**6. Discussion**

*Plant Communities and Their Environment*

**% EPI coverage in an area)**

Field: HEA pipe with cap and herbaceous plants

Field: HEA and

Forest: HEA and herbaceous plants

Forest: hydrocarbon seep and herbaceous plants

trees

Forest: hydrocarbon seep and trees

EPI

Forest: hydrocarbon seep and EPI

Forest: HEA and

Forest: HEA and

EPI

Field: groundwater seep and EPI

**Setting Upslope 5–10 m from HEA** 

No response with diverse plant community (<5%)

EPI absent or rare (<5%)

EPI absent or rare (<5%)

No response with diverse community (<5%)

No response with diverse community (<5%)

No response with diverse community (<5%)

No response with diverse community (>5%)

EPI absent or rare (<5%)

EPI absent or rare (<5%)

*attributable to brine that contains elevated concentrations of a suite of elements.*

Information on the herbaceous and woody plant communities along with the distribution of EPI observed within forests and fields at sites A to L at WUT allowed for the resolution of the spatial responses of plants to the presence of HEAs, natural hydrocarbon seep, and groundwater seep (**Table 5**). Species that show growth morphology via rhizome or vine seem to show an ability to occur within 5 m of HEAs, such as EPI, riverbank grape, and Virginia strawberry. Since these patterns were resolved across

**Response of plants and EPI relative to distance from HEA or natural groundwater seep (as approximate** 

**1–5 m from HEA** 

A few plant species evident, some EPI with most species absent (>90%)

EPI dominant (>90%)

EPI dominant (>95%)

A few plant specimens with EPI dominant (>95%)

No plants in path of seepage; EPI evident on edge of drainage

Trees dead; other trees stunted with dead branches near HEAs with dominant EPI (>90%)

Sensitive trees absent from path of groundwater. Tree branches dead along path. Other trees stunted in height

EPI dominant (>95%)

EPI dominant (>95%) along edge of path of groundwater; no EPI in path

**0 m from HEA or seep**

No plants

No EPI; no plants

No plants

No plants

No trees

No trees

No EPI and no plants

No EPI

EPI dominant (>95%)

**or seep**

**or seep**

(<5%)

(<5%)

(25–95%)

Diverse plant community (< 5%)

EPI absent or rare

EPI absent or rare

Loss of diversity, shorter plants within drainage path

No plants in drainage path of seepage to Lake Huron

Sensitive trees absent; tree branches on side of HEA dead; other trees stunted in height

EPI dominant, usually >50% of specimens

EPI dominant (>95%) along edge of path of groundwater; no EPI

*Findings from this study demonstrate the plant communities respond to the HEA and seeps based on water drainage,* 

in path

*Summary of response patterns for vegetation found in association with hydrocarbon extraction area, groundwater seep in a field, and hydrocarbon seep in a forest setting, represented as approximate % coverage of* 

Sensitive trees absent from path of groundwater. Tree branches dead along drainage path. Other trees stunted in height

**126**

**Table 5.**

*EPI in an area.*

Wiikwemkoong Unceded Territory history identifies the community-associated HEAs with disturbed land, and this led to the expulsion of oil men during 1905 [21, 31]. Such identification of disturbance was attributed to the construction of infrastructure like roads as well as clearing of forest in addition to using valuable farmland for HEAs. Community members also described the presence of large barrels used to separate oil from water in fields and forests [21]. The oil men would direct the oil-water slurry through pipes to these barrels. When the decision was made to evict the oil men, the HEAs were burned, and this common disturbance history contributed to the responses of herbaceous and woody plants described in this study. Oral history also identifies that these burned areas were considered scars on Mother Earth that were very slow to recover. However, this recovery of the HEAs was inferred to be slower than expected and resulted in different plants at these sites compared with adjacent areas [21]. Since 109 years passed from the time the HEAs were burned until the initial assessments during 2014, this represents a unique opportunity for learning, to understand how the herbaceous and woody plants responded to this common disturbance history [17]. This understanding arises from un-replicated activity associated with large-scale disturbance of fields and forests at WUT due to the development of HEAs. Such activities represent an opportunity for learning that is consistent to Carpenter's [17] recommendation to consider ecological settings to quantify interactions involving species and document responses of plants and animals to large-scale environmental perturbations. Carpenter [17] recommended that such perturbations, if studied, often provide the chance to document nonrandom change; a reasonable way to interpret such change is with causal inference. In an earlier study [18], a similar idea was expressed about severe perturbations representing a chance to document response of plants and animals but provided the caveat that such events possibly generate unique responses that are difficult to quantify and apply to other settings. Using this documentation of the response of herbaceous and woody plants near HEAs, it pointed to the use of EPI as a bioindicator of the plant community responses to brine as a way to find HEAs. At WUT, it is useful to use EPI as a bioindicator, as it is the only species consistently found within 1 m of HEAs. Other species, such as Virginia strawberry, also show distributions near HEAs, likely attributable to growth morphology via vine. Due to the wide distribution and salinity tolerance of EPI, it is probable this species could be evaluated for use to resolve the response of plants to HEAs beyond WUT.

This study reports the observed responses of herbaceous and woody species to episodic exposure to brine in a setting with a common disturbance history. These observations at WUT identified a pattern of reduced diversity of herbaceous and woody species as well as increased coverage of EPI in proximity to drainage from HEAs and natural seeps in fields, and FOD8-1 and FOC4-3 woodlands. These plant communities demonstrate a spatial response to water that originates from HEAs and natural seeps with rapid transition from diverse plant community to dominance by EPI over short distances despite similar exposure to sunlight and a common disturbance history. The identification of this response pattern involving a reduction of plant diversity and dieback of overstory tree branches was directly attributable to brine found near HEAs and seepage in fields and forests, representing an ecotone

that defines the zone of disturbance. Observations from site C during September 2017 demonstrated that chlorosis will start within a few days of the arrival of brine; at this site, the brine is able to travel an extended distance from the source, due to the topography, causing stress and death to plants all along the drainage path. Site G demonstrated the response of herbaceous and woody species that reflects natural seepage of hydrocarbons and brine with similar patterns of species selection leading to nearly full coverage of the area by EPI. In contrast, the capped well at site I showed evidence of very little disturbance at 5 m and the focal presence of EPI directly around the pipe. Species such as Virginia strawberry and multiflora rose that grow with vines appear alongside EPI. Long-term responses include herbaceous plant communities essentially absent in close proximity to HEAs and natural seeps as well as an overstory tree canopy dominated by species somewhat tolerant to salt with dead branches near the source of brine.

Other observations from HEAs identified additional plant associations within these areas. Specifically, all HEAs include a few very mature common buckthorn (*Rhamnus cathartica* L.) and/or glossy buckthorn (*Rhamnus frangula* Mill.). It is inferred the seeds of these nonindigenous buckthorn were accidentally introduced to WUT during the 1800s via transport on equipment used for HEAs [21]. Inspections always reveal that buckthorn has spread extensively outward, in a radial pattern, from each of the HEAs. Hence, when buckthorn is found at WUT, surveys will follow these nonindigenous trees, to see if they lead to large specimens in proximity to an HEA. Another consistent observation is that one apple tree (often *Malus domestica* Borkh.) was always planted upslope from each of the HEAs. Further, in a field with numerous HEAs represented as metal pipes, one apple tree is located upslope and within 10 m of each pipe [21]. Oral history from WUT revealed the oil men regarded an apple tree as good luck and a source of food during the autumn season. At WUT, the presence of a large (>30 cm DBH) apple tree in close association with buckthorn is now used as preliminary indicators of possible presence of HEAs in an area.

Studies at WUT [21] documented soil at HEAs containing elevated hydrocarbon concentrations, especially for soil in contact with wood from the former facilities, whereas soil concentrations of hydrocarbons rapidly declined with distance from HEAs, attributed to bacterial degradation of the hydrocarbons over time [21]. These low concentrations of soil hydrocarbons downslope from HEAs provide additional evidence that it is brine from the HEAs that plants are responding to in these areas. The response pattern of the plants, including EPI, to brine at WUT forms the framework, as represented in **Table 5**, as a guide to find lost HEAs as well as understand influence of brine from natural seeps on plant communities.

A literature review documented a range of responses of herbaceous and woody species to brine from HEAs, but none was found for water arising directly from oil shale formations. The study in Oklahoma, USA, for plants downslope of HEAs attributed responses to the brine from the HEAs [6]. A separate study reported that herbaceous and woody plants recovered initially from a brine leak at an impoundment within 1 year after the leak was stopped with no soil treatments; plant community recovery was attributed to frequent rain washing the brine away [15]. At the site of this brine leak [16], the plant community 4 years later was populated by a diversity of herbaceous and woody species, attributed to the seed bank and live adjacent vegetation [15, 16]. Another study reported treatments for bare soils within 1 m deep former reserve pits used to store drill cuttings, drilling fluid, and brine, as preparation for replanting [12]. This bare earth was disked, mulch added, irrigated, and then seeded with local range grasses as well as planted seedlings. Success of seed germination and seedling survival was higher on mulch-treated soils than untreated soils. Over time, the mulch-treated soils showed declines in the

**129**

30 km2

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

seeded and planted species due to colonization by other local species. This mulch treatment led to the identification that establishment of salt-tolerant plants in the reserve pits following treatment can act as the basis for future plant establishment and reclamation; without treatment, seeding, and/or planting of seedlings, the pits require extended periods before plants naturally establish on these soils. Another study recommended the use of local, native plant species for seeding on land

disturbed by hydrocarbon extraction activities, with emphasis on species adapted to the soils associated with the area that often show elevated tolerance to soil salinity [38]. Such seeding recommendations included the use of local sources, due to likely adaptations to regional climate and soils, as the process of reestablishing vegetation on sites disturbed by HEAs is challenging due to the chemistry as well as other physical factors, such as soil compaction [3, 6, 32]. As a means to address challenges for seeding and planting on high-salinity soils, computer software was recently

Other areas of study are warranted, to resolve the morphological and physiological response of herbaceous and woody species associated with HEAs and natural seeps, based on observations at WUT. For example, anecdotal observations indicated a trend that herbaceous species near HEAs often had fewer and smaller flowers compared with specimens in adjacent areas. Other plants showed differences in height and leaf size in proximity to HEAs. This study did not provide for the opportunity to quantify the range of possible responses of plants to exposure to brine arising from HEAs. If the source of stress on these plants was not known, the differences in flowering, plant height, leaf size, etc. could be documented as a phenological response to regional factors, not local responses to brine exposure. Such opportunities for documentation of response of plants, including separation of cause between stresses in proximity to HEAs, may be useful in the future. The HEAs may also be resulting in genotypic changes to plants, due to long-term episodic exposure to brine. Plants like prairie smoke (*Geum triflorum* Pursh) have been observed periodically at WUT in close proximity to HEAs, whereas the USDA identifies this plant as having no tolerance to soil salinity. It may be interesting to resolve if prairie smoke has developed tolerance to elevated soil salinity at WUT. Responses of aquatic plants to brine exposure represent another understudied topic. At site F, the brine-oil slurry drained downslope to the shoreline of Smith's Bay. In the area of the shoreline, white residue was evident on the rocks on the shoreline and in the water. This area also lacked SAV, while adjacent areas demonstrated SAV among the rocks. These varied themes represent candidate areas for further study, to resolve the range of apparent responses of plants relative to episodic environmental stress from brine arising from HEAs and separate them from phenological responses to

This study resolved the response of plant communities to a common disturbance history as well as the episodic release of brine from HEAs and seeps within about

. The resolution of the response of herbaceous and woody species and EPI to HEAs and natural seeps represents a framework that could be applied elsewhere, to assess the intensity of disturbance as well as to find lost HEAs. The ecotone of disturbance at WUT for HEAs is defined by the brine drainage area within a local area of subsidence where EPI is able to dominate the herbaceous plant community. It is probable EPI is able to achieve dominance in these areas due to growth via rhizome and can ameliorate the extreme chemical concentrations in brine. Another consideration at WUT is the native plant community contains very few species tolerant of elevated soil salinity [25] and led to the opportunity for EPI to dominate areas with HEAs. This study has confirmed the distribution of EPI is useful to represent contemporaneous disturbances to herbaceous and woody species attributable to HEAs and natural seeps in forests and fields and applicable to other areas with HEAs.

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

presented to guide such activities [39].

regional processes like climate.

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

seeded and planted species due to colonization by other local species. This mulch treatment led to the identification that establishment of salt-tolerant plants in the reserve pits following treatment can act as the basis for future plant establishment and reclamation; without treatment, seeding, and/or planting of seedlings, the pits require extended periods before plants naturally establish on these soils. Another study recommended the use of local, native plant species for seeding on land disturbed by hydrocarbon extraction activities, with emphasis on species adapted to the soils associated with the area that often show elevated tolerance to soil salinity [38]. Such seeding recommendations included the use of local sources, due to likely adaptations to regional climate and soils, as the process of reestablishing vegetation on sites disturbed by HEAs is challenging due to the chemistry as well as other physical factors, such as soil compaction [3, 6, 32]. As a means to address challenges for seeding and planting on high-salinity soils, computer software was recently presented to guide such activities [39].

Other areas of study are warranted, to resolve the morphological and physiological response of herbaceous and woody species associated with HEAs and natural seeps, based on observations at WUT. For example, anecdotal observations indicated a trend that herbaceous species near HEAs often had fewer and smaller flowers compared with specimens in adjacent areas. Other plants showed differences in height and leaf size in proximity to HEAs. This study did not provide for the opportunity to quantify the range of possible responses of plants to exposure to brine arising from HEAs. If the source of stress on these plants was not known, the differences in flowering, plant height, leaf size, etc. could be documented as a phenological response to regional factors, not local responses to brine exposure. Such opportunities for documentation of response of plants, including separation of cause between stresses in proximity to HEAs, may be useful in the future. The HEAs may also be resulting in genotypic changes to plants, due to long-term episodic exposure to brine. Plants like prairie smoke (*Geum triflorum* Pursh) have been observed periodically at WUT in close proximity to HEAs, whereas the USDA identifies this plant as having no tolerance to soil salinity. It may be interesting to resolve if prairie smoke has developed tolerance to elevated soil salinity at WUT. Responses of aquatic plants to brine exposure represent another understudied topic. At site F, the brine-oil slurry drained downslope to the shoreline of Smith's Bay. In the area of the shoreline, white residue was evident on the rocks on the shoreline and in the water. This area also lacked SAV, while adjacent areas demonstrated SAV among the rocks. These varied themes represent candidate areas for further study, to resolve the range of apparent responses of plants relative to episodic environmental stress from brine arising from HEAs and separate them from phenological responses to regional processes like climate.

This study resolved the response of plant communities to a common disturbance history as well as the episodic release of brine from HEAs and seeps within about 30 km2 . The resolution of the response of herbaceous and woody species and EPI to HEAs and natural seeps represents a framework that could be applied elsewhere, to assess the intensity of disturbance as well as to find lost HEAs. The ecotone of disturbance at WUT for HEAs is defined by the brine drainage area within a local area of subsidence where EPI is able to dominate the herbaceous plant community. It is probable EPI is able to achieve dominance in these areas due to growth via rhizome and can ameliorate the extreme chemical concentrations in brine. Another consideration at WUT is the native plant community contains very few species tolerant of elevated soil salinity [25] and led to the opportunity for EPI to dominate areas with HEAs. This study has confirmed the distribution of EPI is useful to represent contemporaneous disturbances to herbaceous and woody species attributable to HEAs and natural seeps in forests and fields and applicable to other areas with HEAs.

*Plant Communities and Their Environment*

with dead branches near the source of brine.

that defines the zone of disturbance. Observations from site C during September 2017 demonstrated that chlorosis will start within a few days of the arrival of brine; at this site, the brine is able to travel an extended distance from the source, due to the topography, causing stress and death to plants all along the drainage path. Site G demonstrated the response of herbaceous and woody species that reflects natural seepage of hydrocarbons and brine with similar patterns of species selection leading to nearly full coverage of the area by EPI. In contrast, the capped well at site I showed evidence of very little disturbance at 5 m and the focal presence of EPI directly around the pipe. Species such as Virginia strawberry and multiflora rose that grow with vines appear alongside EPI. Long-term responses include herbaceous plant communities essentially absent in close proximity to HEAs and natural seeps as well as an overstory tree canopy dominated by species somewhat tolerant to salt

Other observations from HEAs identified additional plant associations within these areas. Specifically, all HEAs include a few very mature common buckthorn (*Rhamnus cathartica* L.) and/or glossy buckthorn (*Rhamnus frangula* Mill.). It is inferred the seeds of these nonindigenous buckthorn were accidentally introduced to WUT during the 1800s via transport on equipment used for HEAs [21]. Inspections always reveal that buckthorn has spread extensively outward, in a radial pattern, from each of the HEAs. Hence, when buckthorn is found at WUT, surveys will follow these nonindigenous trees, to see if they lead to large specimens in proximity to an HEA. Another consistent observation is that one apple tree (often *Malus domestica* Borkh.) was always planted upslope from each of the HEAs. Further, in a field with numerous HEAs represented as metal pipes, one apple tree is located upslope and within 10 m of each pipe [21]. Oral history from WUT revealed the oil men regarded an apple tree as good luck and a source of food during the autumn season. At WUT, the presence of a large (>30 cm DBH) apple tree in close association with buckthorn is now used as preliminary indicators of possible presence of

Studies at WUT [21] documented soil at HEAs containing elevated hydrocarbon concentrations, especially for soil in contact with wood from the former facilities, whereas soil concentrations of hydrocarbons rapidly declined with distance from HEAs, attributed to bacterial degradation of the hydrocarbons over time [21]. These low concentrations of soil hydrocarbons downslope from HEAs provide additional evidence that it is brine from the HEAs that plants are responding to in these areas. The response pattern of the plants, including EPI, to brine at WUT forms the framework, as represented in **Table 5**, as a guide to find lost HEAs as well as

A literature review documented a range of responses of herbaceous and woody species to brine from HEAs, but none was found for water arising directly from oil shale formations. The study in Oklahoma, USA, for plants downslope of HEAs attributed responses to the brine from the HEAs [6]. A separate study reported that herbaceous and woody plants recovered initially from a brine leak at an impoundment within 1 year after the leak was stopped with no soil treatments; plant community recovery was attributed to frequent rain washing the brine away [15]. At the site of this brine leak [16], the plant community 4 years later was populated by a diversity of herbaceous and woody species, attributed to the seed bank and live adjacent vegetation [15, 16]. Another study reported treatments for bare soils within 1 m deep former reserve pits used to store drill cuttings, drilling fluid, and brine, as preparation for replanting [12]. This bare earth was disked, mulch added, irrigated, and then seeded with local range grasses as well as planted seedlings. Success of seed germination and seedling survival was higher on mulch-treated soils than untreated soils. Over time, the mulch-treated soils showed declines in the

understand influence of brine from natural seeps on plant communities.

**128**

HEAs in an area.
