Impact of Native Grasses and Cheatgrass (Bromus tectorum) on Great Basin Forb Seedling Growth

Re-establishing native communities that resist exotic weed invasion and provide diverse habitat for wildlife are high priorities for restoration in sagebrush ecosystems. Native forbs are an important component of healthy rangelands in this system, but they are rarely included in seedings. Understanding competitive interactions between forb and grass seedlings is required to devise seeding strategies that can enhance establishment of diverse native species assemblages in degraded sagebrush communities. We conducted a greenhouse experiment to examine seedling biomass and relative growth rate of common native forb species when grown alone or in the presence of a native bunchgrass or an exotic annual grass. Forb species included bigseed biscuitroot (Lomatium macrocarpum [Nutt. ex Torr. & A. Gray] J.M. Coult. & Rose), sulphur-flower buckwheat (Eriogonum umbellatum Torr.), hoary aster (Machaeranthera canescens [Pursh] Gray), royal penstemon (Penstemon speciosus Douglas ex Lindl.), and Munro's globemallow (Sphaeralcea munroana [Douglas ex Lindl.] Spach ex Gray); and neighboring grass species included bottlebrush squirreltail (Elymus elymoides [Raf.] Swezey), Sandberg bluegrass (Poa secunda J. Presl); and cheatgrass (Bromus tectorum L.). Forbs and grasses were harvested after 6, 9, or 12 wk of growth for biomass determination and calculation of relative growth rates (RGR) of forbs. Neither bunchgrass reduced biomass of any forb. RGR was reduced for royal penstemon when grown with either native grass and for Munro's globemallow when grown with bottlebrush squirreltail. Although only assessed qualitatively, forbs with vertically oriented root morphologies exhibited no reduction in RGR when grown with native grasses, compared to forbs with dense lateral branching, similar to the root morphology of native grasses. Biomass of forbs was reduced by 50% to 91% and RGR by 37% to 80% when grown with cheatgrass. Understanding native forb interactions with native grasses and cheatgrass will aid land managers in selecting effective seed mixes and making better use of costly seed.     

Immature Seedling Growth of Two North American Native Perennial Bunchgrasses and the Invasive Grass Bromus tectorum

Pseudoroegneria spicata (Pursh) A. Löve and Elymus wawawaiensis J. Carlson & Barkworth are two native perennial grasses widely used for restoration in the Intermountain West. However, the rapid establishment and spread of Bromus tectorum L., an invasive annual grass, has led to a decline in the abundance of native perennial grasses. Proliferation of B. tectorum has been attributed to its early germination, superior cold-temperature growth, profuse root production, and high specific leaf area (SLA). To enhance restoration success, we compared B. tectorum to commercially available plant materials of two perennial rangeland bunchgrasses, P. spicata (cv. Whitmar, cv. Goldar, and Anatone Germplasm) and E. wawawaiensis (cv. Secar), for germination, seedling morphological traits, and growth rates at the immature seedling stage. We monitored germination and immature seedling growth in a growth chamber in two separate experiments, one under low (5/10°C) and the other under high (15/20°C) day/night temperatures. Compared to the average of the two perennials, B. tectorum was 93% (77%) greater at high (and low) temperature for root∶shoot length ratio, but only 14% (14%) greater for root∶shoot biomass ratio and 12% (19%) lower for SLA. This suggests that B. tectorum’s substantial investment in surface area of roots, rather than in shoot length, root biomass, or leaf area, may be responsible for the annual’s success at the early seedling stage. Compared to E. wawawaiensis, P. spicata averaged 65% (41%) higher shoot biomass, 39% (88%) higher root biomass, and 70% (10%) higher absolute growth rate, but 25% (15%) lower SLA and 15% (36%) lower specific root length (SRL) at high (and low) temperatures, respectively. Although P. spicata’s greater productivity may initially make for better seedling establishment than E. wawawaiensis, it may also prove disadvantageous in competitive or highly resource-limited environments where high SLA or SRL could be an advantage.     

Factors Affecting Bromus Tectorum Seed Bank Carryover in Western Utah

Cheatgrass (Bromus tectorum L.) is a winter annual weed that presents a serious obstacle to rangeland restoration in the Intermountain West. The objective of this study was to evaluate factors regulating the size and persistence of cheatgrass carryover seed banks on semiarid sites in western Utah. We prevented current-year seed production in each of four habitats, then tallied emerging seedlings over the next 44 yr. Twoyr. Two iterations of the study were conducted during consecutive years. One year before initiation of each iteration, we estimated seed rain at each site. Above-average precipitation in 1998–1999 resulted in relatively high seed rain (13942 seeds·m⁻²) for the first iteration, whereas seed rain for the second iteration averaged only 3567·m⁻² because of drought conditions in 1999–2000. Mean total number of seedlings emerging from carryover seeds for the first and second iterations were 1304 and 270 seedlings·m⁻². Seedling emergence from carryover seed was positively correlated with production-year seed rain (R² = 0.69). The fraction of seed rain that carried over tended to be lower when precipitation the year following production favored fall emergence of the transient seed bank. First-year emergence of carryover seeds averaged 96% of total emergence, whereas third-year emergence averaged < 1% and was zero for six of eight cases. Carryover seeds persisted somewhat longer at the xeric black greasewood site than at more upland sites. Our study shows that cheatgrass seeds rarely persist beyond the second carryover year even on semiarid sites. Emergence from the carryover seed bank can be predicted from site attributes and precipitation patterns in previous years.     

Nutrient Availability in Rangeland Soils: Influence of Prescribed Burning,Herbaceous Vegetation Removal,Overseeding with Bromus Tectorum,Season, and Elevation

Soil nutrient availability influences plant invasions. Resin capsules were used to examine soil nutrient bioavailability along 2 sagebrush–grassland elevation transects in the east Tintic Range (Utah) and Shoshone Range (Nevada). In the fall of 2001, treatments were applied to 3 replicate plots at each site, which included prescribed burning, herbaceous vegetation removal, and controls. Cheatgrass (Bromus tectorum L.) was overseeded in small subplots within each treatment. Following treatments in each plot, resin capsules were installed at 15-cm depth in a shrub interspace and a B. tectorum–overseeded area. Nutrient availability was integrated during late fall to spring and spring to late fall for 2 years. Herbaceous vegetation removal increased availability of nitrate (Nevada and Utah) and Ca and Mg (Nevada only) but only during the second sampling period (growing season). Availability of K and ortho-P (Nevada and Utah) and nitrate (Nevada only) was greater on prescribed burned plots. For Utah, availability of ortho-P, K, Ca, Mg, and Fe generally increased with increasing elevation. Availability of Ca, Mg, K, and Fe was greatest during late fall to spring integration periods for Nevada. Overseeding with B. tectorum interacted with the burn treatment to influence availability of Ca, Mg, and Fe (Nevada sites only). Patterns of nutrient availability can be explained by a combination of decreased root uptake in relation to mineralization, differences in soil water content with season and elevation, and nutrient release from vegetation and soil as a consequence of prescribed burning. Herbaceous vegetation removal and burning can raise nitrate availability and increase risk of invasion by nitrophilic species such as B. tectorum. Nutrient availability can be out of phase with plant growth; plants capable of taking up nutrients during cold periods may have a competitive advantage. Resin capsules have utility in quantifying the effects of treatments on the availability of many soil nutrients.     

Crested Wheatgrass Control and Native Plant Establishment in Utah

Effective control methods need to be developed to reduce crested wheatgrass (Agropyron cristatum [L.] Gaertner) monocultures and promote the establishment of native species. This research was designed to determine effective ways to reduce crested wheatgrass and establish native species while minimizing weed invasion. We mechanically (single- or double-pass disking) and chemically (1.1 L · ha^?1 or 3.2 L · ha^?1 glyphosate–Roundup Original Max) treated two crested wheatgrass sites in northern Utah followed by seeding native species in 2005 and 2006. The study was conducted at each site as a randomized block split plot design with five blocks. Following wheatgrass-reduction treatments, plots were divided into 0.2-ha subplots that were either unseeded or seeded with native plant species using a Truax Rough Rider rangeland drill. Double-pass disking in 2005 best initially controlled wheatgrass and decreased cover from 14% to 6% at Lookout Pass and from 14% to 4% at Skull Valley in 2006. However, crested wheatgrass recovered to similar cover percentages as untreated plots 2–3 yr after wheatgrass-reduction treatments. At the Skull Valley site, cheatgrass cover decreased by 14% on herbicide-treated plots compared to an increase of 33% on mechanical-treated plots. Cheatgrass cover was also similar on undisturbed and treated plots 2 yr and 3 yr after wheatgrass-reduction treatments, indicating that wheatgrass recovery minimized any increases in weed dominance as a result of disturbance. Native grasses had high emergence after seeding, but lack of survival was associated with short periods of soil moisture availability in spring 2007. Effective wheatgrass control may require secondary treatments to reduce the seed bank and open stands to dominance by seeded native species. Manipulation of crested wheatgrass stands to restore native species carries the risk of weed invasion if secondary treatments effectively control the wheatgrass and native species have limited survival due to drought.     

沙地雀麦种子土表萌发条件及其对幼苗生长的影响

采用正交试验设计的方法,对影响沙地雀麦土壤表面播种种子萌发的因素及适宜萌发的环境条件进行研究,结果表明:沙地雀麦种子在25℃、20%土壤水分、100%相对湿度、回干处理、播后镇压条件下的萌发成苗能力较好.其中,对种子萌发成苗影响较大的因素是空气相对湿度和土壤水分,其次是种子回干处理和播后镇压.     

Establishment of Native Species in Soils From Russian Knapweed (Acroptilon Repens) Invasions

Russian knapweed (Acroptilon repens [L.] DC.), an exotic perennial forb, has invaded many native ecosystems in western North America. Russian knapweed's success is attributed to allelopathy, extensive tap rooting, zinc accumulation in soils, and a lack of North American predators. Revegetation following chemical control slows exotic reestablishment, but the impacts of Russian knapweed-invaded soils on the establishment of native forbs and shrubs have not been determined. In a greenhouse experiment, we monitored the establishment of two native forbs, Indian blanketflower (Gaillardia aristata Pursh) and purple prairie clover (Dalea purpurea Vent.) and two native shrubs, winterfat (Krascheninnikovia lanata [Pursh] A.D.J. Meeuse & Smit syn. Ceratoides lanata) and Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis [Hook.] Nutt.) in soils obtained from three Russian knapweed invasions and adjacent noninvaded areas. We analyzed soils collected near Greybull and Riverton, Wyoming, and Greeley, Colorado, for cation exchange capacity, organic matter, electroconductivity, pH, and total nitrogen, carbon, and plant-available potassium, zinc, manganese, copper, and phosphate. We documented seedling emergence of the four natives and Russian knapweed every two days for 14–17 weeks, harvested seedlings biweekly to assess their growth, and determined their zinc accumulation. All species established in invaded soil and seedlings were larger in invaded than in noninvaded soils. Invaded rangeland soils had greater organic matter (8.6% and 1.1% in invaded vs. 2.5% and 0.4% in noninvaded soils) and lower pH (7.4 in invaded versus 8.0 noninvaded soils). Zinc concentrations in invaded soils (from 0.15 to 6.56 mg · kg^-1) were not high enough to limit plant growth. Reports that Russian knapweed is a hyper-accumulator of zinc are not supported by our seedling data, which suggests that previously invaded soils may not limit native seedlings.     

外施氮肥、生长调节剂对结缕草幼苗生长的影响

以结缕草（Zoysia japonica）‘青岛’幼苗为材料,进行外施尿素及4种植物生长调节剂处理,研究各处理对其生长速度、比叶重、草坪质量、叶绿素含量、可溶性糖和可溶性蛋白含量的影响,旨在探讨加快结缕草幼苗生长速度和成坪时间的方法,为其推广应用提供理论依据。结果表明：外施尿素、GA和BR对结缕草幼苗的生长具有促进作用,其中最佳的处理浓度分别是尿素为6 g·m^-2,GA为0.56 μM,BR为1.0 μM;0.56 μM GA显著提高结缕草幼苗的生长速度和草坪质量（P<0.05）;外施6 g·m^-2尿素和1.0 μM BR则显著增加结缕草幼苗草坪质量、比叶重和叶绿素含量（P<0.05）;外施6 g·m^-2尿素、0.56 μM GA和1.0 μM BR对结缕草幼苗叶片可溶性糖和可溶性蛋白含量有显著的促进作用（P<0.05）。     

优质蛋白饲料饲喂仔猪的效果试验

以10%优质蛋白饲料配制的仔猪料与市售高档仔猪料进行饲养试验.经46d喂养,日增重试验组为670g、对照组为673g,差异不显著(P＞0.05).试验组饲料报酬为1.79 : 1,明显优于对照组的1.92 : 1,试验组比对照组饲料报酬提高6.77%.每kg增重饲料成本试验组为4.994元,比对照组的5.664元降低0.67元,经济效益提高12%.     

Evaluating the Effectiveness of Low Soil-Disturbance Treatments for Improving Native Plant Establishment in Stable Crested Wheatgrass Stands

Past seedings of crested wheatgrass (Agropyron cristatum [L.] Gaertn. and A. desertorum [Fisch. ex Link] Schult.) have the potential to persist as stable, near-monospecific stands, thereby necessitating active intervention to initiate greater species diversity and structural complexity of vegetation. However, the success of suppression treatments and native species seedings is limited by rapid recovery of crested wheatgrass and the influx of exotic annual weeds associated with herbicidal control and mechanical soil disturbances. We designed a long-term study to evaluate the efficacy of low-disturbance herbicide and seed-reduction treatments applied together or alone and either once or twice before seeding native species. Consecutive herbicide applications reduced crested wheatgrass density for up to 6 ? 7 yr depending on study site, but seed removal did not reduce crested wheatgrass abundance; however, in some cases combining herbicide application with seed removal significantly increased densities of seeded species relative to herbicide alone, especially for the site with a more northern aspect. Although our low-disturbance treatments avoided the pitfalls of secondary exotic weed influx, we conclude that crested wheatgrass suppression must reduce established density to values much lower than 4 ? 7 plants/m², a range that has not been obtained by ours or any previous study, in order to diminish its competitive influence on seed native species. In addition, our results indicated that site differences in environmental stress and land-use legacies exacerbate the well-recognized limitations of native species establishment and persistence in the Great Basin region.     

胰岛素在能量影响猪卵泡发育中的作用

胰岛素是体内具有重要生理作用的激素。能量是影响猪生长的主要因素。能量通过胰岛素,IGF-Ⅰ及葡萄糖等代谢信号作为媒介,影响垂体促性腺激素的分泌,这些代谢信号也可以直接作用于卵巢,影响性腺激素的分泌及卵泡的发育。而胰岛素是这其中较重要的代谢信号之一。本文将介绍胰岛素在能量影响猪卵泡发育中的作用。     

Plant and Bird Community Dynamics in Mixed-Grass Prairie Grazed by Native and Domestic Herbivores

Native colonial and large ungulate herbivores infrequently coexist on contemporary landscapes but frequently would have in the past, and understanding these interactions is important for conservation in working landscapes—those lands managed for biological and economic objectives. Although many factors contribute to grassland bird declines, consistent and long-term removal of native herbivores from western grasslands promotes homogenous landscapes that are now uniformly grazed by cattle (Bos taurus). This shift in grassland disturbance patterns limits habitat availability for specialized grassland species. We investigated vegetation and bird community dynamics in pastures grazed by domestic cattle and a native colonial herbivore, the black-tailed prairie dog (Cynomys ludovicianus). The study occurred in the northern mixed-grass prairie of the United States on four experimental pastures stratified by the proportion of prairie dog occupancy to create an ecological gradient. Vegetation and bird surveys were conducted from 2012 to 2015 on and off prairie dog colonies. Vegetation and bird communities were not different along the experimental pasture gradient but did differ relative to location on versus off town. Prairie dogs induced changes in the plant community with midstatured grasses like side-oats grama (Bouteloua curtipendula) and green needlegrass (Nassella viridula) being associated with off-colony sites while on-colony sites were associated with disturbance-tolerant species such as fetid marigold (Dyssodia papposa). The bird community responded to changes in vegetation structure resulting from prairie dogs with grasshopper sparrows (Ammodramus savannarum) being more abundant off colonies in areas with greater vegetation structure, while bird species with more complex life histories, such as the upland sandpiper (Bartramia longicauda), were associated with both on ? and off ? prairie dog colonies. Our findings demonstrate the importance of maintaining spatial heterogeneity in working landscapes and show that native colonial herbivores can help achieve this in the presence of herbivory by domestic cattle.     

用植株转化法将GUS基因导入桑树幼苗的研究

为探讨简便易行的农杆菌介导的转化方法 ,用工程农杆菌A 110株 (LBA4 4 0 4 /pIG12 1 Hm)对桑幼苗子叶腋隙进行刺伤感染 ,感染部位长出的桑芽表型异常。取其基因组DNA进行分子生物学鉴定 ,结果显示 :以基因组DNA为模板 ,经PCR反应后得到特异性扩增片段用SalⅠ酶解 ,酶切产物与预计大小完全相符 ;用GUS基因作探针进行Southern杂交和用Km基因作探针对基因组DNA进行Southern杂交 ,均获得较强的杂交信号。     

电场处理对羊柴种子萌发及幼苗生长的影响

用不同强度的匀强电场作用羊柴种子一定时间，实验测定电场对幼苗发芽率、含水量和根系的影响。多重比较结果表明：不同电场强度对羊柴种子萌发生长的影响程度不同，用恰当电场处理羊柴种子可以提高种子发芽率、幼苗生长和根系发达程度。     

贡蕉不同种苗类型对植株生长及产量性状的影响

贡蕉是热带亚热带地区重要经济作物。种植的种苗来源主要有组培苗和吸芽苗,不同种苗类型对田间管理要求不同,从而影响植株生长和产量性状。本研究采用不同种苗类型为材料,探讨贡蕉生育期的生长指标和产量性状之间的差异。结果表明：吸芽苗相对于组培苗,在幼苗期内球茎高度和宽度、粗根系直径上为极显著差异,分别增加了653.43％、391.24％、198.36％;抽蕾期假茎粗度、叶片宽度、假茎高度达到极显著差异,分别增加了18.36％,17.01％,16.82％;采收期果穗重、果指重、果指背长、果穗长上呈显著性差异,分别增加了34.50％、32.01％、24.33％、17.18％。再进一步相关性分析发现,果穗重量与内球茎高度和宽度、果穗长和果指粗呈现极显著正相关,相关系数分别为0.93、0.98、0.96和0.94。由此可见,在自然条件下发育而成的吸芽种苗,具有较大的球茎器官,养分贮存足,发苗快,植株长势强,更易丰产稳产,研究结果对贡蕉高效种植管理技术提供理论依据。     

Limitations to Postfire Seedling Establishment: The Role of Seeding Technology,Water Availability,and Invasive Plant Abundance

Seeding rangeland following wildfire is a central tool managers use to stabilize soils and inhibit the spread of invasive plants. Rates of successful seeding on arid rangeland, however, are low. The objective of this study was to determine the degree to which water availability, invasive plant abundance, and seeding technology influence postfire seedling establishment. Across four fire complexes, whole plots were either seeded using a rangeland drill, seeded by hand where seeds could be placed at an exact depth, or left as unseeded controls. Irrigation and weeding treatments were applied to subplots within whole plots in an incomplete factorial design. In three of the four fires, seeding method was the single factor limiting establishment with seedling density over sevenfold higher in the hand-seeded compared to the drill-seeded treatments. In contrast to our hypotheses, water and weeding had no positive effect on seedling establishment in any of the four fires; however, background weed density was relatively low. The native community recovered at all sites with minimal bunchgrass mortality. These results strongly suggest a need for a decision framework that evaluates postfire seeding needs relative to natural recovery. Based on these initial results, it appears modest improvements in seeding technology may yield substantial increases in seeding success.     

半胱胺不同添加方式对育肥猪生产性能的影响试验

试验选用体重60kg左右的杜长大三元杂种猪24头，按体重、性别随机分为3组。对照组饲喂基础日粮，试验Ⅰ组饲喂基础日粮并持续添加CS150mg／kg；试验Ⅱ组饲喂基础日粮并间隔性添加CS150mg／kg。每隔6d添加1d。结果表明，试验Ⅰ组和Ⅱ组与对照组相比，平均日增重分别提高5．08％和2．73％，料重比下降1．61％和2．14％；头均增收3．07％和1.13％。     

Enriched Topographic Microsites for Improved Native Grass and Forb Establishment in Reclamation

Low seed germination and seedling establishment are the greatest challenges for revegetation success. Topographic microsites are known to enhance seed germination and seedling establishment due to their unique soil properties and provision of shelter from elements and herbivores; soil amendments can supply organic matter and nutrients for plant establishment and growth when limited. We investigated the effect of three topographic microsites and six soil amendments and their additive effects on three disturbed grasslands in central and southern Alberta, Canada. Treatments were topographic microsites of mounds, pits, and flats, with and without amendments (erosion control blanket, hay, straw, manure, hydrogel, control) and were seeded with four native grasses and three native forb species. Seedling emergence and survival and soil temperature and water content were assessed over two seasons and plant cover over three seasons. The effect of microsites and amendments was not additive. The addition of erosion control blanket, hay, and straw to flat sites was just as productive as on topographic microsites. These amendments increased grass and forb emergence and buffered soil temperature. Mounds increased first year forb emergence and reduced over winter survival rates for grasses and forbs. Pits were not beneficial for revegetation. The effect of topographic microsites and amendments was influenced by site conditions.     

白三叶浸提液对蒲公英细胞膜透性及相关生理指标的影响

蒲公英（Taraxacum mongolicum Hand.）是白三叶（Trifolium repense L.）建植中主要的杂草,通过测定白三叶植株水浸液对蒲公英种子发芽特性、幼苗生长和生理指标的影响,明确白三叶浸提液对蒲公英种子和幼苗的化感作用及其机制。结果表明：以酚类为主的白三叶植株水浸液对蒲公英的发芽率、生长指标有显著的影响,高浓度（0.04～0.05 g·mL^-1）下有抑制作用,而且随着浓度的增加抑制作用越为明显,同时在浓度超过0.04 g·mL^-1时,白三叶植株水浸液可造成蒲公英叶绿素含量减少、改变呼吸强度和增加生长素（IAA）在植物体内的积累,胚根长和呼吸强度表现出“低促高抑”的现象。白三叶植株水浸液可改变蒲公英细胞膜透性,造成电解质外渗,同时可溶性糖、可溶性蛋白、脯氨酸、丙二醛等含量随白三叶植株水浸液浓度增高而明显增加。     

A Comparison of Bromus tectorum Growth and Mycorrhizal Colonization in Salt Desert vs. Sagebrush Habitats

Cheatgrass (Bromus tectorum) has recently invaded marginal low-elevation salt desert habitats across the Great Basin. We tested the hypothesis that cheatgrass seed produced in populations from the more stressful salt desert vs. upland sagebrush habitats should grow differently in salt desert soils compared to adjacent upland sagebrush soil, and vice versa. We evaluated growth, incidence of flowering, and arbuscular mycorrhizal fungi (AMF) colonization of plants grown in the soils from which their seeds were collected vs. in the reciprocal soils from the nearest sagebrush or salt desert site in three large basins in northern Nevada. Simultaneously we measured nutrient cations, available nitrogen and phosphorus, percent carbon and nitrogen, texture, and dry-down characteristics in all soils. We found that salt desert soils were generally more nutrient poor and more saline than their upland (sagebrush) counterparts; salt desert soils also generally had a higher percentage of sand compared to their upland counterparts and were consistently drier. The most dramatic plant responses to soil and seed source were 1) lower aboveground biomass of mature plants in most salt desert soils compared to sagebrush soils, or lower biomass in plants grown from salt desert seed; 2) lower root:shoot ratios in plants grown in salt desert soil across two of three basins, irrespective of seed source; 3) a higher percentage of flowering individuals from salt desert seed sources at harvest, irrespective of soil source; 4) depressed AMF colonization of plants in salt desert soils; and 5) strong influence exerted by seed source on AMF, whereby sagebrush-originating plants grown in sagebrush soils had greater AMF colonization compared to salt desert soils but salt desert-originating seedlings had very low AMF colonization rates irrespective of soil source. These results suggest that both population level and soil-based controls are important as this widespread weed moves into marginal habitat.