Ecological Archives A020-008-A1

Chad C. Jones, Steven A. Acker, and Charles B. Halpern. 2010. Combining local- and large-scale models to predict the distributions of invasive plant species. Ecological Applications 20:311–326.

Appendix A. Descriptions of species data sets used in modeling.

TABLE A1. Summary of data sets used.


Contains absence data?

No.of sample points1

Plot area (m2)

Dates sampled

Olympic National Park exotics inventory2





Elwha River restoration area exotics survey2





Alpine and subalpine plant community survey plots3




1990, 1999

Olympic National Park exotic plant management team data2





LTEM Elwha vegetation survey2





Collette DeFerrari data set4





Ann Lezberg data set5





Olympic National Forest exotics survey2





Olympic habitat development study6





Olympic National Forest ecology plots7





Vegetation and landform database development study2





Olympic National Park herbarium records2





Personal observations2





1Number of plots from this data set included in the current study.

2Unpublished data.

3See Appendix A1 and A2 in Houston et al. (1994).

4DeFerrari and Naiman (1994).

5Lezberg et al. (2001).

6See Carey and Harrington (2001) and Reutebuch et al. (2004).

7Henderson et al. (1989).


Olympic National Park Exotics Inventory

The objectives of this inventory were to determine the distribution of exotic species within Olympic National Park and to identify the habitats most susceptible to invasion. Sampling was conducted in four types of areas: developed sites, and along roads, trails, and rivers. Developed sites and road, trail, or river segments were randomly chosen from all those within ONP and multiple plots were systematically sampled within each area or segment. All plots were 100 m2 but of differing shape. Plots in developed sites were 10 × 10 m. Plots along roads and trails were 1 × 100 m (located along the trail or road edge). Plots along rivers varied in shape to include only riparian vegetation. In each plot, presence of all exotic species was recorded. For the current study, 112 plots in 27 developed sites, 76 plots in 18 road segments, 29 plots in 10 trail segments, and 30 plots in 9 river segments were included. Data were collected in 2001 and are on file at Olympic National Park Headquarters, Port Angeles, Washington, USA.

Elwha River Restoration Area Exotics Survey

The objective of this survey was to document the locations and population sizes of exotic plant species within the Elwha River Restoration Area (river miles 5–16). The survey focused on riparian areas (within 50 m of the river) and developed areas within 1.5 km of the river (including roads, power line corridors, trails, and administrative sites). Reservoir shorelines were surveyed by boat; other areas were surveyed by foot. The centers of each population of 26 target exotic species within the surveyed area were recorded. Data were collected in 2001. Only species presence was recorded, thus none of these points were used to indicate absence in the current study. Data and additional information are on file at Olympic National Park Headquarters, Port Angeles, Washington.

Alpine and Subalpine Plant Community Survey Plots (Mountain Goat Study)

These data were collected to characterize and classify vegetation in the summer range of mountain goats in the Olympic Mountains (Houston et al. 1994). Cover for all plant species was estimated in plots ranging from 20 to 100 m2. Sampling areas were based on the summer range of the mountain goats. Within each sampling area, plots were located and sized to characterize areas of homogeneous vegetation. Data were collected from 771 plots in 69 sampling areas between 1981 and 1990. Some of the plots focused on populations of the rare plant, Astragalus cottonii; these plots were also resampled in 1999.

For this project we only used plots that were 100 m2 and sampled since 1990. In one instance there were two plots within 12 m of each other totaling 107 m2; this pair was included as a single data point. Contact: Ed Schreiner, USGS Biological Resource Division, Olympic Field Station, Port Angeles, Washington.

Olympic National Park Exotic Plant Management Team Data

These points indicate infestations of Geranium robertianum, Hedera helix, and Ilex aquifolium located by the Olympic National Park Exotic Plant Management Team. None of these points indicate the absence of any species. Contact: Dan Campbell, North Coast – Cascades Exotic Plant Management Team, Olympic National Park, Port Angeles, Washington.

LTEM Elwha Vegetation Survey

The objective of this project was to determine if physical characteristics could be used to predict the distribution of plant communities within the Elwha River Valley. Plots were randomly located within the valley, stratified by 500 m elevation bands and lower, middle or upper reaches of the river. Plots were either 400 m2 or 625 m2 depending on tree density (larger plots where trees were less dense). Cover (%) of all understory species was recorded. Contact: Andrea Woodward, USGS0–FRESC, Seattle, Washington.

Collette DeFerrari Data set

This study examined patterns of exotic species abundance and distribution at multiple spatial scales in the Hoh and Dungeness River watersheds (DeFerrari and Naiman 1994). Plots included both upland and riparian areas. All species (both native and exotic) were identified in plots that were either 50 m2 (riparian plots) or 100 m2 (upland plots). For this project plots were geo-referenced based on hand drawn maps. We verified locations based on recorded elevation, slope, aspect, and distance to the nearest road or trail; plots that could not be accurately verified to within 50 m were excluded in the current study (resulting in 10 riparian and 66 upland plots). Because of their small size, riparian plots were used to indicate presence of a target species (not presence–absence).

Ann Lezberg Data set

This study compared the development of understory vegetation and overstory structure among four age classes of low elevation forests on the Olympic Peninsula with a focus on the relationships between plant morphological characteristics and overstory structure (Lezberg et al. 2001). Understory data were collected in four to six 100 m2 plots in each of 20 forest stands on the western Olympic Peninsula.

Olympic National Forest Exotic Inventory

This project was designed by the Olympic National Forest to assess the distribution and abundance on exotic species in the forest, with an emphasis on roadside habitat. There were a total of 3193 plots sampled between 1995 and 2003. There are three major plot types: (1) 400 m2 circular plots, (2) plots encompassing road segments that are ~12 m wide and 150–200 m long, and (3) irregular polygons ranging in size from 200 m2 to 40 ha. The presence or absence of the target invasive species was recorded in each of these plots. For the current project we eliminated all plots greater than 2500 m2, which left 2881 plots. Contact: Joan Ziegltrum, Olympic National Forest, Olympia, Washington.

Olympic Habitat Development Study

This data set is from a large-scale silvicultural experiment conducted by the USDA Forest Service in Olympic National Forest. The project assessed the effects of variable-density thinning in mid-rotation forests on animals, understory vegetation, and canopy structure (Reutebuch et al. 2004). Plots were assigned to treatment or control and 100 m2 subplots were used to measure the understory. Eight sites were located throughout Olympic National Forest (Carey and Harrington 2001). Vegetation was sampled at two sites in 2002 (3 years after treatment) and two additional sites in 2004 (7 years after treatment). Pretreatment data were not available at the necessary scale. To avoid effects of the experimental treatments, we only included untreated subplots. Contact: Leslie Brodie, Forestry Sciences Laboratory, USDA Forest Service, Olympia, Washington.

Olympic National Forest Ecology Plots

These plots were used to classify and describe the forested plant associations of the Olympic National Forest (Henderson et al. 1989). Plots were distributed throughout the National Forest and ranged in size from 250 to ~1600 m2. Most plots were sampled between 1980 and 1986, although some were resampled as recently as 2003. We only included 21 plots where one of the target species was present. Contact: Robin Lesher, Mt. Baker–Snoqualmie National Forest Headquarters, Everett, Washington.

Vegetation and Landform Database Development Study

The objective of these plots was to assess the accuracy of vegetation classification maps based on satellite imagery for Olympic National Park. Understory vegetation was sampled in 1/40th acre plots (~101 m2). Plots were systematically placed along 1.5 mile long transects, located to best capture variation in the vegetation of ONP. Species with <5% were not consistently recorded; thus, only plots in which the target species were recorded as present were included in the current study (one plot). Data are on file at Olympic National Park Headquarters, Port Angeles, Washington.

ONP Herbarium Specimen Records

We included locations where specimens of the three target species were collected for the Olympic National Park Herbarium. We included locations only if they could be geo-referenced to within 50 m (five points). Data and specimens are on file at Olympic National Park Headquarters, Port Angeles, Washington.

Personal Observations

These points are locations on the Olympic Peninsula where the authors personally observed the species (four points).


Houston, D. B., E. G. Schreiner, and B. B. Moorhead. 1994. Mountain goats in Olympic National Park: biology and management of an introduced species. Scientific Monograph NPS/NROLYM/NRSM–94/25.

DeFerrari, C. M., and R. J. Naiman. 1994. A multi–scale assessment of the occurrence of exotic plants on the Olympic Peninsula, Washington. Journal of Vegetation Science 5:247–258.

Lezberg, A. L., C. B. Halpern, and J. A. Antos. 2001. Clonal development of Maianthemum dilatatum in forests of differing age and structure. Canadian Journal of Botany 79:1028–1038.

Carey, A. B., and C. A. Harrington. 2001. Small mammals in young forests: implications for management for sustainability. Forest Ecology and Management 154:289–309.

Reutebuch, S. E., C. A. Harrington, D. D. Marshall, and L. C. Brodie. 2004. Use of large–scale silvicultural studies to evaluate management options in Pacific Northwest forests of the United States. Forest Snow and Landscape Research 78 (1–2):191–208.

Henderson, J. A., D. H. Peter, R. D. Lesher, and D. C. Shaw. 1989. Forested plant associations of the Olympic National Forest. USDA Forest Service Region 6 Ecology Technical Paper 001–88.

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