Non-native shrub species in the genus Tamarix (saltcedar, tamarisk) have colonized hundreds of thousands of hectares of floodplains, reservoir margins, and other wetlands in western North America. Many resource managers seek to reduce saltcedar abundance and control its spread to increase the flow of water in streams that might otherwise be lost to evapotranspiration, to restore native riparian (streamside) vegetation, and to improve wildlife habitat. However, increased water yield might not always occur and has been substantially lower than expected in water salvage experiments, the potential for successful revegetation is variable, and not all wildlife taxa clearly prefer native plant habitats over saltcedar. As a result, there is considerable debate surrounding saltcedar control efforts. We review the literature on saltcedar control, water use, wildlife use, and riparian restoration to provide resource managers, researchers, and policy-makers with a balanced summary of the state of the science. To best ensure that the desired outcomes of removal programs are met, scientists and resource managers should use existing information and methodologies to carefully select and prioritize sites for removal, apply the most appropriate and cost-effective control methods, and then rigorously monitor control efficacy, revegetation success, water yield changes, and wildlife use.

http://charlesvanriper.com/gallery/cartimages/pdf/control_of_tamarix.pdf

Control of Tamarix in the Western United States: implications for water salvage, wildlife use, and riparian restoration.

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.

http://charlesvanriper.com/gallery/cartimages/pdf/rethinking_avian_response.pdf

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

We compared the native bees visiting the flowers of three species of invasive plants, saltcedar (Tamarix spp.) and white and yellow sweet clover (Melilotus albus, M. officinalis), with those visiting seven concurrently blooming native plant species in mid-summer at three sites in Capitol Reef National Park, Utah. Overall, as many total species of bees visited the flowers of the three invasive plant species as visited the seven natives. On average, invasive species were visited by twice as many bee species as were natives. With a single exception, visitors of invasives were generalist bees, rather than specialists. Colletes petalostemonis, the only native legume specialist recorded, was an abundant forager on the flowers of both species of Melilotus, demonstrating that at least some specialist bees will move to invasive plants that are closely related to their usual hosts. Species abundant on the flowers of invasives tended to collect both pollen and nectar, suggesting that bees are using pollen o...

Might Flowers of Invasive Plants Increase Native Bee Carrying Capacity? Intimations From Capitol Reef National Park, Utah

This study investigated the impact of invasion by an alien hybrid willow (the white-crack willow, Salix × rubens) on the abundance and diversity of terrestrial arthropods along the lower Tarago River in south-eastern Australia in spring and summer. Canopy arthropods were sampled by branch clippings, flying insects by sticky traps, and arthropod stream inputs by floating pan traps in willow-invaded and uninvaded river sections. Willow-invaded river sections had a significantly lower abundance and diversity of canopy arthropods, but the abundance and diversity of flying insects did not differ between willow-invaded and native sections. Overall input of terrestrial arthropods was lower in willow-invaded sections but this depended on sampling date. In general, differences in arthropod abundance between willow-invaded and native river sections were greater in spring than summer, which may reflect seasonal changes in resource availability in native river sections. Morphospecies composition also differed significantly between willow-invaded and native sections. These changes in abundance, diversity, and composition of terrestrial arthropods following plant invasion of the riparian zone may indirectly alter in-stream food webs and have important effects on higher-order consumers in the riparian zone.

Willow (Salix rubens) invasion of the riparian zone in south-eastern Australia: reduced abundance and altered composition of terrestrial arthropods

The Madrean Archipelago, or Sky Island, region of the southwestern United States and northern Mexico is recognized for its great biological diversity and natural beauty. This conference brought together scientists, managers, and other interested parties to share their knowledge about the region and to identify needs and possible solutions for existing and emerging problems. It provided a forum to update the state-of-knowledge acquired since the first conference in 1994. The proceedings contains over 100 articles and additional abstracts from the plenary sessions and from concurrent sessions covering biogeography, ecosystem monitoring, science-based management, cultural resources/history, invasive species, hydrology and biodiversity, conservation planning, ecology, fire, conservation practice, and global climatic change. Abstracts in Spanish are included. The summary of an open forum at the end of the conference provides additional thoughts about current and future needs for the Madrean Archipelago.

Connecting mountain islands and desert seas: Biodiversity and management of the Madrean Archipelago II

We examined diets of six insectivorous bird species (n = 202 individuals) from two vegetation zones along the Colorado River in Grand Canyon National Park, Arizona, 1994. All bird species consumed similar quantities of caterpillars and beetles, but use of other prey taxa varied. Non-native leafhoppers (Opsius stactagolus) specific to non-native tamarisk (Tamarix chinensis) substantially augmented Lucy's Warbler (Vermivora luciae) diets (49%), while ants comprised 82% of Yellow-breasted Chat (Icteria virens) diets. Yellow Warbler (Dendroica petechia) diets were composed of 45% aquatic midges. All bird species consumed the non-native leafhopper specific to tamarisk. Comparison of bird diets with availability of arthropod prey from aquatic and terrestrial origins showed terrestrial insects comprised 91% of all avian diets compared to 9% of prey from aquatic origin. Seasonal shifts in arthropod prey occurred in diets of three bird species, although no seasonal shifts were detected in arthropods sampl...

http://charlesvanriper.com/gallery/cartimages/pdf/Diets_insectivorous_birds.pdf

Helen K. Yard

Papers

Diets of Insectivorous Birds Along the Colorado River in Grand Canyon, Arizona

Lucy's Warbler (Vermivora luciae)

Lucy's Warbler (Oreothlypis luciae)