Elementos de la economía interna

General Technical Report GTR-694

The goals of the Federal Noxious Weed Program (USDA APHIS 2006) are to prevent the introduction of non-native plants into the United States and to prevent the spread of newly introduced invasive plants within the United States. The program focus is to minimize the threat to the nation’s agriculture and environment. Species on the federal noxious weed list may not be introduced into the United States or moved between the states. Such importa- tion or movement may be allowed under specific permit conditions.

Washington State’s Noxious Weed Board updates the state noxious weed list each year and coordinates education and control efforts throughout the state. The state noxious weed list separates species into three categories, based on their current distribution in the state, their potential for harm, and required control measures (Washington State Noxious Weed Control Board 2006). Class A noxious weeds have limited distribution in the state and a high potential for harm should they become well established. Class B noxious weeds are limited in distribution in parts of Washington State, but very abundant in other parts of the 96

state. Class C noxious weeds are widespread in Washington State. State law requires control of all Class A noxious weed infestations, as well as Class B designates (regions of the state where that species is not well established). County weed boards and districts may also require control of other Class B and Class C noxious weeds.

As a routine part of their duties, the Forest botanists work to prevent noxious weed infestations, to document noxious weed sightings, and to develop noxious weed con- trol plans (USDA Forest Service 2005). To be most effec- tive in preventing new infestations, however, the Forest must not only be able to detect new infestations and new species, but also to predict where and how these species may spread.

Both the Forest Botany and Forest Ecology Programs have high quality, long-term data regarding the distribution of all vascular plants on the Forest. Because of this, we are able to assess where non-native plants occur on the Forest. In addition, the different data collection methods allow us a unique opportunity to assess how different sampling schemes detect non-native plants.

Specifically, we address the following questions: 1) Which non-native vascular plants occur on the Forest? 2) In which ranger districts and counties do they occur? 3) Do the two sampling schemes (botany surveys and

ecology plots) detect the same non-native species? 4) Do the botany surveys and ecology plots detect similar

numbers of non-native plants?

METHODS

Existing datasets

The botany survey database contains all vascular plant, bryophyte, and lichen species recorded by a professionally trained botanist in a specific area. These areas are usually tied to a specific project: proposed roads, trails, or timber sales, for example. Because project areas are usually easily accessible by vehicle or foot, the survey areas are often associated with roads or trails. Area surveyed ranges from 0.1–712 acres. Survey intensity ranges from complete surveys for small areas to intuitive controlled surveys for larger areas (Nelson 1985). Botany survey dates range from 1990 to 2005.

The ecology plot database contains all vascular plant, bryophyte, and lichen species recorded by a professionally trained plant ecologist in an ecology plot. To classify and characterize the vegetation types of the Forest (Henderson et al. 1992), ecologists established 3,097 plots across the Forest. An additional 1,169 ecology plots have also been established to document benchmarks of species composition and stand conditions, to monitor changes over time, to measure stand growth and productivity, to describe condi- tions and successional patterns of different plant associa- tions, and to calibrate and validate species habitat models. Ecology plots are deliberately placed to minimize the influ- ence from roads and trails. Plot sizes are typically 0.15– 0.20 acre, but range from 0.001 to 0.5 acres, depending on structure and extent of the homogeneous community. Ecology plot installation dates range from 1979 to 2005.

The noxious weed database contains all records of reported noxious weeds on the Forest. Reporters of noxious weeds include botanists, ecologists, county weed program specialists, knowledgeable Forest employees, and know- ledgeable members of the public.

Analysis

To understand the current status and distribution of non- native plants on the Forest, we compiled a list of all non- native vascular plants known to occur on the Forest, query- ing our botany survey, ecology plot, and noxious weed databases for all vascular plants. We classified the resulting list of species as native or non-native, based on the regional flora (Hitchcock et al. 1955–69; Hitchcock and Cronquist 1973), the PLANTS database (USDA Natural Resources Conservation Service 2006), recent work on Pacific Northwest Hieracium spp. (Wilson 2006) and professional opinion. Using the existing databases and GIS, we docu- mented the presence of each non-native species by ranger district and by county.

Species whose native or non-native status could not be readily determined were not included in this analysis (i.e., Poa pratensis). Because Washington State classifies

Phalaris arundinacea L. as a noxious weed (Washington

General Technical Report GTR-694

To compare detection rates of area-based and plot- based sampling schemes, we tallied the number of detec- tions of noxious weeds, other non-native plants, and all non-native plants recorded in the botany survey database and in the ecology plot database.

Results for surveys, plots, and weed sightings in Chelan and Kittitas Counties were not included in this analysis. Although the Mt. Baker-Snoqualmie National Forest manages some National Forest System lands in these counties, most are managed by the Okanogan and Wenatchee National Forests.

RESULTS

Species and Distribution

Our analysis indicates that 148 non-native plants have been reported to occur on the Forest (tables 1 and 2). Of these, 34 are noxious weeds (table 1), 25 are escaped garden orna- mentals not currently listed as weeds (table 2), and 17 do not appear in the regional flora (table 3, Hitchock and Cronquist 1973). Noxious weeds and other non-native plants occur in every county and ranger district on the Forest (table 4).

Of the reported noxious weeds, the Forest had one known site of a State Class A noxious weed (Heracleum

mantegazzianum Sommier & Levier), which was controlled

in 2001. In addition, 17 State Class B noxious weeds are known to occur on the Forest, as are 13 State Class C nox- ious weeds. At least 1,080 acres of the Forest are infested with noxious weeds; most of these are along highways, roads, trails, and railroad and powerline right of ways.

Buddleja davidii Franch., Polygonum cuspidatum Sieb. &

Zucc., Polygonum sachalinense F. Schmidt ex Maxim., and

Polygonum × bohemicum (J. Chrtek & Chrtková) Zika &

Jacobson are mostly known to occur in riparian areas. Of the 28 plant families represented, Asteraceae and Poaceae had the highest number of non-natives (fig. 2; table 4). In addition, more noxious weeds were members of the Asteraceae than any other plant family.

Nine noxious weeds are ubiquitous on the Forest, occurring on all four ranger districts and in all five counties (table 1): Cirsium arvense (L.) Scop., Cirsium vulgare

(Savi) Ten., Cytisus scoparius (L.) Link, Geranium rober-

tianum L., Hypericum perforatum L., Hypochaeris radicata

L., Leucanthemum vulgare Lam., Polygonum × bohemicum, and Senecio jacobaea L.

Detection

Neither a project area-specific approach (botany surveys) or a systematic, plot-based approach (ecology plots) detected every single noxious weed or non-native plant known to occur on the Forest (tables 4 and 5). The most frequently detected non-native species on the Forest for both sampling schemes was Mycelis muralis (L.) Dumort. (table 4). The most frequently detected noxious weed in the botany survey database was L. vulgare, while for the ecology plots it was

C. vulgare (table 4).

Botany surveys detected 25 different species of nox- ious weeds; ecology plot installation detected 13 different species (tables 4 and 5).