Effects of Tamarix removal on the community dynamics of riparian birds in a semiarid grassland

Invasion of riparian habitats by non‐native plants is a global problem that requires an understanding of community‐level responses by native plants and animals. In the Great Plains, resource managers have initiated efforts to control the eastward incursion of Tamarix as a non‐native bottomland plant (Tamarix ramosissima) along the Cimarron River in southwestern Kansas, United States. To understand how native avifauna interact with non‐native plants, we studied the effects of Tamarix removal on riparian bird communities. We compared avian site occupancy of three foraging guilds, abundance of four nesting guilds, and assessed community dynamics with dynamic, multiseason occupancy models across three replicated treatments. Community parameters were estimated for Tamarix‐dominated sites (untreated), Tamarix‐removal sites (treated), and reference sites with native cottonwood sites (Populus deltoides). Estimates of initial occupancy (ψ₂₀₀₆) for the ground‐to‐shrub foraging guild tended to be highest at Tamarix‐dominated sites, while initial occupancy of the upper‐canopy foraging and mid‐canopy foraging guilds were highest in the treated and reference sites, respectively. Estimates of relative abundance for four nesting guilds indicated that the reference habitat supported the highest relative abundance of birds overall, although the untreated habitat had higher abundance of shrub‐nesters than treated or reference habitats. Riparian sites where invasive Tamarix is dominant in the Great Plains can provide nesting habitat for some native bird species, with avian abundance and diversity that are comparable to remnant riparian sites with native vegetation. Moreover, presence of some native vegetation in Tamarix‐dominated and Tamarix‐removal sites may increase abundance of riparian birds such as cavity‐nesters. Overall, our study demonstrates that Tamarix may substitute for native flora in providing nesting habitat for riparian birds at the eastern edge of its North American range.     

Planning Riparian Restoration in the Context of Tamarix Control in Western North America

Throughout the world, the condition of many riparian ecosystems has declined due to numerous factors, including encroachment of non‐native species. In the western United States, millions of dollars are spent annually to control invasions of Tamarix spp., introduced small trees or shrubs from Eurasia that have colonized bottomland ecosystems along many rivers. Resource managers seek to control Tamarix in attempts to meet various objectives, such as increasing water yield and improving wildlife habitat. Often, riparian restoration is an implicit goal, but there has been little emphasis on a process or principles to effectively plan restoration activities, and many Tamarix removal projects are unsuccessful at restoring native vegetation. We propose and summarize the key steps in a planning process aimed at developing effective restoration projects in Tamarix‐dominated areas. We discuss in greater detail the biotic and abiotic factors central to the evaluation of potential restoration sites and summarize information about plant communities likely to replace Tamarix under various conditions. Although many projects begin with implementation, which includes the actual removal of Tamarix, we stress the importance of pre‐project planning that includes: (1) clearly identifying project goals; (2) developing realistic project objectives based on a detailed evaluation of site conditions; (3) prioritizing and selecting Tamarix control sites with the best chance of ecological recovery; and (4) developing a detailed tactical plan before Tamarix is removed. After removal, monitoring and maintenance as part of an adaptive management approach are crucial for evaluating project success and determining the most effective methods for restoring these challenging sites.     

Success of Active Revegetation after Tamarix Removal in Riparian Ecosystems of the Southwestern United States: A Quantitative Assessment of Past Restoration Projects

Invasion by the non‐native tree Tamarix has led to implementation of restoration projects aimed at maintaining the ecological integrity of many riparian communities in the southwestern United States. These restoration efforts may include Tamarix removal, manipulation of hydrologic regimes, and active revegetation of native species. The goal of this study was to determine which site characteristics are correlated with restoration success, defined in terms of reductions of undesirable species such as Tamarix and establishment of desirable, native species. To accomplish this, vegetative and environmental data were collected at 28 sites in the southwestern United States where active revegetation was completed after Tamarix removal. These data were incorporated into regression tree models with predictor variables that included number of years since removal (1–18 years) and multiple management, climate, soils, and hydrological variables to determine success of Tamarix control, revegetation success, and general plant community responses. Our results suggest that there are easily measurable site characteristics that are associated with greater native cover and richness, planting success, and Tamarix control. Close proximity to perennial water, sufficient precipitation, recent flooding, and good drainage as well as coarser soil texture, and lower soil pH all favored native species. Overall, those site characteristics associated with native species success were the same as those related to lower Tamarix cover. These quantitative models are intended to assist researchers and land managers to design more effective riparian restoration efforts in this critical arid lands ecosystem.     

Tamarisk biocontrol,endangered species risk and resolution of conflict through riparian restoration

A long-standing debate between wildlife agencies and biological control researchers and practitioners concerns Diorhabda carinulata Desbrochers (Coleoptera: Chrysomelidae) introduced to suppress invasive Tamarix spp. (Tamaricaceae), and potential impacts of Tamarix defoliation on endangered southwestern willow flycatchers using this non-native plant as nesting habitat in some western riparian ecosystems. The conflict and ensuing legal actions are currently centered on the presence of D. carinulata within the breeding range of the flycatcher in the Virgin River watershed, which has led to APHIS termination of permits supporting the biocontrol development program and has also affected other programs to develop biocontrol agents against environmental weeds. Central to concerns over wildlife is the lack of rehabilitation of native vegetation where biocontrol is expected, so there are current and planned efforts to promote restoration of native cottonwood-willow habitat to mitigate the anticipation decline in Tamarix cover. A strategic approach to riparian restoration is outlined which could facilitate sustainable, and scientifically documented recovery of this iconic habitat type. While the results of these efforts will not be known immediately, the process which is leading to riparian restoration has brought specialists from both sides of the debate together in search of resolution via collaboration, and if successful, may allow re-initiation of the Tamarix biocontrol program attendant with habitat enhancement for wildlife species of conservation concern.     

The effects of riparian restoration following saltcedar (Tamarix spp.) biocontrol on habitat and herpetofauna along a desert stream

Amphibians and reptiles (herpetofauna) have been linked to specific microhabitat characteristics, microclimates, and water resources in riparian forests. Our objective was to relate variation in herpetofauna abundance to changes in habitat caused by a beetle used for Tamarix biocontrol (Diorhabda carinulata; Coleoptera: Chrysomelidae) and riparian restoration. During 2013 and 2014, we measured vegetation and monitored herpetofauna via trapping and visual encounter surveys (VES) at locations affected by biocontrol along the Virgin River in the Mojave Desert of the southwestern United States. Twenty‐one sites were divided into four riparian stand types based on density and percent cover of dominant trees (Tamarix, Prosopis, Populus, and Salix) and presence or absence of restoration. Restoration activities consisted of mechanically removing non‐native trees, transplanting native trees, and restoring hydrologic flows. Restored sites had three times more total lizard and eight times more yellow‐backed spiny lizard (Sceloporus uniformis) captures than other stand types. Woodhouse's toad (Anaxyrus woodhousii) captures were greatest in unrestored and restored Tam‐Pop/Sal sites. Results from VES indicated that herpetofauna abundance was greatest in the restored Tam‐Pop/Sal site compared with the adjacent unrestored Tam‐Pop/Sal site. Tam sites were characterized by having high Tamarix cover, percent canopy cover, and shade. Restored Tam‐Pop/Sal sites were most similar in habitat to Tam‐Pop/Sal sites. Two species of herpetofauna (spiny lizard and toad) were found to prefer habitat components characteristic of restored Tam‐Pop/Sal sites. Restored sites likely supported higher abundances of these species because restoration activities reduced canopy cover, increased native tree density, and restored surface water.     

Do riparian plant community characteristics differ between <Emphasis Type="Italic">Tamarix</Emphasis> (L.) invaded and non-invaded sites on the upper Verde River,Arizona?

Invasion by Tamarix (L.) can severely alter riparian areas of the western U.S., which are globally rare ecosystems. The upper Verde River, Arizona, is a relatively free-flowing river and has abundant native riparian vegetation. Tamarix is present on the upper Verde but is a minor component of the vegetation (8% of stems). This study sought to determine whether riparian vegetation characteristics differed between sites where Tamarix was present and sites where Tamarix was absent during the invasion of the upper Verde. We hypothesized that herbaceous understory and woody plant communities would differ between Tamarix present and absent sites. Our hypothesis was generally confirmed, the two types of sites were different. Tamarix present sites had greater abundance of all vegetation, native understory species, graminoids, and native trees, and a positive association with perennial native wetland plant species. Tamarix absent sites had greater abundance of exotic plants and upland adapted plants and an association with greater abiotic cover and litter. These results are contrary to other reports of Tamarix association with depauperate riparian plant communities, and suggest that Tamarix invasion of a watershed with a relatively natural flow regime and a robust native plant community follows similar establishment patterns as the native riparian plant community.     

Restoration Ecology and Invasive Riparian Plants: An Introduction to the Special Section on Tamarix spp. in Western North America

River systems around the world are subject to various perturbations, including the colonization and spread of non‐native species in riparian zones. Riparian resource managers are commonly engaged in efforts to control problematic non‐native species and restore native habitats. In western North America, small Eurasian trees or shrubs in the genus Tamarix occupy hundreds of thousands of hectares of riparian lands, and are the targets of substantial and costly control efforts and associated restoration activities. Still, significant information gaps exist regarding approaches used in control and restoration efforts and their effects on riparian ecosystems. In this special section of papers, eight articles address various aspects of control and restoration associated with Tamarix spp. These include articles focused on planning restoration and revegetation; a synthetic analysis of past restoration efforts; and several specific research endeavors examining plant responses, water use, and various wildlife responses (including birds, butterflies, and lizards). These articles represent important additions to the Tamarix spp. literature and contain many lessons and insights that should be transferable to other analogous situations in river systems globally.     

Tamarix as Habitat for Birds: Implications for Riparian Restoration in the Southwestern United States

Exotic vegetation has become a major habitat component in many ecosystems around the world, sometimes dramatically changing the vegetation community structure and composition. In the southwestern United States, riparian ecosystems are undergoing major changes in part due to the establishment and spread of the exotic Tamarix (saltcedar, tamarisk). There are concerns about the suitability of Tamarix as habitat for birds. Although Tamarix habitats tend to support fewer species and individuals than native habitats, Arizona Breeding Bird Atlas data and Birds of North America accounts show that 49 species use Tamarix as breeding habitat. Importantly, the relative use of Tamarix and its quality as habitat vary substantially by geographic location and bird species. Few studies have examined how breeding in Tamarix actually affects bird survivorship and productivity; recent research on Southwestern Willow Flycatchers has found no negative effects from breeding in Tamarix habitats. Therefore, the ecological benefits and costs of Tamarix control are difficult to predict and are likely to be species specific and site specific. Given the likelihood that high‐quality native riparian vegetation will not develop at all Tamarix control sites, restoration projects that remove Tamarix but do not assure replacement by high‐quality native habitat have the potential to reduce the net riparian habitat value for some local or regional bird populations. Therefore, an assessment of potential negative impacts is important in deciding if exotic control should be conducted. In addition, measurable project objectives, appropriate control and restoration techniques, and robust monitoring are all critical to effective restoration planning and execution.     

Importance of low-flow and high-flow characteristics to restoration of riparian vegetation along rivers in arid south-western United States

1. Riparian vegetation in dry regions is influenced by low‐flow and high‐flow components of the surface and groundwater flow regimes. The duration of no‐flow periods in the surface stream controls vegetation structure along the low‐flow channel, while depth, magnitude and rate of groundwater decline influence phreatophytic vegetation in the floodplain. Flood flows influence vegetation along channels and floodplains by increasing water availability and by creating ecosystem disturbance. 2. On reference rivers in Arizona's Sonoran Desert region, the combination of perennial stream flows, shallow groundwater in the riparian (stream) aquifer, and frequent flooding results in high plant species diversity and landscape heterogeneity and an abundance of pioneer wetland plant species in the floodplain. Vegetation changes on hydrologically altered river reaches are varied, given the great extent of flow regime changes ranging from stream and aquifer dewatering on reaches affected by stream diversion and groundwater pumping to altered timing, frequency, and magnitude of flood flows on reaches downstream of flow‐regulating dams. 3. As stream flows become more intermittent, diversity and cover of herbaceous species along the low‐flow channel decline. As groundwater deepens, diversity of riparian plant species (particularly perennial species) and landscape patches are reduced and species composition in the floodplain shifts from wetland pioneer trees (Populus, Salix) to more drought‐tolerant shrub species including Tamarix (introduced) and Bebbia. 4. On impounded rivers, changes in flood timing can simplify landscape patch structure and shift species composition from mixed forests composed of Populus and Salix, which have narrow regeneration windows, to the more reproductively opportunistic Tamarix. If flows are not diverted, suppression of flooding can result in increased density of riparian vegetation, leading in some cases to very high abundance of Tamarix patches. Coarsening of sediments in river reaches below dams, associated with sediment retention in reservoirs, contributes to reduced cover and richness of herbaceous vegetation by reducing water and nutrient‐holding capacity of soils. 5. These changes have implications for river restoration. They suggest that patch diversity, riparian plant species diversity, and abundance of flood‐dependent wetland tree species such as Populus and Salix can be increased by restoring fluvial dynamics on flood‐suppressed rivers and by increasing water availability in rivers subject to water diversion or withdrawal. On impounded rivers, restoration of plant species diversity also may hinge on restoration of sediment transport. 6. Determining the causes of vegetation change is critical for determining riparian restoration strategies. Of the many riparian restoration efforts underway in south‐western United States, some focus on re‐establishing hydrogeomorphic processes by restoring appropriate flows of surface water, groundwater and sediment, while many others focus on manipulating vegetation structure by planting trees (e.g. Populus) or removing trees (e.g. Tamarix). The latter approaches, in and of themselves, may not yield desired restoration outcomes if the tree species are indicators, rather than prime causes, of underlying changes in the physical environment.     

Reduction of riparian arthropod abundance and diversity as a consequence of giant reed (Arundo donax) invasion

The non-indigenous perennial grass, Arundo donax, is an aggressive invader of riparian areas throughout California and many sub-tropical regions of the world, and is hypothesized to provide poorer quality habitat for native wildlife in riparian systems. We sampled aerial and ground-dwelling insects and other terrestrial arthropods associated with Arundo, native willow vegetation (Salix spp.), and mixtures of the two vegetation types during two seasons to determine how Arundo influences invertebrate composition in a low gradient stream in central California. The total number of organisms, total biomass and taxonomic richness of aerial invertebrates associated with native vegetation was approximately twice that associated with Arundo vegetation, while mixed vegetation supported intermediate arthropod levels. Shannon-Weaver (Weiner) diversity associated with native vegetation stands was also higher than that of Arundo vegetation. Ground-dwelling assemblages did not show differences as great as aerial assemblages which are more critical to foraging avian species. These results indicate that vegetation type is a significant factor reducing the abundance and diversity of invertebrates in this, and presumably in many other riparian ecosystems where this invasive species has become a dominant component. Arundo invasion changes the vegetation structure of riparian zones and in turn, may increasingly jeopardize its habitat value for birds and other wildlife whose diets are largely composed of insects found in native riparian vegetation.     

The influence of floods and precipitation on <Emphasis Type="Italic">Tamarix</Emphasis> establishment in Grand Canyon,Arizona: consequences for flow regime restoration

Decoupling of climate and hydrology combined with introduction of non-native species creates novel abiotic and biotic conditions along highly regulated rivers. Tamarix, a non-native shrub, dominates riparian assemblages along many waterways in the American Southwest, including the Colorado River through Grand Canyon. We conducted a tree-ring study to determine the relative influences of climate and hydrology on Tamarix establishment in Grand Canyon. Riparian vegetation was sparse and annually scoured by large floods until completion of Glen Canyon Dam, which allowed pioneer species, including Tamarix, to expand. Post-dam floods in the mid-1980s were associated with high Tamarix mortality but also initiated a large establishment event. Subsequent establishment has been low but continuous with some exceptions. From 1984 to 2006 establishment increased during years of high, late-summer flows followed by years of low precipitation. This combination provided moist surfaces for Tamarix establishment and may have caused reduced erosion of seedlings or reduced competition from native plants. Attempts to mimic pre-dam floods for ecosystem restoration through planned flood releases also have affected Tamarix establishment. Early (March 1996) and late (November 2004) restoration floods limited establishment, but a small restoration flood in May 2000 followed by steady summer flows permitted widespread establishment. Flood restoration is not expected to prevent Tamarix spread in this system because historic flood timing in May–July coincides with seed release. To decrease future Tamarix establishment, river managers should avoid floods during peak Tamarix seed release, which encompasses the historic spring and early summer flooding period. Tamarix dominance may be reduced by early spring floods that initiate asexual reproduction of clonal shrubs (e.g., Salix exigua, Pluchea sericea).     

Rethinking Avian Response to Tamarix on the Lower Colorado River: A Threshold Hypothesis

Many of the world’s large river systems have been greatly altered in the past century due to river regulation, agriculture, and invasion of introduced Tamarix spp. (saltcedar, tamarisk). These riverine ecosystems are known to provide important habitat for avian communities, but information on responses of birds to differing levels of Tamarix is not known. Past research on birds along the Colorado River has shown that avian abundance in general is greater in native than in non‐native habitat. In this article, we address habitat restoration on the lower Colorado River by comparing abundance and diversity of avian communities at a matrix of different amounts of native and non‐native habitats at National Wildlife Refuges in Arizona. Two major patterns emerged from this study: (1) Not all bird species responded to Tamarix in a similar fashion, and for many bird species, abundance was highest at intermediate Tamarix levels (40–60%), suggesting a response threshold. (2) In Tamarix‐dominated habitats, the greatest increase in bird abundance occurred when small amounts of native vegetation were present as a component of that habitat. In fact, Tamarix was the best vegetation predictor of avian abundance when compared to vegetation density and canopy cover. Our results suggest that to positively benefit avian abundance and diversity, one cost‐effective way to rehabilitate larger monoculture Tamarix stands would be to add relatively low levels of native vegetation (～20–40%) within homogenous Tamarix habitat. In addition, this could be much more cost effective and feasible than attempting to replace all Tamarix with native vegetation.     

Impacts of an invasive willow (Salix × rubens) on riparian bird assemblages in south‐eastern Australia

We explored how a woody plant invader affected riparian bird assemblages. We surveyed 15 200‐m‐long transects in riparian zones in a much‐changed landscape of eastern Victoria, Australia. Abundance, species‐richness, foraging‐guild richness and composition of birds were compared in transects in three habitat types: (i) riparian zones dominated by the invasive willow Salix × rubens; (ii) riparian zones lined with native woody species; and (iii) riparian zones cleared of almost all woody vegetation. We also measured abundance and richness of arthropods and habitat structure to explore further the effects of food resources and habitat on the avifauna. We observed 67 bird species from 14 foraging guilds. Native riparian transects had more birds, bird species and foraging guilds than willow‐invaded or cleared transects. Habitat complexity increased from cleared to willow‐invaded to native riparian transects, as did abundance of native and woodland‐dependent birds. Native shrub and trees species had more foliage and branch‐associated arthropods than did willows, consistent with a greater abundance and variety of foraging guilds of birds dependent on this resource. Willow spread into cleared areas is unlikely to facilitate greatly native bird abundance and diversity even though habitat complexity is increased. Willow invasion into the native riparian zone, by decreasing food resources and altering habitat, is likely to reduce native bird biodiversity and further disrupt connectivity of the riparian zone.     

Wide-Area Estimates of Stand Structure and Water Use of Tamarix spp. on the Lower Colorado River: Implications for Restoration and Water Management Projects

Tamarix spp. removal has been proposed to salvage water and allow native vegetation to recolonize western U.S. riparian corridors. We conducted wide‐area studies on the Lower Colorado River to answer some of the scientific questions about Tamarix water use and the consequences of removal, combining ground surveys with remote sensing methods. Tamarix stands had moderate rates of evapotranspiration (ET), based on remote sensing estimates, averaging 1.1 m/yr, similar to rates determined for other locations on the river and other rivers. Leaf area index values were also moderate, and stands were relatively open, with areas of bare soil interspersed within stands. At three Tamarix sites in the Cibola National Wildlife Refuge, groundwater salinity at the site nearest to the river (200 m) was relatively low (circa 2,250 mg/L) and was within 3 m of the surface. However, 750 and 1,500 m from the river, the groundwater salinity was 5,000–10,000 mg/L due to removal of water by the Tamarix stands. Despite the high groundwater salinity, the sites away from the river did not have saline surface soils. Only 1% of the mean annual river flow is lost to Tamarix ET on the Lower Colorado River in the United States, and the opportunities for water salvage through Tamarix removal are constrained by its modest ET rates. A possible alternative to Tamarix removal is to intersperse native plants among the stands to improve the habitat value of the riparian zone.     

Impact of Non-Native Plant Removal on Lizards in Riparian Habitats in the Southwestern United States

Many natural processes in the riparian cottonwood (Populus deltoides) forest of the Middle Rio Grande (MRG) in the southwestern United States have been disrupted or altered, allowing non‐native plants such as saltcedar (Tamarix spp.) and Russian olive (Elaeagnus angustifolia) to establish. We investigated reptilian responses to restoration efforts by sampling communities of lizards at 12 study sites invaded by non‐native plants along the MRG in New Mexico for 7 years (2000–2006). Sites within three regions were randomly assigned to one of the three treatments to remove non‐native plants and woody debris, or as untreated controls. We used pitfall and funnel traps to capture, mark, and release lizards from June to September. Principal components analysis of 15 vegetation variables identified five factors that best explained variation among sites before and after removal of non‐native plants. Relative abundances for four of six common species of lizards were associated with vegetation characteristics that significantly changed after plant removal. Species were either positively associated with the more open, park‐like understory found in treated sites or negatively associated with debris heaps and thickets of non‐native plants found in untreated sites. Eastern fence lizards (Sceloporus consobrinus) and New Mexico whiptails (Aspidoscelis neomexicana) increased in relative abundance after non‐native plants were removed. Overall, removal of non‐native plants seems beneficial, or at least is non‐damaging, to lizard communities of the MRG forest. Providing information on habitat associations of lizard communities will help land managers balance management objectives with other considerations, such as providing important wildlife habitat.     

Influence of riparian condition on aquatic macroinvertebrate communities in an agricultural catchment in south-eastern Australia

Riparian vegetation is known to affect aquatic macroinvertebrate communities through contributions of organic matter and shading. Despite the widespread degradation of riparian vegetation in Australia, there are relatively few studies examining the effect of changes in riparian vegetation on in-stream macroinvertebrate assemblages on individual catchments. In particular, information is lacking on the responses of macroinvertebrate communities in catchments dominated by agriculture, where farms that are managed at the paddock scale result in riparian vegetation condition varying over relatively short distances. In this study, macroinvertebrate assemblages were assessed from 12 reaches along a 25-km section of a small agricultural stream in south-eastern Australia. Riparian condition was assessed using in-stream coarse woody debris (CWD) levels and the rapid appraisal of riparian condition (RARC) index, a numerical system for categorising the health of riparian areas that incorporates sub-indices reflecting habitat continuity, vegetation cover, plant debris levels, native vegetation dominance, and other indicative features. There was a significant positive correlation between RARC scores and macroinvertebrate taxon richness (p < 0.01), and also between CWD scores and macroinvertebrate taxon richness (p < 0.05). In contrast, there was no significant correlation observed between riparian condition and the other macroinvertebrate indices (abundance, Shannon diversity, SIGNAL and SIGNAL2). Macroinvertebrate communities were significantly different in stream reaches from different riparian condition categories (ANOSIM; p < 0.05). Our results indicate that efforts to rehabilitate riparian vegetation may have a positive effect on in-stream biota even when implemented at a relatively small scale by individual landholders.     

Interactions between Tamarix ramosissima (Saltcedar), Populus fremontii (Cottonwood), and Mycorrhizal Fungi: Effects on Seedling Growth and Plant Species Coexistence

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.     

High‐resolution riparian vegetation mapping to prioritize conservation and restoration in an impaired desert river

In highly impaired watersheds, it is critical to identify both areas with desirable habitat as conservation zones and impaired areas with the highest likelihood of improvement as restoration zones. We present how detailed riparian vegetation mapping can be used to prioritize conservation and restoration sites within a riparian and instream habitat restoration program targeting 3 native fish species on the San Rafael River, a desert river in southeastern Utah, United States. We classified vegetation using a combination of object‐based image analysis (OBIA) on high‐resolution (0.5 m), multispectral, satellite imagery with oblique aerial photography and field‐based data collection. The OBIA approach is objective, repeatable, and applicable to large areas. The overall accuracy of the classification was 80% (Cohen's κ = 0.77). We used this high‐resolution vegetation classification alongside existing data on habitat condition and aquatic species' distributions to identify reaches' conservation value and restoration potential to guide management actions. Specifically, cottonwood (Populus fremontii) and tamarisk (Tamarix ramosissima) density layers helped to establish broad restoration and conservation reach classes. The high‐resolution vegetation mapping precisely identified individual cottonwood trees and tamarisk thickets, which were used to determine specific locations for restoration activities such as beaver dam analogue structures in cottonwood restoration areas, or strategic tamarisk removal in high‐density tamarisk sites. The site prioritization method presented here is effective for planning large‐scale river restoration and is transferable to other desert river systems elsewhere in the world.     

Effects of Stream Restoration on Woody Riparian Vegetation of Southern Appalachian Mountain Streams,North Carolina,U.S.A

Riparian revegetation, such as planting woody seedlings or live stakes, is a nearly ubiquitous component of stream restoration projects in the United States. Though evaluations of restoration success usually focus on in‐stream ecosystems, in order to understand the full impacts of restoration the effects on riparian ecosystems themselves must be considered. We examined the effects of stream restoration revegetation measures on riparian ecosystems of headwater mountain streams in forested watersheds by comparing riparian vegetation structure and composition at reference, restored, and degraded sites on nine streams. According to mixed model analysis of variance (ANOVA), there was a significant effect of site treatment on riparian species richness, basal area, and canopy cover, but no effect on stem density. Vegetation characteristics at restored sites differed from those of reference sites according to all metrics (i.e. basal area, canopy cover, and species composition) except species richness and stem density. Restored and degraded sites were structurally similar, with some overlap in species composition. Restored sites were dominated by Salix sericea and Cornus amomum (species commonly planted for revegetation) and a suite of disturbance‐adapted species also dominant at degraded sites. Differences between reference and restored sites might be due to the young age of restored sites (average 4 years since restoration), to reassembly of degraded site species composition at restored sites, or to the creation of a novel anthropogenic ecosystem on these headwater streams. Additional research is needed to determine if this anthropogenic riparian community type persists as a resilient novel ecosystem and provides valued riparian functions.     

Evaluating the efficacy of seasonal grazing and livestock exclusion as restoration tools for birds in riparian habitat of the Okanagan Valley,British Columbia,Canada

Riparian habitat supports the highest density and diversity of songbirds in Western North America despite covering less than 1% of the land area. Widespread destruction and degradation of riparian habitat, especially by livestock grazing, has led to habitat restoration efforts. In 2000, restoration activities in the form of permanent and seasonal exclusion of livestock from riparian areas were initiated to improve habitat for the endangered Western Yellow‐breasted Chat (Icteria virens auricollis) population, which is dependent on early successional shrub habitat for nesting, in the Okanagan Valley of British Columbia, Canada. We assessed the effectiveness of livestock exclusion by examining temporal changes in the abundance, richness, and breeding performance of birds in restoration and reference sites. The abundance of W. Yellow‐breasted Chats significantly increased between 2002 and 2013 in areas where restoration activities occurred. However, restoration did not have significant effects on the abundance, richness, or breeding performance of other riparian birds at the restoration sites independent of temporal changes that occurred at reference sites. Our results provide evidence that limiting livestock grazing in temperate riparian areas can lead to recovery of endangered riparian songbirds that rely on early successional shrub habitat but may have limited effects on common species that are not strictly reliant on this habitat.