Search Results (10)

The goal of our study was to evaluate the long-term (>12 years) influence of stocking density and herd rotation frequency on plant and soil microbial community and carbon dynamics in three working ranches in Texas. One ranch utilized a high stocking density and high-frequency (HIGH) rotation where cattle were moved multiple times each day; the second ranch used a medium stocking density and rotation frequency (MED) where herds were moved every 2–3 weeks; and the third ranch used a low stocking density with continuous grazing (LOW). Neither plant nor microbial diversity measures differed between the ranches, but plant functional and microbial community compositions differentiated management strategies. The MED ranch was characterized by a plant community dominated by little bluestem (Schizachyrium scoparium) and had the greatest soil organic matter content (2.8%) and soil respiration rates compared to the LOW (SOM = 2.2%) and HIGH (SOM = 2.1%) ranches. The HIGH ranch had a relatively high abundance and diversity of forbs and introduced grasses, and the LOW ranch had an even mixture of tall, introduced, and cool-season grasses. All three ranches had relatively high levels of Gram-positive bacteria (>70%) with MED having a higher relative abundance of bacteria important for carbon cycling. Furthermore, network analyses suggest that soil microbial communities at all ranches were highly synergistic and exhibited well-defined ecological niches. Differences in soil properties between ranches tended to be minor and suggest that grazing strategies can differ without any substantial shifts in soil and microbial function. Full article

Creating xeric landscapes in lawns and prairies is a significant challenge and practical need in arid urban environments. This study examined the drought resistance of some C4 grass species for constructing urban lawns and prairies. A factorial experiment based on randomized complete block designs with four replications was conducted. Experimental treatments were two irrigation levels (100% and 50% Field Capacity (FC)) and five warm-season grass species (Andropogon gerardii Vitman, Sorghastrum nutans (L.) Nash, Panicum virgatum L., Schizachyrium scoparium (Michx.) Nash, and Bouteloua curtipendula (Michx.) Torr.). The effects of drought on physiological, morphological, and qualitative characteristics of the grass species were analyzed. Drought conditions induced a decrease in all the measured traits. However, fewer physiological, morphological, and qualitative characteristics were affected by drought stress on Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, compared to the other two species. Overall, warm-season grasses of Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, had greater adaptability to drought stress, making them promising C4 grass species for prairie or lawn landscaping in arid urban environments. Landscape professionals and decision-makers should consider using Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, as these were the most resilient grass species for drought-tolerant prairie landscaping schemes. Sorghastrum nutans and Panicum virgatum may be used as a second priority if a more diverse variety of grasses is required for drought-resilient prairie or lawn landscaping in arid cities. Full article

Prairie and savanna ecosystems have declined dramatically worldwide. In the Southeastern United States, longleaf pine savannas have been reduced to less than 3% of their pre-European range. Restoring longleaf pine across the area has become a regional goal. Little bluestem (Schizachyrium scoparium (Michx.) Nash) is critical to carrying the ecologically important fire through this ecosystem in some longleaf pine savannas. Little bluestem has a range that spans most of north America and is thought to display ecotypic variation. As a part of a longleaf pine restoration project in Camden, SC, we investigated whether the seed source of little bluestem and the site preparation techniques impacted the survival and growth of broadcasted seeds. In the field and greenhouse, we compared locally and commercially sourced seeds and field site preparation techniques including discing, raking, or no treatment. At the end of the growing season, there were significantly more plants grown from seeds collected locally compared to plants from seeds available commercially. Plants grown from locally collected seeds also invested more heavily in roots than plants grown from commercial seeds. Site preparation techniques did not appear to significantly impact plant survival. Collecting seed locally will help to ensure long-term restoration success by establishing populations of plants that are adapted to the local environmental conditions. Full article

Gulf cordgrass (Spartina spartinae [Trin.] Merr. ex Hitchc.) and seacoast bluestem (Schizachyrium scoparium [Michx.] Nash var. littorale [Nash] Gould) are dominant native warm season grasses in the Texas Coastal Prairies and Marshes ecoregion. Mature Gulf cordgrass nutritive value is considered poor for grazing animals, while seacoast bluestem nutritive value is considered fair to good in spring and early summer. We compared season of burn effects on crude protein (CP) and neutral detergent fiber (NDF) of these grasses. Our study employed four patches (200–305 ha) burned in a patch-burn grazing system (two winter, two summer 2016). Forage samples were collected before burning and every 3 d for 40 d after burning, then weekly for 50 d. Regardless of season of burning, CP was adequate for maintaining a lactating beef cow 90 d post-burning. Although peak CP in Gulf cordgrass following burning did not differ between seasons, CP increased more quickly following winter burning, when it rose abruptly for ~6.4 d and then increased more slowly to its peak at ~30 d post burn, after which it declined. After summer burning, CP of Gulf cordgrass did not increase significantly, and then declined after reaching its peak at ~29 d post burn. Gulf cordgrass NDF declined more rapidly following summer burning than winter burning but remained low for a longer period after winter burning. In seacoast bluestem, CP increased following winter burning, peaking at ~11 d after burning, but there was little change following summer burning, which did not peak until 31 d post burn. NDF of seacoast bluestem declined similarly in both seasons. This study indicates that prescribed fire during winter is more beneficial for improving the nutritive value of Gulf cordgrass and seacoast bluestem than summer burning. Full article

Coastal dunes are sensitive indicators of climate change: it is expected that higher precipitation and warmer temperature will promote vegetation growth and sand stabilization. Alternatively, dunes may become active during severe droughts, which would reduce plant cover and increase sand mobility. Consequently, it is relevant to explore community shifts and self-organization processes to better understand how coastal dunes vegetation will respond to these projected changes. Primary succession allows the exploration of community assembly and reorganization processes. We focused on three environmental variables (bare sand, temperature, and precipitation) and five successional groups (facilitators, colonizers, sand binders, nucleators, and competitors). For 25 years (from 1991 to 2016), species turnover was monitored in 150 permanent plots (4 × 4 m) placed on an initially mobile dune system located on the coast of the Gulf of Mexico. The spatiotemporal dynamics observed during primary succession were consistent with the facilitation nucleation model. As late colonizers grew and expanded, psammophytes became locally extinct. The spatial patterns revealed that ecological succession did not occur evenly on the dunes. In addition, the increased mean yearly temperature during the last decades seemed to be associated with the accelerated increment in plant cover and species richness, which had not been registered before in Mexico. Full article

Forage management and environmental conditions affect water soluble carbohydrate (WSC) storage, and, in turn, influence ruminant forage utilization in silvopastoral systems. The objective was to determine effects of four dependent variables: forage species [(non-native, C₃ (orchardgrass (Dactylis glomerata L.)) and native C₄ mix (8:1:1 big bluestem (Andropogon gerardii Vitman), little bluestem (Schizachyrium scoparium Michx. Nash) and indiangrass (Sorghastrum nutans L.))]; fertility (poultry litter and an unfertilized control); forage sampling date (mid-May, late-May, early-June, mid-June, and late-June); and hour of day (0800, 1100, 1400, and 1700 h) on WSC accumulation in a silvopasture. Concentrations of WSC (g kg DM⁻¹) were greater (p ≤ 0.05) for C₃ forages, with poultry litter not impacting WSC accumulation. Overall, WSC was greatest in mid-June, with the lowest WSC concentration observed at 0800 compared to 1100, 1400, and 1700 h (p ≤ 0.05). Therefore, harvesting forages later in the day resulted in greater WSC. A stepwise regression model indicated acid detergent fiber, ash, and forage P concentration were the best predictors (R₂ = 0.85, p ≤ 0.05) of forage WSC. These results may be useful in future studies aimed at explaining diurnal cattle grazing preference and optimum forage harvest timing in silvopastoral systems. Full article

Managing grasslands for forage and ground-nesting bird habitat requires appropriate defoliation strategies. Subsequent early-summer species composition in mixed stands of native warm-season grasses (Indiangrass (IG, Sorghastrum nutans), big bluestem (BB, Andropogon gerardii) and little bluestem (LB, Schizachyrium scoparium)) responding to harvest intervals (treatments, 30, 40, 60, 90 or 120 d) and durations (years in production) was assessed. Over three years, phased May harvestings were initiated on sets of randomized plots, ≥90 cm apart, in five replications (blocks) to produce one-, two- and three-year-old stands. Two weeks after harvest, the frequencies of occurrence of plant species, litter and bare ground, diagonally across each plot (line intercept), were compared. Harvest intervals did not influence proportions of dominant plant species, occurrence of major plant types or litter, but increased that of bare ground patches. Harvest duration increased the occurrence of herbaceous forbs and bare ground patches, decreased that of tall-growing forbs and litter, but without affecting that of perennial grasses, following a year with more September rainfall. Data suggest that one- or two-year full-season forage harvesting may not compromise subsequent breeding habitat for bobwhites and other ground-nesting birds in similar stands. It may take longer than a year’s rest for similar stands to recover from such changes in species composition. Full article

Agricultural intensification in America has replaced native warm-season grasses (NWSG) with introduced forages causing wildlife habitat loss and population declines for the northern bobwhite (Colinus virginianus) and similar ground-nesting birds. Reintroducing NWSGs onto managed grasslands to reverse grassland bird population declines lacks information about appropriate multi-purpose management. Post-season nesting habitat quality of mixed NWSGs (indiangrass (IG, Sorghastrum nutans), big bluestem (BB, Andropogon gerardii) and little bluestem (LB, Schizachyrium scoparium)) responding to previous-year(s) harvest intervals (treatments, 30-, 40-, 60-, 90 or 120-d) and duration (years in production), were assessed on late-spring-early-summer re-growths. Yearly phased harvestings were initiated in May on sets of randomized plots, ≥90-cm apart, in five replications (blocks) to produce one-, two-, and three-year old stands by the third year. Sward heights and canopy closure were recorded a day before harvest, followed a week after by visual estimates of ground cover of plant species and litter. Harvesting increased post-season grass cover and reduced forbs following a high rainfall year. Harvested plot swards showed no treatment differences, but were shorter and intercepted more sunlight. Similarly, harvest duration increased grass cover with no year effect but reduced forbs following a high rainfall year. One- or two-year full-season harvesting of similar stands may not compromise subsequent bobwhite nesting-cover provided post-season harvesting starts after the breeding cycle is completed. Full article

Interest in management of native warm-season grasses for multiple uses is growing in southeastern USA. Forage quality response of early-succession mixed stands of big bluestem (BB, Andropogon gerardii), indiangrass (IG, Sorghastrum nutans), and little bluestem (SG, Schizachyrium scoparium) to harvest intervals (30-, 40-, 60-, 90 or 120-d) and durations (one or two years) were assessed in crop-field buffers. Over three years, phased harvestings were initiated in May, on sets of randomized plots, ≥90 cm apart, in five replications (blocks) to produce one-, two-, and three-year-old stands, by the third year. Whole-plot regrowths were machine-harvested after collecting species (IG and LB) sample tillers for leafiness estimates. Species-specific leaf area (SLA) and leaf-to-stem ratio (LSR) were greater for early-season harvests and shorter intervals. In a similar pattern, whole-plot crude protein concentrations were greatest for the 30-d (74 g·kg⁻¹ DM) and the least (40 g·kg⁻¹ DM) for the 120-d interval. Corresponding neutral detergent fiber (NDF) values were the lowest (620 g·kg⁻¹ DM) and highest (710 g·kg⁻¹ DM), respectively. In vitro dry matter and NDF digestibility were greater for early-season harvests at shorter intervals (63 and 720 g·kg⁻¹ DM). With strategic harvesting, similar stands may produce quality hay for beef cattle weight gain. Full article

Tolerance to frequent defoliations is critical for native warm-season grasses managed for forage and wildlife habitat. Yield response of big bluestem (Andropogon gerardii), indiangrass (Sorghastrum nutans), and little bluestem (Schizachyrium scoparium) to treatments (30-, 40-, 60-, 90- or 120-d harvest intervals) and durations were assessed on early-succession mixed stands. Over three years, phased harvestings were initiated in May, on sets of randomized plots, in five replications to produce one-, two-, and three-year old stands, by the third year. Each plot had marked indiangrass and big bluestem plants which were hand-clipped on harvest-days before whole-plot harvesting. Species yields were greater in first- than second-year plots but not affected by treatments. June–September yields in 2008 were greatest for the 30-d, and more in the first- (8472 kg ha⁻¹) than second-year (7627 kg ha⁻¹) plots. In 2009, yields were also greater in first- than second-year plots but without treatment effects. Recovery yields showed no treatment effect, but were about 67% less for second- compared to first-year plots and much less than plots never harvested before. Data suggest that harvesting similar mixed native warm-season grass stands at 30- to 40-d intervals may provide good hay yields without compromising post-season stand recovery for multiple uses. Full article