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bluestem (Schizachyrium scoparium (Michx.) Nash [Poaceae]) selected germ-plasm lines 'NU-1', PI 676262; 'NU-2', PI 676263; 'UC-1', PI 676264; 'UC-2', PI 676265; 'UO-1', PI 676266; 'UO-2', PI 676267; and 'UO-3', PI 676268 are synth...
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bluestem (Schizachyrium scoparium (Michx.) Nash [Poaceae]) selected germ-plasm lines 'NU-1', PI 676262; 'NU-2', PI 676263; 'UC-1', PI 676264; 'UC-2', PI 676265; 'UO-1', PI 676266; 'UO-2', PI 676267; and 'UO-3', PI 676268 are synthetic populations selected for canopy morphology. We open-pollinated 727 plants representing 19 accessions to produce seeds for a synthetic population. Accessions were from Texas (12), Rhode Island (1), Wyoming (1), South Dakota (2), and 3 were cultivars. The synthetic population consisted of 4644 plants. After mass selection for canopy morphology, resistance to leaf rust (Puccinia andropogonis [Pucciniaceae]), resistance to culm lodging, and tolerance to a high pH soil, 476 plants remained. We used a cluster analysis to group the selected plants into 7 synthetic populations. Variables used for clustering within each canopy morphology were flowering date, plant height, canopy width, abaxial leaf color hue, value, and chroma; adaxial leaf color hue, value, and chroma; leaf blade length score, leaf blade width score, adaxial leaf angle score, and culm-base leafiness score. The 7 germplasm populations are useful for the breeding and (or) development of cultivars for wildlife habitat, grazing utilization, roadside stabilization, renewable energy, and (or) horticultural landscapes in the southern Great Plains of the US.
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Fire suppression has removed an important ecological force previously responsible for shaping many plant communities throughout the world. Upland areas of north-central Mississippi that have been protected from fire are now closed...
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Fire suppression has removed an important ecological force previously responsible for shaping many plant communities throughout the world. Upland areas of north-central Mississippi that have been protected from fire are now closed-canopy forests including species known to be uncommon as bearing/witness trees in upland portions of the landscape (historically off-site species) and sparse ground cover vegetation. Anecdotal evidence suggests that warm-season grasses were prevalent in the understory of these communities, which could have provided more consistent fuel. We corroborate the historic presence of these grasses by looking at their natural co-occurrence with oak regeneration (a requisite of self-replacing stands of oaks found historically). Restoration of these communities has typically focused on burning and off-site tree thinning. Utilizing a restoration experiment implementing these treatments, we found significantly reduced understory leaf litter in treatment areas. To test which variables associated with restoration treatments were most important for the survival of these grasses, we measured the effect of leaf litter removal and its interaction with environmental conditions on the survival of transplanted shoots. Survival of little bluestem increased with decreasing canopy density and decreasing leaf litter. Leaf-litter removal did not increase survival, nor did it interact with either pre-treatment leaf litter depth or canopy density. These results show that little bluestem benefits from conditions expected historically: increased light and possibly fire.
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Anthropogenic nitrogen deposition and projected increases in rainfall variability (the frequency of drought and heavy rainfall events) are expected to strongly influence ecosystem processes such as litter decomposition. However, h...
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Anthropogenic nitrogen deposition and projected increases in rainfall variability (the frequency of drought and heavy rainfall events) are expected to strongly influence ecosystem processes such as litter decomposition. However, how these two global change factors interact to influence litter decomposition is largely unknown. I examined how increased rainfall variability and nitrogen addition affected mass and nitrogen loss of litter from two tallgrass prairie species, Schizachyrium scoparium and Solidago canadensis, and isolated the effects of each during plant growth and during litter decomposition. I increased rainfall variability by consolidating ambient rainfall into larger events and simulated chronic nitrogen deposition using a slow-release urea fertilizer. S. scoparium litter decay was more strongly regulated by the treatments applied during plant growth than by those applied during decomposition. During plant growth, increased rainfall variability resulted in S. scoparium litter that subsequently decomposed more slowly and immobilized more nitrogen than litter grown under ambient conditions, whereas nitrogen addition during plant growth accelerated subsequent mass loss of S. scoparium litter. In contrast, S. canadensis litter mass and N losses were enhanced under either N addition or increased rainfall variability both during plant growth and during decomposition. These results suggest that ongoing changes in rainfall variability and nitrogen availability are accelerating nutrient cycling in tallgrass prairies through their combined effects on litter quality, environmental conditions, and plant community composition.
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A commercial blend of 2 selected class germplasm of little bluestem (Schizachyrium scoparium (Michx.) Nash var. scoparium [Poaceae]) was released in 2015 for rangeland and wildlife habitat restoration seedings in South Texas. Carr...
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A commercial blend of 2 selected class germplasm of little bluestem (Schizachyrium scoparium (Michx.) Nash var. scoparium [Poaceae]) was released in 2015 for rangeland and wildlife habitat restoration seedings in South Texas. Carrizo Blend little bluestem is a post-harvest blend of STN-1 76 Germplasm and STN-461 Germplasm little bluestems. These selections were made from evaluations of 95 native populations of little bluestem collected from southern Texas that were compared with available commercialstandards at 3 evaluation sites in the region. Upon selection, seed stock for release of the 2 selections was grown in isolation using outplants grown from the original wild seed collections to maintain the genetic integrity of the source populations. Carrizo Blend little bluestem represents the first selected, ecotypic seed source of little bluestem for use in South Texas.
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Aims Serpentine barrens of the Mid-Atlantic United States are globally rare, grass-dominated ecosystems thought to exclude C3 species and characterized by unique soil composition. However, like many grassland ecosystems globally, ...
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Aims Serpentine barrens of the Mid-Atlantic United States are globally rare, grass-dominated ecosystems thought to exclude C3 species and characterized by unique soil composition. However, like many grassland ecosystems globally, these sites are presently facing encroachment by surrounding forest. In this ecosystem, the tendril climbing vine, Smilax rotundifolia, forms dense thickets around barrens that typically precede forest encroachment. While numerous factors speculatively initiate and promote encroachment in these systems, few studies have examined photosynthetic responses of serpentine grasses to changes in resource availability initiated by encroachers or physiological ability of encroaching S. rotundifolia to colonize high-light barren environments. We sought to understand both environmental and physiological dynamics of encroachment along an irradiance gradient in these systems. Methods At three serpentine barren sites in southeastern Pennsylvania, physiological responses of the native grasses Sorghastrum nutans and Schizachyrium scoparium to increased shading by S. rotundifolia were examined. Additionally, the physiological performance of S. rotundifolia in the forest understory was compared to that in sunlit barrens environments. Light-saturated photosynthesis (A_(sat)), stomatal conductance (g_s), instantaneous transpiration efficiency (ITE), maximum efficiency of photosystem II (F_v/F_m), midday leaf water potential (ψ_(leaf)) and specific leaf area (SLA) were measured for all species over the course of the 2014 growing season. Two-way analyses of variance were used to assess changes in these parameters across growing environments, as well as seasonally for each species. Multiple regression analyses were also performed to investigate the influence of vapor pressure deficit (D) and leaf temperature (T_(leaf)) on A_(sat) and ITE. Important Findings Light-saturated photosynthesis was significantly greater in S. rotundifolia growing in sun than in the shade (P < 0.001) and early in the season (P = 0.012). Sun S. rotundifolia had up to 27% greater A_(sat) than shaded plants. Even with reduced ψ_(leaf) in the barrens, S. rotundifolia maintained high gs though A_(sat) was limited by high D later in the growing season. These data are in agreement with recent research suggesting that plants are not subject to water limitation in Mid-Atlantic barrens. Unexpectedly, shaded grasses at the encroachment interface did not exhibit any significant reduction in A_(sat). Declines in grass photosynthesis do not likely occur until S. rotundifolia rhizomes transition into monotypic thickets, completely excluding grasses. Encroachment by S. rotundifolia appears to be primarily facilitated by its ability to capitalize on light resources early on in the summer growing season, when environmental conditions are less stressful.
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Aims Serpentine barrens of the Mid-Atlantic United States are globally rare, grass-dominated ecosystems thought to exclude C<sub>3</sub> species and characterized by unique soil composition. However, like many grassland ecosystems...
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Aims Serpentine barrens of the Mid-Atlantic United States are globally rare, grass-dominated ecosystems thought to exclude C<sub>3</sub> species and characterized by unique soil composition. However, like many grassland ecosystems globally, these sites are presently facing encroachment by surrounding forest. In this ecosystem, the tendril climbing vine, Smilax rotundifolia , forms dense thickets around barrens that typically precede forest encroachment. While numerous factors speculatively initiate and promote encroachment in these systems, few studies have examined photosynthetic responses of serpentine grasses to changes in resource availability initiated by encroachers or physiological ability of encroaching S. rotundifolia to colonize high-light barren environments. We sought to understand both environmental and physiological dynamics of encroachment along an irradiance gradient in these systems. Methods At three serpentine barren sites in southeastern Pennsylvania, physiological responses of the native grasses Sorghastrum nutans and Schizachyrium scoparium to increased shading by S. rotundifolia were examined. Additionally, the physiological performance of S. rotundifolia in the forest understory was compared to that in sunlit barrens environments. Light-saturated photosynthesis (A<sub>sat</sub>), stomatal conductance (g<sub>s</sub>), instantaneous transpiration efficiency (ITE), maximum efficiency of photosystem II (F<sub>v</sub>/F<sub>m</sub>), midday leaf water potential (ψ<sub>leaf</sub>) and specific leaf area (SLA) were measured for all species over the course of the 2014 growing season. Two-way analyses of variance were used to assess changes in these parameters across growing environments, as well as seasonally for each species. Multiple regression analyses were also performed to investigate the influence of vapor pressure deficit (D) and leaf temperature (T<sub>leaf</sub>) on A<sub>sat</sub> and ITE. Important Findings Light-saturated photosynthesis was significantly greater in S. rotundifolia growing in sun than in the shade ( P < 0.001) and early in the season ( P = 0.012). Sun S. rotundifolia had up to 27% greater A<sub>sat</sub> than shaded plants. Even with reduced ψ<sub>leaf</sub> in the barrens, S. rotundifolia maintained high g<sub>s</sub> though A<sub>sat</sub> was limited by high D later in the growing season. These data are in agreement with recent research suggesting that plants are not subject to water limitation in Mid-Atlantic barrens. Unexpectedly, shaded grasses at the encroachment interface did not exhibit any significant reduction in A<sub>sat</sub>. Declines in grass photosynthesis do not likely occur until S. rotundifolia rhizomes transition into monotypic thickets, completely excluding grasses. Encroachment by S. rotundifolia appears to be primarily facilitated by its ability to capitalize on light resources early on in the summer growing season, when environmental conditions are less stressful.
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Sericea lespedeza (Lespedeza cuneata cv. Interstate 76) and little bluestem (Schizachyrium scoparium cv. Aldous) were raised from seed in a glasshouse, transplanted into 5.7-1 pots and placed into open-top chambers (OTC) on 6 June...
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Sericea lespedeza (Lespedeza cuneata cv. Interstate 76) and little bluestem (Schizachyrium scoparium cv. Aldous) were raised from seed in a glasshouse, transplanted into 5.7-1 pots and placed into open-top chambers (OTC) on 6 June 1999. Following a 7-day adjustment period, each of six OTCs (duplicate OTCs per treatment) was ventilated with either air that had been carbon-filtered (CF) to remove ambient ozone (O_3); non-filtered (NF), representative of ambient air; or enriched to twice-ambient O_3 concentration (2X). Primary-growth forage was harvested on days 7, 32, 46, 59 and 72 following the start of fumigation, and regrowth forage from the first primary-growth harvest was harvested on days 36, 54 and 72 following the start of fumigation. Dry matter (DM) yield of either forage species did not differ among treatments except in the final regrowth period when yield of sericea lespedeza was greater for the NF than 2X O_3 treatment. In vitro DM digestibility (IVDMD) and concentrations of crude protein (CP), soluble phenolics (SP) and condensed tannins (CT) in primary-growth sericea lespedeza did not differ between treatments, but NF primary-growth forage had higher concentration of protein-precipitating tannins (PPT) than did 2X primary-growth forage. Concentrations of neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) were higher in NF and 2X than in CF primary-growth sericea lespedeza. Similarly, concentrations of NDF and ADL were higher, and IVDMD was lower for NF and 2X than for CF regrowth sericea lespedeza. Concentrations of ADF and ADL were lower, whereas IVDMD, in vitro NDF digestibility (IVNDFD) and concentrations of CP and SP were greater, in CF than in NF and 2X primary-growth little bluestem. Percentages IVDMD and IVNDFD and concentrations of CP and SP in NF primary-growth little bluestem were greater than those in forage exposed to 2X O_3 treatment. No significant differences were observed among treatments in percentages IVDMD and IVNDFD, or concentrations of cell wall constituents or SP in little bluestem regrowth. Nutritive quality of little bluestem was decreased by <2%, and that of sericea lespedeza by ～7% as a result of increased concentrations of cell wall constituents and decreased in vitro digestibility of NF and 2X compared with CF forages. Results indicate that existing and projected O_3 levels can drive alterations in forage quality of select warm-season forages sufficient to have nutritional and economic implications for their utilization by ruminant herbivores.
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Invasive plants frequently have competitive advantages over native species. These advantages have been characterized in systems in which the invading species has already become well established. Surprisingly, invader impacts on na...
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Invasive plants frequently have competitive advantages over native species. These advantages have been characterized in systems in which the invading species has already become well established. Surprisingly, invader impacts on native communities currently undergoing invasion are lacking from most ecological studies. In this work we document and quantify shifting patterns in plant community structure in a native ecosystem (remnant tallgrass prairie) undergoing invasion by the invasive exotic Sorghum halepense (Johnsongrass). Further, we use manipulative field and greenhouse studies to quantify impacts of potential allelochemicals contained in whole-plant S. halepense leachates on growth of the dominant native grass, Schizachyrium scoparium (Little Bluestem), and tested the inhibitory effects of the potential soil legacy of S. halepense on the native grass in the greenhouse. Plant diversity indices revealed three distinct plant communities within the remnant prairie: a native community, a densely S. halepense invaded area, and a transitional zone between the two. Dominance of the native grass, determined by relative percent cover, significantly declined with increased S. halepense invasion via rhizomatous growth. Annual global positioning system monitoring of the S. halepense invasion front was used to quantify advancement into native prairie, documented at an average rate of 0.45 m year~(-1). In the manipulative field and greenhouse studies, native S. scoparium treated with invasive S. halepense leachate had significantly less biomass and fewer inflorescences than control plants. These findings indicate the prolific clonal growth in conjunction with the plant chemistry of S. halepense play a significant role in displacement of the native grass.
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Dominant species play crucial roles in determining plant community structure and ecosystem function. Cultivars of the dominant prairie grasses are widely used in prairie restoration and are selected for characters such as high bio...
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Dominant species play crucial roles in determining plant community structure and ecosystem function. Cultivars of the dominant prairie grasses are widely used in prairie restoration and are selected for characters such as high biomass production, increased reproductive output, and stress tolerance. Genetic differences exist between cultivar and non-cultivar population sources of dominant tallgrass prairie species, which may have implications for plant performance in prairie restoration. We measured net photosynthesis (Anet), stomatal conductance (gs), and water use efficiency (WUE) in cultivar and non-cultivar dominant tallgrass prairie species Andropogon gerardii Vitman, Sorghastrum nutans (L.) Nash, and Schizachyrium scoparium (Michx.) Nash in both a greenhouse experiment and an experimental tallgrass prairie restoration. We found indicators of enhanced physiological performance (higher Anet, gs, and/or WUE) in cultivar population sources of all three dominant grass species relative to non-cultivars. For A. gerardii, cultivars exhibited higher Anet and WUE than non-cultivars. For S. nutans, cultivars exhibited higher gs, whereas non-cultivars showed higher WUE. Lastly, cultivars of S. scoparium showed higher WUE than non-cultivar population sources. Our results show that population selection of dominant species in restoration can have consequences for plant performance, which may have implications for competitive interactions that affect community structure (i.e. diversity) and ecosystem function (i.e. aboveground net primary production) during the reassembly of prairie systems.
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