Alien plant species threat assessment and management prioritization for Sequoia-Kings Canyon and Yosemite National Parks

Abstract

This document reports the results of alien species surveys at Sequoia-Kings Canyon and Yosemite national parks. It includes the findings of a comprehensive literature review of the biology and ecology of all alien plant species found during these surveys and the ranking of those species for prioritizing management and control programs. Surveys primarily targeted areas of human disturbance, such as campgrounds, corrals, developments, roads, trails and pastures. Alien species richness was compared across elevational gradients within the parks. To compare and contrast species composition among sites, an exploratory cluster analysis of the sites included in the speciesrichness-by-elevation figures was conducted using ordination techniques. All alien species discovered during the directed surveys were grouped into one of four management priority categories based on their attributes, potential impacts, and geographical extent (tables 6 and 7). Category 1 species are aliens that are currently restricted to a relatively small number of sites in each park and have either been shown to greatly affect native vegetation or have a high probability of causing serious impacts. Category 2 species are restricted to a relatively small number of sites and are ones that generally have a lesser effect on native vegetation. Category 3 species are broadly distributed in the parks, are apparently increasing their ranges within the parks, and are those that have been shown to have a great impact on native vegetation. Category 4 species are those that were detected by the surveys but not assigned to one of the three ranked categories and are considered low priority.

The role of environmental gradients in non‐native plant invasion into burnt areas of Yosemite National Park, California

“…(2001) recorded 130 non‐native species in areas of anthropogenic use in YNP, and these species tended to be more common near areas of human disturbance (Moore & Gerlach, 2001). In contrast, only 35% of the species recorded by Gerlach et al . (2001) and Moore and Gerlach (2001) were found in the NRI and the TNC surveys.…”

“…Propagule pressure is considered to be an extremely important factor in the establishment and spread of invasive species; the greater the potential pool of invasive species, the greater the likelihood some will become established into areas where they disperse (Lonsdale, 1999; Mack et al ., 2000). Gerlach et al . (2001) recorded 130 non‐native species in areas of anthropogenic use in YNP, and these species tended to be more common near areas of human disturbance (Moore & Gerlach, 2001).…”

“…Species composition of different plant communities within these vegetation zones varies with the influence of different abiotic factors, including temperature, soil moisture, soil structure, aspect, light environment and fire history (Parker, 1982; Botti, 2001). There are 1338 species of vascular plants in the park, of which 130 (9.5%) are non‐native (Botti, 2001; Gerlach et al ., 2001). Three of the non‐native species are listed by the California Invasive Plant Council as being among the most widespread and invasive non‐native plant species in the state (Anderson et al ., 1999).…”

Predicting patterns of non‐native plant invasions in Yosemite National Park, California, USA

“…Non‐native species have also been associated with areas of disturbance, either natural (e.g. fire or flooding; Rejmánek, 1989; Mack & D’Antonio, 1998) or human related (Macdonald et al ., 1988; Cowie & Werner, 1993; Gerlach et al ., 2003), and also influenced by abiotic factors, such as historical land use and management (Mack et al ., 2000).…”

Postfire Downy Brome (Bromus tectorum) Invasion at High Elevations in Wyoming

“…Although it has been present in Wyoming since the early 1900s, in recent years downy brome has increased its distribution, notably in the higher-elevation western counties (Wyoming Pest Detection Program 2010). Downy brome populations have been recorded at high elevations in the Rocky Mountains (2,700+ m [8860+ ft]; Bromberg et al 2011;Brown and Rowe 2004) and in California (2,500 m [8200 ft]; Gerlach et al 2003;Keeley and McGinnis 2007), but Bradley and Mustard (2006) suggest a near 0% probability of downy brome invasion at elevations higher than 2,500 m in the Great Basin. Although these reports indicate the ability of downy brome to establish self-sustaining populations at high elevations, little evidence documents change in downy brome abundance at high elevations following wildfire.…”