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This chapter outlines the techniques and lessons that have been learned from the long history of tamarisk management. It first charts the history of tamarisk control and presents several examples that illustrate how the described methods have been successfully implemented. These methods include flooding, biological control in the form of defoliation by Diorhabda spp. leaf beetles, mechanical control strategies such as bulldozing and root plowing, and chemical control such as the use of herbicides. The case studies include the Pecos River Ecosystem Project in Texas, the Dinosaur National Monument in northwestern Colorado and northeastern Utah, and the large-scale tamarisk removal in Utah. The chapter also considers the costs, impacts, and trade-offs in the use of various tamarisk management options and concludes by suggesting an integrated tamarisk and ecosystem management.

This chapter presents a “bird's eye” view of tamarisk and examines some issues surrounding the management of tamarisk in riparian woodlands. The focus on birds is based on the fact that they are a relatively well-studied group that can provide important insights into the role of tamarisk in riparian ecosystems. Because the decline of native riparian habitat occurred concurrently with the spread of tamarisk, this invasive species has been portrayed as a key factor in the reduction of riparian breeding bird numbers. The chapter begins with an overview of the early perceptions and realities of why and how birds use tamarisk before turning to a discussion of the history of tamarisk control and its effects on birds. It then considers some of the changing perspectives about the management of tamarisk and riparian habitats in western North America.

This chapter focuses on the history and impact of tamarisk biological control in the form of defoliation by Diorhabda spp. leaf beetles. The beetles have become controversial despite their spectacular success as biological control agents. The chapter first presents a brief history of weed biological control before turning to the selection of tamarisk as a biocontrol target and the leaf beetle as biocontrol agent. It then examines the biology of leaf beetles, including their taxonomy and phenology, in order to have a better understanding of their current and future impact on riparian ecosystems as well as their use as a tamarisk management tool. It also considers how beetles congregate to defoliate tamarisk and concludes by discussing the long-term outlook for Diorhabda in tamarisk control.

This chapter focuses on the question of what vegetation would and should be established after tamarisk removal. Tamarisk is the dominant woody species in many riparian areas of the US southwest. Its management has been a prominent environmental and political issue since the 1970s. For many years, the general public understanding was that tamarisk was a malicious invader actively dominating native riparian landscapes. It was thought to be displacing the native cottonwood and willow trees through competition and excessive water use and providing poorer wildlife habitat than native riparian plant species. The chapter begins with an overview of revegetation and restoration effort following tamarisk removal as well as the costs and benefits of revegetation. It then presents the findings of a study on revegetation projects in Arizona, Nevada, and New Mexico, highlighting the factors that contribute to successful post-tamarisk revegetation. It also explains how success can be defined, measured, and modeled and concludes by making a case for revegetation as a key component in the planning and design phases of tamarisk management projects and not only as a step in this process.

This chapter focuses on evapotranspiration (ET) by tamarisk in the Colorado River basin. In particular, it considers whether restoration of tamarisk-invaded rivers and riverbanks could result in increased water savings. The chapter begins with a background on tamarisk and its reputated use of large quantities of water as an aggressive invasive species before looking at anecdotal examples and studies that have led to some confusion about the potential of tamarisk control for water savings. It then presents an excerpt from a discussion by a panel of experts convened in November 2008 to address major questions regarding ET by tamarisk in the Colorado River basin, such as ET rates for replacement vegetation, the role of infestation density in overall ET rates, or whether tamarisk control and restoration actions can save water and increase stream flows in the Colorado River system.

This chapter describes tamarisk management at Bosque Del Apache National Wildlife Refuge, located on the Rio Grande in central New Mexico, from a resource manager's perspective. The Refuge was established in 1937 as a wintering area for migratory birds, particularly the sandhill crane (Grus canadensis). To maintain habitat for the thousands of birds and other wildlife that depend on the Refuge, tamarisk had to be controlled and if possible eradicated from floodplain areas. The chapter begins with an overview of the Refuge's early experiences with tamarisk establishment and control during the years 1942–1992 before turning to its implementation of adaptive management techniques for larger-scale research projects from 1992 to 2000. It then considers the Refuge's successes with respect to establishment of native plants and the challenges it encountered, along with its focus on landscape level tamarisk control in 2000–2010. Finally, it discusses the Refuge's prospects and steps for tamarisk control and management in 2010 and beyond.

This chapter describes some of the methods that have been used to map tamarisk infestations and predict distribution and abundance in North America, including field surveys, online databases, remote sensing, and spatial models. These methods have had varying degrees of success, and some may have better applications under specific site conditions or at specific geographic locations. Field surveys are still the most common means of mapping tamarisk distributions for land managers, providing a critical foundation for some of the new methods and techniques being used to predict tamarisk distribution. The types of tamarisk data collected from the field can range from a location coordinate taken from a global positioning system (GPS) to a mapped polygon of a stand with detailed site descriptions.

This chapter explores the ecohydrology of tamarisk, with particular emphasis on water use, salt tolerance, potential for salinizing flood plains, drought tolerance and rooting depths, and ecological interactions with native plants on western rivers. It presents the working hypothesis that tamarisk is adapted to water stress, with low to moderate water use that tends to replace mesic vegetation when conditions on flow-regulated rivers become unsuitable for those species, rather than as an invasive species that displaces and out-competes native species under all conditions. It includes data on the annualized rates of evapotranspiration, transpiration, and stomatal conductance by tamarisk stands on western US rivers. It also cites the lack of evidence that simply removing tamarisk from a riverbank will improve salinity or allow native mesic vegetation to return.

This chapter explores the impact of tamarisk on the use of riparian habitats by invertebrates with respect to detritus quality and quantity, predator-prey relationships, food sources, and vegetation structure. Invertebrates are a major component of the riparian ecosystem in areas where Tamarix is densest. Understanding invertebrate diversity and abundance in Tamarix stands is therefore critical to understanding its ecology. The chapter begins with an overview of the value of tamarisk as a habitat for invertebrates and goes on to describe invertebrate assemblages observed in tamarisk. It then considers the interactions between tamarisk and invertebrate herbivores, along with the effects of the beetle Diorhabda spp. (biological control) on the invertebrate assemblages of tamarisk stands. It also discusses the impact of changes in invertebrate abundances on vertebrates.

This chapter examines the fire ecology of Tamarix and the role of fire in riparian ecosystems. Tamarisk invasion has been linked to increased wildfire frequency and intensity in riparian ecosystems of the arid West, with negative socioeconomic and ecological consequences. The chapter begins with an overview of fire characteristics in Tamarix stands, focusing on the species's fuel composition, the impact of fire behavior on vegetation structure, and Tamarix response to fire. It then considers the consequences of Tamarix's fire behavior for the community-level dynamics of riparian habitats, with particular emphasis on the physical effects of biological control on tamarisk fire behavior and post-fire tamarisk recovery. It also discusses the implications of tamarisk flammability for tamarisk management, taking into account the use of prescribed fire.

This chapter documents the introduction, naturalization, and control of Tamarix in the United States between 1818 and 1952. It discusses the three phases of the history of tamarisk in the United States: during phase one (c.1800–1938), tamarisks were celebrated and imported for qualities deemed beneficial; during phase two (1938–1952), the plants were disparaged for the same qualities and viewed as monsters; phase three ushered in the first era of federally organized tamarisk suppression, which continued into the 1970s. The chapter examines a number of projects devoted to control of tamarisk and other phreatophytes, including those that investigated upper Rio Grande water issues in 1936–1937 and Pecos River issues in 1939–1940, the New Mexico Salt Cedar Interagency Council, the Pacific Southwest Federal Inter-Agency Technical Committee's Subcommittee on Phreatophytes, and the Safford Valley initiative in 1944.

This chapter assesses the value of Tamarix using a philosophical framework that involves eliminating the notion of intrinsic value in favor of two other notions: conditional value and self-generated value. In order to assess the value of the tamarisk, the chapter considers how it functions in the systems in which it participates and how those functions affect human thriving. It also discusses the importance of maintaining a human scale for goodness and some of the reasons why people believe that the tamarisk is good (or bad). Furthermore, it compares conditional goods with unconditional goods as well as self-generated goods with other-generated goods. It argues that the tamarisk has no value outside of a context and that it is neither good nor bad. The tamarisk (like any other species) is a conditional good because it is good under some conditions, and bad under others.

This chapter discusses the botany and horticulture of tamarisk. Plants of the genus Tamarix L. (Tamaricaceae, one of four families in the order Caryophyllales) are large shrubs or small trees comprising more than forty species and hybrids. Species in the genus are native to mostly arid environments from North Africa and the Mediterranean basin eastward to northern India and west-central China. Its center of distribution appears to be in the dry valleys of the Middle East and northwest to Pakistan, but it has been widely planted for centuries, so native ranges are indeterminate. The chapter begins with a botanical description of the tamarisk plant before considering its ethnobotanical uses. It then examines the introduction of tamarisk in North America and its propagation as an ornamental landscape plant. It also looks at the geographical distribution of tamarisk.

This concluding chapter assesses the future of Tamarix ecology and management in North America. It first considers the debate over whether Tamarix is bad for riparian ecosystems and should always be eliminated, citing the passenger-driver model to help clarify perceptions about the behavior of this invasive species, as well as the moral component of this debate. It then tackles the issue of revegetation: what vegetation would and should be established after tamarisk removal. It also discusses tamarix monocultures as opposed to mixed stands; differences among the regions tamarix occupies; large-scale restoration projects that include tamarix removal as a primary component; and the methods used in tamarix control, including biological control in the form of defoliation by Diorhabda spp. leaf beetles. Finally, the chapter reflects on the future of Tamarix in the context of management and climate change.

The interaction among water, sediment, landforms, and human environmental manipulation on the Northern Rio Grande has produced a distinctive assemblage of plants in the riparian (or near-channel) community. The fluvial landforms and the sediment of which they are composed are often not immediately visible in field investigations because of the dense cover of riparian vegetation. In aerial photography—the primary source of data for historical river-channel change and sedimentation- riparian vegetation is often the only aspect of the near-channel environment that is amenable to interpretation and mapping. Vegetation also provides information about the date of emplacement of the sediments on which it grows, information useful in tracking contaminants introduced into the system during known time periods. Vegetation communities therefore provide useful keys to identifying the distribution of near-channel sediments and the contaminants they contain. This chapter briefly reviews the origin and changes in riparian vegetation in the study area, including its connections with geomorphic systems. Almost all major rivers in the American Southwest have undergone considerable geomorphic and vegetation change since the early nineteenth century when channel margins were the sites of bogs, lakes, abandoned meanders (sloughs), and marshes. Most major rivers had broad, sandy channels with braided configurations and meandering low-flow channels. Even small tributaries had marshy areas created by beavers. The riparian vegetation originally evolved in association with frequent extensive flooding. Removal of the beavers, the development of gullies and arroyos, land-management schemes, changes in climate, and the construction of dams changed the streams into single-thread or compound channels that flooded less often. The Rio Grande’s recent history is typical of the larger region except for the extensive recent engineering works that restrict the active channel and flood plains. There are few detailed descriptions of the channel and riparian vegetation before major human intervention, but generally, most firsthand observers indicate that the Northern Rio Grande was broad and shallow, with meandering subchannels frequently altered by flooding. After channel migration, cottonwood, willow, and cattail colonized the newly exposed alluvial surfaces. Early in the twentieth century, the cottonwood groves near the river rarely developed trees more than about 10 m high before more changes in the channel destroyed them.