Search

The potential nitrogen-fixing bacterial diversity in the rhizospheric soil of the native switchgrass (Panicum virgatum L.) from Tall Grass Prairies of Northern Oklahoma was studied using a partial region of nitrogenase structural gene—nifH. Eleven clone libraries constructed from nifH amplicons gave 407 good-quality sequences. More than 70% of sequences showed similarity of nifH with uncultured bacteria (< 98%). The dominance of sequences affiliated with Deltaproteobacterial nifH was observed, followed by Betaproteobacterial nifH sequences. The nifH gene library was dominated by the genera Geobacter, Rhizobacter, Paenibacillus, and Azoarcus. Sequences affiliated with rhizobia, such as Bradyrhizobium, Methylocystis, Ensifer, etc., were also in the rhizosphere in small numbers. From Deltaproteobacteria, five genera, namely Geobacter, Pelobacter, Geomonas, Desulfovibrio, and Anaeromyxobacter, contributed to 48% of the total sequences suggesting the dominance of group Deltaproteobacteria in the rhizosphere of native switchgrass. Considering the percent similarity of the nifH sequences with cultivated bacteria, this study demonstrated the presence of novel bacterial species in switchgrass rhizospheric soil from Tall Grass Prairie. [ABSTRACT FROM AUTHOR]

Monitoring net ecosystem carbon dioxide (CO2) exchange (NEE) using eddy covariance (EC) flux towers is quite common, but the measurements are valid at the scale of tower footprints. Alternative ways to quantify and extrapolate EC-measured NEE across potential production areas have not been explored in detail. To address this need, we used NEE measurements froma switchgrass (Panicum virgatum L.) ecosystem and detailed meteorological measurements from the Oklahoma Mesonet and developed empirical relationships for quantifying seasonal (April to October) sums of NEE across potential switchgrass establishment landscapes in Oklahoma, USA. We identified ensemble areas for potential switchgrass expansion regions and created thematic maps of switchgrass productivity using geostatistics and geographic information systems (GIS) routines. The purpose of this study was to explore if model parametrizations based on high temporal frequency meteorological forcing can be used for reliable estimates of NEE for evaluating the source-sink status of carbon. Rectangular hyperbolic light-response curve and temperature response functions were fitted using EC measurements to estimate gross primary production (GPP) and ecosystem respiration (ER), respectively, on a seasonal scale. Model performance validated by comparing EC-measured seasonal NEE for 3 yr showed good-to-strong agreement (.29 < R² < .91; p < .05). Additionally, total seasonal NEE estimates were validated with measured biomass data in three additional locations. The estimated seasonal average net ecosystem production (NEP = -NEE) was 3.97 ± 1.92 (SD) Mg C ha-1. However, results based on a simple linear model suggested significant differences in NEP between contrasting climatic years. Overall, the results from this study indicate that this new scaling-up approach involving high temporal resolution meteorological data may be a helpful tool for assessing spatiotemporal heterogeneity of switchgrass production and the potential of switchgrass fields to sequester carbon in the Southern Great Plains of the United States. [ABSTRACT FROM AUTHOR]

Woody plant encroachment is an ongoing global issue. In the Southern Great Plains of the United States, the rapid encroachment and coalescence of woody plants are transforming herbaceous-dominated rangelands into woodlands with a detrimental impact on water quality and quantity. In this study, we conducted modeling simulations to assess how converting juniper (Juniperus virginiana) woodland and low to moderately productive grassland into switchgrass (Panicum virgatum) biomass production system would affect streamflow and sediment yields in the Lower Cimarron River, Oklahoma. First, the grassland areas in the basin were divided into productivity classes suitable for rangeland activities based on the soil productivity index. Next, the Soil and Water Assessment Tool was used to develop the basin hydrologic model, calibrated and validated for streamflow in five gaging stations with a percent bias of <10%, Nash–Sutcliffe Efficiency index of >0.76, and R2 of >0.77. Then, the model was used to simulate evapotranspiration (ET), streamflow, groundwater recharge, and sediment loads under different land use conversion scenarios. Results showed that converting existing juniper woodlands, ~4% of the basin, to switchgrass had limited impacts on the water budget and sediment yield. A hypothetical scenario of converting low to moderately productive rangeland to switchgrass increased annual ET by 2.6%, with a decrease in streamflow by 10.8% and a reduction in sediment yield by 39.2% compared to the baseline model. Results indicated that switchgrass could be considered a potential land use alternative to address the juniper encroached grassland with minimal loss in streamflow but a substantial reduction in sediment yield in the southcentral region of the Great Plains. [ABSTRACT FROM AUTHOR]

Termite researchers on The Nature Conservancy's Joseph H. Williams Tallgrass Prairie Preserve in northeast Oklahoma have long been interested about nutritional resources used by subterranean termites inhabiting the Preserve. In 12-week choice and no-choice laboratory feeding tests, subterranean termites were fed a mixture of stems-and-leaves, or roots only, of four predominant grasses growing on the Preserve: Indiangrass – Sorghastrum nutans L; Switchgrass – Panicum vigatum L; Big Bluestem – Andropogan gerardii Vitman; and Little Bluestem – Schizachyrium scoparium (Michx.). Termites consumed all of these food choices but preferred roots compared with stems and leaves. In choice feeding tests, termites preferred Switchgrass roots. In no-choice feeding tests, roots of Indiangrass and Big Bluestem were consumed in greatest amounts. All four grasses were palatable to Reticulitermes tibialis, a subterranean termite common throughout the Preserve. [ABSTRACT FROM AUTHOR]

The southern Great Plains of the USA has great potential to produce biofuel feedstock while minimizing the dual stresses of woody plant encroachment and climate change. Switchgrass (Panicum virgatum) cultivation, woody biomass captured during removal of the encroaching eastern redcedar (Juniperus virginiana) to restore grasslands and thinning of the native oak forest can provide an integrated source of feedstock and improve ecosystem services. In north‐central Oklahoma, we quantified productivity and ecosystem water use of switchgrass stands and degraded ecosystems encroached by eastern redcedar and compared these to native oak forest and tallgrass prairie ecosystems. We measured aboveground net primary productivity (ANPP) using allometric equations (trees) and clip plots (herbaceous), and evapotranspiration (ET) using a water balance approach from gauged watersheds, and calculated water use efficiency (WUE = ANPP/ET) from 2016 to 2019. Among vegetation cover types, ANPP averaged 5.1, 5.4, 6.0, and 7.8 Mg ha−1 year−1 for the prairie, oak, eastern redcedar, and switchgrass watersheds and was significantly greater for switchgrass in 2018 and 2019 (2 and 3 years post establishment) when it reached 8.6 Mg ha−1 year−1. Averaged across 2017–2019, ET was significantly greater in the forested watersheds than the grassland watersheds (1022 mm year−1 for eastern redcedar, 1025 mm year−1 for oak, 874 mm year−1 for prairie, and 828 mm year−1 for switchgrass). The mean WUE was significantly greater (9.47 kg ha−1 mm−1) for switchgrass than for the prairie, eastern redcedar, and oak cover types (6.03, 6.02, and 5.31 kg ha−1 mm−1). Switchgrass offered benefits of greater ANPP, less ET, and greater WUE. Our findings indicate that an integrated biofuel feedstock system that includes converting eastern redcedar encroached areas to switchgrass and thinning the oak forest can increase productivity, increase runoff to streams, and improve ecosystem services. [ABSTRACT FROM AUTHOR]

Perennial bioenergy crops have been shown to increase soil organic carbon (SOC) stocks, potentially offsetting anthropogenic C emissions. The effects of perennial bioenergy crops on SOC are typically assessed at shallow depths (<30 cm), but the deep root systems of these crops may also have substantial effects on SOC stocks at greater depths. We hypothesized that deep (>30 cm) SOC stocks would be greater under bioenergy crops relative to stocks under shallow‐rooted conventional crop cover. To test this, we sampled soils to between 1‐ and 3‐m depth at three sites in Oklahoma with 10‐ to 20‐year‐old switchgrass (Panicum virgatum) stands, and collected paired samples from nearby fields cultivated with shallow rooted annual crops. We measured root biomass, total organic C, 14C, 13C, and other soil properties in three replicate soil cores in each field and used a mixing model to estimate the proportion of recently fixed C under switchgrass based on 14C. The subsoil C stock under switchgrass (defined over 500–1500 kg/m2 equivalent soil mass, approximately 30–100 cm depth) exceeded the subsoil stock in neighboring fields by 1.5 kg C/m2 at a sandy loam site, 0.6 kg C/m2 at a site with loam soils, and showed no significant difference at a third site with clay soils. Using the mixing model, we estimated that additional SOC introduced after switchgrass cultivation comprised 31% of the subsoil C stock at the sandy loam site, 22% at the loam site, and 0% at the clay site. These results suggest that switchgrass can contribute significantly to subsoil organic C—but also indicated that this effect varies across sites. Our analysis shows that agricultural strategies that emphasize deep‐rooted grass cultivars can increase soil C relative to conventional crops while expanding energy biomass production on marginal lands. [ABSTRACT FROM AUTHOR]

Desmodesmus maximus is a potential candidate for algal biofuel production. It was cultivated for lipid enhancement in four different types of wastewater used as algal growth media. After growing Desmodesmus maximus for period of 10 days in four different types of waste water, it was found that swine wastewater collected from Swine Research Center of Oklahoma state university was the best media because of the faster biomass yield and lipid content in the algal biomass. The specific growth rate of algal strain grown in swine waste water was found to be 0.88 µ/d with doubling time T 2 of 1.3 h which shows the better quantity of algal biomass. Algal lipids comprised 72.3 % (dry weight %) of the biomass. In our study wastewater was used as a nutrient source for biofuel production while remediating the waste. Calcined waste eggshells doped with lanthanum and switchgrass biochar were used to catalyze the conversion of algal lipid to biodiesel. Our study found that Biochar doped 950 degree Celsius CaO provided the optimal catalyst. The physicochemical characteristics of wastewater were analyzed and it was found that swine wastewater contains all the vital macro and micronutrients required for the optimal growth of this microalgae. The catalyst synthesized from waste eggshells was characterized by FTIR-ATR, SEM-EDX techniques and N 2 physisorption by Brunauer–Emmett–Teller (BET) theory. The resulting produced biodiesel was analyzed by 1H NMR, 13C NMR, GC-MS techniques. Conversion to biodiesel was 99 % efficient with the optimized catalyst. The catalyst was subjected to 10 runs of transesterification to study reusability. After 10 runs the reused catalyst still provided 77 % conversion efficiency. The result obtained shows that Desmodesmus maximus grown in swine wastewater yields a very good quality and quantity of biodiesel. The waste eggshells and switchgrass can be utilized as renewable heterogeneous catalysts because of their highly porous nature and a more specific surface area that acts as a catalyst in the transesterification reaction of biodiesel. • Utilization of swine waste water as an algae growth media for lipid enhancement of Desmodesmus maximus. • Synthesis of renewable heterogeneous catalyst using chicken waste eggshells doped with switch grass biochar. • The catalyst calcined at Biochar doped 950 ºC CaO catalyst is a very novel, renewable heterogeneous catalyst which gave a biodiesel conversion of 99 %. • The catalyst is reusable upto 10 runs of transesterification reaction with 77 % conversion efficiency in the 10th run. • The biodiesel produced using the Biochar doped 950 ºC CaO catalyst has the fuel properties within the limit of ASTM and EN standards. [ABSTRACT FROM AUTHOR]

Perennial grasses, such as switchgrass ( Panicum viragatum) and Miscanthus ( Miscanthus × giganteus), are potential choices for biomass feedstocks with low-input and high dry matter yield per hectare in the USA and Europe. However, the biophysical potential to grow bioenergy grasses varies with time and space due to changes in environmental conditions. Here, we integrate the dynamic crop growth processes for Miscanthus and two different cultivars of switchgrass, Cave-in-Rock and Alamo, into a land surface model, the Integrated Science Assessment Model (ISAM), to estimate the spatial and temporal variations of biomass yields over the period 2001-2012 in the eastern USA. The validation with observed data from sites across diverse environmental conditions suggests that the model is able to simulate the dynamic response of bioenergy grass growth to changes in environmental conditions in the central and south of the USA. The model is applied to identify four spatial zones characterized by their average yield amplitude and temporal yield variance (or stability) over 2001-2012 in the USA: a high and stable yield zone (HS), a high and unstable yield zone (HU), a low and stable yield zone (LS), and a low and unstable yield zone (LU). The HS zones are mainly distributed in the regions with precipitation larger than 600 mm, and mean temperature range 292-294 K during the growing season, including southern Missouri, northwestern Arkansas, southern Illinois, southern Indiana, southern Ohio, western Kentucky, and parts of northern Virginia. The LU yield zones are distributed in southern parts of Great Plains with water stress conditions and higher temporal variances in precipitation, such as Oklahoma and Kansas. Three bioenergy grasses may not grow in the LS yield zones, including western parts of Great Plains due to extreme low precipitation and poor soil texture, and upper part of north central, northeastern, and northern New England due to extreme cold conditions. [ABSTRACT FROM AUTHOR]

Switchgrass (Panicum virgatum L.) is a perennial C4 grass native to North America that is being developed as a feedstock for cellulosic ethanol production. Industrial nitrogen fertilizers enhance switchgrass biomass production but add to production and environmental costs. A potential sustainable alternative source of nitrogen is biological nitrogen fixation. As a step in this direction, we studied the diversity of nitrogen-fixing bacteria (NFB) associated with native switchgrass plants from the tallgrass prairie of northern Oklahoma (United States), using a culture-independent approach. DNA sequences from the nitrogenase structural gene, nifH, revealed over 20 putative diazotrophs from the alpha-, beta-, delta-, and gammaproteobacteria and the firmicutes associated with roots and shoots of switchgrass. Alphaproteobacteria, especially rhizobia, predominated. Sequences derived from nifH RNA indicated expression of this gene in several bacteria of the alpha-, beta-, delta-, and gammaproteobacterial groups associated with roots. Prominent among these were Rhizobium and Methylobacterium species of the alphaproteobacteria, Burkholderia and Azoarcus species of the betaproteobacteria, and Desulfuromonas and Geobacter species of the deltaproteobacteria. [ABSTRACT FROM AUTHOR]

Storage studies were conducted in 2009 and 2010 on large round (1.83 m × 1.53 m) and square (1.22 m × 1.22 m × 2.44 m) switchgrass bales stored for 6 months. Round and square bales were stored outside under different conditions: tarped (on pallets, gravel and ground) and untarped (on pallets, gravel and ground). Round and square bales were also stored inside and served as a control treatment. During both years, outside tarped bales resisted moisture accumulation and thus dry matter losses were equivalent to bales stored inside. The average dry matter loss for the round and square bales stored inside was 0.6% compared to 0.9 and 2.8% for the tarped round and square bales stored outside, respectively. However, untarped round (11.3%) and square (32.7%) bales on an average had greater dry matter loss than the tarped round (0.9%) and square (2.8%) bales. The untarped square bales consistently had higher moisture contents than untarped round bales which resulted in greater dry matter loss in untarped square bales. Hemicellulose content was more severely affected than cellulose content during storage. In 2010, untarped square bales stored on gravel, ground and pallets lost 30%, 24% and 16% of hemicellulose content, respectively. [ABSTRACT FROM AUTHOR]

Perennial grasses may provide a renewable source of biomass for energy production. Biomass yield, nutrient concentrations, and nutrient removal rates of switchgrass ( Panicum virgatum L.), giant miscanthus ( Miscanthus x giganteus), giant reed ( Arundo donax L.), weeping lovegrass [ Eragrostis curvula (Shrad.) Nees], kleingrass ( Panicum coloratum L.), and Johnsongrass ( Sorghum halepense (L.) Pers.) were evaluated at four N fertilizer rates (0, 56, 112, or 168 kg N ha) on a Minco fine sandy loam soil in southern Oklahoma. Species were established in 2008 and harvested for biomass in winter of 2009 and 2010. Biomass yield (dry matter basis) did not show a strong relationship with N fertilizer rate ( p = 0.08), but was affected by year and species interactions ( p < 0.01). Weeping lovegrass and kleingrass produced 29.0 and 16.0 Mg ha in 2009, but only 13.0 Mg ha and 9.8 Mg ha in 2010, respectively. Biomass yields of giant reed, switchgrass, and Johnsongrass averaged 23.3, 17.8, and 6.0 Mg ha, respectively. Giant miscanthus established poorly, producing only 4.7 Mg ha. Across years, giant reed had the highest biomass yield, 33.2 Mg ha at 168 kg N ha, and the highest nutrient concentrations and removal rates (162 to 228 kg N ha, 23 to 25 kg P ha, and 121 to 149 kg K ha) among the grasses. Although giant reed demonstrated tremendous biomass production, its higher nutrient removal rates indicate a potential for increased fertilization requirements over time. Switchgrass had consistently high biomass yields and relatively low nutrient removal rates (40 to 75 kg N ha, 5 to 12 kg P ha, and 44 to 110 kg K ha) across years, demonstrating its merits as a low-input bioenergy crop. [ABSTRACT FROM AUTHOR]

Native virus-plant interactions require more understanding and their study will provide a basis from which to identify potential sources of emerging destructive viruses in crops. A novel tymovirus sequence was detected in Asclepias viridis (green milkweed), a perennial growing in a natural setting in the Tallgrass Prairie Preserve (TGPP) of Oklahoma. It was abundant within and frequent among A. viridis plants and, to varying extents, within other dicotyledonous and one grass (Panicum virgatum) species obtained from the TGPP. Extracts from A. viridis containing the sequence were infectious to a limited number of species. The virus genome was cloned and determined to be closely related to Kennedya yellow mosaic virus. The persistence of the virus within the Oklahoma A. viridis population was monitored for five successive years. Virus was present in a high percentage of plants within representative areas of the TGPP in all years and was spreading to additional plants. Virus was present in regions adjacent to the TGPP but not in plants sampled from central and south-central Oklahoma. Virus was present in the underground caudex of the plant during the winter, suggesting overwintering in this tissue. The RNA sequence encoding the virus coat protein varied considerably between individual plants (≈3%), likely due to drift rather than selection. An infectious clone was constructed and the virus was named Asclepius asymptomatic virus (AsAV) due to the absence of obvious symptoms on A. viridis. [ABSTRACT FROM AUTHOR]

Switchgrass (Panicum virgatum L.) is an important herbaceous species for use in biofuel production. Genetic improvement of biomass yield and related traits of switchgrass will help ensure efficient feedstock production. To understand the genetics of biomass yield and related traits, 46 full-sib families, including 30 derived using a nested design, were evaluated during 2008 and 2009 in spaced-plant nurseries at Ardmore and Burneyville, OK, following a honeycomb design. Parental genotypes were evaluated adjacent to the family nurseries at Ardmore. Mean biomass yields of full-sib families ranged from 1.32 to 2.18 kg plant-1. One family outperformed checks, while 16 other families performed as well as checks. Results showed a preponderance of additive genes in controlling biomass yield, tillering ability, and spring regrowth. Narrow-sense heritabilities for biomass yield were estimated to be 0.17, 0.14, and 0.24, based on half-sib families, full-sib/half-sib families, and midparent-progeny regression, respectively. Tillering abilities showed similar heritability estimates (0.20-0.24) using either method. For heading and flowering and spring regrowth, the heritability estimates were larger using midparent-progeny regression than using variation among half-sib or full-sib/half-sib families. Heritability for plant height and stem thickness were larger when estimated using half-sib families than full-sib/half-sib families, while the reverse held true for plant spread. Rigorous family evaluation and use of tillering ability, plant height, and stem thickness could be helpful in improving biomass yield in switchgrass. [ABSTRACT FROM AUTHOR]

• Paired watershed is effective in studying runoff response to woody encroachment. • Rooting zone soil moisture increased after converting juniper woodland to grassland. • Juniper removal in central Great Plains resulted in fivefold increase in runoff. Mechanical removal of encroached juniper (Juniperus spp.) is a common practice to restore native grasslands. However, the hydrological responses to grassland restoration remain mostly unquantified for the climate transition zone in the southern Great Plains of the USA where ecosystem evapotranspiration is highly sensitive to the change of vegetation functional type. We used a paired watershed approach to directly quantify the impact of mechanical removal of eastern redcedar (Juniperus virginiana L., redcedar) and restoration to native prairie or establishment of switchgrass (Panicum virgatum L.) on root zone soil moisture and event-based runoff for eight years including three main phases - calibration, transition, and restored grassland in north-central Oklahoma, USA. Results showed that the root zone soil water storage on average increased 1.6 and 1.9 times for restored prairie and switchgrass, respectively, after juniper removal. The regression model estimation based on the relationships established in the calibration phases between event-based runoff from control watershed and the treatment watersheds found that the restored prairie and switchgrass production system increased annual runoff by 4.46 and 4.54 times, respectively. These results indicated that both soil moisture and runoff are highly responsive to land use change in the southern Great Plains. Reestablishment of herbaceous dominance by mechanically removing encroached woody species is closely followed by restoration of soil moisture dynamics and watershed runoff regime. [ABSTRACT FROM AUTHOR]