Invasive Species Overview of the North Woods

A Comphrehensive Guide to Inform the Stewardship and Management of the Uniersity of Rhode Island North Woods

Jessie Adley, Alexandra Beardwood, Karlo Berger, Tyler Correia, Ian O'Hara, Gabrielle Pezich, Dr. Laura Meyerson, Anna Sorgie, and Maggie Watson

NRS 445: Invasive Species Research, Management and Policy

University of Rhode Island

Setting the Stage

The North Woods of the University of Rhode Island’s Kingston campus is an approximately 307-acre tract of land, north of Flagg Road featuring forestland both deciduous and coniferous, wetlands, and headwater streams. The region is a site for experiential learning at the University of Rhode Island as it acts as an outdoor classroom and natural laboratory. The North Woods provides a valuable and highly accessible resource for experiential and project-based learning throughout the University's colleges, schools, and departments. As a mosaic of ecosystems, it welcomes student focus on local, regional, and global challenges of environmental sustainability.

Figure 1. The North Woods Boundary and Adjacent Features. This map highlights the boundaries of the University of Rhode Island's North Woods (307 acres) and its connection to the main campus to the south and the broader forested landscape to the north and east. Data from the Land Use Land Cover 2011 dataset. All data are obtained from RIGIS.

History of the Rhode Island's Forests

The University of Rhode Island sits on the traditional land of the Niantic and Narragansett peoples. Early records suggest that prior to European settlement in the early 1600’s, Rhode Island was more than 95% forested (RIDEM 1960). Throughout Rhode Island, Native American peoples actively managed upland forests using fire as often as twice a year to control the understory and maintain large, widely spaced trees (Butler and Warton 2002). In addition, forests were cleared to create open areas for agriculture and hunting. As a result, Rhode Island forests were a patchwork of different age classes that provided habitat for a wide variety of early successional and mature forest species. 

Early European settlers rapidly cut forests to utilize timber resources and to create extensive pasture-based agricultural lands. By the time of the first state forest survey in 1767 only 31% of Rhode Island was forested (Southern New England Forestry Association), and forest cover reached an all-time low of <25% by 1887 (Butler and Wharton 2002). With the discovery of the productive farmland soils throughout the upper Midwest, many early farms established in Rhode Island in the late 1700’s and early 1800’s were abandoned as agriculturalists headed west. By the early 1900’s, the Industrial Revolution was providing economic opportunities in urban areas,  leading to additional agricultural abandonment, and natural forest regeneration was occurring throughout Rhode Island and southern New England. 

A growing public recognition about the importance of forests and sustainable forest management led to the establishment of the Rhode Island Forest Commission in 1906, one year after the creation of the U.S. Forest Service (Southern New England Forestry Association). The Commission quickly recognized the plight of the forests across the state and highlighted the urgent need for protection and reestablishment of Rhode Island's forests:

It is a fact well known to most of you that the timber which once covered our hillsides, ameliorating our climate, beautifying the landscape, protecting the watersheds, and constituting one of the most valuable natural resources of the state, has now nearly all disappeared before the woodsman’s axe. It follows, therefore, that the protection and rapid growth of the succession of sprout and seedlings is a problem of interest and importance to the people. - Jesse B. Mowry, First Report of the RI Forest Commission (1907)

In 1930 Rhode Island established the George Washington Memorial Forest, as the first forest reserve in the state (Southern New England Forestry Association).  Changes in forest laws, forest fire suppression, forest conservation, and management practices also contributed to forest restoration, and by the mid-1930’s approximately 65% of Rhode Island was again forested, though the species composition and age structure were very different from the pre-European settlement forests . 

Since the 1960’s, however, the amount of forest land in Rhode Island has been slowly decreasing. Between 1990 and 2000, the population of Rhode Island grew by 4.5%, which increased demand for urban, suburban, and commercial land uses leading to forest conversion (Butler and Warton 2002).  This land development has resulted in extensive fragmentation and parcellation of the existing forestlands throughout the state, with very few large intact forests remaining on the landscape. 

Figure 2. Historical Context of the North Woods.  There are several sites of historical significance around the North Woods, including one historical cemetery within the Henry Eldred farm. Data from the National Register of Historic Places by the Rhode Island Historic Preservation & Heritage Commission and the Rhode Island Advisory Commission on Historical Cemeteries online cemetery database. All data obtained from RIGIS.

The North Woods contains remnant agriculture structures as well as drainage ditches that invite further archeological investigation. In addition, there is an historical cemetery located in the northwest corner within the Henry Eldred farm. The current tree age classes, evidence of past agriculture uses in the soil profiles, and presence of stonewalls indicate that the North Woods shared the history of forest clearing and agricultural abandonment that occurred through the state. The 1944 USGS Kingston quadrangle indicates several acres along the western portion of the North Woods, east of Plains Road, were not forested at that time and multiple houses with connecting roads were present.

University of Rhode Island History

Figure 3. The Oliver Watson Farm House, on the future site of the University of Rhode Island Kingston Campus

The University of Rhode Island began as the state’s Agriculture Experiment station, which was chartered in 1888. The Agriculture Experiment Station opened in 1890 on the 140-acre Oliver Watson Farm that was purchased for $5,000. The Oliver Watson Farmhouse, which has been restored and is listed as an historic landmark, remains on the Kingston campus to the south of the North Woods in the heart of the main campus.

In 1892 the school was renamed the Rhode Island College of Agriculture and Mechanic Arts, and in 1894 the Rhode Island College of Agriculture and Mechanic Arts replaced Brown University as Rhode Island’s Land Grant college. Land Grant Colleges are institutions designated by the state legislature to receive benefits of the Morrill Acts of 1972, 1990 and 1994. The original mission of Land Grant institutions as described in the first Morrill Act was to “teach agriculture, military tactics, and the mechanic arts.”Subsequent acts have expanded that mission in many ways including, with the 1962 McIntire-Stennis Act, to forestry. In 1951 an act of the Rhode Island General Assembly changed the name of Rhode Island State College to the University of Rhode Island. 

Figure 4. Kingston with Rhode Island College and the North Woods in 1944. USGS 7.5 Minute Quadrangle. Based on map symbology, large portions of what are now forested areas within the North Woods were not forested at the time and multiple houses and unpaved roads were present

The Habitats of the North Woods

Ecological Communities

The University campus exhibits many different ecological zones, characterized by topography, soils, and hydrology. These zones have characteristic species of vegetation and wildlife that are beneficial to the research and teaching initiatives on campus. Preserving these existing natural ecosystems and identifying the importance they serve in the greater context of the campus environment should be highlighted with interpretive features such as information trail systems. -Campus Master Plan (2000)

The North Woods contains a mosaic of natural and human-modified or cultural habitats, but it is dominated by forest. According to the Ecological Communities Classification from 2011, 252 acres, or 82% of the total land area, is covered by a combination of deciduous forest, forested wetlands, plantation, and mixed deciduous/coniferous forest. Human cultural communities, including cropland, urban/suburban built, and urban/recreational grasses cover 11% or 36 acres of the North Woods. These community classifications correspond to a parking lot, ground-mounted solar arrays, a recreational sports field, the North Woods Challenge Course, and a borrow pit. The remainder of the North Woods consists of ruderal grassland/shrubland and freshwater communities that typically border the human cultural communities and are concentrated along its western edge. 

Figure 5. Ecological Communities of the North Woods. Number of acres of different Systems, Classes and Communities based on the Ecological Communities Classification, which is a statewide, seamless digital dataset of the ecological communities for the State of Rhode Island, derived using automated and semi-automated methods and based on imagery captured in 2011. Data acquired from RIGIS.

Figure 6. Ecological Communities of the North Woods. The data from this layer consists of ecological communities for the state of Rhode Island, which were derived via automated and semi-automated methods and from imagery captured in 2011. Data used in the production of this dataset were provided by the State of Rhode Island and included 2011 land cover/land use. All data were obtained from RIGIS.

Forest Lands

There are few large and contiguous tracts of forest left in Rhode Island. The 250-acre forested portion of the North Woods exhibits a range of characteristics based on soil types and human disturbances. Most of the area is represented by two main forest communities, with Oak-Hickory forests dominating the dryer soils and Maple-Beech-Birch communities within the wetter soils. The Oak-hickory communities are dominated by northern red oak (Quercus rubra), black oak (Quercus velutina), white oak (Quercus alba),and scarlet oak (Quercus coccinea), as well as younger hickory species, including pignut (Carya glabra) and mockernut (Carya tomentosa) hickory. The Maple-Beech-Birch forest communities are dominated by red maple (Acer rubrum), sweet birch (Betula lenta), yellow birch (Betula alleghaniensis), and scattered American beech (Fagus grandifolia), green ash (Fraxinus pennsylvanica), swamp white oak (Quercus bicolor), and eastern white pine (Pinus strobus). Sassafras (Sassafras albidum), black gum (Nyssa sylvatica), and American chestnut (Castanea dentata) are also found within the understory, along with a relatively diverse community of shrubs. The forest edges and areas of recent human disturbance are represented by a range of pioneering species and species that respond to disturbance, including grey birch (Betula populifolia), paper birch (Betula papyrifera), black cherry (Prunus serotina), black locust (Robinia pseudoacacia), eastern cottonwood (Populus deltoides), Norway maple (Acer platanoides), and eastern red cedar (Juniperus virginiana), among others, including additional invasive species. Black walnut (Juglans nigra) is also found along field edges and within a small grove adjacent to the remnants of a farmhouse. 

Wetlands

According to data from the National Wetlands Inventory, there are 16.1 acres of Freshwater Forested/Shrub Wetland within the North Woods forest lands, much of which is adjacent to a headwater stream that flows south to north through the center of the property. These forested wetlands are primarily red maple (Acer rubrum) swamps with a variety of understory shrubs and herbaceous plants including cinnamon fern (Osmundastrum cinnamomeum), highbush blueberry (Vaccinium corymbosum), and winterberry (Ilex verticillata). In addition to the mapped wetlands, there are several small vernal pools that are frequent outdoor classroom sites in the spring when they are full of breeding frogs, toads and salamanders. Many species take advantage of these ephemeral wetlands to lay eggs in pools of water that disappear in summer and therefore cannot support populations of fish that would otherwise eat the eggs. There are several known vernal pools both within the forest and adjacent to the solar arrays.

Figure 7. Surface Hydrology including wetlands, streams and ponds. Freshwater river and stream features determined from 1:5000 scale aerial photography. Lakes and Ponds identified and delineated from 1997 1:5000 orthophotography. The extent, approximate location, and type of wetlands and deep-water habitats in Rhode Island are based on the National Wetlands Inventory. All data were obtained from RIGIS.

Flora and Fauna of the North Woods

As a Land Grant institution, the University of Rhode Island is committed to the sustainable management of its natural spaces. Biodiversity plays a critical role in a natural area’s ecosystem functions and, in the context of a University resource, provides valuable research and educational opportunities (Hooper et al. 2005). Over 200 species of flora and fauna have been identified in the North Woods, based on observations from University faculty, students, NGO partners, and project team members. Although seemingly comprehensive, it is likely that the North Woods is used by a variety of wildlife species throughout the year that are not listed in this assessment.

Species of Conservation Concern

There is an urgent lack of recent, comprehensive data about rare and endangered species within the North Woods. According to the Rhode Island Natural Heritage Program, which is a partnership between Rhode Island Natural History Survey, RIDEM, The Nature Conservancy, and the University’s Environmental Data Center, there are no current natural heritage records (rare and endangered species) for the North Woods or the Kingston Campus. Within the broader forested landscape, there are three records of species north of Stony Fort Road from the 1980s with habitat support areas directly adjacent to the North Woods: few-flowered nutrush (Scleria pauciflora var. caroliniana) at the edge of the field north of Stony Fort; northern white colic-root (Aletris farinosa) east of the railroad track; and bloodroot (Sanguinaria canadensis) not far to the west of Slocum Road halfway between Stony Fort and the business Yawgoo Bakes. Additionally, there is a record from 1988 of a marbled salamander (Ambystoma opacum) in the swamp beside Stony Fort Road. Observations greater than thirty years old are removed from the RI Heritage Database. Unless these observations are reconfirmed soon, they will be removed from the Rhode Island Heritage Database. The lack of recent data about the distribution of species of conservation concern in the North Woods provides additional incentive for a renewed interest in natural history inventory and research in the North Woods. These and other species may still be present in the North Woods, but state-wide funding and support are currently lacking to observe them. This lack of data presents the University with opportunities for professional research by faculty and students or public outreach through community science such as a “BioBlitz,” a community-based science effort designed to record as many species within a designated location and time period as possible. Overall, the associated heritage records provide a brief overview of the history of rare and endangered species in the North Woods, but there is significant room for improvement. Although no rare species have been detected in the North Woods over the last thirty years, a few species that have been observed are recognized as Species of Greatest Conservation Need in the State of Rhode Island (Terwilliger Consulting Inc. 2015), including bobcat (Lynx rufus), pileated woodpecker (Dryocopus pileatus), red-spotted newt (Notophthalmus viridescens), ribbon snake (Thamnophis saurita), spotted salamander (Ambystoma maculatum), and wood frog (Lithobates sylvaticus). 

Figure 8. Location of Documented Sightings of Rare or Endangered Species Near the North Woods. Stars indicate approximate siting locations and the red polygons are estimated habitat support areas for those species. Data from the Rhode Island Natural Heritage Program provided by the Rhode Island Natural History Survey.

Invasive Species

According to Daniel Simberloff in his book, Invasive Species: What Everyone Needs to Know, an invasive species is an:

"Introduced species that has spread well beyond its arrival point and that perpetuates itself without human assistance."

Invasive species are responsible for many negative impacts on ecosystems, including significant biodiversity declines, loss of valuable public recreational land, and high costs associated with management and control (Born et al. 2005; Jackson 2015). There are a few ecology classes at the University that focus portions of their curriculum on the mitigation, management, and post-restoration of invasive species and their impacts, using the North Woods as a study area. Based on a comparison of the North Woods plant species list to the Invasive Plant Atlas of New England (Mehrhoff et al. 2003) and the Rhode Island Invasive Plant List (RIISC 2020), there are approximately twenty-one known invasive plant species in the North Woods, including Japanese barberry (Berberis thunbergii), which are indicated in bold in the above excel spreadsheet of Flora and Fauna in the North Woods. To best protect native biodiversity in this area, future actions should include further documenting these species (e.g., inventory, growth trends, location(s) within the North Woods) and potentially their removal/mitigation.

In accordance with the goals of the North Woods Stewardship project, a university-wide initiative to develop a plan for the responsible stewardship and management of the North Woods, our group sought to gather data on invasive species within the North Woods. Additionally, we conducted an analysis of the data collected to identify any trends in the data or locations of concern. It is our intention that the data collected and our interpretation of the data and formation of a standing hypothesis will inform best-management practices and aid the project in its continuous efforts to maintain the biodiversity in this area.

Methods

Six total transects were run from North to South over 1000 meters and a known longitude was followed for each. An initial 10 meters in from the path was measured for the first plot of each transect, with each succeeding plot being measured 50 meters in from the last. A five meter radius was measured out at each arriving point for each circular plot where invasive species were identified and percent cover was recorded along with latitude and longitude. Values for percent cover did not necessarily need to add up to 100%. Applications for plant identification were used such as PictureThis® and Seek by iNaturalist. Data analysis began with the conversion of percent cover scores to Braun Blanquet (BB) cover class scores (Braun-Blanquet 1932). By assigning a midpoint value to a range of percent cover values the variation in estimates between different teams of researchers is minimized (Figure 9.). Since one team recorded cover in terms of stem count; a conversion factor was determined based on that team's field observations and species recorded.

Figure 9. Braun Blanquet cover class scores

Levels of disturbance were quantified for each plot by referencing historical imagery and ranking the disturbance per plot based on a simple weighted suitability analysis. The analysis assigned the potential disturbances for a plot a weight based on the intensity of the disturbance and the time it occurred (Figure 10.). Disturbances that occurred after 1950 were given additional weight due to the increased global trade and consumer demand following WWII. (Simberloff 2010.)

Figure 10. Disturbance ranking per plot.

Each plot was tracked through time using RI aerial imagery from the years 1932, 1951, 1962, 1972, 1981, 1988, 1997, 2008, 2011, 2018, and 2014 (URI Environmental Data Center 2021). Each plot was scored based on whether or not the disturbance in question had occurred within 50m of the plot at least one time (Figure 10.). These weighted scores were then summed for each plot in Excel to create an overall disturbance rank for that plot. Next, the disturbance rank was graphed against the average invasive cover score for each plot using Rstudio. A linear regression was used to investigate a potential relationship between these two variables. Part two of the analysis aimed to gather general trends in invasive species distribution and abundance. The total instances of invasive species per each transect was graphed against the transect number in Rstudio (Figure 14.).

Figure 11. Kingston, RI: North Woods Aerial Photography: 1988

Remember that each species can only occur once in each plot (max. 100% cover) but may be seen multiple times throughout the transect. Next, invasive species BB cover scores were summed for each plot and a heatmap was created using the coordinates for each plot. 

Figure 12. Kingston, RI: North Woods Aerial Photography: 1997

Data

Hypothesis

Our hypothesis is that the presence of invasive species in the North Woods is a result of anthropogenic interference and is directly correlated to the degree of disturbance. Species are often introduced to a region as a result of human interaction; as a result, newly-disturbed areas are highly susceptible to invasion. Our hypothesis is supported by the data collected on invasive species within the North Woods, which shows a positive relationship between disturbance and invasive species density. Overall, anthropogenic development of the Western region of the North Woods has made that plot of land more susceptible to biological invasions and resulted in an intense takeover by a number of invasive herbaceous (and some woody) species.

Results

A total of 14 non-native invasive species were collectively identified in the North Woods area along the six run transects. Our findings confirm our Human Disturbance Hypothesis; the scatter plot in (Figure 13.). Shows a positive correlation between disturbance level and average invasive species percent cover per plot.

Figure 13. Scatter plot comparing the relationship between disturbance level and average invasive species percent cover (BB Scores). The linear regression shows a positive relationship between the two variables. R^2 = .301

The regression analysis confirmed this positive relationship and R^2 = .301. Transects 0-2 coincide with the western side of the North Woods where most if not all of the recent disturbance was observed; as a result its no surprise these transects received the highest total disturbance scores of 90, 35, and 41 respectively. Transect 0, plot 1 scored the highest in disturbance ranking with a score of 9; historical imagery confirms all disturbance categories listed in (Figure 10.) except for structures (pre/post1950). The trend of increased invasives in more highly disturbed areas can also be seen in (Figure 14.) which compares the distribution of invasives in North Woods to the number of recorded instances on invasive species per transect; transects 0-2 dominated, with 63, 25, and 16 instances of invasives respectively .

Figure 14. Bar graph showing the distribution of invasives in North Woods by number of recorded instances per transect. Remember that each species can only occur once in each plot (max. 100% cover) but may be seen multiple times throughout the transect.

Heat-Density Map

Figure 15. ArcGIS heat/density map from sum of BB cover scores for each plot. Each point represents a plot within a transect. Note the area of disturbance and compare it to Fig. 3 1981 historical aerial imagery.

Invasive Species of the North Woods

The species identified are as followed: Amur Honeysuckle (Lonicera maackii), Arroyo Williow (Salix lasiolepis), Asian Bittersweet (Celastrus orbiculatus), Autumn Olive (Elaeagnus umbellata), Black Locust (Robinia psuedoacacia), Common Privet (Ligustrum vulgare), Desert False Indigo (Amorpha fruticosa), False Glossy Buckthorn (Frangula alnus), Japanese Knotweed (Reynoutria japonica), Lady's Thumb (Persicaria maculosa), Morrow's Honeysuckle (Lonicera morrowii), Mugwort (Artemesia vulgaris), Mullein (Verbascum thapsus), Multiflora Rose (Rosa multiflora), Princess Pine (Lycopodium obscurum), Purple Crown Vetch (Securigeravaria), Tatarian Honeysuckle (Lonicera tatarica), and Woodvamp (Decumaria barbara).

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Invasive Alien Species

At the University of Rhode Island's North Woods

Amur Honeysuckle (Lonicera maackii)

Amur honeysuckle was imported as ornamental into New York in 1898 through the New York Botanical Garden. It has been widely planted for wildlife cover and soil erosion control but long ago escaped from plantings and began reproducing on its own and spreading into natural areas. It is adaptable to a range of conditions from sun to deep shade and wet to dry. It occurs in disturbed habitats including forest edges, forest interiors, floodplains, old fields, pastures, and roadsides. Disturbance increases the likelihood of invasion. Amur honeysuckle grows especially well on calcareous soils.

Ecological Threat

Amur honeysuckle impedes reforestation of cut or disturbed areas and prevents reestablishment of native plants. It leafs out earlier than most natives and form dense thickets too shady for most native species. Additionally, researchers in the Midwest found increased nest predation of robins using Amur honeysuckle as a result of plant structure which facilitates access to nests by predators such as snakes. While the carbohydrate-rich fruits of exotic honeysuckles provide some nutrition for birds and rodents in winter, they do not compare to the lipid-rich fruits of native species that provide greater energy to sustain migrating birds.

How to Identify

1. Plant is upright, deciduous shrub up to 15-20 ft. high; pith of mature stems is hollow and white or tan.

2. Leaves are opposite, ovate with a tapered tip, lightly pubescent, and up to 3½ in. long.

3. Flowers paired, tubular, white to pinkish, fading to yellow, less than 1 in. long, borne from leaf axils, five petals, upper four fused; fruits are red to orange-red berries produced in late summer and persist through the winter.

Arroyo Williow (Salix lasiolepis)

Arroyo willow is native throughout California and elsewhere in the western United States, below 7000 feet (2200 m). It is generally found in riparian areas within a variety of vegetation associations, including forests, chaparral and grasslands.

Ecological Threat

Invasive willow species use river corridors as pathways to spread and impact ecosystems by altering the water-table regime, modifying surface hydraulic and geomorphological processes, displacing native species, reducing biodiversity, and increasing erosion. Such impacts have direct consequences to the economy and human life. Furthermore, human activities as a whole have been increasing pressure on riparian zones, affecting social benefits provided by these ecosystems such as flood mitigation, water quality, erosion control, and groundwater recharge.

How to Identify

1. Arroyo willow is a large, sprawling, multi-trunked shrub or small tree, usually less than 30 feet (10 m) high. It is winter deciduous, but often retains some leaves throughout the year. Arroyo willows are riparian, needing a consistent source of fresh water. They often form dense groves where there is a shallow water table or seep.

2. Leaves are elongate, usually less than 6 inches (15 cm) long and 1 inch (2.5 cm) wide; mature leaves are often oblanceolate. Leaf tip is narrowly to broadly acute. Leaf margins may be smooth or shallowly, irregularly serrate or scalloped. Leaves are shiny green above, made pale below by waxy particles and short white hairs.

3. Flowers are dense, cylindrical clusters of tiny flowers, catkins, appear February – May before new leaves appear. Petals and sepals   are absent. Male and female flowers occur on different plants. At the base of each male or female flower is a small, dark flower bract that is covered with long, shaggy, whitish hairs. Also, each flower has a small gland that secret nectar to attract pollinating insects. Male catkins are 1-3 inches long (3-7 cm) colored yellow or greenish yellow by the abundant pollen. Each flower consists of two stamens that are united at their bases. Female catkins are slightly smaller and green in color. Female flowers consist of a green, bowling-pin-shaped pistil and a small stalk. The ovary + style tapers to two, small, two-lobed stigmas.

4. Seeds are tiny (<1/32 inch or 1 mm) and embedded in a woolly mass of tangled hairs that lifts and carries the seeds away on the air currents.

Asian Bittersweet (Celastrus orbiculatus)

Asian bittersweet was introduced into the United States in the 1860s as an ornamental plant and it is still widely sold for landscaping despite its invasive qualities. It is often associated with old home sites, from which it has escaped into surrounding natural areas. It occurs in forest edges, open woodlands, fields, hedgerows, coastal areas, salt marshes and disturbed lands. While often found in more open, sunny sites, its tolerance of shade allows it to invade forested areas.

Ecological Threat

Asian Bittersweet is a vigorous growing plant that threatens native vegetation from the ground to the canopy level. Thick masses of vines sprawl over shrubs, small trees and other plants, producing dense shade that weakens and kills them. Shrubs and trees can be killed by girdling and by uprooting as a result of excessive weight of the vines. In the Northeast, Bittersweet appears to be displacing the native American bittersweet (Celastrus scandens) through competition and hybridization.

How to Identify

1. Plant is upright, deciduous shrub up to 15-20 ft. high; pith of mature stems is hollow and white or tan.

2. Leaves are opposite, ovate with a tapered tip, lightly pubescent, and up to 3½ in. long.

3. Flowers paired, tubular, white to pinkish, fading to yellow, less than 1 in. long, borne from leaf axils, five petals, upper 4 fused; fruits are red to orange-red berries produced in late summer and persist through the winter.

Autumn Olive (Elaeagnus umbellata)

Autumn olive was introduced into the United States in 1830 and widely planted as an ornamental, for wildlife habitat, as windbreaks and to restore deforested and degraded lands. Autumn olive is found from Maine to Virginia and west to Wisconsin in grasslands, fields, open woodlands and other disturbed areas. It is drought tolerant and thrives in a variety of soil and moisture conditions. Because autumn olive is capable of fixing nitrogen in its roots, it can grow on bare mineral substrates.

Ecological Threat

Autumn Olive invades old fields, woodland edges, and other disturbed areas. It can form a dense shrub layer which displaces native species and closes open areas. Autumn Olive is native to China and Japan and was introduced into North America in 1830. Since then, it has been widely planted for wildlife habitat, mine reclamation, and shelterbelts. It is a non-leguminous nitrogen fixer.

How to Identify

1. Autumn Olive is a deciduous shrub from 3-20 ft. (0.9-6.1 m) in height with thorny branches. It is easily recognized by the silvery, dotted underside of the leaves.

2. Leaves are alternate, 2-3 in. (5-8 cm) long and 1 in. (2.5 cm) wide. The margins are entire and undulate. Leaves are bright green to gray green above and silver scaly beneath with short petiole.

3. Small, yellowish tubular flowers are abundant and occur in clusters of 5 to 10 near the stems from February to June.

4. Fruits are round, red, juicy drupes which are finely dotted with silvery to silvery-brown scales. Each drupe contains one seed. Fruits ripen from August to November.

Black Locust (Robinia psuedoacacia)

Southeastern United States; on the lower slopes of the Appalachian Mountains, with separate outliers north along the slopes and forest edges of southern Illinois, Indiana, and Missouri. Black locust is an early successional plant, preferring full sun, well drained soils and little competition. It is commonly found in disturbed areas such as old fields, degraded woods, and roadsides. Due to its rapid growth, black locust has been promoted by state and federal agencies and nurseries, and is sometimes planted in or near prairies, oak savannas and native woodland edges. 

Ecological Threat

Black locust poses a serious threat to native vegetation in dry and sand prairies, oak savannas and upland forest edges, outside of its historic North American range. Native North American prairie and savanna ecosystems have been greatly reduced in size and are now represented by endangered ecosystem fragments. Once introduced to an area, black locust expands readily into areas where their shade reduces competition from other (sun-loving) plants. Dense clones of locust create shaded islands with little ground vegetation. Lack of ground fuel limits the use of fire in natural disturbance regimes. The large, fragrant blossoms of black locust compete with native plants for pollinating bees.

How to Identify

1. Black locust is a fast growing tree that can reach 40 to 100 feet in height at maturity. While the bark of young saplings is smooth and green, mature trees can be distinguished by bark that is dark brown and deeply furrowed, with flattopped ridges.

2. Seedlings and sprouts grow rapidly and are easily identified by long paired thorns.

3. Leaves of black locust alternate along stems and are composed of seven to twenty one smaller leaf segments called leaflets. Leaflets are oval to rounded in outline, dark green above and pale beneath.

4. Fragrant white flowers appear in drooping clusters in May and June and have a yellow blotch on the uppermost petal. Fruit pods are smooth, 2 to 4 inches long, and contain 4 to 8 seeds.

Common Privet (Ligustrum vulgare)

There are no species of Ligustrum native to the U.S. Privets have been introduced to the U.S. since the 1800s and some species even earlier. They are commonly used as hedges in yards, gardens and other landscapes from which they have escaped and are now well established in the wild. All four privet species featured here have been reported to be invasive in the mid-Atlantic region; some are recognized as invasive elsewhere in the eastern U.S. and nationwide. They thrive in floodplains, fields, disturbed forests and forest edges.

Ecological Threat

Privets form dense thickets that shade out and take the place of native shrubs and herbaceous plants. The shady thickets make conditions unsuitable for native seedlings. Phenolic compounds in the leaves protect plants from leaf-feeding insects which include native herbivorous species.

How to Identify

1. Privets are deciduous or semi-evergreen shrubs that grow from 8-20 ft. tall; trunks with multiple stems with long leafy branches; the presence or absence of hairs and type of hairs on stems is helpful in distinguishing species.

2. Leaves are opposite, simple, entire, short-stalked, ranging in length from 1-3 in. and varying in shape from oval, elliptic to oblong.

3. Flowers are small, white and tubular with four petals and occur in clusters at branch tips; fragrant; late spring to early summer (May to July); length of corolla tube length ranges from 1/10 in. (Chinese) to ¼ in. (border); anthers exceed the corolla lobes (Chinese and California); fruit is small black to blue-black oval to spherical drupe (i.e., a fleshy fruit with 1-several stony seeds inside), mature late summer to fall.

Desert False Indigo (Amorpha fruticosa)

Amorpha fruticosa is a fast-growing, deciduous shrub that grows in wetlands and disturbed habitats. It is native to North America but has spread across Asia and Europe, likely through its use as an ornamental plant. It is now generally accepted to be among the most invasive alien species in Europe. It has a high reproductive capacity, forms dense thickets and outcompetes native flora, changing successional patterns and reducing biodiversity.

Ecological Threat

This invasive plant is native to southern and eastern states in America. It has an extensive root system and spread rapidly, especially along stream and river corridors in the Northwest. It displaces riparian species and there is little information about how to control it. Cutting the plants may cause re-sprouting, but persistent cutting to get rid of the seeds can help control the overall spread.

How to Identify

1. Desert False Indigo is a deciduous shrub that typically grows to 4-12' (less frequently to 20') tall with a spread often in excess of its height. It is native to moist open woodland areas, floodplains, stream banks and swamp margins from central to eastern Canada south throughout much of the U. S. into northern Mexico. It features compound, odd-pinnate leaves (each to 12" long).

2. Each leaf contains 11 to 35 spiny-tipped, oval to elliptic, dull gray-green leaflets (to 2" long) with glandular dots and toothless margins. Tubular scented flowers (each to 3/8" long) bloom in May-June in dense, spike-shaped clusters (racemes) to 8" long.

3. Each flower has a single-petaled purple corolla and 10 protruding stamens with showy orange-yellow anthers. Flowers are followed by fruits in small, resinous-dotted, 1-2 seeded pods (to 1/2" long) which mature in July and August.

False Glossy Buckthorn (Frangula alnus)

Glossy False Buckthorn has shiny leaves but no thorns, despite its name. It is closely related to Common buckthorn (Rhamnus cathartica), but has alternate leaves. This shrub arrived in the United States from Europe before 1800. By 1950 it was recognized as a potentially invasive species. Birds eat its red fruits and disperse its seeds. It is more shade-tolerant than many invasives, and thrives in forest understories.

Ecological Threat

False Glossy Buckthorn invades moist woodlands and disturbed areas throughout the Northeast and Midwest. Its rapid growth and prolific seed production make this plant an aggressive invader that can form dense thickets which shade and displace native understory plants, shrubs, and tree seedlings. This plant is native to Europe and was first introduced into the United States in the mid 1800s as an ornamental.

How to Identify

1. Frangula alnus is a large shrub or small tree that can grow to heights of 30 ft. (9.1 m). Its bark is gray to brown with white lenticels.

2. The dark green leaves are shiny, alternate (sometime opposite) and simple with prominent venation.

3. The flowers are inconspicuous, pale greenish-yellow to yellow in color and occur in clusters in the leaf axis. Flowering occurs from May through September.

4. The fleshy fruit ripens from red to a dark purple or black color. You can see ripe fruit beginning about July through September.

Japanese Knotweed (Reynoutria japonica)

Japanese knotweed was probably introduced into the United States in the late 1800s. First used as an ornamental plant, it has also been planted for erosion control and landscape screening. It is designated a noxious weed in the state of Washington. Japanese knotweed occurs across the U.S. and has been reported to be invasive in natural areas throughout the northeast into Georgia and west to Missouri, with additional infestations in Oregon and Washington. It can tolerate a wide variety of challenging conditions, including deep shade, high salinity, high heat, and drought. Knotweed is commonly found near water sources, such as along streams and rivers, and in a variety of low-lying areas like ditches, waste places, utility rights-of-way and around old home sit

Ecological Threat

It spreads quickly to form dense thickets and pushes out native plant species. Knotweed poses a significant threat to riparian areas where it can survive flooding events and rapidly colonize scoured shores and islands. Once established, populations are extremely persistent.

How to Identify

1. Plants are upright, shrubby, herbaceous perennial 4-10 ft. tall with stems that are smooth, stout and hollow; stem leaf junctures are swollen and surrounded by a membranous sheath called an “ocrea” which is typical of the family.

2. Leaves are variable; about 6 in. long by 3-4 in. wide, broadly oval to somewhat triangular with a truncated base and a tapered tip.

3. Flowers are tiny greenish to white colored and occur in attractive sprays in summer; fruits are winged on three sides; seeds are triangular, dark brown, shiny and about 1/10 in. long.

Lady's Thumb (Persicaria maculosa)

The non-native Lady's Thumb is a common plant that has been observed in most counties of Illinois; it probably occurs in every county of the state. Habitats include marshy areas, edges of streams and drainage canals, mudflats, roadside ditches, moist weedy meadows, vacant lots, fallow fields and edges of cultivated fields, edges of yards and gardens, moist areas along railroads, and waste areas. This species prefers disturbed areas, but it can invade higher quality wetlands to a limited extent. Lady's Thumb is native to Europe.

Ecological Threat

Lady's Thumb can be very competitive with crop plants, particularly in moist areas, and has an ability to spread rapidly once introduced to an area and displace native species.

How to Identify

1. Lady's Thumb is an annual forb that can reach 6-30 in. (15.2-76.2 cm) in height and can be either erect or sprawling.

2. Leaves are elongate, narrow and pointed at the base and tip. Stems have swollen nodes with papery sheaths (ocrea). Ocrea have long, hair-like bristles on the mar

3. Flowering occurs from June to October, when pink flowers develop at the apex of the stems. Flowers are 0.13 in. (0.3 cm) long and occur in groups.

4. Seeds are smooth, dark colored, dry, and 3 angled.

Morrow's Honeysuckle (Lonicera morrowii)

Morrow’s honeysuckle was imported in the 1800s for use as an ornamental, for wildlife food and cover as well as for soil erosion control. Widely planted through the 20th century it is recognized as highly invasive species impacting natural areas as well as managed parks, gardens and other lands. Morrow’s honeysuckle is fairly common in the mid-Atlantic region, often co-occurring with Amur honeysuckle. It is found from Wisconsin to Maine and Missouri to North Carolina. It is shade tolerant but will flower and fruit more in full sun. Morrow’s honeysuckle invades forest edges and interiors, floodplains, pastures, old fields, roadsides and other disturbed areas.

Ecological Threat

Morrow’s Honeysuckle forms dense thickets and outcompetes and displaces native shrubs, trees and herbaceous plants. Its dense growth can impede reforestation efforts. It invades open woodlands, old fields and other disturbed sites and can spread rapidly with help from birds and mammals which disperse its seeds. Like Amur honeysuckle, Morrow’s honeysuckle likely also encourages increased nest predation due to its branching structure. While the fruits of exotic honeysuckles provide some nutrition for birds and mice in winter, their carbohydrate-rich quality is no match for the lipid-rich fruits of many native species that sustain migrating birds.

How to Identify

1. Plants are multi-stemmed, upright, deciduous shrub that grows to 7 ft. tall; pith of mature stems is hollow and white or tan in contrast to solid white pith of native shrub honeysuckle species.

2. Leaves are opposite, 1-2 in. long, elliptic to oblong, on short stalks, sparsely hairy above, permanently hairy underneath.

3. Flowers are paired, borne from leaf axils, white, tubular (lower half) with 5 separate (unfused) petal lobes, spring (late April-early May); fruits paired, red to orange, many-seeded berries mature in July and persist through the winter.

Mugwort (Artemesia vulgaris)

Mugwort is native to Europe and eastern Asia, where it has historically been used as a medicinal herb. Seed may have been first introduced to North America as early as the 16th century by Jesuit missionaries in Canada. It was also introduced throughout the continent as a contaminant in ship ballast and nursery stock.

Ecological Threat

Mugwort spreads aggressively via an extensive rhizome system and can form large stands that displace native species. It is considered a problematic weed of nurseries, orchards, sports fields, forest edges, and roadsides. Mugwort is wind-pollinated and therefore produces a lot of pollen that can be distributed over long distances, causing severe symptoms in allergic humans. Mugwort is difficult to eradicate because its rootstock overwinters in the ground and it has a large seed bank.

How to Identify

1. A perennial herb that can grow from 24-63 in (60-160 cm) high. The stems are branched and purplish-brown. The ascending stems are covered with short hairs. A. vulgaris is rhizomatous, and often produces vegetative colonies of plants. It is native to northeastern Asia and extreme northwestern North America (Alaska).

2. The simple lobed leaves are papery, pubescent, and dark green on the upper surface. Leaves are alternate. The leaves near the base are elliptic and oblong, lobed deeply almost to the midrib. The leaves midstem are elliptic to ovate, 1.2-4 in (3-10 cm) long by 0.6-2.4 in (1.5-6 cm) wide and lobed pinnately or bipinnately. Leaf margins may be serrate.

3. The flower head has disk flowers only, and lacks the strap-shaped flowers. At the bud stage flowers are whitish green and become dull yellowish green to purplish green with maturity.

4. The fruits develop and mature from August to October and are obovate or ovate achenes.

Mullein (Verbascum thapsus)

Common mullein was first introduced into the U.S. in the mid-1700's, where it was used as a piscicide, or fish poison, in Virginia. It quickly spread throughout the U.S. and is well established throughout the eastern states. Records show that it was first described in Michigan in 1839 and on the Pacific coast in 1876, probably due to multiple introductions as a medicinal herb. 

Ecological Threat

Common mullein threatens natural meadows and forest openings, where it adapts easily to a wide variety of site conditions. Once established, it grows more vigorously than many native herbs and shrubs, and its growth can overtake a site in fairly short order. Common mullein is a prolific seeder and its seeds last a very long time in the soil. An established population of common mullein can be extremely difficult to eradicate. 

How to Identify

1. Common mullein, also known as wooly mullein, is an erect herb. First year mullein plants are low-growing rosettes of bluish gray-green, feltlike leaves that range from 4-12 inches in length and 1-5 inches in width. Mature flowering plants are produced the second year, and grow to 5 to 10 feet in height, including the conspicuous flowering stalk.

2. The five-petaled yellow flowers are arranged in a leafy spike and bloom a few at a time from June-August.

3. Leaves alternate along the flowering stalks and are much larger toward the base of the plant. The tiny seeds are pitted and rough with wavy ridges and deep grooves and can germinate after lying dormant in the soil for several decades.  

Multiflora Rose (Rosa multiflora)

Multiflora rose was introduced to the eastern United States in 1866 as rootstock for ornamental roses. Beginning in the 1930s, the U.S. Soil Conservation Service promoted it for use in erosion control and as “living fences” to confine livestock. State conservation departments recommended multiflora rose as cover for wildlife. More recently, it has been planted in highway median strips to serve as crash barriers and reduce automobile headlight glare. Its tenacious growth habit was eventually recognized as a problem on pastures and unplowed lands, where it disrupted cattle grazing, and, more recently, as a pest of natural ecosystems. It is designated a noxious weed in several states, including Iowa, Ohio, New Jersey, Pennsylvania and West Virginia.

Ecological Threat

Multiflora Rose grows aggressively and produces large numbers of fruits that are eaten and dispersed by a variety of birds. Dense thickets of multiflora rose exclude most native shrubs and herbs from establishing and may be detrimental to nesting of native birds.

How to Identify

1. Rosa multiflora is a multistemmed, thorny, perennial shrub that grows up to 15 ft. (4.6 m) tall. The stems are green to red arching canes which are round in cross section and have stiff, curved thorns.

2. Leaves are pinnately compound with 7-9 leaflets. Leaflets are oblong, 1-1.5 in. (2.5-3.8 cm) long and have serrated edges. The fringed petioles of Rosa multiflora usually distinguish it from most other rose species.

3. Small, white to pinkish, 5-petaled flowers occur abundantly in clusters on the plant in the spring.

4. Fruit are small, red rose hips that remain on the plant throughout the winter. Birds and other wildlife eat the fruit and disperse the seeds.

Princess Pine (Lycopodium obscurum)

Lycopodium obscurum, commonly called rare clubmoss, ground pine, or princess pine, is a North American species of clubmoss in the family Lycopodiaceae. It is native to the eastern United States and southeastern Canada from Georgia to Minnesota to Nova Scotia. It grows in the understory of temperate coniferous and deciduous forests, where it is involved in seral secondary succession, growing in clonal colonies some years after disturbance has occurred. It has also been found in Japan, Taiwan, Korea, Russian Far East, and northeastern China.

Ecological Threat

As with all invasive species its over-abundance can threaten the biodiversity of a region.

How to Identify

 1. Perennial from extensively rooting, deep creeping rhizomes; stems erect, 7 - 30 cm tall, unbranched towards base, densely branched above, bushy, tree-like.

2. Many, dense, in 6 (sometimes to 8) vertical rows, sharp pointed, linear-lance-shaped.

3. Spore clusters grow in axils of greenish to yellowish brown, pointed, broadly egg-shaped bracts densely clustered in single, stalkless cones, 1 - 3 cm long, at stem tips.

Purple Crown Vetch (Securigera varia)

Purple Crown Vetch is a nonnative species found throughout the contiguous United States and southern Canada. Purple Crown Vetch also occurs in Hawaii but does not occur in Alaska. Most reports indicate that Purple Crown Vetch is native to Eurasia, and it may also be native to northern Africa. Although Purple Crown Vetch is widely distributed in North America, it is most common in areas near sites where it was planted. In the northern and central parts of the United States, Purple Crown Vetch is most common and can be invasive

Ecological Threat

Securigera varia reproduces and spreads rapidly by rhizomes as well as seeds. It forms dense thickets in open, disturbed areas such as fields and roadsides. Once established it is difficult to remove. Securigera varia is native to Europe, Asia and Africa. It was first introduced into North America around the 1950s and has been widely planted for erosion control.

How to Identify

1. Securigera varia is a low-growing, herbaceous vine that usually forms thickets up to 3 ft. (0.9 m) in height.

2. The leaves are dark green pinnately compound with 9 to 25 pairs of leaflets and a terminal leaflet. Leaflets are 0.75 in. (1.9 cm) long.

3. Flowering occurs in the summer. The pea-like, fragrant flowers are white to pink to purple and resemble a large clover flower because they are found in long-stalked clusters.

4. Seed pods are segmented, pointed, borne in crown-like clusters. The straw colored seeds are less than 0.3 in. (0.9 cm) long, round, flat, and winged.

Tatarian Honeysuckle (Lonicera tatarica)

This plant is a native of eastern Asia and was first introduced into North America as an ornamental in 1752.

Ecological Threat

Lonicera tatarica readily invades open woodlands, old fields, and other disturbed sites. It can spread rapidly due to birds and mammals dispersing the seeds and can form an extremely dense understory thicket which can restrict native plant growth and tree seedling establishment.

How to Identify

1. Lonicera tatarica is a multistemmed, upright, woody, deciduous shrub that grows up to 10 ft. (3 m) tall. The bark is light gray and can often peel in vertical strips.

2. The leaves are opposite, ovate, 1.5-2.5 in. (3.8-6.4 cm) long and blue-green. Often, it is one of the first shrubs to leaf out in the spring.

3. Flowers develop in pairs in the axils of the leaves in May to June. Flowers are deeply 5-lobed, tubular, usually pink to red and rarely white.

4. The abundant paired berries are 0.25 in. (0.6 cm) in diameter, ripen to an orange to red color and often persist throughout winter.

Woodvamp (Decumaria barbara)

Decumaria barbara, commonly called climbing hydrangea or woodvamp, is a species plant in the Hydrangea family. It is native to southeastern United States, where it is widespread. Its typical natural habitat is wet bottomland forest, although it is also found in rich mesic forests in the Appalachian Mountains.

Ecological Threat

As with all invasive species its over-abundance can threaten the biodiversity of a region.

How to Identify

1. Woody semi-evergreen vine

2. Domed clusters of creamy white fragrant flowers are borne in late spring to early summer 1-2 feet from the climbing surface.

3. Dark green, glossy, elliptical semi-evergreen leaves turn buttery yellow in fall

Discussion

The North Woods, has seen years of evolving land use practices and has subsequently been affected by the disturbance of past (and recent) agriculture and development. Changes in land use are the predominant cause of new introduction and spread of invasive species (Moustakas & Katsanevakis 2018). Aerial photography archived in the ArcGIS historical database has documented the evolution of land use since 1939 and acts as a key reference to our Human Disturbance Hypothesis. It appears that certain parts of the area were cleared for farming, some having been cleared not once, but twice after 1938. The ever-changing landscape of the Western side of the North Woods due to human activity has facilitated the rather aggressive invasion of a number of invasive herbaceous (and some woody) species. The heat map in helps to visualize the positive relationship between human disturbance and density of invasive species; note the area of highest invasive species cover sum and compare it to (Figure 16.) Aerial photography from 1981. 

Figure 16. Kingston, RI: North Woods Aerial Photography: 1951

It was also noted that the soil hydrologic group of the areas least disturbed fall under C and D, which are soils that have slow infiltration rates and very slow infiltration rates, respectively. 

Figure 17. A map of soil hydrologic groups of the North Woods. Soils in hydrologic group D are not suitable for farming or housing development.

This could have impeded the introduction of invasive species as these areas were less desirable to develop and farm on. There is also a 6-acre Superfund site located at the northwest end of the North Woods that received unregulated disposal of solid wastes from the 1930s up until the late 1960s. An additional and rather recent disturbance was the installation of the solar farms also located at the northwest end of the North Woods.  

Suggestions & Recommendations

We recommend a Horizon Scanning of the North Woods in order to identify any potential threats of emerging invaders. The application of this method could aid in future conservation efforts to protect the area from further invasion impacts and could become a valuable tool in assessing the risk of future introductions, whether they be intentional or accidental. Metadata documentation may also be helpful in providing extra information on any given invasive species found in the North Woods such as seed viability, means of dispersal, etc., as it may aid in calculating a species’ probability of causing significant detriment to the native ecosystem. Creating large spatio-temporal datasets is known to be fundamental in monitoring and managing invasive species (Moustakas & Katsanevakis 2018). A conceptual framework in invasive species prevention presents the idea of  limiting their spatial dispersal. Davies and Sheley 2007 put forward a management plan that works to limit the dispersal of invasive species by identifying prospective spatial dispersal vectors combined with plant seed dispersal ecology.

Literature Cited

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Aulakh, J. 2017. Integrated Management of Mugwort (Artemisia Vulgaris L.): Combining Chemical and Nonchemical Control Tactics, Nitrogen Fertilization, and Overseeding portal.nifa.usda.gov/web/crisprojectpages/1009011-integrated-management-of-mugwort-

“Black Locust | Woody Invasive Species of the Great Lakes Basin.” WIGL, 12 Aug. 2021, woodyinvasives.org/woody-invasive-species/black-locust/#1571683267259-c65fd76c- 7490fa11-61a14714-3122ef93-98d1e12e-55ea.

Born, W., Rauschmayer, F., & Bräuer, I. (2005). Economic evaluation of biological invasions—a survey. Ecological Economics, 55, 321–336.

Braun-Blanquet, J. (1932) Plant sociology: The study of plant communities. McGraw Hill, New York.

Butler, B.J. and E.H. Warton (eds). 2002. The forests of Rhode Island. USDA Forest Service, Northeastern Research Station. Accessed May 13, 2021 at https://www.nrs.fs.fed.us/pubs/inf/ne_inf_155_02.pdf

CABI. “Japanese Knotweed.” Invasive Species, 4 Nov. 2021, www.invasive-species.org/species/japanese-knotweed.

“Crown Vetch.” Missouri Department of Conservation, 2012, mdc.mo.gov/sites/default/files/2020-04/crownvetch.pdf.

Fire Effects Information System. Frangula alnus. US Department of Agriculture.  https://www.fs.fed.us/database/feis/plants/shrub/fraaln/all.html 

Fryer, Janet L. “Celastrus Orbiculatus.” Fire Effects Information System (FEIS), 2011, www.fs.fed.us/database/feis/plants/vine/celorb/all.html.

Hooper, D.U., Chapin, F.S., Ewel, J.J., Hector, A., Inchausti, P., Lavorel, S., Lawton, J.H., Lodge, D.M., Loreau, M., Naeem, S., & Schmid, B. (2005). Effects of biodiversity on ecosystem functioning: a consensus of current knowledge. Ecological Monographs, 75, 3–35.

“Invasive Plant Species Assessment Working Group.” In.Gov, 2021, www.in.gov/dnr/files/Crown_vetch.pdf.

Klein, Helen, and Et. Al. “Common Mullein Verbascum Thapsus L.” https://Accs.Uaa.Alaska.Edu/, 2 Aug. 2011, accs.uaa.alaska.edu/wp-content/uploads/Verbascum_thapsus_BIO_VETH.pdf.

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Figure 1. The North Woods Boundary and Adjacent Features. This map highlights the boundaries of the University of Rhode Island's North Woods (307 acres) and its connection to the main campus to the south and the broader forested landscape to the north and east. Data from the Land Use Land Cover 2011 dataset. All data are obtained from RIGIS.

Figure 2. Historical Context of the North Woods.  There are several sites of historical significance around the North Woods, including one historical cemetery within the Henry Eldred farm. Data from the National Register of Historic Places by the Rhode Island Historic Preservation & Heritage Commission and the Rhode Island Advisory Commission on Historical Cemeteries online cemetery database. All data obtained from RIGIS.

Figure 3. The Oliver Watson Farm House, on the future site of the University of Rhode Island Kingston Campus

Figure 4. Kingston with Rhode Island College and the North Woods in 1944. USGS 7.5 Minute Quadrangle. Based on map symbology, large portions of what are now forested areas within the North Woods were not forested at the time and multiple houses and unpaved roads were present

Figure 5. Ecological Communities of the North Woods. Number of acres of different Systems, Classes and Communities based on the Ecological Communities Classification, which is a statewide, seamless digital dataset of the ecological communities for the State of Rhode Island, derived using automated and semi-automated methods and based on imagery captured in 2011. Data acquired from RIGIS.

Figure 6. Ecological Communities of the North Woods. The data from this layer consists of ecological communities for the state of Rhode Island, which were derived via automated and semi-automated methods and from imagery captured in 2011. Data used in the production of this dataset were provided by the State of Rhode Island and included 2011 land cover/land use. All data were obtained from RIGIS.

Figure 7. Surface Hydrology including wetlands, streams and ponds. Freshwater river and stream features determined from 1:5000 scale aerial photography. Lakes and Ponds identified and delineated from 1997 1:5000 orthophotography. The extent, approximate location, and type of wetlands and deep-water habitats in Rhode Island are based on the National Wetlands Inventory. All data were obtained from RIGIS.

Figure 8. Location of Documented Sightings of Rare or Endangered Species Near the North Woods. Stars indicate approximate siting locations and the red polygons are estimated habitat support areas for those species. Data from the Rhode Island Natural Heritage Program provided by the Rhode Island Natural History Survey.

Figure 9. Braun Blanquet cover class scores

Figure 10. Disturbance ranking per plot.

Figure 11. Kingston, RI: North Woods Aerial Photography: 1988

Figure 12. Kingston, RI: North Woods Aerial Photography: 1997

Figure 13. Scatter plot comparing the relationship between disturbance level and average invasive species percent cover (BB Scores). The linear regression shows a positive relationship between the two variables. R^2 = .301

Figure 14. Bar graph showing the distribution of invasives in North Woods by number of recorded instances per transect. Remember that each species can only occur once in each plot (max. 100% cover) but may be seen multiple times throughout the transect.

Figure 16. Kingston, RI: North Woods Aerial Photography: 1951