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Eryngium sparganophyllum is an imperiled plant species with a small geographic range in the southwestern United States and northern Mexico and is restricted to wetlands known as cienegas. We compiled information on its population status,... more
Eryngium sparganophyllum is an imperiled plant species with a small geographic range in the southwestern United States and northern Mexico and is restricted to wetlands known as cienegas. We compiled information on its population status, habitat, life history, and threats to inform conservation and recovery efforts and to guide future research. Of the six historically documented populations, this species has been extirpated at two and remains extant in four. Extractions of groundwater or diversions of spring discharge are the greatest threats, exacerbated by reduced groundwater inflow to cienegas because of regional drought and temperature increases. Eryngium sparganophyllum is locally common in its known sites, but woody encroachment may be a threat, as field data in Arizona reveal the plants to be more abundant in open sun than under tree canopy. Plants flower within their first year and host a wide range of invertebrate visitors. Experimental techniques confirm seed viability with a morphophysiological dormancy; however, patterns of seedling establishment in the wild remain undocumented. Reintroduction at two sites is being implemented and long-term monitoring of survivorship and fecundity of these transplants is necessary to guide future recovery efforts.
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[From CAB Abstracts] Riparian areas in southwestern American deserts support native plant communities that are more dense, structurally complex, productive and species-rich than those of the adjacent xeric uplands. Riparian areas attract... more
[From CAB Abstracts] Riparian areas in southwestern American deserts support native plant communities that are more dense, structurally complex, productive and species-rich than those of the adjacent xeric uplands. Riparian areas attract human settlement and, as a result, riparian exotic plants have become an issue. The factors that have facilitated the influx of exotics into riparian corridors and the ways in which riparian ecosystem functions have been affected are discussed (with the impact of saltcedars (Tamarix spp.) as an example). High exotic abundance may be aided by flooding (enhancing dispersal and establishment opportunities), the introduction of grazing animals and other anthropogenic influences, e.g. road development and agriculture. Some woody exotics are now widespread and locally abundant in southwestern riparian areas, including Elaeagnus angustifolia, Ailanthus altissima, Tamarix spp. and Nicotiana glauca. There are probably over 100 naturalized exotic herbaceous species, the most successful of which are probably the grasses, e.g. Cynodon dactylon, Sorghum halepense, Polypogon monspeliensis and Bromus spp. Constructive options for restoring functionality to southwestern desert riparian ecosystems are discussed.
Research Interests: Geography, Environmental Science, Plant Ecology, Natural Resources, Conservation Biology, and 14 moreRestoration Ecology, Arid Land Ecology, Invasive species ecology, Ecology, Desert Ecology, North American Southwest, Big Dams, Riparian Ecology, Phenology, Environmental Sustainability, Hydrology and Ecohydrology, Plant Ecophysiology, Novel ecosystems, and Arizona State University
... Recruitment of Fremont cottonwood (Populus fremontii) and Goodding willow (Salix gooddingii) depends on (1) large prior-year floods to remove herbaceous cover; (2) high spring flows or rains to stimulate germination on floodplains... more
... Recruitment of Fremont cottonwood (Populus fremontii) and Goodding willow (Salix gooddingii) depends on (1) large prior-year floods to remove herbaceous cover; (2) high spring flows or rains to stimulate germination on floodplains above the zone of frequent flood inundation ...
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Research Interests: Botany, Perception, Plant Ecology, Natural Resources, Conservation Biology, and 15 moreHydrology, Environmental Studies, Environmental History, History of Science, Restoration Ecology, Biology, Invasive species ecology, Ecohydrology, Restoration, Biogeography, Riparian Ecology, Biological Sciences, Environmental Sciences, Riparian Ecosystems, and River Management
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Eryngium sparganophyllum is an imperiled plant species with a small geographic range in the southwestern United States and northern Mexico and is restricted to wetlands known as cienegas. We compiled information on its population status,... more
Eryngium sparganophyllum is an imperiled plant species with a small geographic range in the southwestern United States and northern Mexico and is restricted to wetlands known as cienegas. We compiled information on its population status, habitat, life history, and threats to inform conservation and recovery efforts and to guide future research. Of the six historically documented populations, this species has been extirpated at two and remains extant in four. Extractions of groundwater or diversions of spring discharge are the greatest threats, exacerbated by reduced groundwater inflow to cienegas because of regional drought and temperature increases. Eryngium sparganophyllum is locally common in its known sites, but woody encroachment may be a threat, as field data in Arizona reveal the plants to be more abundant in open sun than under tree canopy. Plants flower within their first year and host a wide range of invertebrate visitors. Experimental techniques confirm seed viability with a morphophysiological dormancy; however, patterns of seedling establishment in the wild remain undocumented. Reintroduction at two sites is being implemented and long-term monitoring of survivorship and fecundity of these transplants is necessary to guide future recovery efforts.
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On 20 July 2010, the inflatable bladder dams that created the Tempe [Arizona, USA] Town Lake ruptured, emptying the lake and exposing sediments that had been submerged for a decade. Among the 20 species of plants subsequently germinating... more
On 20 July 2010, the inflatable bladder dams that created the Tempe [Arizona, USA] Town Lake ruptured, emptying the lake and exposing sediments that had been submerged for a decade. Among the 20 species of plants subsequently germinating we found three introduced taxa previously rare, misidentified or unknown in Arizona: Ammannia coccinea (Rottb.), Cyperus michelianus subsp. pygmaeus (Rottb. Asch & Graebn) and Ludwigia erecta (L.) H. Hara.
Research Interests: Aquatic Ecology, Wetlands, Aquatic botany, Urban Studies, Invasive species ecology, and 25 moreInvasive Species, Wetland Ecology, Rivers, Invasion Ecology, Floristics, Plant Taxonomy (Taxonomy), Biological invasions, River Ecology, Urban And Regional Planning, Seed dormancy, Plant Taxonomy, Ephemerality, Urban Parks, Seed bank, Dams, Invasive Alien Species, Sonoran Desert, Cyperaceae, Lake Sediments, Arizona History, Introduced species, Lythraceae, Onagraceae, Reclamation, and Flood Mangement
Conservationists should assess organisms on environmental impact rather than on whether they are natives.
Research Interests: Environmental Philosophy, Environmental Education, Conservation Biology, Environmental Studies, Environmental History, and 9 moreComputer Networks, Restoration Ecology, Environmental Ethics, Biological invasions, Environmental Sustainability, Restoration ecology (Environment), Databases, Software, and Science and Technology Studies
Riparian fire studies in the American Southwest have focused on flow-regulated rivers and typically show increase in introduced Tamarix, a species with high resprout capacity, and declines in Populus. Effects of fire, however, can vary... more
Riparian fire studies in the American Southwest have focused on flow-regulated rivers and typically show increase in introduced Tamarix, a species with high resprout capacity, and declines in Populus. Effects of fire, however, can vary with environmental setting. We examined riparian fire along the free-flowing Upper San Pedro River (Arizona) by making temporal comparisons supplemented by spatial contrasts between burned and unburned sites. Pre-fire, Populus fremontii and Salix gooddingii were dominant species, with Tamarix sparse in the understory. Species differed in mortality and resprout rates, producing post-fire vegetation change. Mortality was highest for Tamarix, intermediate for Salix, and lowest for Populus, and also varied among size classes. Resprout rate was low for Populus, high for Salix, and also high for the few surviving Tamarix. The net effect was changes in population size structure (relative shifts towards larger Populus but smaller individuals of other species) and forest composition (decreased abundance of Tamarix relative to Populus and Salix), and in spatial distribution of stems. Tamarix’s low ability to survive fire resulted from competitive suppression by Populus and Salix, with their dominance a product of the site’s flow regime. Results indicate that post-fire outcomes within the riparian Southwest are variable and context-dependent.
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Rivers are conduits for materials and energy; this, the frequent and intense disturbances that these systems experience, and their narrow, linear nature, create problems for conservation of biodiversity and ecosystem functioning in the... more
Rivers are conduits for materials and energy; this, the frequent and intense disturbances that these systems experience, and their narrow, linear nature, create problems for conservation of biodiversity and ecosystem functioning in the face of increasing human influence. In most parts of the world, riparian zones are highly modified. Changes caused by alien plants — or environmental changes that facilitate shifts in dominance creating novel ecosystems — are often important agents of perturbation in these systems. Many restoration projects are underway. Objective frameworks based on an understanding of biogeographical processes at different spatial scales (reach, segment, catchment), the specific relationships between invasive plants and resilience and ecosystem functioning, and realistic endpoints are needed to guide sustainable restoration initiatives. This paper examines the biogeography and the determinants of composition and structure of riparian vegetation in temperate and subtropical regions and conceptualizes the components of resilience in these systems. We consider changes to structure and functioning caused by, or associated with, alien plant invasions, in particular those that lead to breached abiotic- or biotic thresholds. These pose challenges when formulating restoration programmes. Pervasive and escalating human-mediated changes to multiple factors and at a range of scales in riparian environments demand innovative and pragmatic approaches to restoration. The application of a new framework accommodating such complexity is demonstrated with reference to a hypothetical riparian ecosystem under three scenarios: (1) system unaffected by invasive plants; (2) system initially uninvaded, but with flood-generated incursion of alien plants and escalating invasion-driven alteration; and (3) system affected by both invasions and engineering interventions. The scheme has been used to derive a decision-making framework for restoring riparian zones in South Africa and could guide similar initiatives in other parts of the world.
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Dryland rivers are characterized by high spatio-temporal variability in water resources, with alternating wet and dry reaches and fluctuating stream flow rates. To investigate response to this dynamic, riparian plant communities from... more
Dryland rivers are characterized by high spatio-temporal variability in water resources, with alternating wet and dry reaches and fluctuating stream flow rates. To investigate response to this dynamic, riparian plant communities from perennial, temporally intermittent, and ephemeral-flow reaches of the Hassayampa River and an ephemeral tributary (southwestern USA) were characterized over a three year period, and soil seed banks (emergence method) were assessed. Variance through time in cover and diversity of wetland (hydric) species was lowest at perennial sites and highest at ephemeral flow sites. Wetland plants established along the active channel of the ephemeral reach following a 10-year recurrence interval flood, and compositional similarity between perennial and ephemeral sites was high during this wet year. About half of the wetland species growing at ephemeral flow sites were present in floodplain soil seed banks. Wetland species emerged from soils of the ephemeral Hassayampa River (but not of the ephemeral tributary) but their density and diversity declined with distance downstream of the perennial reach. Wetland species in the seed banks of ephemeral-flow sites were a nested subset of those at wetter sites, raising the possibility of dispersal from upstream sites. These results indicate that wetlands develop episodically on ephemeral reaches of spatially intermittent rivers of the Sonoran Desert following high winter runoff, and suggest that the wetland plants arise from local seed banks and off-site sources. The study also suggests that riverine restoration success is sensitive to location within a stream network: upon re-watering, sites closer to perennial reaches will have greater capacity to self-assemble wetland plant communities.
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After a long period in which fuel loads were sparse, fire recently has occurred with high frequency in the ungrazed riparian zone of the Upper San Pedro River in southern Arizona’s Chihuahuan Desert. We studied four accidental fires that... more
After a long period in which fuel loads were sparse, fire recently has occurred with high frequency in the ungrazed riparian zone of the Upper San Pedro River in southern Arizona’s Chihuahuan Desert. We studied four accidental fires that occurred during 1994–2003 (two in different years at the same site). Woody vegetation was contrasted between three burned sites and matched spatial controls, and before and after the most recent fire. Herbaceous vegetation was sampled in multiple years producing a chronosequence of time since fire (from 4 months to 8 years). Riparian fire was associated with reductions in woody plant species diversity and canopy cover. In contrast, fire caused a short-term (2 year) pulse of herbaceous plant diversity, driven by annual species, and persistent increase in herbaceous cover. Path analysis indicated that the increase in herbaceous cover was mediated in part by the reduction in tree canopy cover. Ordination (nonmetric multidimensional scaling) and regression analysis also indicated that canopy cover and/or fire played a role in structuring the herbaceous community, although its effects were secondary to that of hydrologic factors (stream flow rate, seasonal flood size). By converting riparian forests to grasslands and savannahs, fire may be shifting structure of the Upper San Pedro floodplain vegetation closer toward conditions present during past centuries when fire was frequent in the upland desert grasslands and embedded riparian corridor.
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Little is known about the composition and function of the mycorrhizal fungal community in riparian areas, or its importance in competitive interactions between Populus fremontii, a dominant tree in southwestern United States riparian... more
Little is known about the composition and function of the mycorrhizal fungal community in riparian areas, or its importance in competitive interactions between Populus fremontii, a dominant tree in southwestern United States riparian forests which forms arbuscular and ectomycorrhizas, and Tamarix ramosissima, an introduced tree species that has spread into riparian areas. The objectives of this study were to determine the mycorrhizal status of Tamarixand to evaluate the effect of mycorrhizal fungal inoculation on Tamarix growth and on the coexistence between Tamarix and Populus.Arbuscular mycorrhizal fungal colonization of Tamarix was very low in both field and greenhouse grown roots, but levels of colonization by dark septate endophytes were high. Fungal inoculation had little effect on Tamarix seedling growth in monoculture. When Populus and Tamarix were grown together in a greenhouse pot experiment, fungal inoculation reduced the height and biomass of Tamarix but had no effect on Populus. Fungal inoculation shifted coexistence ratios. When Tamarix and Populuswere grown together, Tamarixplants averaged 20 of pot biomass in the uninoculated control but only 5 of pot biomass in the inoculated treatment. These results indicate that Tamarix is non-mycotrophic and that in this greenhouse experiment inoculation altered patterns of coexistence between Populus and Tamarix.
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This study focuses on the relationships between plant dispersal syndromes and plant distributions at the community scale. Species composition and cover are reported from 29 10 × 20-m vegetation plots along five topographic cross-sections... more
This study focuses on the relationships between plant dispersal syndromes and plant distributions at the community scale. Species composition and cover are reported from 29 10 × 20-m vegetation plots along five topographic cross-sections in the riparian zone of the Hassayampa River Preserve, Arizona. We find that spatial patterns of dispersal guilds vary within the flood plain of this semiarid region river. Our main results are: (1) wind-dispersed species are fairly evenly distributed at all elevations and distances from the river, whereas cover of animal-dispersed species increases with elevation above, and at greater distances from, the river; (2) wind-dispersed species are proportionally more abundant in the pioneer Populus–Salix community, whereas plants in the late-seral Prosopis community are predominantly animal-dispersed; (3) most of the species classified as obligate-wetland and facultative-wetland are wind-dispersed, whereas facultative-upland and obligate-upland species are mostly animal-dispersed; and (4) there are significantly fewer wind-dispersed species in areas of high total vegetation cover. These results may reflect successional patterns resulting from periodic flooding. Low areas close to the river flood more frequently and with greater intensity than areas farther from the river. Many pioneer species that establish in disturbed areas are wind-dispersed. Over successional time, pioneer species cede to more drought tolerant species that are predominantly animal-dispersed.
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A portion of Arizona’s San Pedro River is managed as a National Riparian Conservation Area but is potentially affected by ground-water withdrawals beyond the conservation area borders. We applied an assessment model to the Conservation... more
A portion of Arizona’s San Pedro River is managed as a National Riparian Conservation Area but is potentially affected by ground-water withdrawals beyond the conservation area borders. We applied an assessment model to the Conservation Area as a basis for monitoring long-term changes in riparian ecosystem condition resulting from changes in river water availability, and collected multi-year data on a subset of the most sensitive bioindicators. The assessment model is based on nine vegetation bioindicators that are sensitive to changes in surface water or ground water. Site index scores allow for placement into one of three condition classes, each reflecting particular ranges for site hydrology and vegetation structure. We collected the bioindicator data at 26 sites distributed among 14 reaches that had similar stream flow hydrology (spatial flow intermittency) and geomorphology (channel sinuosity, flood-plain width). Overall, 39% of the riparian corridor fell within condition class 3 (the wettest condition), 55% in condition class 2, and 6% in the driest condition class. Condition class 3 reaches have high cover of herbaceous wetland plants (e.g., Juncus and Schoenoplectus spp.) along the perennial stream channel and dense, multi-aged Populus-Salix woodlands in the flood plain, sustained by shallow ground water in the stream alluvium. In condition class 2, intermittent stream flows result in low cover of streamside wetland herbs, but Populus-Salix remain abundant in the flood plain. Perennial wetland plants are absent from condition class 1, reflecting highly intermittent stream flows; the flood plain is vegetated by Tamarixa small tree that tolerates the deep and fluctuating ground water levels that typify this reach type. Abundance of herbaceous wetland plants and growth rate of Salix gooddingii varied between years with different stream flow rates, indicating utility of these measures for tracking short-term responses to hydrologic change. Repeat measurement of all bioindicators will indicate long-term trends in hydro-vegetational condition.
Research Interests: Environmental Monitoring, Rivers, Multidisciplinary, Populus, Arizona, and 18 moreRiver water, Ground Water, Plants, Site index, Surface Water, Riparian vegetation, Arid Region, Environmental monitoring and assessment, Theoretical Models, Repeated Measures, Ecosystem, Growth rate, Plant Development, Conservation of Natural Resources, Environmental, San Pedro River, Vegetation Structure, and Stream Flow
• This study examined the activity, species richness, and species composition of the arbuscular mycorrhizal fungal (AMF) community of Populus–Salix stands on the Verde River (Arizona, USA), quantified patterns of AMF richness and... more
• This study examined the activity, species richness, and species composition of the arbuscular mycorrhizal fungal (AMF) community of Populus–Salix stands on the Verde River (Arizona, USA), quantified patterns of AMF richness and colonization along complex floodplain gradients, and identified environmental variables responsible for structuring the AMF community.• Samples from 61 Populus–Salix stands were analyzed for AMF and herbaceous composition, AMF colonization, gravimetric soil moisture, soil texture, per cent organic matter, pH, and concentrations of nitrate, bicarbonate phosphorus and exchangeable potassium.• AMF species richness declined with stand age and distance from and elevation above the channel and was positively related to perennial species cover and richness and gravimetric soil moisture. Distance from and elevation above the active channel, forest age, annual species cover, perennial species richness, and exchangeable potassium concentration all played a role in structuring the AMF community in this riparian area.• Most AMF species were found across a wide range of soil conditions, but a subset of species tended to occur more often in hydric areas. This group of riparian affiliate AMF species includes several not previously encountered in the surrounding Sonoran desert.This study examined the activity, species richness, and species composition of the arbuscular mycorrhizal fungal (AMF) community of Populus–Salix stands on the Verde River (Arizona, USA), quantified patterns of AMF richness and colonization along complex floodplain gradients, and identified environmental variables responsible for structuring the AMF community.Samples from 61 Populus–Salix stands were analyzed for AMF and herbaceous composition, AMF colonization, gravimetric soil moisture, soil texture, per cent organic matter, pH, and concentrations of nitrate, bicarbonate phosphorus and exchangeable potassium.AMF species richness declined with stand age and distance from and elevation above the channel and was positively related to perennial species cover and richness and gravimetric soil moisture. Distance from and elevation above the active channel, forest age, annual species cover, perennial species richness, and exchangeable potassium concentration all played a role in structuring the AMF community in this riparian area.Most AMF species were found across a wide range of soil conditions, but a subset of species tended to occur more often in hydric areas. This group of riparian affiliate AMF species includes several not previously encountered in the surrounding Sonoran desert.
Research Interests: Microbiology, Soil, Carbon, Plant Biology, Symbiosis, and 25 moreChina, Fungi, France, Biological Sciences, Environmental Sciences, Arbuscular mycorrhizal fungi, AM fungi, Coastal Sand Dunes, Nitrogen, Soil Ecology and Biology, Artemisia, Species Richness, Mycorrhiza, Plant Roots, Poaceae, Riparian, Semiarid, Soil Microbiology, Ecosystem, Phosphates, Mycorrhizae, Seasons, Revista Chilena de Historia Natural, Soil Texture, and Glomeromycota
Large expanses of riverine marsh are rare in the desert Southwest, given the dry surface of many floodplain soils. Along the Hassayampa River, riverine marsh underwent a 5-fold increase (from 2% to 9% of the floodplain-channel area) after... more
Large expanses of riverine marsh are rare in the desert Southwest, given the dry surface of many floodplain soils. Along the Hassayampa River, riverine marsh underwent a 5-fold increase (from 2% to 9% of the floodplain-channel area) after a large winter flood in 1993. Flood waters eroded terraces that had aggraded during frequent, smaller floods, widened the channel from about 3 to 50 m, and recharged the floodplain aquifer. The net effect of these changes was a lowering of the floodplain surface relative to the water table, a variable of critical importance to riparian plant composition in arid-land rivers. Olney’s bulrush (Scirpus americanus Pers.), southern cattail (Typha domingensis Pers.), jointed rush (Juncus articulatus L.), and other obligate wetland species were abundant in 1993 and 1994 on areas with saturated surface soils or shallow water tables and often were intermixed with seedlings of early-seral tree species, including Fremont cottonwood (Populus fremontii S. Watson), Goodding willow (Salix gooddingii Ball), and salt cedar (Tamarix chinensis Loureiro and related species). The gain in riverine marsh and young cottonwood-willow stands occurred at the expense of mature cottonwood-willow forests and deep-rooted, velvet mesquite (Prosopis velutina Woot.) woodlands. Another large flood in 1995 scoured the channel of most existing vegetation and aggraded the 1993 flood channel. Early-seral tree species again established in moist soils exposed by the slowly receding flood waters. However, redevelopment of extensive marsh habitat was precluded by sediment deposition that increased the elevation of the floodplain surface relative to the water table. These changes highlight the transitory nature of riverine marsh and other vegetation patch types in the dynamic floodplains of alluvial, arid-land rivers and underscore the importance of maintaining flood flows of varying magnitude to maintain patch type diversity.
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Previous studies have revealed the close coupling of components of annual streamflow hydrographs and the germination and establishment ofPopulus species. Key hydrograph components include the timing and magnitude of flood peaks, the rate... more
Previous studies have revealed the close coupling of components of annual streamflow hydrographs and the germination and establishment ofPopulus species. Key hydrograph components include the timing and magnitude of flood peaks, the rate of decline of the recession limb, and the magnitude of base flows. In this paper, we retrospectively examine establishment of four woody riparian species along the Bill Williams River, Arizona, USA, in the context of annual patterns of streamflow for the years 1993–1995. The four species examined were the nativePopulus fremontii, Salix gooddingii, andBaccharis salicifolia and the exoticTamarix ramosissima. We modeled locations suitable for germination of each species along eight study transects by combining historic discharge data, calculated stage-discharge relationships, and seed-dispersal timing observations. This germination model was, a highly significant predictor of seedling establishment. Where germination was predicted to occur, we compared values of several environmental variables in quadrats where we observed successful establishment with quadrats where establishment was unsuccessful. The basal area of mature woody vegetation, the maximum annual, depth to ground water, and the maximum rate of water-table decline were the variables that best discriminated between quadrats with and without seedlings. The results of this study suggest that the basic components of models that relate establishment ofPopulus spp. to annual patterns of streamflow may also be applicable to other woody riparian species. Reach-to-reach variation in stage-discharge relationships can influence model parameters, however, and should be considered if results such as ours are to be used in efforts to prescribe reservoir releases to promote establishment of native riparian vegetation.
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Abstract: Populus spp. (cottonwood) and Salix spp. (willow), the dominant overstory trees in many western riparian forests, are disturbance-adapted species with short seed dispersal periods. Changes to flood cycles often lead to a... more
Abstract: Populus spp. (cottonwood) and Salix spp. (willow), the dominant overstory trees in many western riparian forests, are disturbance-adapted species with short seed dispersal periods. Changes to flood cycles often lead to a decrease in recruitment success and survival of ...
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umans have long been fasci- nated by the dynamism of free-flowing waters. Yet we have expended great effort to tame i rivers for transportation, water sup- ply, flood control, agriculture, and ; f
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Flow regimes are strong determinants of riparian vegetation structure. Flow regimes vary among rivers of the American Southwest because of intrinsic hydrogeomorphic differences and because of differing degrees and types of human... more
Flow regimes are strong determinants of riparian vegetation structure. Flow regimes vary among rivers of the American Southwest because of intrinsic hydrogeomorphic differences and because of differing degrees and types of human influence. This study reports on a survey of river reaches in the Gila and Bill Williams drainage basins of Arizona. that varied in flow permanence (perennial, intermittent, ephemeral), presence or absence of an upstream flow-regulating dam, and presence or absence of municipal effluent as a water source. The study focused on abundance patterns of Tamarix ramosissima, a species introduced to North America, relative to those of Populus fremontii and Salix gooddingii, which historically were common pioneer trees in the region. Analysis indicated that Tamarix was significantly more abundant than Populus-Salix at sites with intermittent flow (and thus where groundwater seasonally declined below rooting zones of shallow-rooted phreatophytes) and at sites below flow-regulating dams. Populus-Salix, in contrast, was the dominant forest type along free-flowing, perennial rivers. In reaches with ephemeral flow, including those below diversion dams, all forest types were sparse or absent and xeric shrublands predominated. Riparian ecosystem restoration projects are underway along several rivers in the American Southwest, most of which have a goal of increasing the abundance of Populus-Salix forests. These data affirm the importance of flow regime restoration for re-establishing Populus-Salix as the dominant pioneer forest type.
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We study if homebuyers in Tucson, Arizona care about the condition of natural habitats and if they have preferences between natural and manmade habitats. Using field work data we examine whether homebuyers willingness to pay is influenced... more
We study if homebuyers in Tucson, Arizona care about the condition of natural habitats and if they have preferences between natural and manmade habitats. Using field work data we examine whether homebuyers willingness to pay is influenced by the biological condition of the neighboring riparian habitat and how homebuyers value alternative manmade green areas, specifically golf courses. We also explore
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A methodology is described that allows determination of instream flow requirements for maintenance of riparian trees. Tree-ring data revealed strong relationships between tree growth and stream flow volume for riparian species at Rush... more
A methodology is described that allows determination of instream flow requirements for maintenance of riparian trees. Tree-ring data revealed strong relationships between tree growth and stream flow volume for riparian species at Rush Creek, an alluvial stream within an arid setting; these relationships allowed development of models that predict growth rates from hydrologic variables. The models can be used to assess instream flow requirements under the assumption that certain levels of growth are necessary to maintain the population. There is a critical need for development and use of instream flow methodologies for riparian vegetation, since present methodologies focus on needs of aquatic animals (e.g., fish) and may underestimate needs of the entire riparian ecosystem.
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Several riparian restoration projects are underway in the arid southwestern United States, many centered on urban rivers. In the Phoenix metropolitan area (Arizona), multiple projects are ongoing or planned along the Salt River. Several... more
Several riparian restoration projects are underway in the arid southwestern United States, many centered on urban rivers. In the Phoenix metropolitan area (Arizona), multiple projects are ongoing or planned along the Salt River. Several factors constrain the urban Salt River projects: the occasional surface flows released from the upstream diversion dam are no longer hydraulically connected to the deepened groundwater table in all reaches; upstream diversion and flow-regulating dams create barriers to the flow of fine sediments, seeds and other materials; channelization has disconnected the river from its historic floodplain; and many of the tributary-mainstem connections have been severed. Actions are not being undertaken to reverse these changes; rather, attempts are being made to create localized oases by transporting pumped groundwater via delivery channels to sustain trees planted at the termini of drip-irrigation lines, and by re-shaping the land surface to create ponds and perched aquifers. In addition to these planned restorations, pockets of riparian vegetation have developed naturally along the Salt River in areas where new urban water sources have become available. We are investigating the diversity and dynamics of these self-assembled plant communities, and comparing them to the areas of focused restoration as well as to regional free-flowing reference rivers. Analysis indicates that input of water from urban storm drains sustains a diverse (but spatially limited) riparian plant community along the Salt River, albeit one whose composition reflects, in part, the urbanized landscape and thus deviates from the palette of the intended restoration plantings. In effect, the urban storm drains are functioning as tributaries and connecting the river with its watershed. The new riparian ecosystems at these storm drain outflows and at the planned restoration areas will inevitably differ from those at regional reference rivers, unless historical ecosystem processes, connections, and landscape settings are restored, an unlikely occurrence in this and most urban settings.
Research Interests: Water Availability, Land Use Change, Populus, Population structure, Biotic interactions, and 11 moreData Collection, Water Table, Species Composition, Physiological Response, Southwestern United States, Plant species, River Management, San Pedro River, Wildlife Habitat, Vegetation Structure, and Basal Area
[From CAB Abstracts] Riparian areas in southwestern American deserts support native plant communities that are more dense, structurally complex, productive and species-rich than those of the adjacent xeric uplands. Riparian areas attract... more
[From CAB Abstracts] Riparian areas in southwestern American deserts support native plant communities that are more dense, structurally complex, productive and species-rich than those of the adjacent xeric uplands. Riparian areas attract human settlement and, as a result, riparian exotic plants have become an issue. The factors that have facilitated the influx of exotics into riparian corridors and the ways in which riparian ecosystem functions have been affected are discussed (with the impact of saltcedars (Tamarix spp.) as an example). High exotic abundance may be aided by flooding (enhancing dispersal and establishment opportunities), the introduction of grazing animals and other anthropogenic influences, e.g. road development and agriculture. Some woody exotics are now widespread and locally abundant in southwestern riparian areas, including Elaeagnus angustifolia, Ailanthus altissima, Tamarix spp. and Nicotiana glauca. There are probably over 100 naturalized exotic herbaceous species, the most successful of which are probably the grasses, e.g. Cynodon dactylon, Sorghum halepense, Polypogon monspeliensis and Bromus spp. Constructive options for restoring functionality to southwestern desert riparian ecosystems are discussed.
Research Interests: Environmental Education, Science Communication, Water, Conservation Biology, Hydrology, and 14 moreRestoration Ecology, Invasive species ecology, Arid environments, Environmental Policy and Governance, Ecology, North American Southwest, Big Dams, Biodiversity, Riparian Ecology, Environmental Sustainability, Human-wildlife conflicts, Invasive species (Environment), Riparian Ecosystems, and Novel ecosystems
Research Interests: Management, Engineering, Ecological Engineering, Optical Engineering, Biochemistry, and 218 moreBioinformatics, Genetics, Microbiology, Stochastic Process, Set Theory, Environmental Science, Geomorphology, Software Engineering, Relational Database, Social Work, Agronomy, European integration, Health Economics, Psychopharmacology, Higher Education, Pain, Cognition, Computational Biology, Electron Backscatter Diffraction (EBSD), Political Science, Catalysis, Theory of Mind, Molecular Evolution, Kinetics, Photochemistry, Photosynthesis, Collective Action, Politics, Social Capital, Theory, Magnetic Resonance Imaging, Arsenic, Medical Microbiology, Symbiosis, Taxonomy, Quality of life, Environmental Management, Attention, Quantum Mechanics, Life Sciences, Virology, Systems Analysis, Risk, Cell Migration, Interaction, Social Comparison, Self Care, User Interface, Titanium, Interface Design, X ray absorption spectroscopy, Accounting Education, Cell Biology, High Energy Physics, Transmission Electron Microscopy, Post Compulsory Education, High Energy Density Physics, Risk assessment, Social Perception, Molecular Biophysics, Water Pollution, Horizontal Gene Transfer, Adolescent, Image segmentation, Multidisciplinary, Prefrontal Cortex, Comparative psychology, Biological Engineering, Comparative, Monte Carlo Methods, Veterinary, Antibiotic Resistance, Middleware, Social Cognitive Affective Neuroscience, Stochastic processes, Theriogenology, India, Biological Sciences, Social Science & Medicine, Biodiversity Conservation, Self Efficacy, Drosophila, Dogs, SEM, Software, Social behavior, Seasonality, Ionosphere, Water Supply, Humans, Models, Autonomous Robots, Biomedical Research, Electromagnetic Radiation, Sampling methods, Primary School, Strontium, Virus, Hair, Questionnaire, Chlorophyll Fluorescence, Multidrug Resistance, Case Study, Graphic User Interface Design, Female, Animals, Drug Resistance, Biomonitoring, Classical, Male, Ground Water, Lead, Insects, Immunosuppression, Reaction Time, Care, Young Adult, Transfer, Stability Analysis, Lead Exposure, Quantum Efficiency, Validity, Education Reform, Magnetic Susceptibility, Hazardous Materials, Nitrogen, Noun, Sediments, Ecological, FOkker Planck Equation, Dairy Cow, Wolbachia, Proteins, Sediment, Task analysis, Random Processes, Awareness, Stimuli, Species Richness, Capsid, Milk products, Riparian, Skin Diseases, Semiarid, Riparian vegetation, Introduced species, System Security, Wave propagation, Instructional Science, Chesapeake Bay, Middle Aged, Home Range, Positive Feedback, Surface and Coatings Technology, Cells, Magnetics, Authorisation, Non-Repudiation, Data Model, LM, Adult, X ray diffraction, Particle Size, Ingestion, Geophysical, Water and Health, Neoplasms, Multiple regression analysis, Biological Process, Comparative European Politics, Culture of Poverty, Nematoda, Pollutant, Perceptual, Learning Motivation, Value added, Risk Assessment, Efflux Pumps, Social Behavior, Low Latency, Water Microbiology, Plant Community, Indexation, Large Scale, Differential equation, Cell Wall, Human Behavior and the Social Environment, Antimicrobial photodynamic therapy, Environmental Toxicology and Chemistry, Graft Rejection, Sensitivity and Specificity, Application Server, Active Transport, Lifelong Education, Cross sectional Study, Two Dimensions, Food Chain, Arsenic Poisoning, Internet, Simulation Model, Quaternaire, Statistical Testing, Capsid Protein, Oxidation-Reduction, Pregnancy Rate, DNA marker, Reflection Coefficient, Trusted Third Party, Bay, Energetic particles, Nails, Elementary Particles, Stream Flow, Estrous cycle, Cell Motility, Collective Resistance, Hematopoietic Stem Cell Transplantation, and Molecular Sequence Data
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Hector Galbraith, 1 Jeff Price, 2 Mark Dixon, 3 and Julie Stromberg3 Development of HSI Models to Evaluate Risks to Riparian Wildlife Habitat from Climate Change and Urban Sprawl REFERENCE: Galbraith, H., Price, J., Dixon, M, Stromberg,... more
Hector Galbraith, 1 Jeff Price, 2 Mark Dixon, 3 and Julie Stromberg3 Development of HSI Models to Evaluate Risks to Riparian Wildlife Habitat from Climate Change and Urban Sprawl REFERENCE: Galbraith, H., Price, J., Dixon, M, Stromberg, J., " Development of HSI ...
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... Mt. Graham red squirrel (Tam-iasciurus hudsonicus grahamensis). Spruce ... sities. Deciduous trees included Populus tremu-loides Michx., Quercus gambelii Nutt., Acer gla-brum Torr., and Salix scouleriana Barratt ex Hook. Herbaceous ...
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Research Interests: Hydrology, Ecology, Invasive Species, Biogeography, Populus, and 19 moreFlood, Plant, Riparian, Vegetation, Riparian vegetation, Introduced species, Novel ecosystems, Invasive Plant, Aridity, Ecosystem, Groundwater flow, western United States, Plant species, Global Ecology, Ecological Applications, Perturbation, River Discharge, Stream Flow, and Basal Area
Understanding the role of seed banks can be important for designing restoration projects. Using the seedling emergence method, we investigated the soil seed banks of two montane, deciduous riparian forest ecosystems of southeastern... more
Understanding the role of seed banks can be important for designing restoration projects. Using the seedling emergence method, we investigated the soil seed banks of two montane, deciduous riparian forest ecosystems of southeastern Arizona. We contrasted the seed banks and extant vegetation of Ramsey Canyon, which is the site of riparian restoration activities, with that of Garden Canyon, which has been less affected by human land uses. Fewer plant species were found at Ramsey Canyon than Garden Canyon, for both the seed bank and extant vegetation, and the vegetation at Ramsey Canyon (seed bank and extant) had consistently drier wetland indicator scores. As well, vegetation patterns within sampling zones (channel margins and adjacent riparian forests) differed between canyons. At Garden Canyon channel margins, the seed bank and extant vegetation had relatively high similarity, with herbaceous wetland perennial species dominating. Extant vegetation in the floodplain riparian forest zone at Garden Canyon had a drier wetland indicator score than the seed bank, suggesting that the floodplains are storing seeds dispersed from wetter fluvial surfaces. Vegetation patterns for Ramsey Canyon channel margins were similar to those for Garden Canyon floodplains. Vegetation patterns in the Ramsey Canyon riparian forest zone were indicative of non-flooded conditions with an abundance of upland species in the soil seed bank and extant vegetation. Channel geomorphology measurements indicated that much of the riparian forest zone at Ramsey Canyon is functionally a terrace, a condition that may be a legacy of channel erosion from historic land uses. Steep, erodible channel slopes may contribute to the low seed bank germinant density at Ramsey Canyon channel margins, and narrower flood-prone area may explain the greater terrestrialization of the vegetation in both sampling zones. We recommend testing the use of donor soils from more diverse stream reaches to restore biodiversity levels at Ramsey Canyon, following restoration activities such as channel-widening. Seed banks from Garden Canyon, for example, although predominantly consisting of herbaceous perennials, would supply species with a range of moisture tolerances, life spans, and growth forms. We also recommend that restorationists take care not to harm seed banks exposed during removal of introduced species; at Ramsey Canyon, soil seed banks were equally diverse in areas with high and low cover of the introduced Vinca major (a legacy of Ramsey Canyon land use).