Sporobolus Heterolepis Research Articles

Influence of vegetation type and climatological conditions on evapotranspiration from extensive green roofs

Evapotranspiration (ET) is the key hydrologic process governing the capacity of a green roof to retain rainfall as it regenerates available water storage space in the green roof substrate (soil) between rainfall events. In this field study, the impact of climatological conditions, vegetation type, and substrate depth on ET rates were evaluated from experimental, modular extensive green roofs installed in three climate regions in Canada: Calgary AB (Prairies), London ON (Great Lakes/St. Lawrence), and Halifax NS (Atlantic/ Maritime). Daily ET rates and cumulative ET over two field seasons were quantified for two substrate depths (10 and 15 cm), substrate only treatments (no vegetation), and four vegetation treatments (monoculture treatments of Sedum spurium, Sporobolus heterolepis, and Aquilegia canadensis, and a mixed species treatment consisting of the three aforementioned species). 73 %, 67 % and 33 % of the cumulative rainfall was returned to the atmosphere via ET over the two field seasons in Calgary, London and Halifax, respectively. Importantly, ET rates were shown to be a strong function of substrate moisture content as well as atmospheric forcing with the relative importance of each varying between the different cities. ET rates were typically greater in the mixed species treatment in comparison to the three monoculture treatments (Sedum spurium, Sporobolus heterolepis, and Aquilegia canadensis) and for deeper substrate depths, although ET rate enhancement with substrate depth was comparatively small. This study provides valuable insights on the impact of climatological conditions and green roof design parameters (i.e., vegetation type and substrate depth) on ET rates.

Using Plugs and Hydrogels to Establish Populations of Prairie Dropseed, a Critical Native Grass, in Restored Prairies in Minnesota

Prairie dropseed [Sporobolus heterolepis (A. Gray) A. Gray] is a critical North American native grass that is often not incorporated into prairie restoration seed mixes due to its low survival and growth rates. This project investigated using hydrogels, landscape plugs, and native field soil to improve the survival and growth of prairie dropseed. At three tallgrass prairie restoration sites at the Minnesota Landscape Arboretum, we planted prairie dropseed plugs in Fall 2019, Spring 2020, and Fall 2020. When grown in the field from 42 to 94 weeks, we found that potting mix–grown plugs had increased growth as measured by dry weight compared with plugs grown in native soils. Soil medium did not influence survival rates. The use of hydrogels did not demonstrate increased survival or growth compared with plugs planted with water. We recommend land managers and restorationists use plugs grown in commercial potting mix rather than grown in native soils, and we found no advantage in using hydrogels over watering at planting.

Endangered Oarisma poweshiek larvae vary their graminoid forage in Manitoba, Canada

Abstract The Poweshiek skipperling (Oarisma poweshiek) is endemic to the tall grass prairie in North America and is now critically endangered globally. Existing populations are scattered among tall grass prairie remnants. However, the host food plants eaten by Poweshiek skipperling larvae, the vegetative and microclimatic descriptions of immature and adult microhabitats, and O. poweshiek behaviour in Manitoba are unknown. We followed Poweshiek skipperling adults in their natural habitat to locate microhabitats where eggs were laid and to observe larval foraging behaviour and development. We measured vegetative, structural, and microclimatic characteristics of microhabitats used by immatures and documented the host species larvae consumed, their general behaviour (on plants; movement within microhabitats), and their developmental schedules. Larvae ate Andropogon gerardi, Muhlenbergia richardsonis, Sporobolus heterolepis, and Schizachyrium scoparium (all Poaceae) in natural tall grass prairie. Larvae appeared to navigate microhabitats to locate host food plants, alternating between shoots of various species throughout their development. Microhabitats seemed to be more open, with drier microclimates, than areas where eggs were not laid. This improved understanding of larval feeding patterns, adult behaviours, and microhabitat attributes may help local grassland stewards and researchers reduce the list of possible causes of decline and identify potential solutions to recover the Poweshiek skipperling.

Morphological and Physiological Responses of Ornamental Grasses to Saline Water Irrigation

Reclaimed water provides a reliable and economical alternative source of irrigation water for landscape use but may have elevated levels of salts that are detrimental to sensitive landscape plants. Landscape professionals must use salt-tolerant plants in regions where reclaimed water is used. Ornamental grasses are commonly used as landscape plants in the Intermountain West of the United States due to low maintenance input, drought tolerance, and unique texture. Six ornamental grass species, including Acorus gramineus (Japanese rush), Andropogon ternarius (silver bluestem), Calamagrostis ×acutiflora (feather reed grass), Carex morrowii (Japanese sedge), Festuca glauca (blue fescue), and Sporobolus heterolepis (prairie dropseed), were evaluated for salinity tolerance. Plants were irrigated every 4 days with a fertilizer solution at an electrical conductivity (EC) of 1.2 dS·m–1 (control) or with a saline solution at an EC of 5.0 dS·m–1 (EC 5) or 10.0 dS·m–1 (EC 10). At 47 days, most species in EC 5 exhibited good visual quality with averaged visual scores greater than 4.6 (0 = dead, 5 = excellent). In EC 10, most A. gramineus plants died, but C. ×acutiflora, F. glauca, and S. heterolepis had no foliar salt damage. At 95 days, C. ×acutiflora, F. glauca, and S. heterolepis in EC 5 had good visual quality with averaged visual scores greater than 4.5. Acorus gramineus, A. ternarius, and C. morrowii showed foliar salt damage with averaged visual scores of 2.7, 3.2, and 3.4, respectively. In EC 10, A. gramineus died, and other grass species exhibited moderate to severe foliar salt damage, except C. ×acutiflora, which retained good visual quality. Plant height, leaf area, number of tillers, shoot dry weight, and/or gas exchange parameters also decreased depending on plant species, salinity level, and the duration of exposure to salinity stress. In conclusion, A. gramineus was the most salt-sensitive species, whereas C. ×acutiflora was the most salt-tolerant species. Festuca glauca and S. heterolepis were more tolerant to salinity than A. ternarius and C. morrowii. Calamagrostis ×acutiflora, F. glauca, and S. heterolepis appear to be more suitable for landscapes in which reclaimed water is used for irrigation. Plant responses to saline water irrigation in this research could also be applied to landscapes in salt-prone areas and coastal regions with saltwater intrusion into aquifers and landscapes affected by maritime salt spray.

Herbicide tolerance in 11 grass species for minimal‐to‐no‐mow golf course rough

AbstractResearch was conducted to determine the tolerance of 11 grass species used in minimal‐to‐no‐mow turf areas to three postemergence herbicides applied at one‐ and twofold the maximum label rates in 2018 and 2019. Grasses were transplanted into field plots in West Lafayette, IN, in 2018 and 2019, allowed time to establish (∼1−2 mo), and then either treated with one application of quinclorac, sethoxydim, and topramezone at two rates or not treated. All 11 grass species had acceptable tolerance (≤20% injury) to quinclorac applied at 0.845 kg acid equivalent (a.e.) ha–1. Quinclorac at 1.69 kg a.e. ha–1 produced moderate injury (≥21% injury) on only little bluestem [Schizachyrium scoparium (Michx.) Nash.], prairie dropseed [Sporobolus heterolepis (A. Gray) A. Gray], and switchgrass (Panicum virgatum L.). Strong creeping red fescue (Festuca rubra L. ssp. rubra Gaudin), which had ≤5% injury from all three herbicides, exhibited the greatest tolerance among grass species tested. With the exception of strong creeping red fescue, sethoxydim significantly injured all other grass species. Injury from topramezone varied among grass species and herbicide rates. Grasses tolerant (≤20% injury) to topramezone at both rates were big bluestem (Andropogon gerardii Vitman), broomsedge bluestem (Andropogon virginicus L.), indiangrass [Sorghastrum nutants (L.) Nash], strong creeping red fescue, and tall fescue [Festuca arundinacea Schreb.; syn. Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.]. Tolerance among species was variable to quinclorac, sethoxydim, and topramezone, and thus turf managers should first identify desired grass species prior to herbicide application.

Invasive grass negatively affects growth and survival of an imperiled butterfly

With only ~1% of native prairie remaining in North America, populations of many prairie-obligate species, including the imperiled Dakota skipper butterfly, have drastically declined in recent decades. Unfortunately, population recovery is impeded by an insufficient understanding of Dakota skipper biology. Because larvae have never been naturally observed in the wild, even basic life history elements including preferred host plant(s) are not well understood, and potential hosts have been inferred from grasses inhabiting remnant sites rather than direct observations. To improve our understanding of Dakota skipper biology and habitat needs and inform recovery efforts, we conducted a no-choice performance experiment offering larvae 1 of 5 commonly occurring native grasses and 2 pervasive invasive grass species found across their historic range. We monitored larvae during key life history intervals and evaluated host plant quality by measuring larval and pupal mass, time to pupation, and survivorship. Larvae fed on all offered host grasses, but mass, phenology, and survivorship varied among treatments. Larvae reared on prairie dropseed and porcupine grass had the highest survival, the shortest time to adulthood, and the greatest mass, whereas larvae provided smooth brome and Kentucky bluegrass fared poorly for all observed metrics. All other grasses offered during the study were deemed ‘medium’ quality. Our results suggest that although larvae can feed on a variety of potential host plants, these hosts vary in quality. Invasive grasses across prairies in North America may pose an ecological trap to the conservation of Dakota skipper and other prairie-obligate Lepidoptera.

Prairie Dropseed Germination Highest with Warm, Moist Conditions

We tested prairie dropseed (Sporobolus heterolepis) using six different germination treatments and found the best results with cold (40 °F), dry storage followed by direct seeding into a commercial germination mix placed in a 75 °F glass-glazed greenhouse with intermittent mist (5 seconds of mist every 8 minutes), and 600-W high-pressure sodium lighting with a 16-hour daylength. We found commercial laboratory viability analysis from tetrazolium staining did not correspond to germination results. Cold (34 °F), moist (2.3 g seed moistened with 2.5 mL deionized water) treatment, also known as cold conditioning, produced significantly less germination and fewer transplantable seedlings, and is not recommended for prairie dropseed.

Plants with Horticultural and Ecological Attributes for Green Roofs in a Cool, Dry Climate

Green roofs are building surface treatments where plants are grown in medium on a rooftop to cool or insulate buildings and/or to ameliorate negative environmental impacts of buildings. We initiated a 2-year study to characterize medium and weather conditions on a rooftop in a cool-dry climate and to identify plant species with horticultural and ecological attributes that survive and thrive on an unirrigated semi-intensive green roof in a cool-dry climate. Eighty-eight cold-hardy, drought-tolerant species with horticultural or ecological attributes were identified and planted into 12.7-cm-deep medium in trays that were placed on a rooftop. Medium temperatures and moistures were recorded, and plant survival and vigor were quantified. Hourly medium temperatures varied from –22.3 to 43 °C. Monthly medium water moistures varied from –2.5 to –73.3 kPa from May to September, and from –7.6 to –195 kPa from October to April. Monthly air temperature, relative humidity and irradiance varied from –9.4 to 21.7 °C, 44% to 80%, and from 206 to 1222 μmol·m−2·s−1. Mean survival scores decreased (4 = 100% survival) from 2.6 with grasses, to 2.3 with succulents, to 1.8 with temperate perennials, to 0 for geophytes (all died). Among grasses, Festuca ovina VNS, Koeleria macrantha 07-901 ND, Panicum virgatum, and Sporobolus heterolepis performed well. Among succulents, Sedum acre, S. album ‘Coral Carpet’, S. cauticola ‘Sunset Cloud’, S. ‘Czar’s Gold’, S. ellecombianum, S. hybridum ‘Immergruchen’, S. requieni, S. sexangulare, S. spurium ‘Dragon’s Blood’, ‘John Creech’, ‘Pearly Pink’, ‘Ruby Mantle’, and ‘Tricolor’ performed well. Among temperature nonsucculent perennials, Allium ceranum and senescens ‘Glaucum’, Geum triflorum, Talinum calycinum, and Thymus praecox ‘Red Creeping’ performed well. Data on Sedum suggested that medium-low temperature was more limiting to survival than moisture level. The differences in species that performed well here, compared with other studies, underscores the importance of regionally specific green roof plant species studies.

Effect of substrate depth on plant community development on a Michigan green roof

Green roofs are gradually being accepted and implemented across North America as they can mitigate many of the negative effects that urban areas have on humans and the environment. As rooftops are filled with living plants, individual species need to be tested for longevity and suitability. Twenty-two plant species including herbaceous perennials, grasses, and sedum were evaluated on a green roof at substrate depths of 4.5, 10, and 20 cm over an eight-year period in East Lansing, Michigan. Plants were irrigated when needed during the first two years, but had to rely on natural rainfall thereafter. All five species of sedum were still present at the end of the eight-year period, but only seven of the 17 herbaceous perennials and grasses survived. Of the herbaceous perennials and grasses, Allium cernuum was by far the dominant species in both the 10 and 20 cm deep zones. Sporobolus heterolepis and Koeleria macrantha also established themselves in the 20 cm zone, but all other species were either only present in trace amounts or had completely disappeared. Substrate moisture was probably the major factor in terms of species survival and a drought during 2016 was likely the cause for the large loss of species. Deeper substrates supported a larger variety of species, but plant species diversity decreased over time at all substrate depths. This study emphasizes the fact that if herbaceous perennials and grasses are to be successful on green roofs, then irrigation may be critical to mitigate drought and maintain species diversity. It also points out the importance of long-term studies to accurately evaluate green roof plant communities and provides the framework for a continuation of the same study in other areas of the world.

Plant survival and growth on extensive green roofs: A distributed experiment in three climate regions

Green rooftops are installed in many climates worldwide to support urban ecosystem services. Across North America, green roofs often make use of the same limited set of plant species, but the effects of regional climates on the survival and growth of a core set of plant species has seldom been investigated. To identify the impact of climate on green roof plant performance, we installed an identical green roof system in three Canadian cities that experience different climate conditions: Calgary, Alberta; London, Ontario; and Halifax, Nova Scotia. The green roofs were monitored across three growing seasons for plant survival, plant height, and canopy density of three species grown in monoculture: Aquilegia canadensis, Sporobolus heterolepis, and Sedum spurium, and a mixture planting with all three species. Green roof vegetation canopy density, plant height and growth rates differed by city, plant species, substrate depth and planting type (monoculture or mixture treatment). Between sites, plant species exhibited different growth phenologies. Mixture treatments performed slightly better than monoculture plantings at each site in canopy density measures but were not significantly greater in plant height measures. The growth rate between years two and three was greatest for the mixture treatment, indicating greater potential for long term survival and performance of mixture plantings. The London, Ontario site, with a relatively moderate climate, supported the best green roof growth and performance compared to the cooler and drier Calgary and the rainier Halifax.

What can we learn from in-soil imaging of a live plant: X-ray Computed Tomography and 3D numerical simulation of root-soil system

Plant roots play a critical role in plant-soil-microbe interactions that occur in the rhizosphere. X-ray Computed Tomography (XCT) has been proven to be an effective tool for non-invasive root imaging and analysis. A combination of XCT, open-source software, and in-house developed code was used to non-invasively image a prairie dropseed (Sporobolus heterolepis) specimen, segment the root data to obtain a 3D image of the root structure, and extract quantitative information from the 3D data, respectively. Based on the explicitly-resolved root structure, pore-scale computational fluid dynamics (CFD) simulations were applied to numerically investigate the root-soil-groundwater system. The plant root conductivity, soil hydraulic conductivity and transpiration rate were shown to control the groundwater distribution. The coupled imaging-modeling approach demonstrates a realistic platform to investigate rhizosphere flow processes and would be feasible to provide useful information linked to upscaled models.

Extracting Metrics for Three-dimensional Root Systems: Volume and Surface Analysis from In-soil X-ray Computed Tomography Data

Plant roots play a critical role in plant-soil-microbe interactions that occur in the rhizosphere, as well as processes with important implications to climate change and crop management. Quantitative size information on roots in their native environment is invaluable for studying root growth and environmental processes involving plants. X-ray computed tomography (XCT) has been demonstrated to be an effective tool for in situ root scanning and analysis. We aimed to develop a costless and efficient tool that approximates the surface and volume of the root regardless of its shape from three-dimensional (3D) tomography data. The root structure of a Prairie dropseed (Sporobolus heterolepis) specimen was imaged using XCT. The root was reconstructed, and the primary root structure was extracted from the data using a combination of licensed and open-source software. An isosurface polygonal mesh was then created for ease of analysis. We have developed the standalone application imeshJ, generated in MATLAB1, to calculate root volume and surface area from the mesh. The outputs of imeshJ are surface area (in mm2) and the volume (in mm3). The process, utilizing a unique combination of tools from imaging to quantitative root analysis, is described. A combination of XCT and open-source software proved to be a powerful combination to noninvasively image plant root samples, segment root data, and extract quantitative information from the 3D data. This methodology of processing 3D data should be applicable to other material/sample systems where there is connectivity between components of similar X-ray attenuation and difficulties arise with segmentation.

Extracting Metrics for Three-dimensional Root Systems: Volume and Surface Analysis from In-soil X-ray Computed Tomography Data.

Plant roots play a critical role in plant-soil-microbe interactions that occur in the rhizosphere, as well as processes with important implications to climate change and crop management. Quantitative size information on roots in their native environment is invaluable for studying root growth and environmental processes involving plants. X-ray computed tomography (XCT) has been demonstrated to be an effective tool for in situ root scanning and analysis. We aimed to develop a costless and efficient tool that approximates the surface and volume of the root regardless of its shape from three-dimensional (3D) tomography data. The root structure of a Prairie dropseed (Sporobolus heterolepis) specimen was imaged using XCT. The root was reconstructed, and the primary root structure was extracted from the data using a combination of licensed and open-source software. An isosurface polygonal mesh was then created for ease of analysis. We have developed the standalone application imeshJ, generated in MATLAB(1), to calculate root volume and surface area from the mesh. The outputs of imeshJ are surface area (in mm(2)) and the volume (in mm(3)). The process, utilizing a unique combination of tools from imaging to quantitative root analysis, is described. A combination of XCT and open-source software proved to be a powerful combination to noninvasively image plant root samples, segment root data, and extract quantitative information from the 3D data. This methodology of processing 3D data should be applicable to other material/sample systems where there is connectivity between components of similar X-ray attenuation and difficulties arise with segmentation.

Locally adapted arbuscular mycorrhizal fungi improve vigor and resistance to herbivory of native prairie plant species

Soil microbial communities contribute to ecosystem function and structure plant communities, but are altered by anthropogenic disturbance. Successful restoration may require microbial community restoration. Inoculation of plants with arbuscular mycorrhizal fungi (AMF) may improve ecological restoration, but AMF species that are locally adapted to native plant communities are often unavailable and commercially propagated AMF are not necessarily locally adapted to the desired plant community target. The disconnect between readily available commercial fungi and later‐successional plants may inhibit successful establishment of the restoration. We tested this concept using four mid‐ to late successional prairie plant species planted with one of three inoculum sources: a locally adapted AMF mix cultured from native prairie, a non‐locally adapted commercial AMF product, or a sterilized background soil control. The inoculated plants (termed nurse plants) were planted in the middle of field plots. In each plot, uninoculated plants (test plants) were planted at 0.5, 1, and 2 m from the nurse plants in order to test whether growth and survival of test plants could be affected by inoculum source. Generally, plants grew larger when inoculated with native AMF compared to commercial inoculum or the control. Later successional species responded most positively to native AMF. Benefits of inoculation also spread to neighbors, as uninoculated late successional test plant, Sporobolus heterolepis, grew larger when its' neighbors were inoculated with native AMF than with commercial AMF or the control. Due to an unanticipated herbivory event, we also assessed the degree to which rate of herbivory or plant tolerance to herbivory is affected by inoculum source. The mid‐ successional nurse plant, Ratibida pinnata, received the majority of the herbivore damage, and when it was inoculated with commercial AMF, it experienced significantly more herbivory than plants inoculated with native AMF or the control. R. pinnata inoculated with native AMF grew significantly larger one month following herbivory, though there was no significant difference in growth in the second year of sampling. This study suggests that native, locally adapted AMF can improve restoration of prairie plant species and these benefits can extend to neighbors up to two meters from the inoculation point.

A Floristic Inventory and Vegetation Survey of Three Dolomite Prairies in Northeastern Illinois

ABSTRACT Dolomite prairies are rare natural plant communities, with a few high-quality examples in northeastern Illinois. In this study, three dolomite prairies located in southwestern Will County, Illinois, were surveyed to assess species composition and quality. Two of the dolomite prairies were located on the Des Plaines Wildlife Conservation Area (i.e., Blodgett Road Dolomite Prairie Natural Area and Grant Creek Nature Preserve) and the third in the Midewin National Tallgrass Prairie (i.e., Exxon Mobil Natural Area). Overall, a total of 438 taxa were recorded: 318 at Blodgett Road, 255 at Exxon Mobil, and 270 at Grant Creek, with 129 common to them all. Of these, 97 were mesic or wet prairie species, 26 were nonnative taxa, and six were native woody species. Three state endangered and two state threatened species were found associated with these dolomite prairies. The Blodgett Road site was dominated by the annual grass Sporobolus vaginiflorus, along with Andropogon gerardii, Sporobolus heterolepis, ...

Descriptiori of a grass feeding whitefly of the genusTetraleurodes(Hemiptera: Aleyrodidae) from the Indo-Myanmar border

A new species of whitefly, Tetraleurodes champaiensis Dubey sp. nov. (Hemiptera: Aleyrodidae) found infesting Sporobolus heterolepis (Poaceae) in Mizoram (India) is described along with measurements, line drawings and scanning electron microscope images. The species differs from Tetraleurodes thenmozhiae Jesudasan & David in being black in color and have bluntly pointed dorsal setae. The puparia of T. thenmozhiae are white and have capitate dorsal setae. The puparia of the new species were found feeding at the basal parts of central grass blades and almost near the ground level. An identification key to grass feeding Tetraleurodes species is provided. There was no ant attendance.

Great Plains Ladies’-tresses, <em>Spiranthes magnicamporum</em>: disjunct in eastern Ontario and a new orchid species for the Ottawa District and Lanark County

We report the discovery of Great Plains Ladies’-tresses, Spiranthes magnicamporum (Orchidaceae), in eastern Ontario, 250 km east of its previously known eastern occurrence in Ontario. The population of more than 500 flowering plants (in 2013) was confined to Prairie Dropseed, Sporobolus heterolepis, grasslands within the Burnt Lands Alvar. Peak flowering was in late September, two weeks later than that of Nodding Ladies’-tresses, Spiranthes cernua, in the same area.

Field establishment of little bluestem and prairie dropseed under managed conditions

Schizachyrium scoparium (Michx.) Nash (Poaceae) (little bluestem) and Sporobolus heterolepis (A. Gray) A. Gray (Poaceae) (prairie dropseed) are ecologically important warm-season grass species for restoration of degraded Midwestern prairie habitats. Information about methods to establish these grass species is limited. Therefore, a combination of treatments were tested in a field setting over 2 y to enhance the success of these 2 species under field-production conditions and for prairie restorations. Treatments consisted of mowing, 3 herbicide rates, and 3 seeding rates. Imazapic ((±)- 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1 H -imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid]) herbicide was applied at rates of 0, 0.14, and 0.28 kg/ha. Seeding rates were 4.5, 9.0, and 13.5 kg/ha (4.0, 8.0, and 12.0 lb/ac) for S. scoparium and 1.9, 4.8, and 7.6 kg/ha (1.7, 4.3, and 6.8 lb/ac) for S. heterolepis . After 2 growing seasons, mowing did not affect S. scoparium density or percent cover. Herbicide-treated plots had greater density and percent cover of S. scoparium than did untreated plots. The 13.5 kg/ha seeding rate for S. scoparium was associated with greater grass density and percent cover than the 2 lower seeding rates. Sporobolus heterolepis was detected in only 4 out of 164 sampling quadrats after 2 growing seasons. Emergence was too poor for data collection or testing of the hypothesis. Although mowing did not appear to influence seedling establishment of S. scoparium , herbicide application and generous seeding rates increased grass density and percent cover.

Seed Germination Characteristics of Prairie Dropseed (Sporobolus heterolepis)

ABSTRACT: Prairie dropseed (Sporobolus heterolepis [A. Gray] A. Gray) is a warm-season grass that is an important component of remnant tallgrass prairies of North America, but is rarely found in restorations. We conducted three experiments to determine germination rates of prairie dropseed under different conditions in an attempt to potentially increase its successful establishment under field conditions. In the first experiment, we evaluated the duration of cold-moist stratification on the germination of prairie dropseed. Seeds were cold-moist stratified for 0, 30, or 60-d at 4 °C and then placed in a dark growth chamber at 26 °C. The other two experiments consisted of seeds planted in three different soil media: 1:1:1 soil:peat:perlite mixture, non-compacted field soil, and compacted field soil. They were then exposed to full irradiance or 50% shade. Germination was highest for seeds cold-moist stratified for 30 or 60 d. Seeds planted in either non-compacted or compacted field soil had higher germinatio...

Responses of two bunchgrasses to nitrogen addition in tallgrass prairie: the role of bud bank demography

Growth of tallgrass prairie plants, many of which maintain substantial bud banks, can be limited by nitrogen (N), water, and/or light. We hypothesized that tallgrass prairie plants respond to increases in N through demographic effects on the bud bank. We tested the effects of a pulse of N on (1) bud bank demography, (2) plant reproductive allocation, and (3) ramet size. We parameterized matrix models, considering each genet as a population of plant parts. Nitrogen addition significantly impacted bud bank demography in two subdominant species of bunchgrass: Sporobolus heterolepis (a C(4) grass) and Koeleria macrantha (a C(3) grass), but had no effect on the size of individual ramets. Emergence from the bud bank and ramet population growth rates (λ) were significantly higher in S. heterolepis genets that received supplemental N. Nitrogen addition also affected the bud demography of K. macrantha, but N addition decreased rather than increased λ. Prospective and retrospective demographic analyses indicated that bud bank dynamics were the most important demographic processes driving plant responses to nutrient availability. Thus, the variation in productivity in these tallgrass prairie species is driven principally by the demography of the bud bank rather than by the physiology and growth of aboveground tillers. Improved understanding of bud bank dynamics may lead to improved predictive models of grassland responses to environmental changes such as altered N deposition and precipitation.