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Russian olive habitat along an arid river supports fewer bird species, functional groups and a different species composition relative to mixed vegetation habitats

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Abstract

The establishment and naturalization of non-native Russian olive (Elaeagnus angustifolia) in southwestern US riparian habitats is hypothesized to have negative implications for native flora and fauna. Despite the potential for Russian olive establishment in new riparian habitats, much of its ecology remains unclear. Arid river systems are important stopover sites and breeding grounds for birds, including some endangered species, and understanding how birds use Russian olive habitats has important implications for effective non-native species management. We compared native bird use of sites that varied in the amount of Russian olive and mixed native/non-native vegetation along the San Juan River, UT, USA. From presence/absence surveys conducted in 2016during the breeding season, we found 1) fewer bird species and functional groups used Russian olive habitats and 2) the composition of species within Russian olive habitats was different from the composition of species in mixed native/non-native habitats. Our results suggest Russian olive may support different bird compositions during the breeding season and as Russian olive continues to naturalize, bird communities may change. Finally, we highlight the paucity of research surrounding Russian olive ecology and stress the need for rigorous studies to improve our understanding of Russian olive ecology.

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... The majority of these studies focused on birds and found that within Russian olive stands, cavity nesting birds decreased (Fischer et al. 2012) and generally fewer bird species were found compared to native or mixed nonnative stands (Mahoney et al. 2019). Others have documented numerous birds using the berries as a food source and the branches as preferred nesting sites (Leatherman 2011). ...
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... Of course, our functional designations were simplistic with only four groups, as the functional roles of ground-dwelling arthropods are less-defined than other communities (e.g., riparian arthropods Fig. 8. Dissimilarity analysis (β-diversity) of ground-dwelling arthropod functional groups (rows) partitioned into incidence-based turnover (β jtu ) and nestedness (β jne ) in the first column, and abundance-based turnover (β BC.BAL ) and nestedness (β BC.GRA ) of elevational site pairs (i.e., each site and its immediately adjacent uphill site) in the second column. (Kennedy et al. 2016), fish (Villéger et al. 2013), or birds (Mahoney et al. 2019)). Further partitioning arthropods into more defined functional groups may yield new insights into their elevational patterns. ...
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Woodlands of the exotic saltcedar (Tamarix chinensis) have replaced forests of native Fremont cottonwood (Populus fremontii) and willow (Salixspp.) along many rivers of the American South-west. In the middle basin of the San Pedro River, saltcedar dominates only at the drier sites where the surface and ground-water conditions no longer support cottonwood–willow forests. At sites with perennial (or near-perennial) stream flow, saltcedar is co-dominant with Fremont cottonwood. However, saltcedar has been declining in importance at these sites, perhaps due to recent occurrence of conditions that favour cottonwood establishment (frequent winter flooding, high rates of stream flow during spring, exclusion of livestock). This shift provides evidence of capacity for self-repair in degraded Sonoran riparian ecosystems. In the upper basin, in contrast, saltcedar has increased in relative abundance at sites that show evidence of ground-water decline, signaling a need for vigilance in river management. Saltcedar is generally sparse in the upper basin, probably due to the combination of cool temperatures and persistence of perennial or near-perennial stream flows in most areas. Throughout the San Pedro River, saltcedar and cottonwood both have been influenced by changing flood patterns. Expansion of Fremont cottonwood populations and initial colonization by saltcedar both correlate with post-1960 increases in fall and winter flood frequency and decreases in summer flood size.
Article
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Understanding patterns of plant population mortality during extreme weather events is important to conservation planners because the frequency of such events is expected to increase, creating the need to integrate climatic uncertainty into management. Dominant plants provide habitat and ecosystem structure, so changes in their distribution can be expected to have cascading effects on entire communities. Observing areas that respond quickly to climate fluctuations provides foresight into future ecological changes and will help prioritize conservation efforts. We investigated patterns of mortality in six dominant plant species during a drought in the southwestern United States. We quantified population mortality for each species across its regional distribution and tested hypotheses to identify ecological stress gradients for each species. Our results revealed three major patterns: (1) dominant species from diverse habitat types (i.e., riparian, chaparral, and low- to high-elevation forests) exhibited significant mortality, indicating that the effects of drought were widespread; (2) average mortality differed among dominant species (one-seed juniper[Juniperus monosperma (Engelm.) Sarg.] 3.3%; manzanita[Arctostaphylos pungens Kunth], 14.6%; quaking aspen[Populus tremuloides Michx.], 15.4%; ponderosa pine[Pinus ponderosa P. & C. Lawson], 15.9%; Fremont cottonwood[Populus fremontii S. Wats.], 20.7%; and pinyon pine[Pinus edulis Engelm.], 41.4%); (3) all dominant species showed localized patterns of very high mortality (24–100%) consistent with water stress gradients. Land managers should plan for climatic uncertainty by promoting tree recruitment in rare habitat types, alleviating unnatural levels of competition on dominant plants, and conserving sites across water stress gradients. High-stress sites, such as those we examined, have conservation value as barometers of change and because they may harbor genotypes that are adapted to climatic extremes. Resumen: El entendimiento de los patrones de mortalidad de poblaciones de plantas durante eventos climáticos extremos es importante para los planificadores de conservación porque se espera que la frecuencia de tales eventos aumente, creando la necesidad de integrar la incertidumbre climática a la gestión. Las plantas dominantes proporcionan hábitat y estructura al ecosistema, así que se puede esperar que cambios en su distribución tengan efectos de cascada en toda la comunidad. La observación de áreas que responden rápidamente a las fluctuaciones climáticas proporciona un panorama de futuros cambios ecológicos y ayudará a la definición de prioridades de esfuerzos de conservación. Investigamos los patrones de mortalidad en seis especies de plantas dominantes durante una sequía en el suroeste de Estados Unidos. Cuantificamos la mortalidad poblacional para cada especie en su área de distribución regional y probamos hipótesis para identificar los gradientes de estrés ecológico para cada especie. Nuestros resultados revelaron tres patrones mayores: (1) las especies dominantes en diversos tipos de hábitats (i.e., ribereño, chaparral y bosques de baja a alta elevación) presentaron mortalidad significativa, lo que indica que los efectos de la sequía fueron extendidos; (2) la mortalidad promedio fue diferente (Juniperus monosperma [Engelm.] Sarg.) 3.3%; Arctostaphylos pungens Kunth, 14.6%; Populus tremuloides Michx., 15.4%; Pinus ponderosa P. & C. Lawson, 15.9%; Populus fremontii S. Wats., 20.7%; y Pinus edulis Engelm., 41.4%); (3) todas las especies dominantes mostraron patrones localizados de mortalidad muy alta (24–100%) consistentes con gradientes de estrés hídrico. Los gestores de tierras deberían planificar para la incertidumbre climática mediante la promoción del reclutamiento de árboles en tipos de hábitat raros, lo que aligeraría los niveles no naturales de competencia sobre las plantas dominantes y conservaría sitios a lo largo de gradientes de estrés hídrico. Los sitios con estrés alto, como los que examinamos, tienen valor de conservación como barómetros de cambio y porque pueden albergar genotipos que están adaptados a cambios climáticos extremos.
Article
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1 The invasion of habitats by non-native plant and animal species is a global phenomenon with potentially grave consequences for ecological, economic, and social systems. Unfortunately, to date, the study of invasions has been primarily anecdotal and resistant to generalization. 2 Here, we use insights from experiments and from long-term monitoring studies of vegetation to propose a new theory in which fluctuation in resource availability is identified as the key factor controlling invasibility, the susceptibility of an environment to invasion by non-resident species. The theory is mechanistic and quantitative in nature leading to a variety of testable predictions. 3 We conclude that the elusive nature of the invasion process arises from the fact that it depends upon conditions of resource enrichment or release that have a variety of causes but which occur only intermittently and, to result in invasion, must coincide with availability of invading propagules.
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Ecology Letters (2011) 14: 702–708 Biological invasions cause ecological and economic impacts across the globe. However, it is unclear whether there are strong patterns in terms of their major effects, how the vulnerability of different ecosystems varies and which ecosystem services are at greatest risk. We present a global meta-analysis of 199 articles reporting 1041 field studies that in total describe the impacts of 135 alien plant taxa on resident species, communities and ecosystems. Across studies, alien plants had a significant effect in 11 of 24 different types of impact assessed. The magnitude and direction of the impact varied both within and between different types of impact. On average, abundance and diversity of the resident species decreased in invaded sites, whereas primary production and several ecosystem processes were enhanced. While alien N-fixing species had greater impacts on N-cycling variables, they did not consistently affect other impact types. The magnitude of the impacts was not significantly different between island and mainland ecosystems. Overall, alien species impacts are heterogeneous and not unidirectional even within particular impact types. Our analysis also reveals that by the time changes in nutrient cycling are detected, major impacts on plant species and communities are likely to have already occurred.
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How anthropogenic climate change will affect hydroclimate in the arid regions of southwestern North America has implications for the allocation of water resources and the course of regional development. Here we show that there is a broad consensus among climate models that this region will dry in the 21st century and that the transition to a more arid climate should already be under way. If these models are correct, the levels of aridity of the recent multiyear drought or the Dust Bowl and the 1950s droughts will become the new climatology of the American Southwest within a time frame of years to decades.
Article
Since its introduction before 1900, Elaeagnus angustifolia has become naturalized in many areas throughout the Rocky Mountains states. Avian and mammalian communities were inventoried at areas of monotypic stands in Colorado, Idaho and Utah. Russian-olive stands tended to support avian communities intermediate in species richness and alpha diversity to native riparian and upslope communities. Beta diversity comparisons indicated stronger relationships between Russian-olive and riparian communities than upslope communities. Small mammal communities contained low species richness, but followed the pattern of intermediate diversity between the native sites. Russian-olive is intermediate in height to the native communities, and frequently establishes along the interface of the two. The species appears to be competitively inferior to native overstory species. The continued expansion of Russian-olive will increase the width of lowland riparian zones at some locations, providing additional habitats for especially those avian species that are associated with tall-shrub vegetation.-from Authors
Article
Russian-olive is a small tree or large multistemmed shrub that was introduced to Canada and the United States from Eurasia in the early 1900s. It was provisioned in large numbers during the last century to prairie farmers as a shelterbelt plant and remains a popular and widely available ornamental. Now invasive within some riparian ecosystems in the western United States, Russian-olive has been declared noxious in the states of Colorado and New Mexico. With traits including high shade tolerance and a symbiotic association with nitrogen-fixing bacteria, Russian-olive has the potential to dominate riparian vegetation and thus radically transform riparian ecosystems. Especially alarming is its capacity to influence nutrient dynamics within aquatic food webs. Our objective is to draw attention to Russian-olive as a potential threat to riparian ecosystems within Canada, especially in the southwest, where invasion is becoming commonplace. We review what is known about its biology and about the threats it poses to native organisms and ecosystems, and we summarize management and control efforts that are currently underway. We conclude by proposing a research agenda aimed at clarifying whether and how Russian-olive poses a threat to riparian ecosystems within western Canada. Nomenclature: Russian-olive; Elaeagnus angustifolia L. ELGAN.
Article
We examined abundance and richness of wood warblers among vegetation types at the Bosque del Apache National Wildlife Refuge and the Rio Grande Nature Center in the Middle Rio Grande Valley of New Mexico. Rarefaction analysis indicated that there were marginally significant differences in species richness between sites. In spring, wood-warbler richness was greater at the Bosque del Apache than at the Nature Center. This pattern reflected the greater likelihood of catching uncommon migrants at the Bosque del Apache than at the Nature Center. The same seven species were most common at both sites although their order of abundance differed between sites. Capture rates of these species were greater at the Nature Center than at the Bosque del Apache in the fall, but not during the spring. In general, variation in capture rates among vegetation types was greater in the Bosque del Apache than in the Nature Center. In particular the capture rates in willow were greater than in other vegetative types.
Article
Avian use of saltcedar (Tamarix chinensis) along the middle Pecos River was compared with similarly collected data along the lower Colorado River and Rio Grande. Use of saltcedar ranked high among all bird groups in all seasons on the middle Pecos River. In contrast, many species do not occur in saltcedar on the lower Colorado River, while few species winter in saltcedar on the lower Rio Grande. Occurrence of granivores and insectivores during winter in saltcedar on the Pecos River may be explained by seed-producing shrubs and annuals within or adjacent to these habitats. Most breeding birds on the Pecos River are summer visitors. These breeding species, though present, do not occur in saltcedar on the Colorado River despite abundant food resources and occur in intermediate abundances on the Rio Grande. Densities of several summer-visiting insectivores have declined markedly on the Colorado River since the proliferation of saltcedar, whereas they have remained relatively stable in other river valleys to the east. Biogeographical considerations, specifically elevational (climatic) gradients, are suggested reasons for this phenomenon.
Article
Vegetation structure and the numbers of shrubs were measured at nest sites of 11 species of riparian birds in a tamarisk (Tamarix ramosissima) community to characterize breeding habitat by species. Discriminant function analysis indicated that riparian birds exhibited significant differences in their use of nesting habitat. Bell's vireo (Vireo bellii), yellow warbler (Dendroica petechia), and yellow-breasted chat (Icteria virens) were relative generalists in their use of nesting habitat, while common yellowthroat (Geothlypis trichas) and Bullock's oriole (Icterus galbula bullockii) were relative specialists. Bell's vireo and American coot (Fulica americana) used the most dissimilar habitats. Willow flycatcher (Empidonax traillii) and yellow warbler used the most similar habitats. Willow flycatcher and yellow warbler consistently used habitat most similar to that used by other species. The tamarisk community created by the operation of Glen Canyon Dam represents the ecological equivalent of native habitat for some riparian birds, and its presence has enhanced breeding habitat for these 11 species of birds.
Article
Investigated the possible importance of indivdual tree species in avian habitat selection by comparing tree species contributions to contributions of horizontal and vertical patchiness and density of vegetation. Individual bird species responded with greater frequency to number of particular species of trees than to any variables depicting structure. Many of the commonly found correlations of bird community relationships to vegetation profiles may be the result of combining analyses of many different bird species with many different tree of plant species associations. Studies of avian habitat use include measures of tree species composition of the sites even if foliage profile or denisty measures alone provide statistically significant results.-from Authors
Article
Exotic species can provide abundant food resources for native consumers, but predicting which native species will respond positively remains a challenge. We studied the foraging behavior of black-capped (Poecile atricapillus) and mountain (P. gambeli) chickadees in western Montana to compare the degree to which these congeric and syntopic consumers exploited larvae of Urophora, an exotic biological control insect living within the seedheads of the invasive forb, spotted knapweed (Centaurea stoebe). Chickadees typically forage within tree or shrub cover, whereas knapweed and hence Urophora larvae thrive in open grassland away from cover. We found that black-capped chickadees were much more likely than mountain chickadees to forage for Urophora. Black-capped chickadees strategically minimized time spent in open habitats by flying out from cover to retrieve knapweed seedheads and immediately returning to cover to extract the larvae. Black-capped chickadees also employed an atypical hovering technique nearly twice as often as their congeners did, particularly when foraging away from cover. Via this hovering technique, birds were able to gather knapweed seedheads from erect plants rather than searching for seedheads on the ground. These shifts in foraging behavior allowed black-capped chickadees to exploit Urophora larvae to a much greater degree than their congeners while minimizing exposure to a high-risk habitat, an outcome with potentially important community-wide consequences. Behavioral flexibility has been used to predict the success of invading species. We suggest that behavioral flexibility may also be used to predict how native species will respond to invasions, particularly the availability of exotic food resources.
Article
Mechanical clearing and herbicide-burn treatments were compared to evaluate salteedar (Tamarix chinensis Lour.) control and recovery along the Rio Grande on the Bosque del Apache National Wildlife Refuge, Socorro, N.M. The herbicide-burn treatment included an aerial application of imazapyr (+/-)-2-[4,5dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3- pyridinecarboxylic acid] + glyphosate [N-(phosphonomethyl)glycine] (0.6 + 0.6 kg ai hat rate) followed 3 years later by a prescription broadcast fire that eliminated > 99% of the standing dead stems. Six years after initial herbicide application, saitcedar mortality was 93%. Mechanical saltcedar clearing entailed removing aerial (trunks and stems) growth by blading, stacking and burning debris, followed by removal of underground plant portions (root crowns) by plowing, raking, and burning stacked material. Saitcedar mortality 3 years after mechanical clearing averaged 70%, which was deemed unsatisfactory. Thus, root plowing, raking, and pile burning was repeated. Three years later, after the second mechanical clearing, saitcedar mortality was 97%. Costs for the herbicide-burn treatment averaged $283 ha(-1), whereas mechanical control costs were $884 ha(-1) for the first surface and root clearing and an additional $585 ha(-1) for the second root clearing. Riparian managers should consider environmental conditions and restoration strategies prior to selecting a saltcedar control approach. Although control costs were significantly lower for the herbicide-burn treatment compared to mechanical clearing in this study, the choice of methods should always consider alternative control strategies for saitcedar. Frequently, combinations of methods result in more efficient, cost-effective results.
Article
Invasion by trees into grasslands is commonly associated with negative consequences to many species of breeding birds. We investigated relationships between abundance of Russian olive (Elaeagnus angustifolia), nesting black-billed magpies (Pica pica), and duck nest success on management areas in southeastern Idaho. Duck nest success tended to vary inversely with abundance of Russian olive at the regional scale, averaging 42.9% on management areas where Russian olive abundance was low, 19.8% where it was moderate, and 6.8% where it was high. Intensive studies during 1992-1993 and 1995-1996 at Sterling Wildlife Management Area (SWMA), an area with especially high abundance of Russian olive and density of nesting magpies, produced mixed evidence on the relationships between Russian olive, magpies, and duck nest success. Survival of artificial duck nests at SWMA increased slightly with increasing distance from Russian olive, but median distance to nearest active magpie nest and to nearest Russian olive did not differ between successful and depredated duck nests. However, median distance between duck nests and nearest active magpie nest was <200 m, and we found only one duck nest that was >400 m from an active magpie nest. Hence, few duck nests at SWMA may have been far enough from magpie nests to provide detectable increase in nest security. We predicted that density of nesting magpies would decrease and success of duck nests would increase after managers removed Russian olive from a 347-ha treatment area midway through our study. Magpies shifted nesting substrate, primarily to tall big sagebrush (Artemisia tridentata) plants following treatment, but neither magpie nest density nor duck nest success changed as predicted. We urge managers to carefully consider the risks of accepting (or introducing) trees in historically treeless areas.
Article
The history of naturalization of Russian olive, Elaeagnus angustifolia L., in Utah is presented. During the first half of this century Russian olive became a common species in cultivation in Utah cities. By 1924 the tree was becoming established in nature in central Utah. Naturalization has been most evident during the last two decades. At present Russian olive is a conspicuous part of the vegetation in the valleys of central and northern Utah. The histories of naturalization of the plant in other western states are similar to that in Utah.
Article
Aim To test the hypothesis that anthropogenic alteration of stream-flow regimes is a key driver of compositional shifts from native to introduced riparian plant species. Location The arid south-western United States; 24 river reaches in the Gila and Lower Colorado drainage basins of Arizona. Methods We compared the abundance of three dominant woody riparian taxa (native Populus fremontii and Salix gooddingii, and introduced Tamarix) between river reaches that varied in stream-flow permanence (perennial vs. intermittent), presence or absence of an upstream flow-regulating dam, and presence or absence of municipal effluent as a stream water source. Results Populus and Salix were the dominant pioneer trees along the reaches with perennial flow and a natural flood regime. In contrast, Tamarix had high abundance (patch area and basal area) along reaches with intermittent stream flows (caused by natural and cultural factors), as well as those with dam-regulated flows. Main conclusions Stream-flow regimes are strong determinants of riparian vegetation structure, and hydrological alterations can drive dominance shifts to introduced species that have an adaptive suite of traits. Deep alluvial groundwater on intermittent rivers favours the deep-rooted, stress-adapted Tamarix over the shallower-rooted and more competitive Populus and Salix. On flow-regulated rivers, shifts in flood timing favour the reproductively opportunistic Tamarix over Populus and Salix, both of which have narrow germination windows. The prevailing hydrological conditions thus favour a new dominant pioneer species in the riparian corridors of the American Southwest. These results reaffirm the importance of reinstating stream-flow regimes (inclusive of groundwater flows) for re-establishing the native pioneer trees as the dominant forest type.
Article
Within the Mojave, Sonoran, and Chihuahuan Desert subdivisions of the North American Desert in the U.S., more than half of 143 total amphibian and rep- tilian species perform as riparian and/or wetland taxa. For the reptiles, but not the amphibians, there is a sig- nificant inverse relationship between riparianness (obli- gate through preferential and facultative to nonriparian) and desertness. In addition to the nondesert species (N=36) present, there are two evolutionary kinds of desert species in the herpetofauna: true desert species (N-20), and desert-included species (N=87); the former are obligate specialists, the latter are facultative gener- alists. Quantitative aspects of desertness, riparianness, species richness, nondesert taxa and others are exam- ined. A large part of the herpetofauna of North America is located extensively and abundantly in riparian habitats. No other terrestrial vertebrate group is a better indicator of the biological health of riparian ecosystems. Within the "warm deserts" of the Southwest United States more than half of the total amphibian and reptilian species perform as riparian and/or wetland taxa. Riparian taxa are obligate, preferential, or facultative components of riparian ecosystems. Thus including the nonriparian condition, four levels of riparianness (R), or riparian dependency, are recognized (Dick-Peddie and Hubbard 1977, Johnson, and others 1987). Moreover, for deserts, in addition to the distinction between desert species and nondesert species, there is a clear distinction between two evolutionary kinds of desert species: true desert species and desert-included species. True desert species are obligate specialists in the real sense that they have evolved within desert environments, while the desert- included species tend to be facultative generalists that include desert environments in their much wider and often widely extensive ecological and geographical distributions. Thus including the nondesert condition, three levels of desertness (D) are recognized (Lowe 1968; and others, 1986):
Article
Riparian vegetation provides important habitat for migrating and breeding birds in the arid south-western United States. Surveys conducted in native cottonwood (Populus fremontii var. wislizeni) and introduced saltcedar (Tamarix chinensis) vegetation during spring, summer and fall were used to compare avian use of these two vegetation types along the Middle Rio Grande Valley in central New Mexico. Bird species richness in cottonwood and saltcedar did not differ during any season, but species composition varied. Overlap in species between the two habitats was lowest in spring and increased in fall, with more species unique to cottonwood than to saltcedar in all seasons. A number of obligate riparian species readily used saltcedar, while others were restricted to areas dominated by native vegetation. Neotropical migrants showed a slight preference for cottonwood in the spring, but some migrant species were detected in saltcedar as well, possibly reflecting the dense nature of this vegetation. However, although saltcedar was used by a number of species, maintenance of native vegetation will be necessary for the persistence of many bird species in the Middle Rio Grande Valley.
Article
Initially introduced to western United States to provide ecosystem services such as erosion control, Tamarix by the mid-1900s had became vilified as a profligate waster of water. This large shrub continues, today, to be indicted for various presumed environmental and economic costs, and millions of dollars are expended on its eradication. In this review, we examine the role of scientists in driving changes in perceptions of Tamarix from valuable import to vilified invader and (in some instances) back to a productive member of riparian plant communities. Scientists over the years have sustained a negative perception of Tamarix by, among other things, (1) citing outmoded sources; (2) inferring causation from correlative studies; (3) applying conclusions beyond the scope (domain) of the studies; and (4) emphasizing findings that present the species as an extreme or unnatural agent of change. Recent research is challenging the prevailing dogma regarding Tamarix’s role in ecosystem function and habitat degradation and many scientists now recommend management shifts from “pest plant” eradication to systemic, process-based restoration. However, prejudice against this and other non-native species persists. To further close the gap between science and management, it is important for scientists to strive to (1) cite sources appropriately; (2) avoid reflexive antiexotic bias; (3) avoid war-based and pestilence-based terminology; (4) heed the levels of certainty and the environmental domain of studies; (5) maintain up-to-date information on educational Web sites; and (6) prior to undertaking restoration or management actions, conduct a thorough and critical review of the literature.
Article
Russian-olive (Elaeagnus angustifolia) is a small Eurasian tree that has escaped from cultivation and become naturalized, primarily along watercourses throughout the western United States. We examined germination and establishment of Russian-olive and plains cottonwood (Populus deltoides), the principal native riparian tree of the Great Plains, under a range of experimental moisture and light conditions. The fewest seedings established under the driest conditions; seedling biomass was predictably lower in the shade; root-to-shoot ratios were higher for cottonwood, higher in the sun, and higher under drier conditions. Several interactions were also significant. The timing of germination and mortality varied between plains cottonwood and Russian-olive: cottonwood germinated in mid-June in all treatments in a single pulse with subsequent mortality; the timing and amount of Russian-olive germination differed substantially across treatments with little net mortality. Differences in life-history traits of these species, including seed size, viability, and dispersal, help explain treatment differences. Russian-olive will likely remain an important component of riparian communities along both unregulated and regulated western rivers because it succeeds under conditions optimal for cottonwood establishment and under many conditions unfavorable for cottonwood. Furthermore, many western states still encourage planting of Russian-olive, and control techniques tend to be labor-intensive and expensive.
Article
Based on a hydrogeological survey and geochemical and isotopic technology, a case study of the Shiyang River Basin is presented to illustrate ground-water resources and geochemistry and their changes caused by the impact of human activity in the arid area of Northwest China. The aquifer is mainly recharged by surface water originating in mountain regions, and there is extensive transfer between rainfall, surface water and ground-water. The deep ground-water is old, approximately 40 ka, and was recharged in a colder and wetter climate environment. The shallower water is mainly palaeowater mixed with limited modern recharge. The sources of salinity are from weathering of rock in mountain areas and from higher evaporation leading to higher salinity along the line of ground-water flow. Human activity, in particular large-scale water resources development associated with dramatic population growth in the last 50 years, has led to tremendous changes in the ground-water regime. Recharge has been reduced by 50% and ground-water abstraction exceeds recharge by 0.41×109 m3 yr−1. Consequently, the ground-water level has fallen widely by between 3 and 5 m, with a maximum fall of 35 m in several towns. These hydrological changes have resulted in a serious degradation of the ecosystem. It is suggested that modernized irrigation technology and new regulation to cover water resources management and allocation within the river basin are urgently needed to achieve sustainable development.
Article
Saltcedar invasion has many economic and environmental effects, including displacement of native riparian vegetation and associated wildlife. A biological control program led to the approval in 1994 of two insects for introduction but was delayed by the presence of the endangered southwestern willow flycatcher (SWWF) in saltcedar. In 2001, the saltcedar leaf beetle was released in six states but not where the SWWF was present. Delays circumvent the benefits that saltcedar suppression could have for other declining species, including many rare or absent in ecosystems dominated by saltcedar. Numerous birds forage within saltcedar vegetation but in lower numbers and diversity than in native stands that provide better habitat and insect resources. Successful establishment by saltcedar leaf beetle resulted in extensive saltcedar defoliation, and observations of wildlife feeding on the beetles in an otherwise depauperate system suggest that biocontrol may enhance habitat quality for many species, including the SWWF. Consideration of the multiple species affected by saltcedar would have allowed more effective invasive plant management in this case, but delays also reflect drawbacks in federal administrative structures related to invasive species management in 'natural areas' as much as problems with a narrow focus on a single species. A functionally integrated approach where research and management decisions are made cooperatively would allow more rational management of invasive species in wildland ecosystems.
Article
Typescript (photocopy). Thesis (M.S.)--Colorado State University, 1990. Includes bibliographical references (leaves [43]-46).
Article
Understanding patterns of plant population mortality during extreme weather events is important to conservation planners because the frequency of such events is expected to increase, creating the need to integrate climatic uncertainty into management. Dominant plants provide habitat and ecosystem structure, so changes in their distribution can be expected to have cascading effects on entire communities. Observing areas that respond quickly to climate fluctuations provides foresight into future ecological changes and will help prioritize conservation efforts. We investigated patterns of mortality in six dominant plant species during a drought in the southwestern United States. We quantified population mortality for each species across its regional distribution and tested hypotheses to identify ecological stress gradients for each species. Our results revealed three major patterns: (1) dominant species from diverse habitat types (i.e., riparian, chaparral, and low- to high-elevation forests) exhibited significant mortality, indicating that the effects of drought were widespread; (2) average mortality differed among dominant species (one-seed juniper[Juniperus monosperma (Engelm.) Sarg.] 3.3%; manzanita[Arctostaphylos pungens Kunth], 14.6%; quaking aspen[Populus tremuloides Michx.], 15.4%; ponderosa pine[Pinus ponderosa P. & C. Lawson], 15.9%; Fremont cottonwood[Populus fremontii S. Wats.], 20.7%; and pinyon pine[Pinus edulis Engelm.], 41.4%); (3) all dominant species showed localized patterns of very high mortality (24-100%) consistent with water stress gradients. Land managers should plan for climatic uncertainty by promoting tree recruitment in rare habitat types, alleviating unnatural levels of competition on dominant plants, and conserving sites across water stress gradients. High-stress sites, such as those we examined, have conservation value as barometers of change and because they may harbor genotypes that are adapted to climatic extremes.
A Vegetation Management Study for the Enhancement of Wildlife along the Lower Colorado River
  • B W Anderson
  • R D Ohmart
Anderson, B.W., Ohmart, R.D., 1984. A Vegetation Management Study for the Enhancement of Wildlife along the Lower Colorado River.
Saltcedar and Russian olive interactions with wildlife. Saltcedar and Russian olive control demonstration act science assessment
  • H L Bateman
  • E H Paxton
Bateman, H.L., Paxton, E.H., 2009. Saltcedar and Russian olive interactions with wildlife. Saltcedar and Russian olive control demonstration act science assessment. In: Shafroth, P.B., Brown, C.A., Merritt, D.M. (Eds.), United States Geological Survey, Scientific Investigations Report. vol 5247. pp. 1-143.
Russian-olive for wildlife and other conservation uses
  • A E Borell
Borell, A.E., 1976. Russian-olive for wildlife and other conservation uses. U S Dep. Agric. Leafl. 517, 8pp.
Riparian Woodlands of the Middle Rio Grande Valley, New Mexico: a Study of Bird Populations and Vegetation with Special Reference to Russian-olive (Elaeagnus Angustifolia)
  • M D Freehling
Freehling, M.D., 1982. Riparian Woodlands of the Middle Rio Grande Valley, New Mexico: a Study of Bird Populations and Vegetation with Special Reference to Russian-olive (Elaeagnus Angustifolia). U.S. Fish and Wildlife Serve, Albuquerque, NM, USA.
The Importance of Riparian Habitat to Migrating Birds. Importance, Preservation and Management of Riparian Habitat: A Symposium
  • L E Stevens
  • B T Brown
  • J M Simpson
  • R R Johnson
Stevens, L.E., Brown, B.T., Simpson, J.M., Johnson, R.R., 1977. The Importance of Riparian Habitat to Migrating Birds. Importance, Preservation and Management of Riparian Habitat: A Symposium, July 9, 1977. General Technical Report RM-43, Tucson, AZ, pp. 156-164 (USDA Forest Service).
  • D J Wuebbles
  • D W Fahey
  • K A Hibbard
  • D J Dokken
  • B C Stewart
USGCRP (U.S. Global Change Research Program), 2017. In: Wuebbles, D.J., Fahey, D.W., Hibbard, K.A., Dokken, D.J., Stewart, B.C., Maycock, T.K. (Eds.), Climate Science Special Report: Fourth National Climate Assessment, Volume I. Washington, DC, USA, https://doi.org/10.7930/J0J964J6.
Factors controlling the establishment of Fremont cottonwood seedlings on the upper Green River, USA
  • Cooper
Relationships between Russian olive and duck nest success in southeastern Idaho
  • Gazada