Principles and Practices for Managing Rangeland Invasive Plants

Abstract

Invasive plants reduce the capacity of ecosystems to provide goods and services required by society, alter ecological processes, and can displace desirable species. They can reduce wildlife habitat quality, riparian area integrity, rangeland economic value, and enterprise net returns. The invasion process is regulated by characteristics of the invading plant and the community being invaded. The presence and spread of invasive plants is often symptomatic of underlying management problems that must be corrected before acceptable, long-term rangeland improvement can be achieved. Disturbance appears to be important early in the invasion process because it creates vacant niches that alien plants can occupy. Control of invasive plants may only open niches for establishment of other undesirable plants unless desirable plants are present to fill the vacated niches. In many instances, rangelands have deteriorated to the point that desirable species are either not present, or in such low abundance that plant community recovery is slow or will not occur without revegetation after invasive plants are controlled. Integrated weed management employs the planned, sequential use of multiple tactics (e.g. chemical, biological, cultural, and mechanical control measures) to improve ecosystem function (energy flow and nutrient cycling) and maintain invasive plant damage below economic levels, and emphasizes managing rangeland ecosystem functions to meet objectives rather than emphasizing a particular weed or control method. Sustainable, integrated invasive plant management strategies require assessing plant impacts, understanding and managing the processes influencing invasion, knowledge of invasive plant biology and ecology, and are based on ecological principles. Invasive plant management programs must be compatible with and integrated into overall rangeland resource management objectives and plans. Because of the complexity of managing invasive plants, it is imperative that relevant ecological and economic information be synthesized into user-friendly decision support systems.

Dispersal of non-native plants by introduced bison in an island ecosystem

“…Bison are famous for their tendency to regularly move over large distances (Berger and Cunningham 1994) and their wallows are therefore widely dispersed and numerous across most of Santa Catalina Island (Figure 1). Bison wallowing creates multiple small-scale disturbances at the soil surface that provide safe sites for seedling establishment (Bossard 1991;Hobbs and Huenneke 1992;Masters and Sheley 2001), ultimately resulting in higher overall germination (Stromberg and Griffin 1996). Importantly, nonnative annual grasses tend to allocate fewer resources to roots and more resources to leaf and seed production than perennial grasses, which allow them to grow more quickly and exploit disturbances better (Stromberg and Griffin 1996;Kotanen 1997;Seabloom et al 2003).…”

“…One correlate of invasion success is the number of seeds dispersed into new areas; the probability that at least some propagules will reach a safe site and successfully germinate increases with seed availability (Williamson 1996;Masters and Sheley 2001; but see Seabloom et al 2003). Moreover, long-distance dispersal events and multiple introduction points can increase the rate of invasion and spatially distribute plant populations, such that extinction of invasive plants at the local level will have reduced impact at a regional scale (Kiviniemi and Eriksson 1999;Fagan et al 2002;National Research Council 2002).…”

Plant community diversity and native plant abundance decline with increasing abundance of an exotic annual grass

“…Invasion by exotic grasses is concerning because they often increase fire frequency and negatively impact native vegetation (Torell et al 1961;Hughes et al 1991;D'Antonio and Vitousek 1992;Brooks et al 2004;Milton 2004). Increases in fire frequency are ecosystem-level changes that can further facilitate invasion and perpetuate the dominance of wildlands by exotic grasses (D' Antonio and Vitousek Exotic plant invasions have been reported to decrease biodiversity, reduce productivity, degrade wildlife habitat, displace native plants, and alter ecosystem functions in wildlands (DiTomaso 2000;Mack et al 2000;Simberloff 2005;Masters and Sheley 2001). However, some ecologists argue the impacts of exotic plants have been exaggerated and that biodiversity and other important plant community characteristics are commonly improved with invasion.…”

Railway side mapping of alien plant distributions in Mpumalanga, South Africa

“…Railway development itself is a disturbance of the environment and has the potential for increasing dissemination of propagules, which makes the ecosystems more susceptible to invasion by alien species (Richardson & Van Wilgen 2004). The disturbed area is particularly important during the early stage of invasion because it creates vacant niches that alien plants can colonise (Masters & Sheley 2001). Rutkovska et al (2013) found that some of the alien taxa in Latvia were associated with topsoil disturbance because of the construction and maintenance of railway lines.…”