Abstract: REVEGETATION STRATEGIES AND TECHNOLOGIES FOR RESTORATION OF NATIVE SHRUB/GRASS COMMUNITIES ON XERIC SALTCEDAR (TAMARIX SPP.) INFESTATION SITES

Critical knowledge gaps exist regarding vegetative recovery in xeric, monotypic saltcedar (Tamarix spp.) stands with no (desirable) understory. On sites not subject to seasonal flooding, shallow water table or irrigation, recovery of desirable vegetation may be the most limiting factor for site stabilization following control measures. Formulation of revegetation strategies that provide site stabilization, resistance to further saltcedar and secondary weed infestation, and acceptable habitat values for affected wildlife species becomes particularly problematic in monotypic saltcedar stands under biological, fire and herbicidal (i.e., non-mechanical) control scenarios. Amount and density of standing biomass (live and dead) remaining after control poses limitations in relation to seeding and planting techniques, seed interception in aerial (broadcast) applications, and seedbed preparation methods. Undisturbed soil surfaces impacted by saltcedar leaf litter accumulation, salinity, hummocky micro-relief, and nutrient limitations restrict potential for successful revegetation. Long duration of saltcedar occupation may deplete needed microbial communities, particularly arbuscular mycorrhizae (AM) symbiotic and host-specific to native revegetation species.

Results of innovative revegetation strategies and technological approaches at study sites on the Rio Grande (near Socorro, NM) and the Colorado River (near Blythe, CA) will be discussed in light of interagency research on biological control and restoration of saltcedar infestations funded by the State Research, Extension and Education Service (CSREES) and the Initiative for Future Agriculture and Food Systems (IFAFS). These approaches include: soil surface and rhizosphere manipulation methods to facilitate removal of standing dead biomass, increase precipitation capture, improve soil moisture retention, and create micro-sites exhibiting lower salinity and increased protection from environmental extremes for improved seed germination; salinity remediation using HydraHume^tm seeding methodologies, including use of seed coating techniques; and mycorrhizal inoculation methods. Influence of pre-treatment soil parameters will also be reviewed, including surface and subsurface texture, pH, sodium adsorption ratio (SAR), electrical conductivity (ECe), and major nutrients.

Contact Information:

Bureau of Reclamation, USDI Denver Technical Service Center
P.O. Box 25007, D-8220
Denver, CO 80225-0007

Kenneth D. Lair, Ph.D. (Primary Contact)
303-445-2005
klair@do.usbr.gov

Sarah L. Wynn, Ph.D.
303-445-2216
swynn@do.usbr.gov

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