**2. Taxonomy and physiological basis for study**

Eastern poison ivy is a member of the Anacardiaceae family (sumac-cashew) and distributed across Eastern North America, whereas western poison ivy (*Toxicodendron rydbergii* (Small ex Rydb.) Greene) is distributed across Western North America [22, 23]. These two species are morphologically variable (e.g., leaf color, size, shape), and they can hybridize within overlapping habitats. Eastern poison ivy shows varied growth forms, with the most common as a woody rhizome that grows underground in all directions, with no nodes but roots and leaves at varied intervals. This variable rooting leads to the establishment of patches over large areas and varying types of soil. An alternate form of EPI demonstrates a woody vine that will climb trees and other hard surfaces. Both growth forms are identified as shade-intolerant and are often found in habitats with direct sunlight such as the edge of forests, along roadways, disturbed areas, fields, and wetlands. Both forms produce the toxin urushiol as a defense mechanism, and these toxins often cause contact dermatitis in two of three humans following exposure to as little as 1 nanogram [24]. These toxins are released from the roots and leaves to the air as oil droplets [24]. On Manitoulin Island, EPI is most commonly found along edges of forests and farm fields, roadways, and other disturbed areas [25]; EPI is considered a rare species in natural forests with closed canopies and wetland areas on the island [25], as this species prefers direct sunlight [22, 23].

All species within the *Toxicodendron* genus show some tolerance to soil salinity, and this provides the plants with the ability to maintain viable populations within disturbed habitats [22]. Kuester et al. [26] reported that elevated tolerance to soil salinity was a common characteristic of successful weed species in North America. The United States Department of Agriculture (USDA) Plants Database (http:// plants.usda.gov/charinfo) provides a standard definition to represent how plants tolerate soil salinity. Such representation of plant tolerance to soil salinity reflects studies of plant growth performance that classified species among four tolerance categories (zero, low, medium, high), to represent range of responses. These USDA responses include zero tolerance to soil solutions with electrical conductivity of 0–2 dS/m, low tolerance to 2.1–4.0 dS/m, medium tolerance to 4.1–8.0 dS/m, and high tolerance to >8.0 dS/m. Plants are defined to tolerate salinity if there is zero to slight reduction in growth (<10%). Eastern poison ivy demonstrates an ability to tolerate elevated concentrations of soil salinity, often within the medium tolerance category [22, 23].

Such reports of tolerance of EPI to soil salinity include a range of responses, depending on the locale of the study [22, 23]. It is likely this range of responses is a direct response to rhizome growth forms with roots and stems extending over large areas. This pattern indicates that the rhizome allows the plant to tolerate a wide range of soil salinities, as well as other forms of local disturbance. The presence of rhizome growth form was identified as the causative factor for rapid reestablishment of EPI after flooding destroyed surface stems and leaves [27, 28]. The observation of tolerance of EPI to environmental disturbance, due to ecological and physiological adaptations, justifies the consideration of EPI as a candidate bioindicator species. The use of EPI as a bioindicator species identifies that the phenological response patterns of the species to different environmental, ecological, and physiological factors is understood. This chapter demonstrates the current understanding of the responses of EPI and plant communities near HEAs and two natural seeps and represents an illustrative example of plant phenology in field and forest ecosystems.

**107**

*Eastern Poison Ivy (*Toxicodendron radicans *L.): A Bioindicator of Natural and Anthropogenic…*

At WUT, oral history combined with TK led to the initial documentation of old and un-abandoned HEAs that were observed to be harming native vegetation as well as fouling agricultural fields. Specifically, resident observations included woody vegetation downslope of old HEAs that were dead or showed dead branches and short height compared with specimens in adjacent habitats that were live and taller. Other observations included livestock that shun hay cut from a field with an HEA releasing an oil-water slurry downslope through the field. These observations led to the abandonment of these HEAs. After these HEAs were abandoned, Premier was invited to participate in the discovery of lost HEAs, and this recent work

It is prudent to briefly review the history of how HEAs were established at WUT during the 1800s, reflecting oral history, government reports, scientific articles, photographs, and letters written by Jesuit missionaries. This history also reveals that an extremely large forest fire occurred across Manitoulin Island during 1865, with areas on WUT having nearly all woody stems burned, and this land described afterward as fully cleared, whereas some wet areas and shorelines were spared [25, 29]. This regional fire disturbance at WUT likely aided development of HEAs, through enhancement of access following the loss of dense forest tracts. A second regional disturbance within the WUT forest has been the recent loss of ash (*Fraxinus* spp.) trees due to invasion by emerald ash borer (EAB, *Agrilus planipennis*). This beetle from Asia invaded southern Canada during the early 2000s and now has spread extensively within North America [30]. At WUT, most ash have perished during the last decade, including black ash (*Fraxinus nigra* Marshall), green ash (*F. pennsylva-*

*nica* Marshall), and white ash (*F. americana* L.) due to the EAB infestation. Initial advancement of HEAs at WUT occurred during the summer of 1865 while other portions of the island burned [31, 32]. The first HEAs were planned to focus on oil and followed the McDougall Treaty involving WUT and Upper Canada, signed during 1862; it is noteworthy to identify that the WUT community did not fully embrace this treaty as only two community members actually signed the document [32, 33]. After this treaty, staff from Milwaukee Petroleum Company arrived at WUT on May 1 of 1865 to negotiate access. After access was tentatively granted by WUT, John Ward, an experienced pioneer in oil well drilling from Oil Springs, Ontario, arrived about a month later. Mr. Ward focused the drilling activity on limestone outcrops found in close proximity to natural oil seeps evident along Smith's Bay shoreline, an area directly accessible by boat. This initial extraction activity yielded a "schooner load" of oil that was shipped south with a request for 500 wooden barrels to be shipped north. However, the oil extraction ended during autumn in 1865 when the Wiikwemkoong community members asked the oil men to leave on short notice; their equipment was reportedly left behind [31, 33].

Representatives from the oil industry returned to WUT during the early 1880s and proceeded to develop a large number of HEAs despite opposition from the community [33]. This development was approved by the Government of Canada, as oil well licenses facilitated access to WUT for lease areas along the recently described Trenton Formation. When these 1880s HEAs were prepared, the initial disturbance involved road construction, as land away from the shoreline was targeted. After roads were prepared, HEAs were constructed in agricultural fields and forest settings. In agricultural fields, site preparation was a relatively simple activity, while forest settings required additional effort. It is probable that some of these forest areas used for HEAs in the 1880s were burned during 1865 and included younger trees. After a site was cleared, then a wooden oil rig was built around the extraction

*DOI: http://dx.doi.org/10.5772/intechopen.88150*

represents the basis for this study.

**3. The setting**

*Eastern Poison Ivy (*Toxicodendron radicans *L.): A Bioindicator of Natural and Anthropogenic… DOI: http://dx.doi.org/10.5772/intechopen.88150*
