NDF values of both species remained constant while leaf IVDMD declined throughout the summer indicating that decline in leaf IVDMD was caused by declining cell wall digestibility. Leaf IVDMD was influenced more by tissue aging than advancing morphological stage. Leaf CP was significantly different between years but not between species indicating leaf CP was largely influenced by environmental factors. In both species and for both years, leaf CP initially declined rapidly to low levels and then stabilized during the vegetative phase. Nutritive value of a single vegetative morphological stage over the growing season was similar to the leaf tissue of the tiller populations. Management decisions by producers depend on accurate assessment of changes in nutritive value during the growing season in tiller populations of these 2 important grasses.

Tolerance to freezing temperatures may be an important factor in the regeneration ecology of winterfat (Ceratoides lanata (Pursh) J.T. Howell). Therefore, growth and freezing tolerance of winterfat seedlings were determined after being grown under different controlled temperatures for 7, 14, 21, or 28 days. Growth of seedlings was greater under day temperatures of 15 and 20 degrees C relative to 5 and 10 degrees C. Freezing tolerance of seedlings was dependent on seedling age and growth conditions. Younger seedlings were more freezing tolerant than older ones grown under the same environmental conditions. Seedlings grown under lower temperatures were more freezing tolerant than those grown under higher temperatures. The lowest observed lethal temperature for 50% mortality (LT50) was -11.8 degrees C for 7-day old seedlings grown under 10/0 degrees C alternating temperatures, and the highest LT50 was about -5 degrees C for seedlings 28 days of age when grown under 29/1 degrees C. Based on seedbed temperatures in the field, the results suggest that freezing temperatures may indeed limit the establishment of winterfat seedlings on Northern Mixed Prairie. Seedbeds with litter accumulations or standing dead plant material may ameliorate low temperature extremes and reduce mortality of winterfat seedlings.

Defoliation effects on grasses have been quantified with measurements of etiolated growth since the 1960's, however, field techniques for measuring etiolated growth of rhizomatous grasses with dispersed tillers have not been reported. Tents constructed with landscape fabric were used in a field study of 2 species of rhizomatous grass. When manufactured, the woven polypropylene fabric is needle punched for air and water permeability. Light that may pass through perforations has no measurable effect on etiolated growth as indicated by a test of single and double layers of fabric. Tents can be sized to shade borders around interior sample areas to prevent translocation from outside tillers to harvested tillers. Landscape fabric tents are light weight and reusable and eliminate breakage, water vapor, and storage problems associated with other covers.

Seed dormancy can hinder stand establishment and delay progress of genetic and plant improvement studies. Our objective was to evaluate the effect of 2 chemical seed treatments on germination and on emergence and survival of 3 warm-season grasses. Freshly harvested seed of kleingrass (Panicum coloratum L.) weeping lovegrass [Eragrostis curvula (Schrad.) Nees] and wilman lovegrass (Eragrostis superba Peyr.) were treated with concentrated H2SO4 or a 2-chloroethanol sodium hypochlorite (CHL) solution and then germinated on blotters or planted in a commercial peat-vermiculite mix. The 3 grasses responded differently to acid and CHL treatment. Acid treatment increased germination of all 3 species but did not increase the emergence and/or 2 week establishment of weeping or wilman lovegrass. The difference between germination and emergence appeared related to chemical injury from the acid treatment that adversely impacted seedling growth and development. Weeping lovegrass responded to CHL treatment with increased germination and emergence. Wilman lovegrass did not respond well to either chemical.

A four-year study was conducted to investigate effects of continuous and short duration grazing in spring on standing crop and tiller density of crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult], along with changes in cover and density of Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle and Young) and green rabbitbrush [Chrysothamnus viscidiflorus (Hook.) Nutt.]. Eight pastures were each stocked with 10 steers (224 kg) beginning in early May. Four grazing treatments consisted of continuous grazing at 0.6 AUM/ha (CONT) or short duration grazing management at 0.6, 0.9, and 1.2 AUM/ha for LOW, MED, and HIGH treatments, respectively. After 4 years, mean tiller density was greatest on LOW paddocks (P = 0.10) (707 tillers/m2). Tiller density on HIGH paddocks did not differ (P > 0.05) from CONT. Density of large (> 15-cm tall) Wyoming big sagebrush increased (P less than or equal to 0.05) across years, but did not vary (P > 0.05) among treatments, at about 9 plants/100 m2. Sagebrush plants < 15-cm tall responded differently (P = 0.02) in CONT compared to HIGH. Small sagebrush density increased under short duration grazing at doubled stocking rate (HIGH) compared to CONT, but LOW and MED did not differ from CONT. We concluded that short duration rotation grazing at a conventional stocking rate decreased neither tillering nor yield of crested wheatgrass. Shrub density and cover changes on LOW were similar to CONT. It does appear, however, that short duration grazing at the doubled stocking rate has the potential to limit crested wheatgrass productivity over time because of enhanced sagebrush seedling survival.

Runoff and sediment yield were evaluated on a sandplain dominated by woody perennial shrubs in north-western NSW, Australia. The site was bladeploughed; and some plots were grazed by sheep and cattle and others exclosed from grazing. Two years after ploughing and exclosure, grazed plots had significantly lower levels of aggregate stability and organic carbon compared with ungrazed plots, but there was no effect of ploughing. Surface pH levels were significantly greater on unploughed plots compared with ploughed plots. Two years after treatment, runoff and sediment yield were greatest on plots with the least disturbance (unploughed and ungrazed) and least on sites with the greatest disturbance (ploughed and grazed). We attribute differences in soil hydrology to the development of a thin physical soil crust on the unploughed-ungrazed plots, which restricted infiltration. On the ungrazed plots, increases in plant cover and biomass, and colonisation of the physical crust by biological elements, are hypothesised to lead to reduced runoff and sediment yield over time.