Warm-season Grasses Research Articles

Seasonal Hay Feeding for Cattle Production in the Fescue Belt

AbstractWe determined how pasture and grazing management practices affected the number of days hay was fed to cattle by season. Data were collected from a survey of Tennessee cattle producers. Days of cattle on hay varied across seasons because of variations in forage production and weather. The number of days hay was fed to cattle varied with pasture-animal management practices such as rotating pastures, forage mixtures, and weed management strategies. Having mixtures of cool- and warm-season grasses reduced the number of days on hay in the winter, spring, and summer months indicating benefits from diversified forages.

Effects of grassland management on overwintering bird communities

ABSTRACTBirds that depend on grassland and successional‐scrub vegetation communities are experiencing a greater decline than any other avian assemblage in North America. Habitat loss and degradation on breeding and wintering grounds are among the leading causes of these declines. We used public and private lands in northern Virginia, USA, to explore benefits of grassland management and associated field structure on supporting overwintering bird species from 2013 to 2016. Specifically, we used non‐metric multidimensional scaling and multispecies occupancy models to compare species richness and habitat associations of grassland‐obligate and successional‐scrub species during winter in fields comprised of native warm‐season grasses (WSG) or non‐native cool‐season grasses (CSG) that were managed at different times of the year. Results demonstrated positive correlations of grassland‐obligate species with decreased vegetation structure and a higher percentage of grass cover, whereas successional‐scrub species positively correlated with increased vegetation structure and height and increased percentages of woody stems, forb cover, and bare ground. Fields of WSG supported higher estimated total and target species richness compared to fields of CSG. Estimated species richness was also influenced by management timing, with fields managed during the previous winter or left unmanaged exhibiting higher estimated richness than fields managed in summer or fall. Warm‐season grass fields managed in the previous winter or left unmanaged had higher estimated species richness than any other treatment group. This study identifies important winter habitat associations (e.g., vegetation height and field openness) with species abundance and richness and can be used to make inferences about optimal management practices for overwintering avian species in eastern grasslands of North America. © 2019 The Authors. Journal of Wildlife Management Published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.

Molecular Dissection of Quantitative Variation in Bermudagrass Hybrids (Cynodon dactylon x transvaalensis): Morphological Traits.

Bermudagrass (Cynodon (L.)) is the most important warm-season grass grown for forage or turf. It shows extensive variation in morphological characteristics and growth attributes, but the genetic basis of this variation is little understood. Detection and tagging of quantitative trait loci (QTL) affecting above-ground morphology with diagnostic DNA markers would provide a foundation for genetic and molecular breeding applications in bermudagrass. Here, we report early findings regarding genetic architecture of foliage (canopy height, HT), stolon (stolon internode length, ILEN and length of the longest stolon LLS), and leaf traits (leaf blade length, LLEN and leaf blade width, LW) in 110 F1 individuals derived from a cross between Cynodon dactylon (T89) and C. transvaalensis (T574). Separate and joint environment analyses were performed on trait data collected across two to five environments (locations, and/or years, or time), finding significant differences (P < 0.001) among the hybrid progeny for all traits. Analysis of marker-trait associations detected 74 QTL and 135 epistatic interactions. Composite interval mapping (CIM) and mixed-model CIM (MCIM) identified 32 main effect QTL (M-QTL) and 13 interacting QTL (int-QTL). Colocalization of QTL for plant morphology partially explained significant correlations among traits. M-QTL qILEN-3-2 (for ILEN; R2 = 11–19%), qLLS-7-1 (for LLS; R2 = 13–27%), qLEN-1-1 (for LLEN; R2 = 10–11%), and qLW-3-2 (for LW; R2 = 10–12%) were ‘stable’ across multiple environments, representing candidates for fine mapping and applied breeding applications. QTL correspondence between bermudagrass and divergent grass lineages suggests opportunities to accelerate progress by predictive breeding of bermudagrass.

Phenotypic plasticity to drought in seedlings of the warm season grass Panicum coloratum is related to collection site

AbstractPhenotypic plasticity is the ability of organisms to modify their phenotype in response to environmental changes. We estimated and compared the amount of phenotypic plasticity in response to drought in seedlings of different accessions of two varieties (var. makarikariense and var. coloratum) of Panicum coloratum, an allogamous warm season perennial grass, introduced and collected in sites in Argentina with different precipitation regimes. Amount of phenotypic plasticity was quantified in shoot/root biomass, blade/sheath biomass, specific leaf area and leaf area ratio (leaf area/total biomass) and mean phenotypic plasticity was estimated. The two genetically distinct varieties differed in the phenotypic plasticity of leaf area ratio (p = 0.008, F‐test), with var. makarikariense showing higher phenotypic plasticity. Accessions within varieties differed in phenotypic plasticity of leaf area ratio, specific leaf area, blade/sheath biomass and mean phenotypic plasticity (p &lt; 0.05, F‐test). A strong relationship (r = 0.82, p &lt; 0.01, F‐test) between mean phenotypic plasticity of each accession and precipitation variability was found. Relationships between phenotypic plasticity of blade/sheath biomass and leaf area ratio with annual mean precipitation were r = 0.86 and r = 0.75, respectively (p &lt; 0.05; p &lt; 0.01, F‐test, respectively). Evidence of a decoupling between phenotypic plasticity of above‐ versus belowground characters was apparent; outcomes on the interpretation of the variability in phenotypic plasticity and the potential applications of this variability are presented.

Pasture-scale vegetation predicts Dickcissel nest-site selection and success in native and exotic grass pastures

AbstractExotic grasses such as bermudagrass (Cynodon dactylon) and tall fescue (Schedonorus arundinaceus) are widely established across the southeastern United States as livestock forage, but their structure and management can limit avian reproductive success. Native warm-season grasses (NWSG) are promoted as sustainable forage alternatives. To examine nesting suitability for tall structure specialists such as Dickcissels (Spiza americana) we established an operational-scale study in northeastern Mississippi, USA, with 4 treatments along a gradient of beef production intensity. Treatments included grazed exotic forages, 2 grazed NWSG treatments including Indiangrass (Sorghastrum nutans) monoculture and NWSG polyculture of Indiangrass, little bluestem (Schizachyrium scoparium), and big bluestem (Andropogon gerardii), and an ungrazed NWSG polyculture treatment. We monitored 208 Dickcissel nests in 2011 and 2012 to evaluate effects of treatment, vegetation structure, fire ants (Solenopsis spp.), and arthropod prey biomass on nest-site selection and nest survival. Survival rates varied among treatments and increased with pasture-scale visual obstruction reading (VOR), being lowest among grazed exotic grass, intermediate in grazed NWSG, and highest in ungrazed NWSG. Although Dickcissels selected nest sites with greater VOR, we found little support for effects of nest-site vegetation on survival. However, nest survival was lower for nests in shrubs that also occurred in pastures with greater shrub cover, and selection for shrubs declined as pasture-scale VOR increased, suggesting a functional response in selection. We found little support for food availability influencing nest survival. These results suggest NWSG pastures increase Dickcissel nest success through greater pasture-scale VOR by reducing Dickcissel selection of shrubs for nest sites, and possibly by reducing predator efficiency. Incorporating NWSG into beef production systems while maintaining availability of tall vegetation could benefit Dickcissels and other tall structure specialists.

Defoliation management and grass growth habits modulated the soil microbial community of turfgrass systems.

Grass species selection and regular mowing are essential for maintaining aesthetic and environmentally sound turfgrass systems. However, their impacts on the soil microbial community, the driving force for soil N cycle and thus the environmental fate of N, are largely unknown. Here, the high throughput sequencing of 16S rRNA gene and internal transcribed spacer (ITS) region was used to evaluate how long-term defoliation management and grass growth habits (propagation types and photosynthetic pathways) modulated the soil microbial community. The investigation included three cool-season C3 grasses (creeping bentgrass, Kentucky bluegrass, and tall fescue) and three warm-season C4 grasses (bermudagrass, St. Augustinegrass, and zoysiagrass). Creeping bentgrass and bermudagrass were managed as putting greens with a lower mowing height; tall fescue spread in a tussock manner via tiller production whereas other grasses propagated in a creeping manner via rhizomes and/or stolons. Ordination analysis showed that both bacterial and fungal communities were primarily separated between putting green and non-putting green systems; and so were N-cycle gene relative abundances, with the putting greens being greater in N mineralization but lower in nitrification. Compared to warm-season grasses, cool-season grasses slightly and yet significantly enhanced the relative abundances of Chloroflexi, Verrucomicrobia, and Glomeromycota. Tall fescue yielded significantly greater bacterial and fungal richness than non-tussock grasses. As the main explanatory soil property, pH only contributed to < 18% of community compositional variations among turfgrass systems. Our results indicate that defoliation management was the main factor in shaping the soil microbial community and grass growth habits was secondary in modulating microbial taxon distribution.

Characterization of Nutrient and Metal Leaching in Roadside Ditches Maintained with Cool and Warm Season Grasses

Roadside ditches play an important role in the quantity and quality of receiving waters. Very little, however, is known about the fate and transport of nutrients and trace metals in roadside ditches, especially their leaching to shallow groundwater. This study sought to document selected water quality constituent levels in infiltrated water (i.e., leachate) in roadside ditches maintained with permanent vegetation. Leachate sampling wells were installed in four roadside ditches, and water samples were collected from the wells following major rainfall events during the years 2016 and 2017. The samples were analyzed for nutrient and metal concentrations. Results indicated that nutrient concentrations in the water samples range from 0.00600 to 0.0107 mg/L for orthophosphate (PO4–P), 0.00500 to 6.80 mg/L for nitrate (NO3–N), 0 to 0.007 mg/L for nitrite (NO2–N), and 0.0100 to 314 mg/L for chloride (Cl−). Concentrations of the metals examined varied between 0.0100 and 104 mg/L in water samples. While there was no specific pattern in both nutrient and metal concentrations when roadside ditches maintained with cool season grass were compared to those of warm season grass ditches, results suggest that grass types will likely affect differently uptake of nutrients and metals in the ditches.

Effects of trees and nitrogen supply on the soil microbiological attributes on integrated crop-livestock systems

ABSTRACT The diversification of plants, as an association between trees and the warm-season grasses, supports soil biodiversity and thus, soil quality. However, based on the prevailing climatic conditions, management techniques employed and because of the several combinations possible in such associations, variations may be observed in this type of response. This study aimed at assessing the microbiological attributes of the soil in two systems (full sunlight, FS, vs. a naturally shaded system composed of Eucalyptus dunnii trees), with two N fertilization levels (zero vs. 300 kg N ha-1year-1) and five perennial warm-season grasses. Soil and root samples were drawn from a depth of 0 to 20 cm when the growing period began. The N fertilization increased the mycorrhizal colonization and the acid phosphatase activity, whereas lowered the soil microbial biomass. A rise in the mycorrhizal colonization and sporulation and C microbial biomass concentration were observed in the soil cultivated with Axonopus catharinensis. The association with trees favored the arbuscular mycorrhizal fungal communities, boosting both colonization and sporulation. However, compared with the FS, the soil microbial biomass and activity of the acid phosphatase enzyme were reduced under the trees. Silvicultural interventions could be intensified to enhance soil quality.

Associations Between Oil and Gas Wells and Arthropod and Vegetation Communities in the Southern Plains

Understanding how energy infrastructure affects local biodiversity and soil characteristics is important for informing restoration and management. However, the rapid rate of modern oil and gas development is beyond the limit of current knowledge and mitigation strategies. In a mixed-grass prairie in western Oklahoma, we assessed the presence and directionality of biodiversity and environmental gradients associated with energy development in an observational framework. Specifically, we sampled arthropods, vegetation, soil temperature, and soil moisture on the edge of active oil well pads and at 1 m, 10 m, and 100 m away from the well pad. Though variable, the abundance and biomass of most arthropod orders was lower on the pad and 1 m away compared with 10 m and 100 m away, suggesting that the pad itself negatively influenced arthropods but that these effects were limited in spatial extent. However, vegetation structure and composition varied more extensively. Vegetation height, shrub cover, and warm season grass cover increased sixfold, threefold, and fourfold, respectively, from on the oil pad to 100 m away. Forb cover was 5× higher at 10 m from the well pad than on the pad, 1 m away, and 100 m away from the pad. Soil surface temperature was lower at sites farther from well pads, but we found no relationship between soil moisture and distance from well pad. Well pad effects on arthropods and soil temperature appear to be limited to the pad itself, though long-term changes in vegetation structure extend significantly beyond the well footprint and demand a better understanding of the effectiveness of restoration activities around well pads.

Six different football shoes, one playing surface and the weather; Assessing variation in shoe-surface traction over one season of elite football.

IntroductionAn optimal range of shoe-surface traction (grip) exists to improve performance and minimise injury risk. Little information exists regarding the magnitude of traction forces at shoe-surface interface across a full season of elite football (soccer) using common football shoes.ObjectiveTo assess variation in shoe-surface traction of six different football shoe models throughout a full playing season in Qatar encompassing climatic and grass species variations.MethodsFootball shoes were loaded onto a portable shoe-surface traction testing machine at five individual testing time points to collect traction data (rotational and translational) on a soccer playing surface across one season. Surface mechanical properties (surface hardness, soil moisture) and climate data (temperature and humidity) were collected at each testing time point.ResultsPeak rotational traction was significantly different across shoe models (F = 218, df = 5, p <0.0001), shoe outsole groups (F = 316.2, df = 2, p < .0001), and grass species (F = 202.8, df = 4, p < 0.0001). No main effect for shoe model was found for translational traction (F = 2.392, p = 0.07).ConclusionsThe rotational (but not translational) traction varied substantially across different shoe types, outsole groups, and grass species. Highest rotational traction values were seen with soft ground outsole (screw-in metal studs) shoes tested on warm season grass. This objective data allows more informed footwear choices for football played in warm/hot climates on sand-based elite football playing surfaces. Further research is required to confirm if these findings extend across other football shoe brands.

Identification of Quantitative Trait Loci for Plant Height, Crown Diameter, and Plant Biomass in a Pseudo-F2 Population of Switchgrass

Switchgrass (Panicum virgatum) is a perennial warm-season grass that produces high biomass yield. Identification of mechanisms for genetic regulation of biomass traits has potential to facilitate genetic manipulation of switchgrass for enhancing biomass yield. The objective of this study was to identify quantitative trait loci for biomass-related traits in a pseudo-F2 population of switchgrass derived from an upland cross with a lowland switchgrass cultivar. Plant height (HT), crown diameter (CD), and plant biomass (PB) were assessed in field studies in 2015 and 2016. Plant height was positively correlated with PB in both years but only correlated with CD in 2016. Positive correlations between CD and PB were found in both years. Six quantitative trait loci (QTLs) were detected, including three QTLs on chromosome 2b for HT (2015) or CD (2016), two 2 QTLs on chromosome 2a for CD and PB in 2016, and one QTL on chromosome 5b for CD in 2016. The logarithm of the odds scores for these QTLs ranged from 4.9 to 8.2, and percentage variance explained ranged from 7.1 to 12.9%. One QTL on chromosome 2b appeared to simultaneously control HT in 2015 and CD in 2016. Homologs of candidate genes related to cell wall development and biosynthesis, hormone regulation, and metabolism were identified within the confidence interval of these QTLs. The findings from this study indicate that these QTLs can be important signals for genetic control of switchgrass growth.

Association of SSR Markers with Cold Tolerance Traits in Diverse Bermudagrass [Cynodon dactylon (L.) Pers.] Accessions

Bermudagrass [Cynodon dactylon (L.) Pers.] is a perennial and typical warm-season grass. It undergoes withering and severe damage under cold stress; thus, cold is considered as a key factor that restricts the widespread use in bermudagrass. Identification of association between molecular markers and cold tolerance-related traits would facilitate the efficient selection of cold tolerant bermudagrass cultivars. A total of 106 diverse bermudagrass accessions, including 4 commercial cultivars and 102 wild germplasms, were tested for cold tolerance and analyzed by 104 simple sequence repeat (SSR) markers. Cold significantly decreased transpiration rate, growth rate and turf quality. There were significant variations in these trait values among the accessions under cold conditions. Two subpopulations were detected in the panel of accessions based on the analysis of 1474 alleles with 104 SSR markers. Clustering analysis revealed that the genetic relationship was affected by the natural habitats. Thirty-four SSR markers were identified to be associated with two or three traits based on the corrected P values (P < 3.5 × 10−4). These markers can be used for genetic improvement of cold tolerance of bermudagrass after further validation.

Genetic diversity and population structure of Brachiaria brizantha (A.Rich.) Stapf accessions from Ethiopia

Brachiaria is a tropical, warm-season grass native to Africa. It is an extensively cultivated forage in the tropics with proven benefits on livestock productivity. Brachiaria is well-known for high biomass production, animal nutrition, carbon sequestration, biological nitrification inhibition, soil conservation, and adaptation to drought and low fertility soils. However, the use of Brachiaria grass for fodder production in Africa has been little explored largely due to lack of cultivars suitable to different production environments. The exploration and use of natural diversity is fundamental for an efficient Brachiaria breeding program. We analysed genetic diversity and population structure of 112 Ethiopian Brachiaria brizantha accessions using 23 microsatellite markers. A total of 459 alleles were detected with an average polymorphic information content of 0.75 suggesting high discriminating ability of these markers. The molecular variance analysis showed a high contribution (86%) of within-cluster differences to the total variation. Three allelic pools revealed by STRUCTURE analysis in 112 accessions were in agreement with the clustering patterns seen in neighbor-joining tree and principal coordinates analyses. A core collection of 39 B. brizantha accessions was constituted. This study concludes a high genetic diversity of Ethiopian B. brizantha accessions and their importance in Brachiaria breeding programs.

Switchgrass as forage and biofuel feedstock: Effect of nitrogen fertilization rate on the quality of biomass harvested in late summer and early fall

Switchgrass (Panicum virgatum L.) is a perennial warm-season grass which has great potential as a forage or bioenergy crop in marginal land. This study was conducted to determine whether nitrogen (N) fertilization could affect biomass quality of switchgrass harvested in late summer and early fall. The effects of four N fertilizer application rates (0, 60, 120, and 240 kg N ha−1) and two harvest times (late summer and early fall) on the quality components of forage and biofuel feedstock and theoretical ethanol yield (TEY) were investigated on a sandy wasteland (Aridisol) in Inner Mongolia, China during the growing seasons of 2015 and 2016. Soil NO3− content was also examined in response to N application rates. Application of 60 kg N ha−1 significantly increased switchgrass crude protein (CP) content, protein yield, and TEY (p < 0.05), but did not affect other quality parameters of forage and biofuel feedstock. Compared with the late summer harvest, CP content and protein yield were significantly lower, while TEY was significantly higher in the early fall harvest (p < 0.05); however, cellulose, hemicellulose, and ash contents showed no significant differences between the two harvest times. Acid detergent fiber (ADF) and neutral detergent fiber (NDF) contents were significantly lower for harvest in early fall than in late summer (p < 0.05). Soil NO3− content in early fall harvest increased significantly with increasing N application rate (p < 0.05), and was lower than that in the switchgrass green-up stage. These findings together with our results on biomass yield and apparent soil N balance suggest that a lower rate of N application appears sufficient to produce good quality forage as well as biomass without negatively affecting feedstock quality, while avoiding the risk of NO3− loss via leaching on a sandy soil. Switchgrass forage quality would be high during summer in terms of CP content, although delaying harvest until fall or even after a killing frost could provide better quality feedstock for bioenergy production.

Cover crop mixture diversity, biomass productivity, weed suppression, and stability.

The diversity-productivity, diversity-invasibility, and diversity-stability hypotheses propose that increasing species diversity should lead, respectively, to increased average biomass productivity, invasion resistance, and stability. We tested these three hypotheses in the context of cover crop mixtures, evaluating the effects of increasing cover crop mixture diversity on aboveground biomass, weed suppression, and biomass stability. Twenty to forty cover crop treatments were replicated three or four times at eleven sites using eighteen species representing three cover crop species each from six pre-defined functional groups: cool-season grasses, cool-season legumes, cool-season brassicas, warm-season grasses, warm-season legumes, and warm-season broadleaves. Each species was seeded as a pure stand, and the most diverse treatment contained all eighteen species. Remaining treatments included treatments representing intermediate levels of cover crop species and functional richness and a no cover crop control. Cover crop seeding dates ranged from late July to late September with both cover crop and weed aboveground biomass being sampled prior to winterkill. Stability was assessed by evaluating the variability in cover crop biomass for each treatment across plots within each site. While increasing cover crop mixture diversity was associated with increased average aboveground biomass, we assert that this was the result of the average biomass of the pure stands being drawn down by low biomass species rather than due to niche complementarity or increased resource use efficiency. At no site did the highest biomass mixture produce more than the highest biomass pure stand. Furthermore, while increases in cover crop mixture diversity were correlated with increases in weed suppression and biomass stability, we argue that this was largely the result of diversity co-varying with aboveground biomass, and that differences in aboveground biomass rather than differences in diversity drove the differences observed in weed suppression and stability.

The mechanism behind lack-of-effect of lanthanum on seed germination of switchgrass.

Switchgrass (Panicum virgatum L.) is a perennial warm-season C4 grass identified as a model species for bioenergy feedstock production. Lanthanum (La) as a rare earth element can stimulate the physiological processes of plant growth. The purpose of this study was to investigate the effect of lanthanum on seed germination of switchgrass. However, no significant differences in seed germination were found. The energy dispersive X-ray analysis showed that abundant lanthanum deposits resided on the pericarp and testa of the seed while few lanthanum deposits were present on the aleurone and endosperm. This phenomenon demonstrates that a semi-permeable layer, which could restrict or impede solute exchange, while allowing the permeability of internal and external water and gas, may be located between the testa and aleurone. Light microscopy and histochemical analysis revealed that the main chemical composition of the semi-permeable layer would be expected to be suberin because the layer was stained yellow with aniline blue. The quantum chemical calculations predict that the intervals between adjacent carbon chains in suberin molecule are so small that lanthanum ([La(H2O)8]3+) cannot pass through the suberin molecule. In conclusion, the seed germination of switchgrass is not affected by lanthanum because the semi-permeable layer restricts the penetration of lanthanum into the embryo.

Dedicated Bioenergy Crops and Water Erosion.

Information on the water quality impact of perennial warm-season grasses (WSGs) when grown in marginal lands as dedicated energy crops is limited. We studied how WSGs affected runoff, sediment, and nutrient losses and related near-surface soil properties to those of no-till corn ( L.) on an eroded soil in southwestern Iowa and a center pivot corner in east-central Nebraska. The experiment at the eroded soil was established in 2012, and treatments included 'Liberty' switchgrass ( L.) and no-till continuous corn. The experiment at the pivot corner was established in 2013 with 'Liberty' switchgrass, 'Shawnee' switchgrass, low-diversity grass mixture, and corn. We simulated rainfall at 63.5 ± 2.8 mm h for 1 h to portray 5-yr return periods and measured water erosion in spring 2017. Time to runoff start and runoff depth did not differ between WSGs and corn. On the eroded soil, sediment and nutrient losses did not differ between treatments. At the pivot corner, sediment (0.71 vs. 0.15 Mg ha) and PO-P (0.037 vs. 0.006 kg ha) losses were five times higher in corn than in WSGs. Near-surface soil properties did not differ on the eroded soil, but at the pivot corner, wet aggregate stability was four times higher and residue cover was 34% higher in WSGs than in corn. Water-stable aggregates were negatively correlated with NO-N and PO-P losses. Overall, WSGs can improve water quality in marginally productive croplands, but their effectiveness appears to be site specific.

Cool-season Grasses for Overseeding Sport Turfs: Germination and Performance under Limiting Environmental Conditions

In the transition zone, warm-season grasses are often overseeded with diploid perennial ryegrass (Lolium perenne L., 2n = 2x = 14) to provide a temporary green surface for winter sporting activities. Because improved cultivars of perennial ryegrass will often persist into summer in overseeded turf, alternative cool-season grasses have been developed to facilitate more rapid transition back to the warm-season species. Limited information is available on these alternative species, especially with regard to their germination characteristics under shade and performance under limiting factors, such as low temperature and restricted photoperiod. Greenhouse and growth chamber studies were designed to test four alternative overseeding grasses in comparison with diploid perennial ryegrass, to verify their potential use in the artificial environment of modern stadiums. Meadow fescue (Festuca pratensis Huds.), tetraploid perennial ryegrass (Lolium perenne L., 2n = 4x = 28), annual ryegrass (Lolium multiflorum Lam.), and spreading diploid perennial ryegrass [Lolium perenne L. subsp. stoloniferum (C. Lawson) Wipff.] were tested. Six different shade treatments were used in the greenhouse study, including 30%, 50%, 70%, 90%, and 100% shade and a nonshaded control (0% shade). Germination was monitored daily over a 21-day period by counting and removing emerged seedlings. The experimental design for this study was a randomized complete block design, with four replications of each species and shade level for a total of 120 experimental units. In the growth chamber study, the same plant material was tested simulating optimal, suboptimal, and critical environmental conditions that can be potentially found within a modern sport facility. In the greenhouse study, the highest final germination was observed with annual ryegrass at 90% shade (98.7%), whereas the lowest for tetraploid perennial ryegrass at 30% shade (58.8%). Annual ryegrass was the fastest emerging species, whereas meadow fescue the slowest. In the growth chamber study, in comparison with perennial ryegrass, the following results may be summarized: 1) meadow fescue and tetraploid ryegrass showed coarser leaf texture, similar growth rates and Normalized Difference Vegetation Index (NDVI) value; 2) annual ryegrass had similar leaf texture, accelerated growth characteristics, and lower NDVI value; and 3) spreading perennial ryegrass displayed finer leaf texture, lower vertical growth, and similar NDVI value.

Carbon and evapotranspiration dynamics of a non-native perennial grass with biofuel potential in the southern U.S. Great Plains

Old world bluestem cultivar WW-B Dahl [Bothriochloa bladhii (Retz.), S. T. Blake] is a non-native perennial C4 bunch grass with biofuel production potential grown predominantly in the Southern U.S. Great Plains. Although this is a popular introduced grass cultivar, data on carbon fluxes and evapotranspiration (ET) from this warm-season grass is rare. In this study, the eddy covariance method was used to measure CO2 and ET from an established stand of bluestem for three years (2013–2015). Year 2015 had the highest gross primary production (GPP; 1358 ± 143 g C m−2) followed by 2014 (1250 ± 31 g C m−2) and 2013 (1024 ± 91 g C m−2). The average loss of GPP as ecosystem respiration (Reco) was 76%. Annual NEE sums were -302 ± 15 g C m−2 in 2013, -265 ± 41 g C m-2 in 2014, and -287 ± 32 g C m−2 in 2015. Results from this study show that the NEE in grasslands in years with normal precipitation that is well distributed may not vary from years with above-normal precipitation. This is because precipitation enhances Reco along with carbon uptake, which may result in lower net carbon uptake in perennial grasslands in higher precipitation years than normal precipitation years. Gross primary production showed a linear relationship with ET (R2 = 0.90) and above ground biomass (R2 = 0.74). Only 26% of the GPP was allocated to above ground biomass indicating a higher allocation of carbon to below ground biomass. The water use efficiency of bluestem (2.9 g C kg-1 of water) matched well with that of native prairies and other dedicated biomass crops grown in the Southern Great Plains. As the demand for cellulosic biofuels is increasing, results from field experiments quantifying seasonal changes in carbon fluxes and ET could be important in understanding the contributions of large-scale production of novel biomass crops to regional carbon and hydrologic cycles.

Evaluating the Utility of Species Distribution Models in Informing Climate Change-Resilient Grassland Restoration Strategy

Tallgrass prairie ecosystems in North America are heavily degraded and require effective restoration strategies if prairie specialist taxa are to be preserved. One common management tool used to restore grassland is the application of a seed-mix of native prairie plant species. While this technique is effective in the short-term, it is critical that species’ resilience to changing climate be evaluated when designing these mixes. By utilizing species distribution models (SDMs), species’ bioclimatic envelopes–and thus the geographic area suitable for them–can be quantified and predicted under various future climate regimes, and current seed-mixes may be modified to include more climate resilient species or exclude more affected species. We evaluated climate response on plant functional groups to examine the generalizability of climate response among species of particular functional groups. We selected fourteen prairie species representing the functional groups of cool-season and warm-season grasses, forbs, and legumes and we modeled their responses under both a moderate and more extreme predicted future. Our functional group ‘composite maps’ show that warm-season grasses, forbs, and legumes responded similarly to other species within their functional group, while cool-season grasses showed less inter-species concordance. The value of functional group as a rough method for evaluating climate-resilience is therefor supported, but candidate cool-season grass species will require more individualized attention. This result suggests that seed-mix designers may be able to use species with more occurrence records to generate functional group-level predictions to assess the climate response of species for which there are prohibitively few occurrence records for modeling.