Photosynthesis and Water Relations of Two Savanna Grasses as Influenced by Shade and Water Stress

Net CO2 assimilation and plant water relations of the African savanna grasses Panicum maximum Jacq. and Tliemeda triandra Porrsk. were measured under controlled conditions. We hypothesised that 1; triandra would be better adapted to higher light and temperature conditions and could withstand greater moisture stress than could P. maximum, as T. tria11dra is commonly found in open areas, whereas P. maximum dominates in the shade of trees. Plants of both species were transplanted into a common soil in large pots and placed under shade (approximately 150 µrnoVm1/s photon flux density (PFD)) or high light (approximately 1200 µmoVm1/s PFD) conditions, with either no imposed drought or periodic drought. Both species responded similarly to stressors of shade and drought. Few significant interactions between species ·and light regime or species and water regime were found, Species responded similarly if grown together or in a monoculture. Therefore, this study did not indicate competitive reactions or ecophysiological reasons why P. maximum should dominate shady habitats, and T. triandra should dominate open grasslands

Influence of Climate on Annual Production of Seven Cold Desert Forage Species

Stepwise regression analyses were used to examine the relationships between annual production of seven cold desert forage species and climate variables at different periods of the year. No significant regressions were found for production of Artemisia arbuscula var. nova, Oryzopsis hymenoides, or Sitanion hystrix with precipitation and temperature. For Artemisia tridentata, Atriplex confertifolia, Ceratoides lanata, and Atriples gardeneri, significant (p<.05) regressions were found between annual production and precipitation during the spring months. For Artemisia tridentata and Atriplex confertifolia, mean monthly temperature in March and April also appeared in the equations. Multiple regression was used to test the null hypothesis that the amount of variation in annual production explained by winter (November-February) or spring (March-June) precipitation was equal to zero. No significant (p<.05) linear relationship was found between winter precipitation and production, whereas such a relationship appeared more likely for spring precipitation and production of Artemixia tridentata, Ceratoides lanata, and Atriplex gardeneri.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Elevated CO\u3csub\u3e2\u3c/sub\u3e further lengthens growing season under warming conditions

Observations of a longer growing season through earlier plant growth in temperate to polar regions have been thought to be a response to climate warming. However, data from experimental warming studies indicate that many species that initiate leaf growth and flowering earlier also reach seed maturation and senesce earlier, shortening their active and reproductive periods. A conceptual model to explain this apparent contradiction, and an analysis of the effect of elevated CO2—which can delay annual life cycle events—on changing season length, have not been tested. Here we show that experimental warming in a temperate grassland led to a longer growing season through earlier leaf emergence by the first species to leaf, often a grass, and constant or delayed senescence by other species that were the last to senesce, supporting the conceptual model. Elevated CO2 further extended growing, but not reproductive, season length in the warmed grassland by conserving water, which enabled most species to remain active longer. Our results suggest that a longer growing season, especially in years or biomes where water is a limiting factor, is not due to warming alone, but also to higher atmospheric CO2 concentrations that extend the active period of plant annual life cycles

The effects of seasons and directions of burning on the native vegetation of the Texas High Plains

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Multiple Defoliation Effects on Herbage Yield, Vigor, and Total Nonstructural Carbohydrates of Five Range Species

Western wheatgrass (Agropyron smithii), blue grama (Bouteloua gracilis), and fourwing saltbush (Atriplex canescens) were subjected to multiple defoliations at moderate and heavy intensities during a 2-year period. Most heavy defoliation treatments drastically reduced herbage yield, vigor, and total nonstructural carbohydrates (TNC) of western wheatgrass. Multiple defoliations were detrimental to vigor and herbage yield of blue grama; however, defoliation treatments did not detrimentally affect root TNC levels. All defoliation treatments severely reduced the number of seedstalks, live crown cover, and TNC of fourwing saltbush, but seedstalk length and live crown diameter were less affected by the defoliation treatments. Both fringed sagewort (Artemisia frigida) and antelope bitterbrush (Purshia tridentata) subjected to two moderate defoliations during quiescence and rapid growth (or flowers developing) remained in fair to good vigor at the end of the growing season. However, both species were detrimentally affected if utilized during the later part of the growing season. Defoliation effects were generally more severe when plants were defoliated at a heavy intensity than when defoliated at a moderate intensity during the same phenological stages. Five- and six-pasture rest-rotation grazing systems were proposed to ensure that grazed plants would receive rest following critical late summer foliage utilization.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Effects of Fire on Grasses of the Texas High Plains

Fall, spring, and summer burning significantly reduced total forage production on a Texas High Plains range. Although herbage yields were less on burned plots, the vigor of the desirable blue grama (Bouteloua gracilis Willd. ex HBK) appeared to be benefited by fires while the vigor of two less desirable grasses appeared to be decreased. Spring burning is recommended over fall burning when moisture accumulation and erosion potential are considered. Recovery from fire was quickest after a summer burn.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Carbohydrate Reserve, Phenology, and Growth Cycles of Nine Colorado Range Species

Nine Colorado range species were studied for two consecutive years to relate the carbohydrate reserve status with phenological stage of development and current annual growth, including leaf, twig, or seedstalk length, or plant height. The species were four-wing saltbush (Atriplex canescens), antelope bitterbrush (Purshia tridentata), little rabbitbrush (Chrysothamnus vicidiflorus), fringed sagewort (Artemisia frigida), scarlet globemallow (Sphaeralcea coccinea), blue grama (Bouteloua gracilis), western wheatgrass (Agropyron smithii), James' cryptantha (Cryptantha jamesii), and pricklypear cactus (Opuntia polyacantha and rhodantha in a mixed stand). Seasonal total nonstructural carbohydrate (TNC) reserve cycles were related to phenological stages of development. Growth of all species appeared to be stimulated by late-summer or fall precipitation. Growth was found to be related inversely to carbohydrate reserve storage. Fourwing saltbush and antelope bitterbrush had typical V-shaped annual carbohydrate reserve cycles, and little rabbitbrush had a somewhat flat or extended V-shaped cycle. Fringed sagewort, scarlet globemallow, and western wheatgrass had flat or extended V-shaped cycles and maintained low reserves for more of the growing season than any of the species with typical reserve cycles. Blue grama was the only species that exhibited a narrow V-shaped cycle. The shape of the seasonal TNC cycle appeared to be a good screening tool for assessing the relative effects of defoliation on different plant species. Plants that replenished reserves rapidly after spring draw-down and regrowth periods, and minimized the part of the growing season with low reserve status, were least affected by defoliation and recovered rapidly from severe defoliation.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Effects of Single and Sequential Defoliations on the Carbohydrate Reserves of Four Range Species

Four range species, fourwing saltbush (Atriplex canescens), antelope bitterbrush (Purshia tridentata), scarlet globemallow (Sphaeralcea coccinea), and blue grama (Bouteloua gracilis) were defoliated heavily (removing 90% of the foliage) at 1 of 5 phenological stages. In addition, other plants were clipped from 1 to 6 times at 3 phenological stages over a 2-year period. Total nonstructural carbohydrate (TNC) reserves of fourwing saltbush and antelope bitterbrush were most sensitive to a single defoliation at the seed-shatter phenological stage. Blue grama was affected most at the rapid growth stage, whereas scarlet globemallow was not significantly affected by any of the single defoliations. A single defoliation proved adequate for determination of the most sensitive season for defoliation. Antelope bitterbrush was affected more by 6 successive intense defoliations than were the other 3 species: scarlet globemallow < blue grama < fourwing saltbush. TNC reserve cycles were severely dampened in antelope bitterbrush, and less so in fourwing saltbush.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Carbohydrate Reserves of Crested Wheatgrass and Russian Wildrye as Influenced by Development and Defoliation

Carbohydrate reserves of crested wheatgrass (Agropyron cristatum) and Russian wildrye (Elymus junceus) were lowest after initial spring growth, but maximum levels were rapidly attained as plants approached maturity. Fall regrowth caused reductions in total available carbohydrate (TAC) stores. More TAC reserves were used to produce new growth if plants were defoliated during spring growth than if defoliated at maturity or quiescence. Autumn TAC storage levels in both crested wheatgrass and Russian wildrye were reduced by all previous defoliations. Autumn reserve storage was directly related to the amount of new growth produced after defoliation. Results indicate that both crested wheatgrass and Russian wildrye are adapted for either fall or early spring grazing and under some circumstances for spring-fall use. Defoliation when plants are rapidly replenishing reserves or before maturity reduces subsequent new growth and carbohydrate reserve stores in the autumn.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Mixtures of Bottom Ash and Soil as a Growth Medium for Three Range Species

Bottom ash from a coal-fired power plant was mixed with soil in varying proportions to determine its effects on germination, growth, and survival of blue grama (Bouteloua gracilis (H.B.K.) Lag. ex Steud.), western wheatgrass (Agropyron smithii Rydb.), and fourwing saltbush (Atriplex canescens (Pursh) Nutt.). Five ash-soil growth mediums were developed, ranging from 100% ash-0% soil to 0% ash-100% soil (control). Bottom ash had no significant effect on the percentage germination of western wheatgrass and fourwing saltbush, but germination of blue grama seeds was reduced by the 100% ash-0% soil treatment. Percentage survival of all three species was not significantly affected by any of the ash-soil treatments. The treatments did, however, exert a significant effect on height growth of all three species. Plant height usually increased as the proportion of soil in the mixtures was increased. In addition, control plants produced significantly more biomass than did plants growing in any of the ash-soil treatments. Some of the physical and chemical properties of the bottom ash may account for its deleterious effects on the growth of these three species. High pH, lack of adequate plant nutrients such as nitrates and potassium, and unfavorable structural characteristics of the bottom ash may have caused reductions in plant growth.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202