Restoration and revegetation associated with control of saltcedar and Russian olive: Chapter 7

Abstract

Rationales for controlling or eliminating saltcedar and Russian olive from sites, river reaches, or entire streams include implicit or explicit assumptions that natural recovery or applied restoration of native plant communities will follow exotic plant removal (McDaniel and Taylor, 2003; Quimby and others, 2003). The vegetation that replaces saltcedar and Russian olive after treatment (“replacement vegetation”), with or without restoration actions, strongly influences the extent to which project objectives are successfully met. It is often assumed or implied that saltcedar and Russian olive removal alone is “restoration,” and many reports equate restoration success with areal extent of nonnative plants treated (for example, Duncan and others, 1993). However, removal of nonnative species alone does not generally constitute restoration. In this chapter, the term “restoration” refers to conversion of saltcedar- and Russian olive-dominated sites to a replacement vegetation type that achieves specific management goals and helps return parts of the system to a desired state. The degree to which a site is “restored” following removal of saltcedar or Russian olive typically depends upon a range of factors, such as (1) the site’s potential for restoration (such as extant soil conditions, site hydrology), (2) the direct and indirect effects of removal (for example, mechanical impacts to the site, effects of herbicides on nontarget vegetation), (3) the efficacy of restoration activities (for example, grading, reseeding, pole planting), and (4) the maintenance of processes that support native vegetation and prevent re-colonization by nonnative communities over the long term. This chapter summarizes and synthesizes the published literature on the topic of restoring native riparian vegetation following saltcedar and Russian olive control or removal. Most of the studies reviewed here are from saltcedar removal, revegetation, and river restoration projects in semiarid and arid parts of the Western United States. The paucity of literature on Russian olive prevents thorough evaluation of specific considerations for restoration following Russian olive removal; however, a few field studies are highlighted. Furthermore, the basic principles of restoration following vegetation removal and the considerations and lessons learned from saltcedar case studies are broadly applicable to sites across the Western United States. We begin with a brief discussion of planning and objective setting. Next, we discuss site factors and context, which are important to consider when selecting and prioritizing sites for restoration. We then review and synthesize the literature on restoration approaches and methods or combinations of methods to apply to particular sites. Throughout this chapter, we highlight what is known on the topics of restoring soils, vegetation, and site conditions following nonnative species removal, as well as future research needs.