Season Grasses Research Articles

The food web of a severely contaminated site following reclamation with warm season grasses

We used the stable isotope 13C to distinguish between food web components that depended on warm season grasses with the C4 photosynthetic pathway and those that depended on plants with the C3 pathway. The study site was contaminated by heavy metals from a zinc smelter that operated near Palmerton, Pennsylvania, U.S.A. C3 plants only contributed 1.16% of aboveground primary productivity, whereas recently seeded (5–7 year old) warm season C4 grasses contributed the remaining 98.84%. Analyses of tissue samples revealed that the carbon content of invertebrates and vertebrates did not reflect the composition of the vegetation. Of 135 samples, 48 (36%) had greater than 75% of their carbon from C4‐derived sources, while 32 (24%) of the samples had less than 25%. However, carbon from C4 grasses passed through to higher trophic levels, as shown by the abundance of predators with a high proportion of C4‐derived carbon. We document three channels of carbon flux through the food web, one based on warm season grasses, now supporting a functioning ecosystem at all key trophic levels, one based on C3 plants, and a third based on detritus. Theoretical and empirical studies have shown that relative configurations of such channels are important to ecosystem stability. Our results suggest that functional groupings of plants based on photosynthetic pathway or other plant traits likely form the basis for food web compartments. By using diverse functional groups of plants for reclamation or restoration, practitioners may be able to aid the development of channels and thereby promote desired ecosystem states.

Metabolite responses to exogenous application of nitrogen, cytokinin, and ethylene inhibitors in relation to heat-induced senescence in creeping bentgrass.

The exogenous application of ethylene inhibitors, cyotkinins, or nitrogen has previously been shown to suppress heat-induced senescence and improve heat tolerance in cool -season grasses. The objectives of this study were to examine metabolic profiles altered by exogenous treatment of creeping bentgrass with an ethylene inhibitor, cytokinin or nitrogen under heat stress and to determine metabolic pathways regulated by those compounds in association with their effectiveness for improving heat tolerance. Creeping bentgrass (Agostis stolonifera) plants (cv. Penncross) were foliar sprayed with 18 mM carbonyldiamide (N source), 25μM aminoethoxyvinylglycine (AVG, ethylene inhibitor), 25μM zeatin riboside (ZR, cytokinin), or a water control, and then exposed to 20/15°C (day/night) or 35/30°C (heat stress) in growth chambers. All three exogenous treatments suppressed leaf senescence, as manifested by increased turf quality and chlorophyll content, and reduced electrolyte leakage under heat stress. Polar metabolite profiling identified increases in the content of certain organic acids (i.e. citric and malic acid), sugar alcohols, disaccharides (sucrose), and decreased accumulations of monosaccharides (i.e. glucose and fructose) with exogenous treatment of N, AVG, or ZR at the previously mentioned concentrations when compared to the untreated control under heat stress. Nitrogen stimulated amino acid accumulation whereas AVG and ZR reduced amino acid accumulation compared to the untreated control under heat stress. These results revealed that the alleviation of heat-induced leaf senescence by N, AVG, and ZR could be due to changes in the accumulation of metabolites involved in osmoregulation, antioxidant metabolism, carbon and nitrogen metabolism, as well as stress signaling molecules.

Comparison of Growth Characteristics, Forage Production and Feed Values of Bermudagrass, Teffgrass and Kleingrass as Annual Forage Crop in Summer

Hyung Soo Park*, Ki Choon Choi, Ji Hea Kim, Sang-Hoon Lee and Jong Seong JungNational Institute of Animal Science, Cheonan, 330-801, KoreaABSTRACTThis study was conducted from 2013 to 2014 to explore the feasibility of the cultivation of warm-season grass as an annual Korean forage crop, while concurrently evaluating the characteristics and forage production of warm-season grass in Korea. The experimental design was a randomized block design(RBD) with three replications. Five bermudagrass[Cynodon dactylon (L.) Pers.] cultivars, two teffgrass(Paspalum notatum Flugge) cultivars, and a Kleingrass[Panicum coloratum L.] cultivar were compared for forage production and quality in the middle region of Korea. After seeding, the numbers of days until seedling emergence for bermudagrass and kleingrass were observed at approximately day 11 and day 12, respectively. The heading dates of teffgrass and kleingrass were on July 12 and July 26, respectively. The dry matter(DM) yield of bermudagrass Tifton 85 was usually greater than the other entries. The crude protein content(CPC) and total digestibility nutrient(TDN) for the teffgrass cultivars were usually greater than the other entries at all study sites. The acid detergent fiber(ADF) and in vitro DM digestibility(IVDMD) were similar across all cultivars. (Key words :Warm season grass, Production, Feed value, Bermudagrass, Teffgrass)

Rapid analysis of composition and reactivity in cellulosic biomass feedstocks with near-infrared spectroscopy.

BackgroundObtaining accurate chemical composition and reactivity (measures of carbohydrate release and yield) information for biomass feedstocks in a timely manner is necessary for the commercialization of biofuels. Our objective was to use near-infrared (NIR) spectroscopy and partial least squares (PLS) multivariate analysis to develop calibration models to predict the feedstock composition and the release and yield of soluble carbohydrates generated by a bench-scale dilute acid pretreatment and enzymatic hydrolysis assay. Major feedstocks included in the calibration models are corn stover, sorghum, switchgrass, perennial cool season grasses, rice straw, and miscanthus.ResultsWe present individual model statistics to demonstrate model performance and validation samples to more accurately measure predictive quality of the models. The PLS-2 model for composition predicts glucan, xylan, lignin, and ash (wt%) with uncertainties similar to primary measurement methods. A PLS-2 model was developed to predict glucose and xylose release following pretreatment and enzymatic hydrolysis. An additional PLS-2 model was developed to predict glucan and xylan yield. PLS-1 models were developed to predict the sum of glucose/glucan and xylose/xylan for release and yield (grams per gram). The release and yield models have higher uncertainties than the primary methods used to develop the models.ConclusionIt is possible to build effective multispecies feedstock models for composition, as well as carbohydrate release and yield. The model for composition is useful for predicting glucan, xylan, lignin, and ash with good uncertainties. The release and yield models have higher uncertainties; however, these models are useful for rapidly screening sample populations to identify unusual samples.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0222-2) contains supplementary material, which is available to authorized users.

Planting grass filter strips: Does it influence the structure and function of riparian habitats of agricultural headwater streams?

AbstractGrass filter strips are strips of cool or warm season grasses planted adjacent to agricultural streams to reduce nutrient, pesticide, and sediment input. This conservation practice is the most frequently planted riparian buffer type in the United States. Previous studies have not evaluated how grass filter strips alter the structure and function of riparian habitats of agricultural streams. Our objective was to examine the research hypothesis that planting grass filter strips will influence the structure and function of riparian habitats of channelized agricultural headwater streams. We sampled riparian vegetation, quantified coarse particulate organic matter input and nutrient input, and measured water temperature within two unplanted riparian habitat sites, two riparian habitat with grass filter strips sites, and two forested riparian habitat sites of agricultural headwater streams in central Ohio. Forested riparian habitats exhibited greater percent maximum frequency of woody vegetation and reduced water temperatures than unplanted riparian habitats and grass filter strips. Forested riparian habitats also exhibited greater canopy cover, woody vegetation taxa richness, and coarse particulate organic matter input than grass filter strips and greater riparian widths and woody vegetation abundance than unplanted riparian habitats. Grass filter strips did not differ in structure and function from unplanted riparian habitats. We conclude that planting grass filter strips does not influence the structure and function of riparian habitats of channelized agricultural headwater streams.

Lactic Acid Bacteria of Potential as a Means of Inhibiting Undesirable Microorganisms in Warm Season Grass Silages

The presence of some microorganisms in silage besides reducing nutritional value and may represent risks to animal and human health due potentially pathogenic microorganisms. Enterobacteria, bacteria of the ge nus Clostridium spp and bacteria of the genus Listeria spp develop in badly fermented silage, in which pH drop is slower. After silos opening, yeasts, fungi and Bacillus spp initiate aerobic degradation, leading to pH rising and reappearing of Clostridium spp, Listeria spp and enterobacteria. Thus, development control those microorganisms by adequate fermentation is extremely important, since besides reducing silage quality, many are pathogenic or produce substances that are harmful to animal and human heal th.

Broad‐scale variation of fungal‐endophyte incidence in temperate grasses

Summary The strength of many interactions between plants and other organisms changes across regional gradients. For example, the relevance of plant‐herbivore interactions increases with primary production. Likewise, biotic interactions collectively become more intense from the poles to the equator. Yet, the regional variation of the interaction between grasses and systemic fungal endophytes, which provide resistance to biotic and abiotic environmental factors (i.e. herbivory and drought), is poorly understood. We compiled 1008 records of the incidence level of fungal endophytes (Epichloë, Ascomycetes: Clavicipitaceae) on wild populations of 48 cool season grasses, encompassing 10 biomes across a broad latitudinal expanse and primary production gradient. Symbiosis incidence was analysed as a function of mean primary production, precipitation, temperature and latitude of each site, which in turn were obtained from climatic and satellital sources. Across a 30‐fold variation of mean primary production, average symbiosis incidence increased from 20% to 70%. The pattern became stronger when the analysis was restricted to the single grass genus Festuca, which accounted for half of the total data. The number of grass populations showing no symbiosis incidence (0%) decreased as primary production increased, whereas those with 100% of incidence increased. Primary production at the regional scale was negatively correlated with latitude but positively with mean annual temperature and precipitation. Symbiosis incidence was similarly correlated with latitude and temperature, and it was not with mean annual precipitation. Synthesis. Different descriptors of this grass‐fungus symbiosis show that average incidence in wild populations world‐wide increases with mean primary production. As at large spatial scales herbivory and temperature increase and aridity decreases with primary production, our results suggest that, at broad‐scales, these biotic and abiotic factors may be important drivers of the symbiosis success.

Using prescribed fire and herbicide to manage rank native warm season grass for northern bobwhite

Converting fields of exotic cool season grass to native warm season grass creates habitat for northern bobwhite (Colinus virginianus). If converted stands are left unmanaged they can become rank, or over-vegetated and unsuitable for grassland wildlife. Northern bobwhite populations have been declining across their range for decades, and maximizing the amount of habitat is vital to increasing their abundance. We investigated prescribed burning followed by herbicide application as a management strategy to improve vegetative composition and structure for northern bobwhite in rank native warm season grass stands. Within 4 study areas using a randomized block design, we applied the following treatments: burn-only, burn then application of 27.7% isopropylamine salt of imazapyr (ISI), burn then application of 7.78% imazapyr 62.22% diuron mixture (imazapyr), and burn then 41% glyphosate application. We measured vegetative parameters related to structure and composition and compared these metrics between treatments using repeated measures analysis of variance blocked by sampling area. We compared grass stands to hypothetical optimum conditions for bobwhite using principle components analysis. The ISI treatment produced levels of forbs and native warm season grass beneficial to bobwhite throughout the study, and was initially most similar to optimum conditions. Glyphosate treatment also produced vegetation beneficial to bobwhite. Imazapyr produced beneficial levels of bare ground during the first growing season but none of our treatments produced beneficial levels after 2 growing seasons. Herbicide treatments initially had greater influence on habitat structure than did the burn-only treatment, but all habitat structure variables were similar among treatments after 2 growing seasons. Our results indicate that management of rank grasslands for northern bobwhite occurring at <2-year intervals provides near optimal levels of native warm season grass and forbs and has potential to create habitat structure. On private lands managed for northern bobwhite where landowners do not have access to disking, we recommend prescribed burning followed by either 2.81 L/ha ISI or 5.62 L/ha glyphosate application using a non-ionic surfactant followed by annual or biennial prescribed burning. We do not recommend the use of imazapyr or burn-only treatments when managing rank grasslands for northern bobwhite habitat because they do not create beneficial levels of native warm season grass or forbs. © 2014 The Wildlife Society.

Variation in the expression of ergot alkaloids between individual tillers of perennial ryegrass.

Epichloë fungal endophytes of cool season grasses are well-known to produce a range of alkaloids of benefit to the host. Some of these compounds are advantageous to agriculture due to qualities that promote pasture persistence (e.g., the loline class of alkaloids confer insect protection) while others are detrimental to the well-being of grazing livestock. The ergot alkaloids (e.g., ergovaline), produced in ryegrass and tall fescue associations, causes poor animal health in farming regions in many countries around the world and further study is required to improve our knowledge on this class of compounds. Here we present the application of a quantitative LC-MS/MS (liquid chromatography coupled to mass spectrometry) method measuring eight ergot alkaloids (chanoclavine, agroclavine, elymoclavine, lysergol, lysergic acid, ergine, lysergyl-alanine, ergovaline) produced by endophyte infected grasses, to monitor levels in individual tillers from multiple plants of a single cultivar of perennial ryegrass (Lolium perenne cv. “Grasslands Samson”) infected with a common toxic endophyte strain (Epichloë festucae var. lolii). Monitoring the expression in individual tillers allows an estimation of the variability within a plant (between tillers) as well as between plants. The study showed that there is significant variation in the concentration of the ergot alkaloids between tillers of a single plant, at or exceeding the level of variation observed between individual plants of a population. This result emphasizes the fundamental importance of robust experimental design and sampling procedures when alkaloid expression assessment is required and these need to be rigorously tailored to the hypothesis being tested.

Comparing drag partition schemes over a herbaceous Sahelian rangeland

AbstractModeling of dust emissions from the surface remains complex, especially in semiarid regions where vegetation must be accounted for because of its potentially important protective effect. Protection is directly linked to the fraction of the soil surface covered by vegetation, but it is also driven by the interaction of vegetation elements with the wind field. The sensitivity of simulated dust emissions to various drag partition schemes—mainly those proposed by Raupach (1992), Marticorena and Bergametti (1995), and Okin (2008)—is evaluated for a typical Sahelian rangeland, covered by a seasonal grass layer, over a complete vegetation cycle. The application of these schemes requires a fine characterization of the vegetation cover; field measurements from an ecological survey are used to derive the geometric dimensions of the grass patches. Models are run with meteorological forcing from automatic weather stations. As a result, the impacts of soil moisture and grass cover are estimated over April to September. Soil moisture inhibits dust emissions by 27% in mass. The different drag partition schemes exhibit distinctive limitations, mostly due to the properties of the Sahelian grass cover, which is composed of large and low patches of short grass, with a strong seasonal dynamics. However, the drag partition schemes result in remarkably coherent estimations of dust emissions. When soil moisture is taken into account, vegetation reduces the total vertical mass fluxes by 6 to 26% of the emissions of a bare soil, depending on the drag partition scheme.

Effect of daily or alternate-day distillers grains supplementation with or without monensin on performance of grazing calves

<h2>ABSTRACT</h2> The objective of these experiments was to determine the effect of daily or alternate day supplementation of dried distillers grains with solubles (DDGS) with or without monensin on performance of grazing calves. Treatments included (1) a negative control with no supplemental feed except free-choice mineral; (2) DDGS offered daily at 1.02kg as-fed per calf, including a mineral premix; (3) daily DDGS and monensin (Rumensin, Elanco, Greenfield, IN) at 1.02kg as-fed per calf, including a mineral premix supplying 160mg of monensin/calf daily; (4) alternate day DDGS to supply 2.04kg as-fed per calf, including the mineral premix offered on alternate days; and (5) alternate day DDGS and monensin to supply 2.04kg as-fed per calf, including a mineral premix and 320mg of monensin/calf on alternate days. Four experiments were conducted which included both steers (n=70) and heifers (n=230) grazing warm season grass based pastures (Exp. 1, 2, and 3) or nontoxic endophyte-infected tall fescue (Exp. 4). Supplementation increased ADG (P≤0.04) by 0.16 to 0.26kg/d in the 4 studies, with an average improvement (P<0.01) of 0.21kg/d. Monensin addition and supplement timing had no effect (P≥0.16) on BW, ADG, or supplemental efficiency in any of the 4 experiments. Supplementation increased ADG of growing beef calves regardless of pasture quality or basal cattle performance. The performance improvement was similar whether supplements were fed daily or on alternate days. Contrary to expected results, monensin inclusion in the supplement had no effect on animal performance or supplemental efficiency.

Switchgrass Field Performance on Two Soils as Affected by Bacterization of Seedlings with Burkholderia phytofirmans Strain PsJN

Switchgrass (Panicum virgatum L.) is a perennial warm season grass capable of growth on marginal lands without major inputs of water and fertilizers. However, full utilization of its agronomic potential as a bioenergy crop requires improvement of its stand establishment, disease resistance, and prevention of the biomass yield variation from year to year. Our program focuses on the utilization of beneficial bacterial endophytes to enhance switchgrass performance under a low-input production system on marginal lands. We demonstrated earlier that inoculation of switchgrass cv. Alamo with a growth promoting endophyte, Burkholderia phytofirmans strain PsJN (PsJN), can significantly enhance seedling vigor and plant growth under both in vitro and greenhouse conditions. In this study, we tested the effects of PsJN bacterization of switchgrass seedlings on stand establishment, plant growth, and biomass yield in three field experiments conducted over 2 years on highly fertile prime land, and on a former tobacco farm with low fertility soil. PsJN bacterization improved growth and development of switchgrass seedlings, significantly stimulated plant root and shoot growth, and tiller number on the low fertility soil (p < 0.001), and enhanced biomass accumulation on both poor (p < 0.001) and rich (p < 0.05) soils, with more effective stimulation of plant growth in low fertility soil than in high fertility soil. The study indicates the potential for the use of PsJN and/or other beneficial bacterial endophytes in the development of low-input switchgrass feedstock production systems.

Selection of an empirical detection method for determination of water-soluble carbohydrates in feedstuffs for application in ruminant nutrition

Water-soluble carbohydrates (WSC) are commercially measured in feedstuffs for use in diet formulation for ruminants. However, we lack information as to which empirical detection assay most correctly measures WSC. The objective of this study was to determine which of two commonly used empirical assays was most appropriate for detection of WSC based on equivalency to results from high performance ion chromatography with pulsed amperometric detection plus soluble starch analysis (HPIC) of the water extract. Empirical analyses used were a reducing sugar assay (RSA) that uses p-hydroxybenzoic acid hydrazide-based reagent with 50:50 glucose:fructose standards, and the phenol-sulfuric acid assay (PSA) with sucrose standards. Twenty samples including cool season grasses (CSG), legume forages, non-forage feedstuffs, silages, or warm season grasses were used. Air dry samples (0.2g) were extracted in 35mL of deionized water for 1h at 40°C with continuous shaking. Water extracts for HPIC and RSA analyses were hydrolyzed with 0.037M H2SO4 at 80°C for 70min. Theoretically, RSA should give essentially the same results as HPIC, excepting that RSA also detects reducing ends of unhydrolyzed molecules. PSA detects all solubilized or suspended carbohydrates. On average, RSA and PSA values were greater than those found for HPIC by 28.2g WSC/kg dry matter (DM). The two classes of feeds that showed differences between PSA and RSA were CSG and silages. For CSG, RSA and PSA were respectively 54.1 and 20.6g WSC/kg DM greater than HPIC; for silages differences were smaller at 8.8 and 15.9g WSC/kg DM. CSG contain fructans, for which RSA gives higher values than does PSA. However, the elevated RSA values for CSG were in excess of differences predicted based on inflated RSA recovery values for fructose measurement (106.5% of actual). Elevated RSA values obtained for CSG suggest that interference is affecting these grasses to a greater degree than other samples. Distillers grains showed an elevated value with PSA (69.1g WSC/kg DM greater than HPIC); this is partially explained by the inflated recovery values for glucose (128.2% of actual) noted for PSA. Neither PSA nor RSA perfectly reflected HPIC values, however PSA gave more similar values. Gross differences between RSA and HPIC for CSG are an issue, particularly without clear, resolvable basis for the discrepancy. Accordingly, PSA is preferred over RSA for detection of WSC. Selection of standards to more closely reflect WSC composition could further improve accuracy.

Relations between low temperature tolerance and color changes in fall and spring seasons of zoysiagrass (Zoysia japonica Steud.)

AbstractZoysiagrass (Zoysia spp.) is warm season grass used for lawns, golf courses and athletic fields. Although it has better low temperature tolerance compared to other warm season grasses, its longer dormant period than cool season grasses prevents its wide usage in transitional and cooler climate zones. This study analyzed the relationships among low temperature tolerance, green color changes during the fall and spring and the dormant period length among seven Zoysia japonica Steud. cultivars and accessions: two cultivars, four Chinese accessions and one Japanese accession. A relationship between low temperature tolerance and color changes due to dormancy and re‐greening up was examined. Plant samples from the tested Z. japonica were cooled to between −8 and −16°C to measure the lethal temperatures at which 50% of plants died (LT50). These LT50 ranged from −7.3 to −10.1°C, with Lanyin No. 3 having the poorest low temperature tolerance. In the field, the color changes from green to brown for the whole plant in the fall and from brown to green in the spring occurred within 15–20 days as determined by digital analysis from fall 2008 to spring 2010. The fall colors changes (going dormant) on November 8, 2008 and November 7, 2009 were positively correlated with the LT50 (r = 0.824 and 0.823, respectively). The spring colors changes (green‐up) on April 24, 2009 and May 19, 2010 were negatively correlated with the LT50 in both 2009 (r = −0.878) and 2010 (r = −0.869). The dormant period length in 2008–2009 was positively correlated (r = 0.765) with the LT50. This study demonstrated that Z. japonica with poor low temperature tolerance has better green‬‬ retention in the fall but less green color in the spring‬‬. Furthermore, Z. japonica, which became dormant later underwent green up later and had a longer dormant period, mainly due to slower green up in spring.‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬

Response of warm–season grasses to N fertilization and salinity

Good knowledge of how growth and physiological traits vary as a function of salt concentration in the soil and different nitrogen fertilization regimes is fundamental for sustainable management of warm–season grasses in sport and recreational areas. The research presented in this paper was conducted in a greenhouse. Plant material was obtained by taking undisturbed soil cores from mature stands. Treatments consisted in combinations of salinity (0, 15, and 30dSm−1) and N rate (0, 5, and 10gNm−2). The species used were Cynodon dactylon×C. transvaalensis ‘Tifway’ and Zoysia japonica ‘Meyer’ as Chloridoideae, and Paspalum vaginatum ‘Salam’, as Panicoideae. Top growth, expressed as cumulative clipping dry weight (DW) and verdure DW, significantly decreased with increasing salinity. Positive effects of N fertilization were observed for cumulative clipping DW, although the growth responses were more pronounced under non-saline and intermediate salinity conditions. Under the highest salinity, no significant increase was observed in response to N rate. ‘Salam’ showed a positive response to N fertilization in terms of root and horizontal stem (rhizomes and stolons) DW though no such response was observed in ‘Tifway’ and ‘Meyer’. The leaf pigment response to salinity varied with the species. All pigments within each species showed similar behavior. In Paspalum, pigment content was not affected by salinity level, though chlorophyll a slightly decreased at the highest salinity level.

Functional response of U.S. grasslands to the early 21st-century drought.

Grasslands across the United States play a key role in regional livelihood and national food security. Yet, it is still unclear how this important resource will respond to the prolonged warm droughts and more intense rainfall events predicted with climate change. The early 21st-century drought in the southwestern United States resulted in hydroclimatic conditions that are similar to those expected with future climate change. We investigated the impact of the early 21st-century drought on aboveground net primary production (ANPP) of six desert and plains grasslands dominated by C4 (warm season) grasses in terms of significant deviations between observed and expected ANPP. In desert grasslands, drought-induced grass mortality led to shifts in the functional response to annual total precipitation (P(T)), and in some cases, new species assemblages occurred that included invasive species. In contrast, the ANPP in plains grasslands exhibited a strong linear function of the current-year P(T) and the previous-year ANPP, despite prolonged warm drought. We used these results to disentangle the impacts of interannual total precipitation, intra-annual precipitation patterns, and grassland abundance on ANPP, and thus generalize the functional response of C4 grasslands to predicted climate change. This will allow managers to plan for predictable shifts in resources associated with climate change related to fire risk, loss of forage, and ecosystem services.

Effects of Set-aside Conservation Practices on Bird Community Structure within an Intensive Agricultural Landscape

Creating and restoring patches of noncrop early-succession vegetation within agricultural landscapes may mitigate grassland bird population declines caused by agricultural land use and intensification. Achieving this goal requires an ability to balance avian benefits with agronomics, which may be facilitated by understanding how bird communities respond to various conservation practices. We evaluated bird richness, abundance, Shannon diversity, and Total Avian Conservation Value in 20 replicates of four Conservation Reserve Program practices in an intensive rowcrop agricultural landscape in the Mississippi Alluvial Valley from May–Jul., 2005–2007. Conservation practices included: (1) large blocks of structurally-diverse early-succession vegetation (6–8 y old trees) and three buffer types; (2) 30 m wide monotypic filter strips with tall dense switchgrass (Panicum virgatum); (3) 30 m wide diverse filter strips with a forb-native warm season grass mixture; and (4) 60 m wide early-succession riparian forest buffers (1–3 y old trees). The breeding bird community was dominated by red-winged blackbirds (Agelaius phoeniceus; 43% of total) and dickcissels (Spiza americana; 42% of total) but commonly included eastern meadowlarks (Sturnella magna), indigo buntings (Passerina cyanea), mourning doves (Zenaida macroura), and northern bobwhite (Colinus virginianus). We observed ≥1.8 × more dickcissels in large blocks and diverse filter strips than other buffers and greater Shannon diversity in large blocks than any buffers (P < 0.05). Diverse filter strips had ≥1.6 × greater overall bird density (7.2 birds/0.6 ha), on average, than all other practices. Based on these data, we conclude that buffers are attractive to farmland breeding birds and may provide important ecological benefits to supplement a conservation management system founded on large blocks of early-succession vegetation.

Investigating seed dormancy in switchgrass (Panicum virgatum L.): Elucidating the effect of temperature regimes and plant hormones on embryo dormancy

Switchgrass (Panicum virgatum L.) is a perennial warm season grass that possesses valuable characteristics as a biofuel crop. Seed dormancy can be a barrier for commercial adoption by negatively impacting stand establishment in the first year. Seed dormancy in switchgrass is classified as non-deep physiological dormancy, where the embryo condition and seed covering tissues may prevent germination. Our lab previously demonstrated that switchgrass seed dormancy was primarily caused by the pericarp/testa, and secondarily by the lemma/palea (bracts). The focus of this research was to explore embryo physiological dormancy and its interaction with environmental cues and surrounding seed layers in five switchgrass varieties with different dormancy levels. Three main objectives were involved: (1) assessing the effect of temperature and light regimes on germination of mature seeds; (2) determining the effect of exogenously applied abscisic acid (ABA), gibberellin (GA), and fluridone (FLU) on germination under either constant or alternate temperatures; and (3) examining the response of physically altered seeds to exogenously applied ABA, GA, and FLU.Incubation of both upland and lowland dormant switchgrass varieties under alternating temperatures (15/30°C) favored germination, while incubation under a constant, warm temperature (30°C) resulted in low percentage germination. In contrast, the low-dormancy cultivar Expresso germinated well at both temperature regimes. Germination in the dark did not differ from an alternating light/dark regime. Exogenous ABA decreased germination in all dormant cultivars studied at both temperature regimes, but the sensitivity of the seeds to ABA was less under alternating temperatures. GA increased germination at a constant temperature in all but one dormant variety. The largest effect of both GA and ABA was observed in seeds with bracts. The promoting effect of FLU on germination was not measured in intact seeds; however, FLU promoted germination at 30°C in seeds with bracts removed, suggesting that the seed covering layers were not permeable to FLU. Collectively, results show that the effect of exogenously applied ABA, GA, and FLU was influenced by temperature, seed covering layers, and seed lot.

Examination of Fire-Related Succession Within the Dry Mixed-Grass Subregion of Alberta With the Use of MODIS and Landsat

Fire is an important disturbance process historically present across the northern Great Plains. Previous research from northern dry mixed-grass prairie suggests that C4 (warm season) grasses replace C3 (cool season) climax species with increasing fire, particularly in the spring. This hypothesis was tested at a landscape scale at Canadian Forces Base Suffield Alberta, by exploring the relationship between ecosystem states (C3 dominant, C3/C4 codominant, C4 dominant) inferred from a MODIS multitemporal plant functional type classification (pseudo R2: 0.598, overall accuracy: 0.74) and interyear fire history digitized from the Landsat archive (1972–2007). Probit regression showed that succession processes were different between range sites, where C4-dominant pixels were positively related to fire (P < 0.001, pseudo R2 = 1) and completely replaced C3-dominant pixels on loamy range sites after 14 fires in 36 yr. In contrast, C3- and C3/C4-codominant pixels were related with fire on Blowouts range sites (P < 0.001, pseudo R2 = 1), where C3/C4-codominant pixels replaced C3-dominant pixels with increasing fire. Finally, there were no statistically significant relationships between ecosystem states and fire for Sands range sites. Analysis of recovery showed that after loamy pixels experienced three to six fires in 18 yr followed by 18 yr of rest, C3-dominant pixels were reduced by over 30% compared to unburned pixels. Finally, intrayear fire timing (2001–2009) was explored with the use of Wilcoxon signed-rank tests between the spatial extent of spring and summer fires, with the use of MODIS burned-area data. Results indicate that fires are not limited to the spring season (P < 0.05), but occur across the entire growing season. Although fire timing does not appear to play a role in driving succession, this ecosystem is generally sensitive to repeated fire, with recovery of C3 climax species taking decades.

중남부지역에서 난지형 목초의 생육특성, 월동성 및 사초생산성 평가

Field studies were conducted from the years 2009 to 2012 in order to determine the cultivation limit as well as to evaluate the characteristics and forage production of warm season grass in Korea. Two bermudagrass [Cynodon dactylon (L.) Pers.] cultivars, two bahiagrass (Paspalum notatum Flugge) cultivars and a Kleingrass [Panicum coloratum L.] cultivar were compared for forage production and quality in the mid-southern regions of Korea. The experimental design was a randomized block design (RBD) with three replications. The number of days to seedling emergence for bremudagrass and bahiagrass was observed as approximately 12 days and 28 days after seeding, respectively. In Kwangju, the heading dates of bahiagrass and kleingrass were 21 August and 10 July, respectively,. Warm season grass did not winter in the mid-regions (Kimjea, Cheonan) of Korea. All of the Bermudagrass cultivars had higher dry matter (DM) than bahiagrass at the first harvest. The dry matter yield of kleingrass was usually greater than the other entries at all study sites. Peak forage DM production of bermudagrass and bahiagrass cultivars occurred in June and July, respectively. The contents of crude protein (CP) and total digestibility nutrient (TDN) for bermudagrass cultivars were usually greater than the other entries at all study sites. Further, acid detergent fiber (ADF) and in vitro DM digestibility (IVDMD) were similar across all cultivars. (