Research -

Accurate research informs productive, on-the-ground action.

Here we are striving to promote -

1. Dialogue and collaboration among scientists to increase the quality and efficiency of such research.
2. The communication of land managers' research needs to researchers to ensure an efficienct transfer of knowledge.

Current Research

We would like to compile a searchable, comprehensive database of current tamarisk related research. If you are conducting or participating in tamarisk or Russian olive research, please fill out our Research Request Form and email it to Clark Tate at ctate@tamariskcoalition.org.

The Tamarisk Coalition is also gathering data for an assessment of tamarisk and Russian olive impacts in the Colorado River watershed - upper and lower basins. The completed assessment will be available to all by spring 2009. We would greatly appreciate any data or information that you can contribute.

Suggested Research

Compiled from the 2006 Tamarisk Symposium Break-Out Sessions

Tamarisk Biology

• Seeds- dispersal (role birds play, seed rain pattern), germination, production (quantity and variability), cold hardiness, dormancy, viability…..
• Range of conditions under which tamarisk can establish, especially determining the ends of the spectrum and regional variation
• Physiology of tamarisk crown buds
• Life span, geographic differences in life span.
• How does hybridization of tamarisk species affect its adaptability to new environments where we may not predict it will occur?

Control Methods

• What is the most cost-effective, environmentally friendly method of tamarisk removal
• Is it possible to wait for old stands to die?

...mechanical

• Compare mortality and cost with the following combination of treatments:
  • Grinding followed by basal bark herbicide application to re-growth vs. cut-stump method;
  • Grinding followed by basal bark herbicide application to re-growth vs. burning followed by basal bark herbicide application to re-growth;
  • Grinding followed by basal bark herbicide application to re-growth vs. grinding followed by foliar herbicide application to re-growth.
• Is mechanical removal the best option because the resulting mulch would provide good micro-habitats for young seedlings?
• Root removal
  • Mortality rates by root removal on dry upland sites without surface or shallow sub-surface water?
  • Root removal on sites with surface and shallow sub-surface water-Is sub-surface water a key factor for re-growth? Is there a critical depth that greatly affects re-growth?

...chemical

• Habitat
  • How long do you have to wait to remove biomass after application?
    • Does length of waiting time depend on environment (river bank vs. upland, etc.)?
  • Or type of removal technique (burning vs. chaining vs. grinding)?
  • Aerial application- is foliar or root absorption the major contributor to efficacy?
  • Response of common restoration species- if wait recommended 2 years before removal, have Habitat residues dissipated enough to allow establishment of important native colonizers?
• Understanding how site differences affect management recommendations.
• Combination of biological control and herbicides.
• Herbicide combination for tamarisk control and control of other invasive weeds- kochia, Russian knapweed, white top and perennial pepperweed.

...biological control

• Key factors for successful tamarisk mortality using goats.
• Diorhabda elongata o Will the beetle restructure or eliminate tamarisk patches? Will results vary by region and patch? o Effect on native species and best restoration practices.
• Biological control for tamarisk seeds.
• Combination of biological control and herbicides.

...fire

• Ideal time for achieving best mortality rate between time of treatment and fire. o Cut-stump, basal bark or grinding followed by basal bark methods, before or after prescribed burning or wildfire event? o Will mortality rates be substantially reduced if fire event occurs before removal? Is there a timing factor? Should you wait 1-2 years after fire event before removal? o After removal, how will mortality rates be affected if fire event occurs one month after initial treatment as compared to 1-5 years after treatment? Is the time of year a factor?

Restoration and Revegetation

• When is passive/active revegetation best? What are the benefits/drawbacks of each?
• Do we have to remove Tamarix to facilitate the next step in restoration projects?
• Is flooding necessary for native species establishment? Tamarix establishment?
• What is the role of shade/light availability in Tamarix control and native species restoration? How does it differ in different situations?
• What is happening in systems where Tamarix is still sparse and where Tamarix has not yet invaded?
• What other processes are going on with succession in existing stands?
• How do other invasive species present with Tamarix change strategies and pose challenges to restoration/revegetation?
• How does restoration fit into broader taxonomical/functional discussions such as rare plants, resource plants, biomass for ethanol, and carbon cycling?
• How do restoration/revegetation strategies/challenges in Northern states differ from the Southwest?
• What are germination/establishment requirements for other native species especially xeric riparian species?
• What is the water consumption of other native species?
• How do the priorities of restoration/revegetation differ on private lands?
• Need more research on related social issues, especially as they relate to private land owners, flow regimes, dams, etc.
• How do priorities/challenges/strategies differ in urban areas?
• Native plants as windbreaks/protection for livestock.
• Compare restoration efforts of old-growth tamarisk vs. waiting for tamarisk to die.

Wildlife Habitat

• Will control change the stream enough to negatively impact or positively impact the native fish and /or non-native fish?
• More data on the effects of tamarisk on small mammals.
• Aquatic communities including fish, aquatic invertebrates, and riparian animals that eat aquatic insects. Should address differences between warm and cool water streams. Tamarisk maybe changing water levels, water temperatures, water quality and stream flow. There is concern among scientists that fish have been ignored because they are a contentious issue; many native Western fish species are on the endangered species list and sport fish compete with native fish species for habitat and food resources.
• Tamarisk may have an indirect effect on native species through its effect on groundwater and surface water resources. There is some data available to describe the effect that tamarisk has on surface water quality in perennial streams, but data is lacking for groundwater and intermittent streams, such as the Gila River.
• Changes in mycorrhizae and the below-ground arthropod community could be occurring due to tamarisk-induced changes in groundwater chemistry or groundwater levels at spring sites.
• More data on the effects of tamarisk on native and domesticated grazers
• Tamarisk effects on the neo-tropical migrant birds that use river corridors as flight routes.
• A more complete understanding of the variation in habitat structure and composition among existing tamarisk patches and regions would aid the process of predicting the response of native species to tamarisk removal.
• There are currently native species (habitat specialists) using tamarisk patches. We need to understand what will happen to these patches in order to know what might happen to the native fauna. We need to study how native species utilize the edges of tamarisk patches because biocontrol efforts are likely to fragment tamarisk stands and create more edge habitat. If edge habitat is increased through tamarisk fragmentation, some native species such as birds and insects that forage on the edges of patches may benefit. However, if tamarisk patches are completely eliminated, so too will be the habitat for specialists.
• More information is needed on how birds, specifically the southwest willow flycatcher, may benefit or suffer through tamarisk removal. Southwest willow flycatcher is a notable habitat specialist that could potentially suffer from tamarisk biocontrol. Sogge et al. [9] suggested that the effect of Tamarix biocontrol on avian fauna would depend on the availability of replacement habitat (e.g. mesquite, cottonwood/willow) and the timing of biocontrol relative to bird reproduction and migration. Longland et al. [10] presented data that suggest that birds may preferentially feed on the Diorhabda beetles at the tamarisk patch edges. They suggested that some birds may benefit from tamarisk biocontrol in the short term due to increased food resources and increased edge habitat. More research is needed to determine how different tamarisk removal mechanisms affect native species.
• A multidisciplinary simulation modeling project could address how changes to tamarisk stands might alter habitat available to native fauna. Tamarisk habitat models could be developed for different regions and patch types, and then virtual biocontrol beetles could be released into the landscape. The focus of the model would be on understanding changes to tamarisk patch size and habitat structure. Ultimately the tamarisk habitat model would be linked to tamarisk use by native species so optimum places for beetle releases could be identified. This kind of modeling effort would require a large scale synthesis of tamarisk habitat data and data that relates native species to tamarisk. This data synthesis could be put on a website that was available to managers, scientists, and the public so it could be used for management efforts outside of the modeling context. The results of these modeling efforts would need to be shared with the public because unplanned beetle releases may be circumvented through education.
• We need to monitor the effect of tamarisk mitigation on native species and we need to make these results available to the scientific community and the public.
• We do not know enough about native communities that are not affected by tamarisk, so it is difficult to understand the effect that tamarisk is having on these communities. In some cases we lack basic natural history information about non-invaded sites and in other cases we do not have any information on the pre-tamarisk community. Tamarisk has been in the US since the 1800s and most locations where it is now prevalent were not well described prior to tamarisk invasion.
• Wildlife has to be considered in restoration goals. What are the implications of various restoration strategies on wildlife? How do we make transitions between communities without losing habitat? What is happening with smaller organisms (i.e. invertebrates, microbes, etc.)?

Sedimentation and Geomorphic Processes

• A clear understanding of interactions among vegetative processes, hydrogeomorphic processes, and anthropogenic effects will elucidate mechanisms for tamarisk establishment and improve the scientific basis of tamarisk control and eradication programs.
• Linkages between tamarisk and hydrogeomorphic processes, including monitoring of changes in bank erosion, sediment transport, and downstream reservoir sedimentation following tamarisk removal.

Biomass

• Utilization
  • BTU’s?
  • Use in heating facilities
  • Use in wood products
  • Other uses?
• Differences among the different tamarisk species that occur in the US in their biomass estimates
• We need a tool to be able to estimate biomass using satellite imagery. Also, how does foliage:biomass ratio change with age and can we tie that into a satellite imagery tool to predict biomass? One thing that could be done would be to take satellite images in different seasons, spring and fall, to compare leaf area index with leaves on and off.
• Type of equipment best used for chipping tamarisk?
• Does standing dead tamarisk represent a significant fire hazard?

Salinity

• How long does it take for soils to become highly alkaline after tamarisk infestation?
• How far and at what rate will salts move down into the soil profile?
• After removal, how long will it take for alkalinity to decrease in soils through natural precipitation? May relate directly to what type of vegetation naturally fills in, or probable success rates of re-vegetation with native plant species.

Mapping and Inventory

• GIS and remote sensing
  • Use of finer resolution data over a broader geographic range for predicting limits of tamarisk invasion.
  • Look at scale and sensitivity,
  • Good ground truth data,
  • Address the temporal problem with data (e.g. ground data and how good is it until you can’t use it anymore),
  • Identify predictive variables for GIS analysis.
• Modeling
  • Still do not have the best signature for tamarisk but need to focus on predicting where it will invade.
  • Problem about use of empirical models versus process models; if tamarisk is genetically plastic then we would run into problems at the boundaries.