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.
To what extent has invasive riparian vegetation (IRV) treatment reversed channel narrowing and reduced dynamism trends? Paired treated and untreated reaches at 15 sites along 13 rivers were compared before and after treatment using repeat aerial imagery to assess long-term (~10 year) channel change due to treatment on a regional scale across the Southwest U.S. Wieting et al. found that IRV treatment significantly increased channel width and floodplain destruction.
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.
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).
Glenn et al. measure transpiration and stomatal conductance to investigate the environmental constraints on an arid-zone riparian phreatophtye, saltcedar (Tamarix ramosissima and related species and hybrids), growing over a brackish aquifer along the Colorado River in the western U.S. Depth to groundwater, meteorological factors, salinity and soil hydraulic properties were compared at stress and non-stressed sites that differed in salinity of the aquifer, soil properties and water use characteristics, to identify the factors depressing water use at the stress site.
In this 2014 poster, Ryan and Harris report preliminary results on a study of evapotranspiration (ET) at the Cibola National wildlife Refuge. They ask whether groundwater responds to a massive change in ET of surface vegetation and assess baseline well and evapotranspiration data as a proxy for the anticipated tamarisk beetle migration.
Bush et al. use a common garden experiment to study drought sensitivity in non-native tamarisk. They found some populations are more sensitive to soil water deficits than others and that freeze-thaw exposure reduces drought sensitivity.
Bush, S.E., Guo, J.S., Dehn, D., Grady, K.C., Hull, J.B., Johnson, E., Koepke, D.F., Long, R.W., Potts, D.L. and Hultine, K.R., 2021. Adaptive versus non-adaptive responses to drought in a non-native riparian tree/shrub, Tamarix spp. Agricultural and Forest Meteorology, 301, p.108342.