• Above-Ground Net Primary Production for Elymus lanceolatus and Hesperostipa curtiseta After a Single Defoliation Event

      Pantel, A.; Romo, J. T.; Bai, Y. (Society for Range Management, 2011-05-01)
      Above-ground net primary production (ANPP) of northern wheatgrass (Elymus lanceolatus [Scribn. J. G. Sm.] Gould) and western porcupine grass (Hesperostipa curtiseta [Hitchc.] Barkworth) was determined after defoliation to a 7.5 cm stubble height on five landform elements in the Northern Mixed Prairie that had been ungrazed for >25 yr. Landform elements included north aspect-concave slopes, north aspect-convex slopes, south aspect-concave slopes, south aspect-convex slopes, and level uplands. ANPP was determined for 2 yr after defoliating plots once in May, June, July, August, September, October, November, or April. Northern wheatgrass and western porcupine grass ANPP varied among landform elements (P < 0.01), but not with the month of defoliation 3 landform element interaction (P > 0.22). Month of defoliation did not influence ANPP of northern wheatgrass (P>0.69), but that of western porcupine grass was reduced by August and September defoliations (P < 0.01). ANPP of both grasses was insensitive to landform element in terms of defoliation responses. Northern wheatgrass ANPP was not responsive to temporal aspects of a single defoliation. With the exception of August and September defoliations, western porcupine grass also was insensitive to a single defoliation in different months. Land managers should consider rest (1 yr nongrazing) following grazing of western porcupine grass in August or September, whereas responses to defoliation in different months suggest northern wheatgrass can be grazed annually.
    • Developmental stages of winterfat germinants related to survival after freezing

      Bai, Y.; Booth, D. T.; Romo, J. T. (Society for Range Management, 1998-11-01)
      Diaspores of winterfat (Eurotia lanata (Pursh) Moq.) collected from 2 locations in the USA and 1 in Canada were imbibed at 10 degree C and grown to 4 different developmental stages (2, 3, 6, and 14 days of incubation), then subjected to cooling temperatures as low as -30 degree C. Differential thermal analysis was used to detect exotherms associated with ice crystal formation in germinants. The temperature at which exotherms occurred was recorded, and the subsequent growth and mortality of germinants were determined. Only 1 exotherm was observed, and that occurred in the low-temperature exotherm range (usually < -10 degree C). Changes in the freezing tolerance of germinants from seed to seedling was a gradual process as indicated by increases in exothermic temperature and mortality with increasing developmental stage. Whether the exotherm indicated a lethal event depended on the developmental stage of the germinant. Germinant survival was also affected by cooling below the exotherm temperature.
    • Early establishment of Douglas-fir and ponderosa pine in grassland seedbeds

      Bai, Y.; Thompson, D.; Broersma, K. (Society for Range Management, 2000-09-01)
      Grassland of interior British Columbia are being encroached upon by Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) and ponderosa pine (Pinus ponderosa Dougl.). A pot experiment placed in the field was conducted to determine the effect of forest and grassland seedbeds on seedling emergence and early establishment of the 2 species with 2 seed collections each. For these seedbeds, structural characteristics were evaluated and the effect of seedbeds water extracts on seed germination was determined. Seedling emergence of both species was significantly reduced by Douglas-fir needles and enhanced by fescue litter and cattle manure compared to mineral soil. The rate of emergence was reduced by Douglas-fir needles and sagebrush litter, and for some collections, by ponderosa pine needles, but was always enhanced by manure compared to mineral soil. Seedling survival was generally not affected by seedbeds. Douglas-fir seedlings emerging earlier in the season survived better, and both Douglas-fir and ponderosa pine seedlings emerging earlier lived longer than these emerging later. Seed germination of ponderosa pine was not affected by the water extract while that of Douglas-fir was reduced by the water extract from sagebrush litter. Therefore, differences in seedling emergence of the 2 species among seedbeds were related more to structural than to chemical characteristics of seedbeds. Successful establishment of the 2 species in grasslands within this region likely relies on the ability of seeds to germinate early in the growing season on seedbeds in which soil moisture is conserved, as summer droughts are severe.
    • Effect of seed moisture on Wyoming big sagebrush seed quality

      Bai, Y.; Booth, D. T.; Roos, E. E. (Society for Range Management, 1997-07-01)
      Seed germination and seedling vigor of Wyoming big sagebrush (Artemesia tridentata Nutt. ssp. wyomingensis) were evaluated following manipulation of seed moisture, a practice benefitting many species. At the time of harvest, seed moisture ranged from 2.3 to 9.0% for 5 collections tested and seeds with moisture between 5 to 6% had the highest and most rapid germination. Seed moisture changed during storage, but germination percentage was not affected by post-harvest seed moisture change, indicating that germination is related more to habitat or genetic variations than the initial moisture content. Seedling vigor increased after storage, suggesting that after-ripening may be required. Seeds of 2 commercial collections were subsequently humidified at 2, 5, 10, and 15 degrees C for up to 15 days, or to 60% moisture content. Seed moisture increased most gradually at 2 degrees C and seeds held at 10 degrees C attained a higher moisture level than at other temperatures. Germination percentage, germination rate, and seedling vigor were similar between treatments and controls regardless of seed moisture change. Imbibition temperature did not affect germination percentage or seedling vigor, but the time to 50% germination decreased with increasing imbibition temperature. We conclude that artificial seed moisture management did not affect germination percentage, germination rate, or seedling vigor of this species when tested under optimum moisture conditions. Germination is more related to habitat or genetic variables than initial seed moisture content.
    • Imbibition temperature affects winterfat (Eurotia lanata (Pursh) Moq.) seed hydration and cold-hardiness response

      Bai, Y.; Booth, D. T.; Romo, J. T. (Society for Range Management, 1999-05-01)
      Winterfat (Eurotia lanata (Pursh) Moq.) diaspores harvested from 1 Canadian and 2 USA sites were imbibed at 0, 5, 10, and 20 degrees C. It was hypothesized that imbibition temperature affects seed hydration which is related to cold-hardiness of winterfat. Weight gain was measured at 8-hour intervals until full hydration, and embryo water content was determined. Water content of fully hydrated seeds differed among collections and lower imbibition temperatures were always associated with greater seed water content. Differences in water content of seeds imbibed at different temperatures was related to cold-hardiness. When water content of embryos was measured, differences among imbibition temperatures existed, but were reduced. Differences in seed water content among imbibition temperatures were mainly due to endosperm other than the embryo because the embryo hydrated faster than other seed parts. Suggestions were made for modeling seed water relations based on this study.
    • Pericarp removal has little effect on sagebrush seeds

      Bai, Y.; Hardegree, S. P.; Booth, D. T.; Roos, E. E. (Society for Range Management, 1999-07-01)
      Sagebrush (Artemisia) is commonly recommended for reclamation and restoration of shrublands of the Western United States and seeds are usually obtained from commercial sources. One result of commercial seed processing is the removal of the pericarp. We tested 2 seedlots of Wyoming big sagebrush (A. tridentata Nutt. ssp. wyomingensis Beetle &Young) to determine if pericarp removal affected properties of seed hydration or seed germ inability under different levels of water stress. In general, pericarp removal had a relatively minor effect on these processes and properties.
    • Preparing sagebrush seed for market: Effects of debearder processing

      Booth, D. T.; Bai, Y.; Roos, E. E. (Society for Range Management, 1997-01-01)
      Debearders are machines originally developed to remove grain from bearded (awned) seed heads of small grains. They are now used in many types of seed cleaning, including preparing sagebrush seed for market. Some people have suggested that debearders may decrease sagebrush seed quality. We tested this hypothesis by using a debearder to process seeds of Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis) and measuring subsequent seed quality. Seed stalks were cut from 2 Wyoming locations, stored in an unheated warehouse, and then processed with a debearder for 2, 4, 6, 8, or 10 min. Seed germination and seedling vigor were tested at 2-month intervals up to 16.5 months after processing. Temperature and relative humidity inside the debearder increased linearly from 14.0 to 22.4 degrees C and from 59.0 to 81.2 % during the 10-min. processing time. However, the moisture content of seed materials did not change during this period. The number of undamaged seeds per gram of material did not change with processing and was similar between collections. Stem length decreased with processing duration while percent of seed with pericarp removed increased. Germination percentage, time to 50 % germination (T50) and seedling vigor were similar among treatments in both collections. Germination percentage increased in the first 4.5 months after processing and then remained at that level up to 16.5 months. Germination rate decreased (T50 increased), but seedling vigor did not change with storage time. We recommend that seed dealers continue to use properly adjusted debearders to process sagebrush seed.
    • Relationship between plant species diversity and grassland condition

      Bai, Y.; Abouguendia, Z.; Redmann, R. E. (Society for Range Management, 2001-03-01)
      Although the maintenance of biodiversity has become one of the goals in ecosystem management, the relationships of diversity to ecosystem characteristics such as level of herbivory, productivity, and vegetation structure are still poorly understood. We examined these relationships in 8 native grassland sites differing in grazing histories and range condition in the Mixed Grassland (6), Moist Mixed Grassland (1) and Aspen Parkland (1) ecoregions of southern Saskatchewan. Range condition, assessed using standard methods, ranged from fair to excellent. The Shannon's diversity index followed a curvi-linear relationship with range condition, increasing from fair to good, but decreasing from good to excellent condition, within a range between 0.66 and 2.58. Species evenness was affected by range condition in a similar manner ranging from 0.44 to 0.86. Species richness varied among sites and plots between 4 and 28 plants 0.25 m(-2), but changed little with range condition. Most structural parameters, such as the cover, height, or thickness of standing plants (live or dead) and litter, increased with range condition especially from good to excellent. The Shannon's diversity index was positively correlated with forb biomass, but not with biomass of any other group or their combination. Grazing regimes that maintain good range condition also maintain species and structural diversity of grasslands.
    • Responses of winterfat seeds and seedlings to desiccation

      Hou, J. Q.; Romo, J. T.; Bai, Y.; Booth, D. T. (Society for Range Management, 1999-07-01)
      Winterfat [Krascheninnikovia lanata (Gueldenstaedt) syn. Ceratoides lanata (Pursh) J.T. Howell, syn. Eurotia lanata (Pursh) Moq.] is a native shrub of mixed prairie of North America. A large portion of hydrated seeds and seedlings can be killed when exposed to seedbed desiccation. Winterfat seeds and young seedlings subjected to varying levels of desiccation were studied to measure the influence of this stress. Germination was unaffected (P > 0.05) when seeds were exposed for 0 to 10 hydration-desiccation cycles (2 hours hydration and 22 hours desiccation cycle(-1) at 20 to 30% relative humidity and 20 degrees C). Linear increases in germination rate (0.6% day(-1) hydration-desiccation cycle(-1)), seedling length (0.1 mm hydration-desiccation cycle(-1)), and seed decay (1.5% hydration-desiccation cycle(-1) occurred with an increasing number of hydration-desiccation cycles. Seedling survival following desiccation decreased 10.4% mm(-1) as seedling length increased from < 2 mm to 10-15 mm. Seedling survival was positively correlated with relative humidity and negatively correlated with duration of desiccation. The difference (P < or = 0.05) in survival between 0 and 90% relative humidity was 62% for seedlings 4-6-mm in length and 70% for seedlings 9-11-mm in length. Seedlings from seeds that germinated rapidly were more tolerant of desiccation than those from seeds germinating slowly. After desiccation in 30% relative humidity, survival of seedlings from seeds germinating on the first day of incubation was 40% greater than those from seeds germinating on the third day of incubation. Electrolyte leakage indicated that desiccation damaged cells. Establishment of winterfat seedlings will be favored by seedbed conditions that protect seedlings from severe and prolonged desiccation and allow fast entry of the radicle into soil.
    • Seed bank and plant community composition, Mixed Prairie of Saskatchewan

      Romo, J. T.; Bai, Y. (Society for Range Management, 2004-05-01)
      Many range managers have suggested that clubmoss (Selaginella densa Rydb.) negatively alters the composition of seed banks and inhibits the establishment of plant species that decrease under improper grazing management. Alternatively it is possible that soil seed banks contain few seeds of decreaser species and composition of the seed bank is independent of clubmoss. The purpose of this study was to determine the composition and diversity of the soil seed bank in relation to the clubmoss cover and compositional characteristics of plant communities in the Northern Mixed Prairie of southwestern Saskatchewan. Cover of vascular plants was determined and soil seed bank samples were collected in 100 grazed plant communities. Soil seed bank samples were incubated in the laboratory with emerging seedlings being identified to species. Eight percent (SE ± 1.9) of emerging seedlings in the seed bank were decreasers, 73% (SE ± 2.8) were increasers, and 19% (SE ± 2.3) were invaders, indicating regeneration of decreaser species might be limited by low numbers of seeds in seed banks. Clubmoss cover was not correlated (P = 0.32 to 0.98) with species richness, species diversity, density of decreasers, density of increasers, density of invaders, and total seedling densities in the seed banks. Seed banks and plant communities shared few species as indicated by a low similarity index (x̄ = 0.31, SE ± 0.02). Species richness (x̄ = 3.6 species per 102 cm2, SE ± 0.18) and diversity (x̄ = 1.00, SE ± 0.05) of seed banks were poorly correlated with characteristics of the plant communities. Range condition score was positively correlated (r = 0.17, P = 0.09) with total seedling densities in the soil seed bank, indicating more seedlings can potentially develop from the seed bank with increasing range condition of plant communities. We reject the hypothesis that clubmoss negatively affects the composition of seed banks. Mechanically disturbing plant communities to control clubmoss is predicted to lead to plant communities that are dominated by increasers and/or invaders. Managing for production of seeds by desired species should be a priority in promoting establishment of desired species.
    • Seed production, seed rain, and the seedbank of fringed sagebrush

      Bai, Y.; Romo, J. T. (Society for Range Management, 1997-03-01)
      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.
    • Technical Note: Measuring moisture content of small seeds

      Booth, D. T.; Bai, Y. (Society for Range Management, 1998-03-01)
      An accurate determination of moisture content in hydrated or partially hydrated seeds is fundamental to understanding early physiological processes in seeds, and the associated environmental interactions that affect seedling vigor, establishment, and survival. One difficulty encountered while measuring the moisture content of imbibed seeds is that water evaporates from the seed during weighing. This is particularly significant for small seeds because they have a large surface area to volume ratio. We developed a procedure using a standard tin capsule and microbalance which was simple, inexpensive, facilitated precise measurement of moisture in hydrated seeds, and provided reliable results with a minimal amount of seeds. The method is recommended as a means for increasing the accuracy of seed weight and seed moisture measurements.
    • Wyoming big sagebrush seed production from mined and unmined rangelands

      Booth, D. T.; Bai, Y.; Roos, E. E. (Society for Range Management, 2003-09-01)
      Wyoming Coal Rules and Regulations require shrubs be returned to mined land and that revegetation "...be self renewing." We evaluated seed production and seed quality of Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis (Beetle Young)) by measuring the effect of mining, herbivory, and environmental modification on seed production at 5 sites on the Dave Johnston Coal Mine near Glenrock, Wyo. Mined-land stands ranged in age from 5 to >20 years. Single sagebrush plants on mined, and adjacent unmined land were treated by: (1) fabric mulch around the base, (2) windbreak on the north and west, (3) both mulch and windbreak, and (4) neither windbreak nor mulch. Plants were fenced and compared with unfenced, untreated, neighboring plants. Seeds were harvested for 3 years and data were collected on seed-stalk numbers, bulk weight of seeds produced, and seed quality. Fenced mined-land plants produced several times more seeds than fenced plants on adjacent unmined land. There was no difference in seed quality. Treatments to modify the plant environment resulted in some benefits but fencing had a greater effect on seed-quality parameters than did planned treatments. We conclude the sagebrush seed-production potential on reclaimed lands such as those of the Dave Johnston Coal Mine is equal to, and often several times greater than that of adjacent unmined lands. However, browsing by wild ungulates can eliminate the mined-land yield advantage.