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Sustaining or Improving Flows

Sustaining or Improving Flows

  • Vegetation response to invasive Tamarix control in southwestern U.S. rivers: a collaborative study including 416 sites

    Gonzalez et al. 2017

    Most studies assessing vegetation response following control of invasive Tamarix trees along southwestern U.S. rivers have been small in scale (e.g., river reach), or at a regional scale but with poor spatial-temporal replication, and most have not included testing the effects of a now widely used biological control. We monitored plant composition following Tamarix control along hydrologic, soil, and climatic gradients in 244 treated and 172 reference sites across six U.S. states. This represents the largest comprehensive assessment to date on the vegetation response to the four most common Tamarix control treatments. Biocontrol by a defoliating beetle (treatment 1) reduced the abundance of Tamarix  less than active removal by mechanically using hand and chain-saws (2), heavy machinery (3) or burning (4). Tamarix abundance also decreased with lower temperatures, higher precipitation, and follow-up treatments or Tamarix  resprouting. Native cover generally increased over time in active Tamarix removal sites, however, the increases observed were small and was not consistently increased by active revegetation. Overall, native cover was correlated to permanent stream flow, lower grazing pressure, lower soil salinity and temperatures, and higher precipitation. Species diversity also increased where Tamarix was removed. However, Tamarix treatments, especially those generating the highest disturbance (burning and heavy machinery), also often promoted secondary invasions of exotic forbs. The abundance of hydrophytic species was much lower in treated than in reference sites, suggesting that management of southwestern U.S. rivers has focused too much on weed control, overlooking restoration of fluvial processes that provide habitat for hydrophytic and floodplain vegetation. These results can help inform future management of Tamarix-infested rivers to restore hydrogeomorphic processes, increase native biodiversity and reduce abundance of noxious species.

    Key words: Diorhabda; exotic species control; management

  • This science module will introduce you to the concepts of water budgets, environmental flows, and water security and provide instruction on using tools that are now available online. River Network assembled already available resources from their partners in the field of ample water, and produced new material to help weave together these concepts and introduce new resources.
     
    The segments may be watched individually but are intended to be watched in sequence so they may build upon each other for greatest understanding.  After watching the module, if you have any questions about the material, or are interested in learning more about how you might see these types of projects pursued in your watershed, please feel free to contact River Network's Science Manager, Adam Griggs. You may also access the videos on the Youtube channel here.
  • Matt Grabau with the Sonoran Institute presents Modeling Shallow Groundwater for Support of Riparian Areas in the Colorado River Delta at TC's 2016 Conference.

  • Gonzalez et al. 2018

    Human activities on floodplains have severely disrupted the regeneration of foundation riparian shrub and tree species of the Salicaceae family (Populus and Salix spp.) throughout the Northern Hemisphere. Restoration ecologists initially tackled this problem from a terrestrial perspective that emphasized planting. More recently, floodplain restoration activities have embraced an aquatic perspective, inspired by the expanding practice of managing river flows to improve river health (environmental flows). However, riparian Salicaceae species occupy floodplain and riparian areas, which lie at the interface of both terrestrial and aquatic ecosystems along watercourses. Thus, their regeneration depends on a complex interaction of hydrologic and geomorphic processes that have shaped key life-cycle requirements for seedling establishment. Ultimately, restoration needs to integrate these concepts to succeed. However, while regeneration of Salicaceae is now reasonably well-understood, the literature reporting restoration actions on Salicaceae regeneration is sparse, and a specific theoretical framework is still missing. Here, we have reviewed 105 peer-reviewed published experiences in restoration of Salicaceae forests, including 91 projects in 10 world regions, to construct a decision tree to inform restoration planning through explicit links between the well-studied biophysical requirements of Salicaceae regeneration and 17 specific restoration actions, the most popular being planting (in 55% of the projects), land contouring (30%), removal of competing vegetation (30%), site selection (26%), and irrigation (24%). We also identified research gaps related to Salicaceae forest restoration and discuss alternative, innovative and feasible approaches that incorporate the human component.

  • Chris Sturm, Colorado Water Conservation Board, presents on Flood Recovery Update from the Colorado Water Conservation Board at the 2016 Conference.
  • Karen Schlatter gives an Update on The Vegetation Response to Environmental Flows and Restoration Treatments in the Colorado River Delta at TC's 2016 Annual Conference. 

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