An Integrated Pest Management Plan for the Bill Williams River National Wildlife Refuge. This plan outlines the biological degradation of native riparian forest habitat along the Lower Colorado River and the invasive species management actions needed to protect and restore riparian forests and marshlands of the Bill Williams River.
DeRango, B., 2023. Integrated Pest Management Plan Bill Williams River National Wildlife Refuge.
A look into the use of invasive Tamarix (saltcedar, tamarisk) as habitat for birds in the southwestern United States and its implications for Tamarix control. While Tamarix habitat supports fewer birds than native habitat, data from Arizona Breeding Bird Atlas and Birds of North America demonstrate that 49 bird species use Tamarix as breeding habitat. The use and quality of Tamarix as bird habitat varies depending on geographic location and species and few studies have quantified the effects of Tamarix habitat on bird survivorship and productivity.
A study that planted 474 trees and measured their growth characteristics for more than a year. Logistic regression was used to evaluate whether tree height, elevation above the river channel, distance to existing cottonwood or coyote willow, soil conductivity, soil texture, planting depth, planting method (mechanical auger vs. hand-digging), and provision of natural and commercial supplements affected survival probability. The authors found that survival probability was greater in auger-dug than hand-dug holes and increased with elevation above the river channel bottom.
A look at beetle-occupied tamarisk sites 11-13 years after initial occupancy to determine long-term vegetative community response. Study found that Tamarix cover across sites initially declined an average of ca. 50% in response to the beetle, but then recovered. Changes in the associated plant community were small but supported common management goals, including a 47% average increase in cover of a native shrub (Salix exigua), and no secondary invasions by other non-native plants.
What site conditions are associated with greater recovery and overall higher cover of willows? Goetz et al. performed a meta-analysis of tamarisk removal and willow (Salix) recovery across the southwest, compiling data from 260 sites where tamarisk was subject to active removal and/or biocontrol and 132 reference sures. Cut-stump method with biological control was the most effective method to improve native species dominance. Willow cover was generally highest in locations with low drought stress, as reflected by soil properties, distance to water, and climate.
A common garden study of six distinct Fremont cottonwood populations across an elevation gradient and covering a range of genetic variation to determine responses to different heat conditions. The common gardens had mean annual temperatures of 11, 17, and 23°C and all received regular watering throughout the growing season.
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.
Nagler et al. test the assumption that removing saltcedar (Tamarix spp.) will save water and create environments more favourable to these native species. They compared sap flux measurements of water used by native species in contrast to saltcedar, and compared soil salinity, ground water depth and soil moisture across a gradient of 200–1500 m from the river's edge on a floodplain terrace at Cibola National Wildlife Refuge (CNWR).
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