Warm-season Grasses Research Articles

Tensile strength of warm and cool season forage grasses in Florida.

Grass tensile strength may have implications on animal preference and on the energy that animals must spend during grazing, and consequently on animal performance (feed intake, daily weight gain and milk, and meat production). Information on grass TS would help to select and screen improved forage cultivars and enable to improve grassland management with better animal performance.

Growth response of warm season grass (Cynodon dactylon) to different salinity levels

Growth response of warm season grass (Cynodon dactylon) to different salinity levels

Characterization and Development of EST-SSR Markers from a Cold-Stressed Transcriptome of Centipedegrass by Illumina Paired-End Sequencing

Centipedegrass (Eremochloa ophiuroides) is an important warm-season grass native to the temperate and tropical regions of China. However, only a few centipedegrass molecular markers were available, which hindered genetic studies. Simple sequence repeats (SSRs) can provide abundant genetic information but the traditional method of their development was time-consuming and labor-intensive. Now, RNA-seq platform provides a relatively fast and financially affordable approach for large-scale development of SSRs. Therefore, the transcriptome of centipedegrass under cold stress was determined using Illumina paired-end sequencing in this study. Based on the 56 million paired-end reads, 45,575 unigenes with an average of 748 nt in length were assembled. A total of 8539 SSR loci were then identified. Among them, the tri-nucleotide SSRs were the most dominant repeat type (60.80%, 5192), followed by mono- (16.56%, 1414), di- (14.28%, 1219), hexa- (3.36%, 287), penta- (2.87%, 245), and tetra-nucleotide (2.13%, 182) repeats. The most frequent repeat units from mono- to hexa-nucleotide repeats were A/T, AG/CT, CCG/CGG, AAAG/CTTT, AGGGG/CCCCT, and AGGGCG/CCCTCG, respectively. We successfully designed 3511 primer pairs, and then, randomly selected 99 pairs to evaluate their interspecific transferability and preliminarily analyze the genetic diversity of centipedegrass accessions. There were 90 primer pairs that could successfully amplify targets in at least one centipedegrass samples, and 81 of them could also function in at least three of six other Poaceae relatives and 79 showed polymorphism. Based on the 79 polymorphic markers, all centipedegrass accessions could be divided into two groups, i.e., group 1 from Guangxi province and group 2 from other regions. The EST-SSRs from this study provided a useful tool and foundation for genetic diversity, linkage mapping, comparative mapping, and molecular marker-aided breeding in centipedegrass.

Exploiting Differential Vegetation Phenology for Satellite-Based Mapping of Semiarid Grass Vegetation in the Southwestern United States and Northern Mexico

We developed and evaluated a methodology for subpixel discrimination and large-area mapping of the perennial warm-season (C4) grass component of vegetation cover in mixed-composition landscapes of the southwestern United States and northern Mexico. We describe the methodology within a general, conceptual framework that we identify as the differential vegetation phenology (DVP) paradigm. We introduce a DVP index, the Normalized Difference Phenometric Index (NDPI) that provides vegetation type-specific information at the subpixel scale by exploiting differential patterns of vegetation phenology detectable in time-series spectral vegetation index (VI) data from multispectral land imagers. We used modified soil-adjusted vegetation index (MSAVI2) data from Landsat to develop the NDPI, and MSAVI2 data from MODIS to compare its performance relative to one alternate DVP metric (difference of spring average MSAVI2 and summer maximum MSAVI2), and two simple, conventional VI metrics (summer average MSAVI2, summer maximum MSAVI2). The NDPI in a scaled form (NDPIs) performed best in predicting variation in perennial C4 grass cover as estimated from landscape photographs at 92 sites (R2 = 0.76, p < 0.001), indicating improvement over the alternate DVP metric (R2 = 0.73, p < 0.001) and substantial improvement over the two conventional VI metrics (R2 = 0.62 and 0.56, p < 0.001). The results suggest DVP-based methods, and the NDPI in particular, can be effective for subpixel discrimination and mapping of exposed perennial C4 grass cover within mixed-composition landscapes of the Southwest, and potentially for monitoring of its response to drought, climate change, grazing and other factors, including land management. With appropriate adjustments, the method could potentially be used for subpixel discrimination and mapping of grass or other vegetation types in other regions where the vegetation components of the landscape exhibit contrasting seasonal patterns of phenology.

Plant microfossils in human dental calculus from Nemrik 9, a Pre-Pottery Neolithic site in Northern Iraq

Samples of dental calculus were taken from 11 human individuals buried at Nemrik 9, a Pre-Pottery Neolithic site in Northern Iraq. All of them represented the time span of ca. 9100–8600 bp. In total, 95 microfossils were retrieved from these samples, including 70 phytoliths, 9 starch granules or clusters of starch, 3 pollens, and 1 xylem fragment. Most microfossils could be attributed to C3 cool season cereals, most likely wheat and barley, which is consistent with previous knowledge about the composition of crops in early farming communities living in the Fertile Crescent. In addition, three phytoliths and one starch granule typical of C4 warm season grasses were recovered including one subangular and faceted starch granule, which might derive from a native grass, but is not diagnostic of any genus. Prior to assigning diagnostic status to this starch, exhaustive reference work on native grass seeds is necessary. The presence of one Phragmites phytolith suggests non-alimentary processing of reeds using teeth or perhaps using the stem of this grass as a toothbrush or toothpick.

Converting exotic forages to native warm-season grass can increase avian productivity in beef production systems

Grasslands are among the most imperiled ecosystems in the world, and establishment of exotic forage grasses and management for uniform utilization may have contributed to population declines of many obligate grassland bird species in North America. Native warm-season grasses (NWSG) are increasingly promoted as viable alternatives to exotic forages currently in production such as bermudagrass (Cynodon dactylon) and tall fescue (Schedonorus arundinaceus), but structure of native bunchgrasses also may offer nesting habitat for birds such as the dickcissel (Spiza americana). Establishing NWSG pastures may thereby create an opportunity for land-sharing, where agriculture incorporates biodiversity-friendly practices. We investigated dickcissel responses to NWSG and grazing at the Prairie Research Unit in Monroe Co., Mississippi (USA), where we established a gradient of management intensity among four treatments in small, operational-scale pastures (6.4–10.5ha). Treatments included grazed exotic forages, two grazed NWSG treatments including Indian grass (Sorghastrum nutans) monoculture and grazed mixed NWSG polyculture of Indian grass, little bluestem (Schizachyrium scoparium), and big bluestem (Andropogon gerardii), and a non-grazed NWSG polyculture treatment. We applied a multi-state capture-recapture model in a Bayesian framework to estimate dickcissel nest density and productivity while accounting for nest stage-specific variation in survival and detection. Nest density and productivity were consistently greater in non-grazed NWSG than grazed exotic pasture, whereas productivity in grazed NWSG treatments was intermediate but declined between years. We also found that variation in survival and density did not always correspond with estimated productivity, and thus solely relying on either parameter may be misleading when making inferences on habitat quality. These results suggest a positive response to NWSG among dickcissels in this system, but grazing may reduce nest site abundance, and consequently productivity. Native warm-season forages may be a viable land-sharing alternative by increasing productivity of tall structure specialists such as dickcissels compared with exotic grass pastures currently in production, but grazing should be managed to ensure abundance of tall vegetation structure for nest sites.

Preliminary assessment of mite infestations on warm-season turfgrasses in Australia

Phytophagous mites were first identified as a problem in warm-season turfgrasses in Australia around 80 years ago. In production turfgrass fields, slower growth and weakening of sod strength by mites can cause serious commercial losses through breakage of harvested rolls. Elsewhere, mite infestation is associated with poor wear resistance coupled with very slow recovery of turf on playing fields, thereby reducing the usage that is possible on such fields. At the same time, knowledge about turfgrass mites is lacking: specifically, which mite group/species is/are causing damage and to which turfgrass species. There has long been an underlying assumption, based mainly on overseas literature, that mites of the family Eriophyidae are the main cause of the distorted growth symptoms frequently seen and attributed to mite damage. During the 2010/11 growing season, an Australia-wide survey was conducted, sampling seven warm-season turfgrass genera to determine the mites present in each case. This paper reports the results of that survey, together with data from more recent mite infestations sampled during the subsequent threeyear period. Based on their frequency of occurrence, tenuipalpid mites from the genus Dolichotetranychus appear to be at least as important as eriophyoid mites on Cynodon spp.; Dolichotetranychus mites were also recorded from two survey samples of Zoysia spp. but not in subsequent sampling. Eriophyoid mites of the genus Aceria were found on Cynodon spp., with possibly a second species on Zoysia species. A number of mixed tenuipalpid/eriophyoid populations have also been found on Cynodon species. A Steneotarsonemus species (Tarsonemidae) was found associated with Pennisetum clandestinum. Grass-webbing tetranychid mites (Oligonychus spp.) also occasionally affect a wide range of warm-season turf and other grasses non-selectively.

Alfalfa (Medicago sativa L.) overseeding on mature switchgrass (Panicum virgatum L.) stand: biomass yield and nutritive value after the establishment year

Perennial crops can positively act on the environment providing a better inter-annual protection of soil cover from water erosion, limiting soil fertility degradation, the risk of nutrient leaching and the exploitation of water for irrigation. Switchgrass (Panicum virgatum L.), a warm-season grass native from North America, has been cultivated for decades as forage crop and only recently as bioenergy crop. Even if several studies reported a positive effect of nitrogen (N) supply on switchgrass yield and quality, potential indirect and direct environmental risks (e.g., eutrophication and greenhouse gas emission) are related to this practice. For this reason grass-legume intercropping can represent a sustainable practice able to increase biomass yield and quality, and at the same time to improve N use efficiency, soil structure and fertility. Based on this, the aim of this study was to evaluate the suitability of switchgrass to Mediterranean environment as forage crop and to improve biomass yield and its nutritional value by intercropping with alfalfa (Medicago sativa L). During spring 2013, in two switchgrass pure stands (varieties Alamo and Blackwell, respectively), alfalfa was established through direct seeding implementing a split-plot experimental design. Our first year results report a positive effect of the intercropping in increasing the total annual yield of the stand, of about 20% with respect to the pure switchgrass stand. However, the presence of alfalfa negatively affected switchgrass yield in the mixture. In both varieties, the crude protein content was higher in the mixture than in the pure switchgrass stands. Conversely, the neutral detergent fibre content in the mixture was lower than in pure switchgrass. Then, our results show that switchgrass-alfalfa intercropping leads to increase the profitability of grassland-based livestock production.

Growing Dedicated Energy Crops on Marginal Lands and Ecosystem Services

Core Ideas Dedicated bioenergy crops can enhance ecosystem services in marginal lands. Ecosystem services vary with the type of marginal land. More field data are needed about the performance of energy crops on marginal lands. Marginal lands are candidates for growing dedicated energy crops such as perennial warm‐season grasses (WSGs) and short‐rotation woody crops (SRWCs), but actual field data on ecosystem services have not been widely discussed. This review (i) discusses potential marginal lands studied for energy crop production, (ii) considers the impacts of energy crops on ecosystem services, and (iii) underlines research needs. Some marginal or degraded lands studied for energy crops include highly erodible, flood‐prone, compacted, saline, acid, contaminated, or sandy soils, reclaimed minesoils, urban marginal sites, and abandoned or degraded croplands. Field data are few but indicate that ecosystem services vary with the type of marginal land, management (i.e., fertilizer or amendment rates), and perennial species. Biomass yields can vary between 1 and 14 Mg ha−1 yr−1 under WSGs and between 0.5 and 9.5 Mg ha−1 yr−1 under SRWCs. Growing energy crops on marginal lands can reduce water and wind erosion, sequester soil C between 0.25 and 4 Mg C ha−1 yr−1, restore contaminated or compacted soils, and improve biodiversity. Fertilization or addition of organic amendments increases biomass yield and C sequestration on marginal lands. Future research on energy crops on marginal lands should evaluate (i) all ecosystem services, (ii) site‐specific management strategies, (iii) species tolerant to adverse climatic, soil, and environmental conditions, and (vi) economic viability, among others. Overall, dedicated bioenergy crops can provide biofuel feedstocks and other ecosystem services, but more experimental data are needed to reduce the uncertainty regarding the performance of energy crops under different types of marginal or degraded lands.

Effects of genotype, wilting, and additives on the nutritive value and fermentation of bermudagrass silage.

Bermudagrass is the main warm-season grass species used for livestock production in the southeastern United States; however, when it is ensiled, the silage fermentation parameters are often less than desirable. The objective of this study was to investigate the effects of management practices on the nutritive value and fermentation characteristics of bermudagrass silage. In Exp. 1, treatments were the factorial combinations of 2 bermudagrass genotypes, 'Jiggs' () and 'Tifton 85' ( sp.), 4 additives, and 2 DM concentrations at ensiling. The additives were 1) untreated control (deionized water), 2) Ecosyl, 3) B500, or 4) sugarcane molasses. The 2 DM concentrations at ensiling were low DM (22% DM) or high DM (53% DM). Treatments were replicated 3 times in a completely randomized design. Silage treated with molasses had a lesser ( < 0.05) pH and greater ( < 0.01) lactate concentrations than the control, Ecosyl, and B500 in silage with low DM concentrations and greater ( < 0.01) in vitro true digestibility (IVTD) and lesser ( < 0.01) ADF concentrations than the other treatments at either DM concentration. Silage treated with B500 had the greatest ( < 0.01) aerobic stability, whereas that treated with molasses had the least aerobic stability. However, all treatments presented long aerobic stability (≥150 h). Jiggs had lesser ( < 0.01) ADF and NDF and NDF digestibility (NDFD) concentrations than Tifton 85 and Tifton 85 had greater ( < 0.01) IVTD than Jiggs in the silage with a high DM concentration. In Exp. 2, Jiggs silage treated with either molasses (20 g molasses [DM]/kg forage [as-fed basis]) or nothing (control, untreated silage) was fed to 16 beef heifers ( sp.) in individual drylot pens in a completely randomized design with 8 replicates for voluntary DMI, in vivo apparent DM digestibility, and NDFD evaluations. There were no differences ( = 0.36) among treatments in NDFD; however, there was a trend ( < 0.08) for greater in vivo apparent DM digestibility and DMI in heifers fed the molasses-treated silage. Microbial inoculants had decreased effects on Jiggs and Tifton 85 bermudagrass silage ensiled at a low DM concentration; however, adding molasses was an effective management practice to improve its nutritive value and fermentation characteristics.

Balancing biofuel production and biodiversity: Harvesting frequency effects on production and community composition in planted tallgrass prairie

Native perennial grasslands have been proposed as a source of feedstocks for the production of second-generation lignocellulosic biofuels in the Midwestern USA. Although the consequences of some management decisions for biomass production and plant community composition are well understood (e.g. fertilization), less is known about the effects of harvesting frequency. We compared a once- and twice-annual harvesting regime at two restored prairies in southwestern Michigan established with identical seed mixtures as part of a large-scale bioenergy experiment. We determined biomass production and species composition in experimental plots and also measured the availability of light, inorganic nitrogen and soil moisture. The plant communities that established at the two sites differed markedly in composition and there was little evidence of convergence after five years. At the site dominated by warm-season C4 grasses, single harvests generally produced more biomass than double harvests. By contrast, biomass production was unaffected by harvesting at the more diverse site. Contrary to our prediction that a summer harvest would increase diversity, we found small and subtle effects on plant community composition. This may be due in part to the timing of our harvest treatment. Our results suggest that a single, end-of-season harvest is the best practice for maximizing biomass production in prairies, especially at sites where warm-season grasses dominate. However, at more diverse sites, two harvests can produce the same total biomass and may support other beneficial ecosystem services. This study indicates that in the short term, double harvests are unlikely to affect plant species diversity or community composition in prairie plantings.

Transcriptional regulation of heat shock proteins and ascorbate peroxidase by CtHsfA2b from African bermudagrass conferring heat tolerance in Arabidopsis.

Heat stress transcription factor A2s (HsfA2s) are key regulators in plant response to high temperature. Our objectives were to isolate an HsfA2 gene (CtHsfA2b) from a warm-season grass species, African bermudagrass (Cynodon transvaalensis Burtt-Davy), and to determine the physiological functions and transcriptional regulation of HsfA2 for improving heat tolerance. Gene expression analysis revealed that CtHsfA2b was heat-inducible and exhibited rapid response to increasing temperature. Ectopic expression of CtHsfA2b improved heat tolerance in Arabidopsis and restored heat-sensitive defects of Arabidopsis hsfa2 mutant, which was demonstrated by higher survival rate and photosynthetic parameters, and lower electrolyte leakage in transgenic plants compared to the WT or hsfa2 mutant. CtHsfA2b transgenic plants showed elevated transcriptional regulation of several downstream genes, including those encoding ascorbate peroxidase (AtApx2) and heat shock proteins [AtHsp18.1-CI, AtHsp22.0-ER, AtHsp25.3-P and AtHsp26.5-P(r), AtHsp70b and AtHsp101-3]. CtHsfA2b was found to bind to the heat shock element (HSE) on the promoter of AtApx2 and enhanced transcriptional activity of AtApx2. These results suggested that CtHsfA2b could play positive roles in heat protection by up-regulating antioxidant defense and chaperoning mechanisms. CtHsfA2b has the potential to be used as a candidate gene to genetically modify cool-season species for improving heat tolerance.

Improving aesthetic and diversity of bermudagrass lawn in its dormancy period

Among warm season grasses, Cynodon dactylon (L.) Pers, commonly called bermudagrass, is one of the species that better tolerates drought stress and is the most widely employed for turf in Italy.When temperatures drop below 0°C, bermudagrass plants enter dormancy and eventually leaves turn brown. In spring, exit from dormancy occurs when soil temperatures persist for several days with an average above 10°C. The management of an ornamental turf during dormancy could include the use of other herbaceous species able to enhance aesthetic quality, although no study has so far been carried out on the potential for combined planting of warm season grasses, wildflowers and/or bulbous species. The present study was carried out to (a) evaluate the possibility of integrating into the dormant Cynodon dactylon x C. Transvaalensis cv. Tifway 419 lawn some plants able to enhance the ornamental aspect and biodiversity, (b) attempt to identify the best species, (c) observe phenomena of competition, and (d) define the protocol for cultivation of a lawn composed of hybrid bermudagrass, bulbous, annual and perennial herbaceous plant species.The experiment was carried out on a mature (over 5 years-old) sward of hybrid bermudagrass on which eight bulbous species (geophytes) were planted and eight species of native forbs (wildflowers) were sown. Forbs that could coexist after two years with bermudagrass were B. perennis and G. molle. Concerning the bulbous species C. pulchellus, M. neglectum, G. nivalis and N. minor were suitable to be planted in a Bermuda grass. The presence of these species on a dormant bermudagrass turf improved the aesthetical quality and the diversity of the vegetation; as the studied species are able to attract pollinating insects therefore, support a habitat. Further studies will be required to test the most suitable forbs as a mix in combination with bulbous species.

Species Composition Changes in Conservation Reserve Program (CRP) Grassland When Managed for Biomass Feedstock Production

Grasslands enrolled in the Conservation Reserve Program (CRP) serve as one of the potential national herbaceous resources for use as a dedicated bioenergy feedstock. The goal of this project was to assess the yield potential and suitability of CRP grassland as a bioenergy feedstock source across the USA in regions with significant CRP land resources. In addition to that goal, one major objective of this project was to assess vegetation composition changes that also occurred on these different CRP grasslands over time with different harvest and fertilization management strategies. Three levels of nitrogen fertilization (0, 56, and 112 kg ha−1) and two harvest timings [peak standing crop (PSC) or end of growing season (EGS)] were evaluated for effects on biomass production and resulting species composition changes. Three sites in regions containing concentrated tracts of CRP grassland and representing variable climatic parameters were analyzed for vegetation composition trends over the course of six growing seasons (2008–2013). Specifically, a mixture of warm-season perennial grasses was evaluated in Kansas (KS), while a cool-season mixture was evaluated in Missouri (MO). North Dakota (ND) contained a mixture of both warm- and cool-season grasses. At the MO and KS sites, nitrogen fertilization significantly altered the grass and legume composition over time by lowering the legume percentage in the stand. In KS and ND, the two sites with warm-season grasses, harvesting in mid-summer at PSC, greatly reduced warm-season grass composition over time in favor of annual cool-season grass invaders or perennial cool-season grasses. Any shift to less desirable or less productive species limits the ability of these lands to provide a sustainable or reliable feedstock for bioenergy production.

Long-term Sandhills prairie responses to precipitation, temperature, and cattle stocking rate

Understanding of Sandhills prairie, the most expansive sand dune region stabilized by perennial grasses in the Western Hemisphere, is limited by lack of long-term vegetation data. We used a 26-year dataset to evaluate Sandhills prairie responses to year-to-year variation in precipitation, temperature, and cattle stocking rate. Basal cover, a measurement that is constant seasonally and used to detect long-term changes in bunchgrass vegetation, was measured in 38–40 permanent plots positioned along four transects spanning 769 ha from 1979 to 2007. Across this period, total basal cover averaged 2.4 % and was dominated by warm-season grasses (81.1 %). Schizachyrium scoparium (little bluestem), the dominant warm-season bunchgrass, consisted of 60.0 % relative basal cover. Warm-season grass and total basal cover responded positively to lag 3-year growing season precipitation indicating delayed responses to improved growing season conditions, but these variables also were positively associated with stocking rate. The positive responses may be due to slow spread of warm-season grasses by vegetative structures in response to favorable growing conditions in light to moderately stocked rangeland. Despite its dominance, however, warm-season grass cover had no influence on cover of other functional groups providing weak support for competition as regulator of Sandhills prairie composition. Forb cover was best related in a negative manner to 3-year running mean total precipitation, a surprising result that maybe signaling factors governing basal responses in prairie remain largely unresolved. Woody species cover, however, was positively associated with mean growing season temperatures indicating potential of these to spread under warming scenarios.

Effect of Aminocyclopyrachlor on Seedling Grasses

When invasive weeds are removed with herbicides, revegetation of native species is often desirable. The extended soil activity of aminocyclopyrachlor is important for long-term weed control but could reduce recovery of native species as well. The effect of aminocyclopyrachlor applied alone or with chlorsulfuron on cool- and warm-season grass species commonly used for revegetation was evaluated. The cool-season grasses included green needlegrass, intermediate wheatgrass, and western wheatgrass, whereas the warm-season grasses were big bluestem, sideoats grama, and switchgrass. A separate experiment was conducted for each species. Aminocyclopyrachlor was applied at 91 to 329 g ha−1 alone or with chlorsulfuron from 42 to 133 g ha−1 approximately 30 d after emergence. Warm-season grasses generally were more tolerant of aminocyclopyrachlor than the cool-season grasses evaluated in this study. Switchgrass and big bluestem were the most tolerant of the warm-season species when aminocyclopyrachlor was applied at 168 g ha−1 and averaged 199 and 150% forage production, respectively, compared with the control. Green needlegrass was the most tolerant cool-season grass. Western wheatgrass was the least tolerant species evaluated because forage production only averaged 32% of the control the year after treatment and thus would not be suitable for seeding if aminocyclopyrachlor was applied. The effect of chlorsulfuron applied with aminocyclopyrachlor varied by grass species. For example, green needlegrass injury 8 wk after treatment (WAT) averaged 30 and 48% when aminocylopyrachlor was applied alone, respectively, but injury was reduced to less than 16% when aminocyclopyrachlor was applied with chlorsulfuron. However, injury on the less-tolerant intermediate wheatgrass ranged from 48 to 92% by 4 WAT when aminocyclopyrachlor was applied alone and from 60 to 86% when chlorsulfuron was included in the treatment.

Dedicated Energy Crops and Crop Residues for Bioenergy Feedstocks in the Central and Eastern USA

AbstractDedicated energy crops and crop residues will meet herbaceous feedstock demands for the new bioeconomy in the Central and Eastern USA. Perennial warm-season grasses and corn stover are well-suited to the eastern half of the USA and provide opportunities for expanding agricultural operations in the region. A suite of warm-season grasses and associated management practices have been developed by researchers from the Agricultural Research Service of the US Department of Agriculture (USDA) and collaborators associated with USDA Regional Biomass Research Centers. Second generation biofuel feedstocks provide an opportunity to increase the production of transportation fuels from recently fixed plant carbon rather than from fossil fuels. Although there is no “one-size-fits-all” bioenergy feedstock, crop residues like corn (Zea maysL.) stover are the most readily available bioenergy feedstocks. However, on marginally productive cropland, perennial grasses provide a feedstock supply while enhancing ecosystem services. Twenty-five years of research has demonstrated that perennial grasses like switchgrass (Panicum virgatumL.) are profitable and environmentally sustainable on marginally productive cropland in the western Corn Belt and Southeastern USA.

A Resource-Based Approach to Assessing Interseeding Success in Reconstructed Tallgrass Prairies

Interseeding is a common method used to increase species richness within established reconstructed grasslands. This process depends upon the ability of the practitioner to produce resource conditions that facilitate seedling emergence in systems where such emergence is often limited. We tested effects of a mowing disturbance on interseeding success by seeding a mix of 10 common tallgrass prairie species into 1-m2 plots within two warm-season grass dominated grasslands. We clipped the vegetation on a subset of the plots once or repeatedly and measured environmental variables including litter depth, soil surface light, soil moisture, and soil nitrate within the first growing season. While clipping consistently increased soil surface light, seeded species emergence varied in response to measured environmental resources between sites. In the lowland site, emergence over two growing seasons was primarily explained by microsite and early season light availability. In the more recently burned upland site, emergence was primarily limited by later season light conditions associated with clipping. Despite this variation, seed additions increased plot-scale species richness irrespective of clipping effects mainly as a result of high establishment of wild bergamot ( Monarda fistulosa ) in both sites. It appears that effects of season-long defoliation management on seedling emergence depend on microsite conditions at seeding and we conclude that soil surface and established vegetation management are necessary when interseeding to increase grassland species richness.

Effects of Root-trimming and Cutting-heights on Growth Performance of Potted Native Warm-season Grasses

Mechanized transplanting of native warm-season grass (NWSG) seedlings raised in biodegradable strip-cups may require trimming outgrown and entwined roots to facilitate individual placement and complete root covering. During establishment, mowing is often used to reduce weed competition and promote tillering. In two randomized complete block split-split-plot design experiments, effects of root-trimming and cutting-height on growth and biomass production of potted NWSGs [big bluestem (BB, &lt;em&gt;Andropogon gerardii&lt;/em&gt; Vitman), eastern gamagrass (GG, &lt;em&gt;Tripsacum dactyloides&lt;/em&gt; L.), indiangrass (IG, &lt;em&gt;Sorghastrum nutans&lt;/em&gt; L.), and switchgrass (SG, &lt;em&gt;Panicum virgatum&lt;/em&gt; L.)] were assessed. Six-week old seedlings were transplanted, with or without root-trimming, and four of each type and species, assigned to 10-, 15-, or 20-cm cutting-height. All plants were fertilized uniformly and watered sufficiently. After a 7-d adjustment period, plants were clipped to 10 cm which promoted tillering. A three-week regrowth was then allowed before the first of three forage harvests, at assigned cutting-heights. Plant heights were recorded every two weeks after transplanting and on each harvest date. Data were analyzed for effects of root-trimming, cutting-height, and species. Root-trimming had no effect on the parameters. Cutting-height had no effect on plant heights except for second GG and SG regrowths, and/or the third BB and SG. Cutting-height affected only SG forage biomass significantly (&lt;em&gt;P&lt;/em&gt; &amp;lt; 0.05) during year1 and every species during year2 with 100%+ greater values at the 20- than the 10-cm. All 20-cm average growth rates and belowground biomass in year2 were greater (&lt;em&gt;P&lt;/em&gt; &amp;lt; 0.001) than the 10-cm by &amp;gt; 100%, but with similar root:total biomass ratios. Overall, species yield increased in the order; IG&amp;lt;BB&amp;lt;GG&amp;lt;SG. With adequate soil moisture and fertility, results indicate that root-trimming may not affect growth or forage biomass of NWSGs during establishment. Mowing NWSGs, during establishment, for up to three 20-cm cuts at ≥ 3-week intervals, may not impact recovery growth or belowground biomass, negatively. Results from field studies are required ahead of practical establishment management recommendations.

The enhancement of invasion ability of an annual grass by its fungal endophyte depends on recipient community structure

Most terrestrial plants establish symbiotic associations with microorganisms that enable them to overcome abiotic or biotic filters in ecosystems. Here we investigated how aerial mutualisms involving invasive species may affect the recipient community’s structure. We hypothesized that the endophyte Epichloe occultans enhances the ability of Lolium multiflorum to establish and colonize, but that success would depend on the structure and invasion resistance of the recipient grassland community. Seeds of L. multiflorum with high (E+) and low (E−) endophyte incidence were sown in plots located in grasslands with or without recent grazing history. Relative cover of L. multiflorum and floristic groups was determined during the growing season. Whereas we did not detect any endophyte effect in sites with grazing history, L. multiflorum cover was 63 % in E+ and 27 % in E− plots in sites without grazing history. As cover of L. multiflorum increased in these sites, the cover of warm- and cool-season grasses decreased in spring, with that of warm-season grasses continuing to decrease in summer. These decreases corresponded to 1.9, 3.7 and 1.6 %, for every % increase of L. multiflorum cover. Path analysis and posterior modelling predicted a greater impact of the endophyte on L. multiflorum cover than of seed addition when resident L. multiflorum cover was ≤20 %. This effect decreased asymptotically as L. multiflorum cover increased beyond 20 %. Our results suggest that the endophyte may boost the invasion ability of L. multiflorum particularly in natural grassland without grazing history with potential longer-term consequences for community structure and dynamics.