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At least 19 recordsLinked to original sources
USGS2005

Fire and the Miocene expansion of C4 grasslands

C 4 photosynthesis had a mid-Tertiary origin that was tied to declining atmospheric CO 2 , but C 4 -dominated grasslands did not appear until late Tertiary. According to the ‘CO 2 -threshold’ model, these C 4 grasslands owe their origin to a further late Miocene decline in CO 2 that gave C 4 grasses a photosynthetic advantage. This model is most appropriate for explaining replacement of C 3 grasslands by C 4 grasslands, however, fossil evidence shows C 4 grasslands replaced woodlands. An additional weakness in the threshold model is that recent estimates do not support a late Miocene drop in p CO 2 . We hypothesize that late Miocene climate changes created a fire climate capable of replacing woodlands with C 4 grasslands. Critical elements were seasonality that sustained high biomass production part of year, followed by a dry season that greatly reduced fuel moisture, coupled with a monsoon climate that generated abundant lightning-igniting fires. As woodlands became more open from burning, the high light conditions favoured C 4 grasses over C 3 grasses, and in a feedback process, the elevated productivity of C 4 grasses increased highly combustible fuel loads that further increased fire activity. This hypothesis is supported by paleosol data that indicate the late Miocene expansion of C 4 grasslands was the result of grassland expansion into more mesic environments and by charcoal sediment profiles that parallel the late Miocene expansion of C 4 grasslands. Many contemporary C 4 grasslands are fire dependent and are invaded by woodlands upon cessation of burning. Thus, we maintain that the factors driving the late Miocene expansion of C 4 were the same as those responsible for maintenance of C 4 grasslands today.

Ecology Letters↗
USGS1990

The California Valley grassland

Grasslands are distributed throughout California from Oregon to Baja California Norte and from the coast to the desert (Brown 1982) (Figure 1). This review will focus on the dominant formation in cismontane California, a community referred to as Valley Grassland (Munz 1959). Today, Valley Grassland is dominated by non-native annual grasses in genera such as Avena (wild oat), Bromus (brome grass), and Hordeum (barley), and is often referred to as the California annual grassland. On localized sites, native perennial bunchgrasses such as Stipa pultra (purple needle grass) may dominate and such sites are interpreted to be remnants of the pristine valley grassland. In northwestern California a floristically distinct formation of the Valley Grassland, known as Coast Prairie (Munz 1959) or Northern Coastal Grassland (Holland and Keil 1989) is recognized. The dominant grasses include many native perennial bunchgrasses in genera such as Agrostis , Calamagrostis , Danthonia , Deschampsia , Festuca , Koeleria and Poa (Heady et al. 1977). Non-native annuals do not dominate, but on some sites non-native perennials like Anthoxanthum odoratum may colonize the native grassland (Foin and Hektner 1986). Elevationally, California's grasslands extend from sea level to at leas 1500 m. The upper boundary is vague because montane grassland formations are commonly referred to as meadows; a community which Munz (1959) does not recognize. Holland and Keil (1989) describe the montane meadow as an azonal community; that is, a community restricted not so much to a particular climatic zone but rather controlled by substrate characteristics. They consider poor soil-drainage an over-riding factor in the development of montane meadows and, in contrast to grasslands, meadows often remain green through the summer drought. Floristically, meadows are composed of graminoids; Cyperaceae, Juncaceae, and rhizomatous grasses such as Agropyron (wheat grass). Some bunchgrasses, such as Muhlenbergia rigens , are found in both montane meadows and moister grasslands. Forbs when present, are typically perennials. East of the interior ranges, grasslands are uncommon although native perennial bunchgrasses in genera such as Stipa , Hilaria and Aristida are common in steppe and desert scrub. Today, Valley Grassland covers nearly 7 million ha or 17% or the state (Huenneke 1989), although other sources list less than half this amount (Jones and Stokes 1987). There is some evidence that extent of the grassland region has not changed since pre-European conditions, although the spatial distribution of grasslands has likely changed substantially (Huenneke 1989). That is, many current grasslands previously may have been dominated by other vegetation types and vice versa. Without question, many former grasslands have been converted to agricultural and urban use (Barry 1972). The Valley Grassland community occurs in regions characterized by a broad range of climatic conditions. Average January temperatures may range from 5°C to 15°C and July temperatures from 15°C to 30°C (NOAA 1988). Annual precipitation ranges from approximately 12 cm to over 200 cm, although all sites are characterized by a summer drought of 4-8 months (Heady 1977). Grasslands are well developed on deep, fine-textured soils although they are not restricted to such conditions (Wells 1962, Adams 1964, Heady 1977).

California↗
USGS2026

Dormant-season prescribed fires can enhance forage quality for two growing seasons in the northwestern Great Plains

Fire is an ecological disturbance that can accelerate nutrient cycling and alter herbivore distribution in grasslands and shrublands. Historically and today, humans have used prescribed fire to enhance forage quality for wild and domestic herbivores, and to achieve other management objectives. Contextual factors such as ecosystem type, seasonality, and fuel characteristics can determine how prescribed fire affects forage quality. For example, forage quality enhancements are relatively short lived in shortgrass steppe and subhumid grasslands but may persist for multiple years in northern mixed-grass prairie and sagebrush steppe. Outcomes near ecosystem boundaries are uncertain. Using 152 independent, small-plot, prescribed burns completed over multiple years at 36 sites in Wyoming and South Dakota, USA, we tested the effects of ecosystem type (northern mixed-grass prairie vs. sagebrush grassland ecotone), burn seasonality (fall vs. spring), and fuel characteristics (ambient vs. added fuel) on forage quality. Across ecosystems, fall fires had strong positive effects on forage quality parameters during the first growing season after fire, and energy benefits that persisted into the second growing season after fire. In northern mixed-grass prairie, spring and fall prescribed fires implemented before the same growing season yielded similar forage quality enhancements for one season. Finally, artificially increased fuel loads had few effects on forage quality. Although forage quality rarely dropped below critical nutrition thresholds for ruminants regardless of burning, our findings suggest relatively consistent, positive forage quality responses to prescribed fire across ecosystem types, seasonality of dormant-season burns, and fuel characteristics. Many improvements lasted through one growing season, and some persisted into a second growing season. Managers could take advantage of short-term nutritional benefits via adaptive management strategies that allow animals access to burned and unburned areas.

South Dakota, Wyoming↗
USGS2021

Science needs of southeastern grassland species of conservation concern: A framework for species status assessments

The unglaciated southeastern United States is a biodiversity hotspot, with a disproportionate amount of this biodiversity concentrated in grasslands. Like most hotspots, the Southeast is also threatened by human activities, with the total reduction of southeastern grasslands estimated as 90 percent (upwards to 100 percent for some types) and with many threats escalating today. This report summarizes the results of a multistakeholder workshop organized by the Southeastern Grasslands Initiative and the U.S. Geological Survey, held in January 2020 to provide a scientific needs assessment to help inform the Species Status Assessment (SSA) process under the U.S. Endangered Species Act, with a focus on grassland species and communities of conservation concern in the southeastern United States. This report reviews the ecology of southeastern grasslands, including influences on their origin, maintenance, and high species richness and endemism; presents findings from the workshop; and discusses science questions, hypotheses, and possibilities for future research projects to help fill key knowledge gaps. Participants in the January 2020 workshop, representing diverse expertise in various topics in southeastern grassland ecology, were tasked with identifying major threats to grassland species in the Southeast as well as potential ways to make the SSA process more efficient and effective. An underlying assumption and starting place for workshop discussion was that an ecosystem-based approach to the SSA process is more cost-efficient than a species-by-species approach, in large part because many species with similar biological requirements can be addressed by the same actions. Nevertheless, one partner in this effort, the U.S. Fish and Wildlife Service, does require specific attention be given to taxa that have been petitioned for Federal listing, though as often as possible these taxa are considered alongside a larger group of priority taxa with an ecosystem approach. For group discussions, workshop participants followed a modified “World Café” method, a structured conversational approach for knowledge sharing. Group discussions focused on five categories of threats to grassland communities and species: (1) habitat loss, fragmentation, and disruption of functional population connectivity; (2) climate change, especially changes in temperature and precipitation, including intensity and seasonality, and impacts on soil moisture, groundwater levels, and other ecosystem parameters; (3) changes to disturbance regimes, as influenced by climate and land-use change, extinctions, and human attitudes and behaviors; (4) invasive species (not limited to nonnative species); and (5) localized or subregional impacts such as sea-level rise. In addition to group discussions, workshop participants—as well as other grassland experts who were unable to attend the workshop—completed a preworkshop survey concerning challenges and opportunities for grassland conservation. Findings reported here under each of these topics represent ideas, problems, hypotheses, and questions identified by a diverse community of grassland managers and researchers which may be addressed by future research and monitoring in southeastern grassland ecosystems to help guide science-based conservation of grassland-dependent species.

Alabama, Arkansas, Florida, Georgia, Kentucky, Lou↗
USGS2007

Using conservation value to assess land restoration and management alternatives across a degraded oak savanna landscape

1. Managers considering restoration of landscapes often face a fundamental challenge - what should be the habitat composition of the restored landscape? We present a method for evaluating an important conservation trade-off inherent in making that decision. 2. Oak savannas and grasslands were historically widespread across central North America but are now rare. Today, in north-west Indiana, USA, habitats spanning a range of woody vegetation density, from nearly treeless open habitats to forests, occur across the conserved landscape where savannas probably once dominated. To understand the benefits of different potential landscape compositions, we evaluated how different proportions of five habitats - open, savanna, woodland, scrub and forest - might affect the conservation value of the north-west Indiana landscape for birds. Two variables of potential conservation importance were examined: species diversity, a measure of avian community richness, and conservation index, the percentage of a bird species' global population occurring on a hectare of landscape, summed across all bird species present. Higher values of conservation index were associated with higher local densities of globally more rare and more threatened species. 3. Conservation index and species diversity were correlated negatively across hypothetical landscapes composed of different proportions of the five habitats. Therefore, a management trade-off existed between conservation index and species diversity because landscapes that maximized species diversity differed from landscapes that maximized conservation index. 4. A landscape of 50% open, 22% savanna, 15% scrub and 13% forest was predicted to represent a compromise at which conservation index and species diversity reached the same percentage of their maxima. In contrast, the current landscape is dominated by forest. 5. Synthesis and applications. We quantified the trade-off between two potential aspects of a landscape's conservation value for birds - the landscape's ability to promote avian species diversity and the landscape's use by threatened avian species. This quantification allowed us to evaluate the ability of different landscape compositions to achieve preferable trade-off compromises, such as maximizing diversity for a given level of landscape use by threatened species. Managers can use these trade-off results to determine which landscape compositions are associated with particular conservation and management priorities.

Journal of Applied Ecology↗
USGS2011

Environmental factors that influence the location of crop agriculture in the conterminous United States

This report presents and describes high-resolution geospatial data identifying the range of environmental conditions that influence the location of cropped agricultural lands in the conterminous United States. Also presented are estimates of the extent of land where environmental constraints limit agricultural production (marginal land) and the extents of land where modifications overcome environmental constraints. The report is the result of the compilation and manipulation of datasets from numerous sources; it consists of an explanatory text and a series of appendixes and associated tables that document the data sources and data-manipulation methods in detail. Environmental factors that influence the extent of crop agriculture are terrain, climate, soil properties, and soil water. It is the combination of these four factors that allow specific crops to be grown in certain areas. Today, in order to maximize production, most of the cultivated croplands and grasslands for commercial agriculture are in areas where crops and livestock are well suited to local conditions. In the United States, cropland (row crops, closely sown crops (except hay), fruits, nuts, vegetables) occupies about 13 percent of the total land area. Grassland and rangeland occupy another 41 percent of the land area. Most crops are grown on land with shallow slope where the temperature, precipitation, and soils are favorable. In areas that are too steep, wet, or dry, landscapes have been modified to allow cultivation. Some of the limitations of the environmental factors that determine the location of agriculture can be overcome through modifications, but others cannot. On a larger-than-field scale, agricultural modifications commonly influence water availability through irrigation and (or) drainage and soil fertility and (or) organic-matter content through amendments such as manure, commercial fertilizer and lime. In general, it is not feasible to modify the other environmental factors, soil texture, soil depth, soil mineralogy, temperature, and terrain at large scales.

Scientific Investigations Report↗
USGS2003

Evolution of CAM and C 4 carbon-concentrating mechanisms

Mechanisms for concentrating carbon around the Rubisco enzyme, which drives the carbon-reducing steps in photosynthesis, are widespread in plants; in vascular plants they are known as crassulacean acid metabolism (CAM) and C 4 photosynthesis. CAM is common in desert succulents, tropical epiphytes, and aquatic plants and is characterized by nighttime fixation of CO2. The proximal selective factor driving the evolution of this CO2-concentrating pathway is low daytime CO2, which results from the unusual reverse stomatal behavior of terrestrial CAM species or from patterns of ambient CO2 availability for aquatic CAM species. In terrestrials the ultimate selective factor is water stress that has selected for increased water use efficiency. In aquatics the ultimate selective factor is diel fluctuations in CO2 availability for palustrine species and extreme oligotrophic conditions for lacustrine species. C4 photosynthesis is based on similar biochemistry but carboxylation steps are spatially separated in the leaf rather than temporally as in CAM. This biochemical pathway is most commonly associated with a specialized leaf anatomy known as Kranz anatomy; however, there are exceptions. The ultimate selective factor driving the evolution of this pathway is excessively high photorespiration that inhibits normal C3 photosynthesis under high light and high temperature in both terrestrial and aquatic habitats. CAM is an ancient pathway that likely has been present since the Paleozoic era in aquatic species from shallow-water palustrine habitats. While atmospheric CO2 levels have undoubtedly affected the evolution of terrestrial plant carbon-concentrating mechanisms, there is reason to believe that past atmospheric changes have not played as important a selective role in the aquatic milieu since palustrine habitats today are not generally carbon sinks, and the selective factors driving aquatic CAM are autogenic. Terrestrial CAM, in contrast, is of increasing selective value under extreme water deficits, and undoubtedly, high Mesozoic CO2 levels reduced the amount of landscape perceived by plants as water limited. Late Tertiary and Quaternary reductions in atmospheric CO2, coupled with increasing seasonality, were probably times of substantial species radiation and ecological expansion for CAM plants. C4 photosynthesis occurs in only about half as many families as CAM, and three-fourths of C4 species are either grasses or sedges. Molecular phylogenies indicate C4 is a more recent innovation than CAM and that it originated in the mid-Tertiary, 20–30 Ma, although some data support an earlier origin. While the timing of the origin of C4 remains controversial, the nearly explosive increase in C4 species is clearly documented in the late Miocene, 4–7 Ma. Increasing seasonality has been widely suggested as an important climatic stimulus for this C4 expansion. Alternatively, based on models of photosynthetic quantum yield at different temperatures and CO2 concentration, it has been hypothesized that the late Miocene C4 expansion resulted from declining atmospheric CO2 levels. This model is most appropriate for explaining the transition from C3 grasslands to C4 grasslands but by itself may not be sufficient to explain the more likely scenario of a late Miocene transition from C3 woodland/ savanna to C4 grasslands. A largely unexplored hypothesis is that climatic changes in late Miocene altered disturbance regimes, in particular the incidence of fires, which today are often associated with maintenance of C4 grasslands. Oceanic charcoal sediments that appear to represent Aeolian deposits from continental wildfires follow a strikingly similar pattern of explosive increase in late Miocene. Climate, CO2, and disturbance are not mutually exclusive explanations and probably all acted in concert to promote the expansion of C4 grasslands. More recently, late Quaternary changes in CO2 may have been responsible for driving major changes in the landscape distribution of C4 species. The theory is sound; however, many of the studies cited in support of this model are open to alternative interpretations, and none has eliminated climatic factors as important selective agents. CAM and C4 evolution required coupling of biochemical pathways with structural changes in photosynthetic tissues, succulence in CAM and Kranz in C4. This was apparently accomplished by piecemeal evolution beginning with mechanisms for recapturing respiratory CO2, although this need not have been so in aquatic CAM species. It has been proposed that the extreme rarity of both pathways in the same plant results from biochemical and structural incompatibilities (Sage 2002). Equally important is the fact that the selective environments are quite different, with CAM evolution thriving on stressful sites inhospitable to C3 species whereas C4 evolution has selected for rapid growth capable of outcompeting associated C3 plants.

International Journal of Plant Sciences↗
USGS2020

Changes in conservation value from grasslands to savannas to forests: How a temperate canopy cover gradient affects butterfly community composition

Temperate savannas and grasslands are globally threatened. In the Midwest United States of America (USA), for example, oak savannas persist today at a small percentage of recent historic coverage. Therefore, restoration of habitats of low and intermediate canopy cover is a landscape conservation priority that often emphasizes returning tree density to a savanna-like target value. Understanding how animal species react to such changes in vegetation structure is important for assessing the value of these restoration plans. We examined how butterfly community attributes in northwest Indiana USA, including community composition, richness, and abundance responded to a grassland-to-forest gradient of canopy cover. Butterfly community composition under intermediate canopy cover differed significantly from community composition in the most open or closed-canopy habitats. Composition of the plant community in flower was a significant predictor of three assessed attributes of the butterfly community—composition, richness, and abundance. Phenology, expressed as day-of-the-year, was also a strong predictor of these butterfly community attributes. Few butterfly species were habitat specialists as adults although canopy cover was a more important predictor of adult community composition than of richness or abundance of butterflies. Therefore, adult butterfly community differences along the canopy cover gradient were less about butterfly communities filled with habitat specialists for different canopy-defined habitats and more about gradual changes in community composition along this gradient. Overall, butterfly community richness was predicted to peak at about 34% canopy cover, butterfly abundance at about 53% canopy cover, community conservation value at about 59% canopy cover, and a combination of desirable conservation attributes–high diversity, high abundance, and high conservation value–was predicted to reach a peak of co-occurrence at about 67% canopy cover suggesting that habitats of intermediate canopy cover might be particularly effective for butterfly conservation in this region.

Indiana↗
USGS2008

Ecological effects of large fires on US landscapes: benefit or catastrophe?

The perception is that today’s large fires are an ecological catastrophe because they burn vast areas with high intensities and severities. However, little is known of the ecological impacts of large fires on both historical and contemporary landscapes. The present paper presents a review of the current knowledge of the effects of large fires in the United States by important ecosystems written by regional experts. The ecosystems are (1) ponderosa pine–Douglas-fir, (2) sagebrush–grasslands, (3) piñon–juniper, (4) chaparral, (5) mixed-conifer, and (6) spruce–fir. This review found that large fires were common on most historical western US landscapes and they will continue to be common today with exceptions. Sagebrush ecosystems are currently experiencing larger, more severe, and more frequent large fires compared to historical conditions due to exotic cheatgrass invasions. Historical large fires in south-west ponderosa pine forest created a mixed severity mosaic dominated by non-lethal surface fires while today’s large fires are mostly high severity crown fires. While large fires play an important role in landscape ecology for most regions, their importance is much less in the dry piñon–juniper forests and sagebrush–grasslands. Fire management must address the role of large fires in maintaining the health of many US fire-dominated ecosystems.

International Journal of Wildland Fire↗
USGS2007

Late Quaternary paleoenvironments of an ephemeral wetland in North Dakota, USA: Relative interactions of ground-water hydrology and climate change

This study of fossils (pollen, plant macrofossils, stomata and fish) and sediments (lithostratigraphy and geochemistry) from the Wendel site in North Dakota, USA, emphasizes the importance of considering ground-water hydrology when deciphering paleoclimate signals from lakes in postglacial landscapes. The Wendel site was a paleolake from about 11,500 14C yr BP to 11,100 14C yr BP. Afterwards, the lake-level lowered until it became a prairie marsh by 9,300 14C yr BP and finally, at 8,500 14C yr BP, an ephemeral wetland as it is today. Meanwhile, the vegetation changed from a white spruce parkland (11,500 to 10,500 14C yr BP) to deciduous parkland, followed by grassland at 9,300 14C yr BP. The pattern and timing of these aquatic and terrestrial changes are similar to coeval kettle lake records from adjacent uplands, providing a regional aridity signal. However, two local sources of ground water were identified from the fossil and geochemical data, which mediated atmospheric inputs to the Wendel basin. First, the paleolake received water from the melting of stagnant ice buried under local till for about 900 years after glacier recession. Later, Holocene droughts probably caused the lower-elevation Wendel site to capture the ground water of up-gradient lakes. ?? 2007 Springer Science+Business Media, Inc.

Journal of Paleolimnology↗
USGS2012

Mapping grasslands suitable for cellulosic biofuels in the Greater Platte River Basin, United States

Biofuels are an important component in the development of alternative energy supplies, which is needed to achieve national energy independence and security in the United States. The most common biofuel product today in the United States is corn-based ethanol; however, its development is limited because of concerns about global food shortages, livestock and food price increases, and water demand increases for irrigation and ethanol production. Corn-based ethanol also potentially contributes to soil erosion, and pesticides and fertilizers affect water quality. Studies indicate that future potential production of cellulosic ethanol is likely to be much greater than grain- or starch-based ethanol. As a result, economics and policy incentives could, in the near future, encourage expansion of cellulosic biofuels production from grasses, forest woody biomass, and agricultural and municipal wastes. If production expands, cultivation of cellulosic feedstock crops, such as switchgrass ( Panicum virgatum L. ) and miscanthus ( Miscanthus species ), is expected to increase dramatically. The main objective of this study is to identify grasslands in the Great Plains that are potentially suitable for cellulosic feedstock (such as switchgrass) production. Producing ethanol from noncropland holdings (such as grassland) will minimize the effects of biofuel developments on global food supplies. Our pilot study area is the Greater Platte River Basin, which includes a broad range of plant productivity from semiarid grasslands in the west to the fertile corn belt in the east. The Greater Platte River Basin was the subject of related U.S. Geological Survey (USGS) integrated research projects.

Colorado;Nebraska;South Dakota;Wyoming↗
USGS2018

The Pothole Hydrology-Linked Systems Simulator (PHyLiSS)—Development and application of a systems model for prairie-pothole wetlands

The North American Prairie Pothole Region covers about 770,000 square kilometers of the United States and Canada (including parts of 5 States and 3 provinces: North Dakota, South Dakota, Montana, Minnesota, Iowa, Saskatchewan, Manitoba, and Alberta). The Laurentide Ice Sheet shaped the landscape of the region about 12,000 to 14,000 years ago. The retreat of the ice sheet left behind low-permeability glacial till and a landscape dotted with millions of depressions known today as prairie potholes. The wetlands that subsequently formed in these depressions, prairie-pothole wetlands, provide critical migratory-bird habitat and support dynamic aquatic communities. Extensive grasslands and productive agricultural systems surround these wetland ecosystems. In prairie-pothole wetlands, the compositions of plant, invertebrate, and vertebrate communities are highly dependent on hydrogeochemical conditions. Regional climate shifts between wet and dry periods affect the length of time that wetlands contain ponded surface water and the chemistry of that ponded water. Land-use change can exacerbate or reduce the effects of climate on wetland hydrology and water chemistry. A mechanistic understanding of the relation among climate, land use, hydrology, chemistry, and biota in prairie-pothole wetlands is needed to better understand the complex, and often interacting, effects of climate and land use on prairie-pothole wetland systems and to facilitate climate and land-use change adaptation efforts. The Pothole Hydrology-Linked Systems Simulator (PHyLiSS) model was developed to address this need. The model simulates water-surface elevation dynamics in prairie-pothole wetlands and quantifies changes in salinity. The PHyLiSS model is unique among other wetland models because it accommodates differing sizes and morphometries of wetland basins, is not dependent on a priori designations of wetland class, and allows for functional changes associated with dynamic shifts in ecohydrological states. The PHyLiSS model also has the capability to simulate wetland salinity, and potential future iterations will also simulate the effects of changing hydrology and geochemical conditions on biota. This report documents the development of the hydrological and geochemical components of the PHyLiSS model and provides example applications.

Open-File Report↗
USGS1972

Review of literature on the endangered masked bobwhite

The masked bobwhite (Colinus virginianus ridgwayi) once inhabited restricted areas in southern Arizona and middle Sonora, Mexico. It probably never was a widespread and abundant bird. Ornithologists discovered this race in 1884, presumably during its final decline in Arizona due to overgrazing and a series of droughts. . It was gone from Arizona by 1900. Apparently the bird was not seriously threatened in Sonora until the 1940's when the cattle industry increased there. Only small and scattered populations remain in Sonora today. Although behavior of the masked bobwhite is similar to that of the closely-related eastern bobwhite (C. v. virginianus), the desert variety prefers a mesquite-grassland habitat at elevations of from 1,000 to 4,000 feet, has a later and shorter nesting season, and has more striking sexual plumage. The male's black head and 'robin's red' breast readily identify the bird. Average annual precipitation in the heart of its Sonoran habitat is 13.5 inches, with 75 percent of that occurring during the 3-month period of July through September. Foods consist of small weed and grass seeds, supplemented with invertebrates and green vegetational growth during the summer rainy season. Early attempts at reintroduction of masked bobwhites into Arizona failed. Experiments on propagation and reestablishment and a life history study are currently being carried out by the Bureau of Sport Fisheries and Wildlife in cooperation with the Arizona Fish and Game Department.

Resource Publication↗
USGS1998

Amphibians of the northern Great Plains

No cry of alarm has been sounded over the fate of amphibian populations in the northern grasslands of North America, yet huge percentages of prairie wetland habitat have been lost, and the destruction continues. Scarcely 30% of the original mixedgrass prairie remains in Nebraska, South Dakota, and North Dakota (See Table 1 in this chapter). If amphibian populations haven’t declined, why haven’t they? Or, have we simply failed to notice? Amphibians in the northern grasslands evolved in a boom-or-bust environment: species that were unable to survive droughts lasting for years died out long before humans were around to count them. Species we find today are expert at seizing the rare, wet moment to rebuild their populations in preparation for the next dry season. When numbers can change so rapidly, who can say if a species is rare or common? A lot depends on when you look.

Book chapter↗
USGS2002

Lots of lightning and plenty of people: An ecological history of fire in the upland southwest

Was the pre-European Southwest a region of wild landscapes, shaped primarily by natural processes like lightning-ignited fire, or did people substantially mold these lands into regional-scale artifacts through their use of fire and other means? Perspectives on this question have varied markedly through time and between scholars, as evident from the quotes interspersed through this chapter (see Box 5.1.). As the American frontier closed around the turn of the nineteenth century, lightning was rarely considered a primary cause of fire, with most fires in western forests assumed to be human-ignited. Native Americans were thought to have been the primary source of burning in the Southwest until EuroAmericans usurped that role after ca. 1850. Today, lightning-ignited fire is widely acknowledged to be an ancient and essential ecological process in the American Southwest (Pyne 1995a:282-283; Swetnam and Baisan 1996a; Bogan et al. 1998), for millennia structuring landscapes from low-elevation desert grasslands to montane forests. However, because the Southwest has been home to people for more than 12,000 years, with large human populations for over 1,000 years (Plog et al. 1988), some scholars continue to assert the dominance of aboriginal burning in the fire regimes of this region (Dobyns 1981; Pyne 1995a, 1996, 1997). This essay focuses on the roles of

Book chapter↗
USGS2010

Herbicide treatment of invasive Vinca major growing with endangered Galium buxifolium, an island endemic

Galium buxifolium E. Greene [Rubiaceae] (sea-cliff bedstraw) is a small shrub restricted to San Miguel and Santa Cruz Islands, in the California Channel Islands. Almost all of the 26 known populations grow on vertical north-facing sea cliffs in native scrub, sandwiched between the sea below and non-native annual grasslands on the terraces above. A notable exception is a popula?tion at Pelican Bay on Santa Cruz Island, growing on the cliff and on thin terrace soils above the cliff in a stand of coastal bluff scrub that is recovering from more than a century of sheep grazing (Figure 1). Ironically, this stand is near the location of the historic Eaton Resort, a charismatic inn frequented by Hollywood glitterati in the early 1900s. Several landscape ornamentals planted there persist today in the area of the Galium population. Italian stone pine (Pinus pinaea) and eucalyptus (Eucalyptus spp.) tower over the site while the invasive groundcover Vinca major L. [Apocynaceae] (greater periwinkle) forms dense mats at the cliff edge that are spreading into the developing native plant stand. Wherever the Galium is found it is intermixed with other native scrub plants in dense communities on moist ocean bluffs. Historic notes and herbarium collections indicate that it may have been more widespread on nearshore terraces adjacent to sea-cliff populations before conversion to grassland. Since Pelican Bay is the only site that we know of where Galium is spreading onto the nearby terrace, we wanted to know whether the Vinca posed a roadblock to upslope population expansion. In 2005 we mapped Vinca and Galium at the site. We also measured Galium individuals to see where the smaller, younger plants were to better understand where the population is expanding. We observed that 1) both the Galium and the Vinca appear to be spreading from the cliff face upslope onto a series of rock outcrops, stone walls and benches, 2) the native scrub community is recovering at the site and 3) the Vinca appears to be moving into the native scrub where it overtops small plants, including those Galium in the smallest size classes. This observed pattern of Vinca displacement of native vegetation has been noted in other places, where it is treated as an invasive weed. We concluded that Vinca may pose a threat to the expansion of both the native scrub and the Galium population that it supports. Therefore, we worked with the US Fish and Wildlife Service and others to develop a research project investigating 1) best techniques for killing Vinca within the boundaries of an endangered plant population and 2) demographic response of Galium to the treatment. Our intent is to push Vinca back to the vertical cliff face to give the natives a chance to establish a vigorous stand. Our conservation goal is to encourage natural establishment of new Galium plants on the terrace along with expansion of the native coastal bluff scrub and Galium population. Our immediate treatment objective is to reduce live Vinca cover by 90 % on the accessible upslope portions of the habitat. Our recovery objective is no net loss of Galium plants 2006-2016.

California↗
USGS2011

Late Quaternary environmental change inferred from phytoliths and other soil-related proxies: Case studies from the central and southern Great Plains, USA

This study investigates stable carbon isotopes ( δ 13 C), opal phytolith assemblages, burnt phytoliths, microscopic charcoal and Sporormiella spores from modern soils and paleosols in Kansas and Oklahoma. Grass and dicot phytoliths in combination with δ 13 C are used as proxies for reconstructing the structure of grasslands and woodlands. Burnt grass phytoliths and microscopic charcoal are evaluated as proxies for reconstructing paleofire incidence. Concentrations of the fungal spore Sporormiella are used as a proxy for assessing large herbivore activity. These proxies were tested on various modern grassland communities of the central and southern Great Plains, including areas with bison, cattle, and small herbivores, and areas under different fire frequencies. Opal phytolith assemblages and δ 13 C values show that before cal 11 ka, C 3 grasses and woody plants predominated in areas that today are dominated by C 4 grasses. The origin of the shortgrass prairie dates back to about cal 10 ka. The origin of the tallgrass prairie, however, is not clear as phytolith data show variable assemblages throughout the Holocene (mixed-grass, tallgrass, and tallgrass–woodland mosaic). Different proxies (burnt phytoliths vs. charcoal) reveal different fire frequencies, but it is apparent that microfossil evidence for fire incidence is closely related to the abundance of woody plants in the landscape. Before cal 12 ka, soils show somewhat elevated concentration of Sporormiella , but lower concentrations than the modern high-density bison and cattle grazing areas. Throughout the Holocene, Sporormiella frequencies are low, which suggests lower large ungulate densities and perhaps high mobility.

Colorado, Kansas, New Mexico, Oklahoma, Texas↗