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Ecological Restoration of Ravenshill Pond: Aquatic invasive Iris
pseudacorus assessment and removal
Giorgio Giovinazzo
Prepared for: Dr. Val Schaefer
ER 390
Restoration of Natural Systems
July 2012
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Acknowledgements
Many thanks to many people are in order. First off, I would like to thank my
friend Jason Slade for putting me contact with Ian Bruce (Environmental Consultant),
second I would like to thank Ian Bruce for putting me in contact with Paul and Adele,
third I would like to thank Paul and Adele on whose property this ecological restoration
project took place. A circle of connections makes the world beautiful. Forth I would like
to thank my love, Miranda Cross for her expertise in plant identification and assistance in
invasive species plant removal. A special thank you goes out to Dr. Val Schaeffer whose
guidance was helpful in relieving the stress of the situation.
Cover Photo: Ravenshill Pond
Abstract
In July 2012 in the district of Sannich, 11 kms from Victoria, BC the invasive species Iris
pseudacorus was assessed and some plants removed/controlled. Also bathymetric
analysis of Ravenshill pond took place in conjunction with ecosystem typing,
aquatic/terrestrial plant survey, pond cores, water data collection, and dam inspection to
assist in the development of a long term invasive Iris eradication/control program.
Bathymetric analysis was conducted to elucidate the ponds features, aquatic and
terrestrial plant survey for future comparative analysis to identify potential invasive
species spreading. Core samples were taken to indentify the underlying ground matrix
and its potential ability to allow heavy machinery into pond area for maintenance,
modification, and control of invasive species. Ecosystem typing was conducted to
confirm that the pond was in fact man made. Water data collected for future
reference/comparative analysis. Bathymetric analysis revealed a max depth of <2m, pond
cores revealed an underlayer of grey clay, ecosystem typing/site series of CwFd-
Kindbergia (Western-Red Cedar, Douglas fir), pond water was slightly acidic, with low
dissolved oxygen. Removal of Iris pseudacorus is labor intensive and requires it is
recommended that machinery be hired to assist in the control/eradication of Iris
pseudacorus.
Introduction
Ravenshill pond acquired its name from a past owner, who modified the wetland
previously on the property by building an earth dam, thereby creating Ravenshill pond
(Ward-Harris, 1979). Ravenshill pond is in the Todd Creek watershed, and water from
the pond drains through a culvert into Bleathman Creek which flows into Prospect Lake.
Ravenshill pond is located in the district of Sannich, on Southern Vancouver Island, BC.
Currently the pond belongs to Paul and Adele who both wish to maintain and create a
habitat where native species flourish. Compromising their wishes is an invasive species
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known as Yellow Flag Iris (Iris pseudacorus), that grows on the wet shores of the pond,
also it creates floating mats which enable it to grow in the shallows of the pond.
This freshwater aquatic ecosystem provides habitat for numerous migratory waterfowl,
and native amphibians. The integrity of this ecosystem needs to be maintained by
controlling invasive species presences. Iris pseudacorus is listed as a noxious invasive
species in British Columbia (IPCBC, 2012). This particular aquatic invasive is
widespread throughout North America, and many areas engage in mechanical removal of
the entire plant, repeated cutting, or the use of herbicides (UoF, 2008). The plant is
believed to displace native species and alter ecosystems. It is suggested that the plant
material be burned, or placed in thick garbage bags for placement in a landfill
(IPCBC,2012).
The objective of this ecological restoration is to map the extent of Iris pseudacorus
within Ravenshill pond, to slow its spread through removal of the plant, and to assess the
conditions for widespread eradication Iris pseudacorus from Ravenshill pond.
2.0 Methods
Study Area
The study area was a 8000m2 subsection of Paul and Adele’s property (Fig. 1, 2), on
southern Vancouver Island within the Coastal Douglas Fir Biogeoclimatic Zone
(Meidinger & Pojar, 1991). This area falls within the Vancouver Island/Olympic
mountain rain-shadow, summers are warm and dry, winters, mild and wet. Average
precipitation varies from 647-1263 mm, with less than 5% as snow (Nuszdorfer et al.
1991). Within the study area is Ravenshill pond, which has numerous patches of invasive
Iris pseudacorus growing within it (Fig.8)
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*Scale 1:100000, Scale bar lower left reads 1355m, North indicator arrow displayed upper right
Figure 1. Location of the site in the District of Sannich,Vancouver Island, B.C. (Map
obtained from Sannich GIS, 2012)
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Figure 2. Study Site and Sampling Method Locations (Photo obtained from Sannich GIS,
2012)
Sampling Methods
The study site was squared off with the use of a compass in order to define the study site
and enclose the pond. After study site was defined pond bathymetric analysis, core
samples, ground cover analysis, ecosystem typing, aquatic/terrestrial plant inventory,
yellow flag iris locations mapping took place. Also dissolved oxygen, pH, total dissolved
solids, and temperature of pond water data was collected with a Fisher pH/temperature
tester, Hanna instruments: EC/TDS tester (pH and temperature data was cross referenced
with Hanna instruments pH/temp (for accuracy). Disolved Oxygen data was collected
with Chemetrics Kit.
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Bathymetric analysis was carried out by grid mapping, and measuring the depth of the
pond with a meter stick. Measurements were taken: North/South longitude every 15m,
West/East every 3m in order to create a bathymetric map (Fig. 3.), depths were
categorized as less than 1m, greater than 1m less than 2m (<1m,>1<2 respectively).
Three core samples were taken to be representative of the area (Fig. 2). Core samples
were obtained through the use of a hollow pipe, hammer, and wooden dowel to push core
out (Ian Bruce (Environmental Consultant) suggestion). Three soil pits were dug
and ground information forms (GIF) filled out to ecosystem type the area. GIF
completion followed the procedure outlined in the field guide insert to the Field Manual
for Describing Terrestrial Ecosystems accessed from:
http://www.ilmb.gov.bc.ca/risc/pubs/teecolo/fmdte/gif.htm#ground%20Inspection%20Fo
rm (July 2012). Soil moisture and nutrient regimes (SMR/SNR) data were decoded
using A field Guide for Site Identification and Interpretation for the Vancouver Forest
Region (Green &Klinka, 1994). For the identification of terrestrial and aquatic plant
species Pojar and MacKinnon’s (1994) Plants of Coastal British Columbia was used in
conjunction with the help of Miranda Cross (plant specialist).
To map the locations of Iris pseudacorus a Garmin etrex GPS was used in conjunction
with aerial photographs obtained from Sannich GIS (2012) (Fig. 8, Table 2.)
Ecological Restoration
After Iris pseudacorus patches were mapped (Fig. 8., Appendix A: Table 2), areas
that were accessible by wheel barrel were selected for Iris pseudacorus removal. Other
Iris pseudacorus patches were selected for seed head removal. Due to labor/access
restraints a number of Iris pseudacorus patches are were left in active status (Fig. 5, 8.
Appendix A: Table 1).
Removal of Iris pseudacorus from the shore (Fig.3) required the use of a pitch fork,
shovel, gloves, and patience. The rhizomes of the plant need to be removed to prevent re-
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growth, thus gloves are required since you must reach into the soil to remove rhizomes,
also since plants contain skin irritants protection is necessary (Sutherland, 1990).
Removal of Iris pseudacorus in floating mat (Fig. 4) form required the use of a saw to cut
mat into a manageable size in order for it to be hauled out and disposed of. After
removal, the native cattail Typha latifolia was planted.
Figure 3. Left Iris pseudacorus before removal, Same area Camera facing pond after
planting of native cattail , Typha latifolia.
Figure 4. Left Iris pseudacorus before removal, Same area different camera angle after
planting of native cattail , Typha latifolia.
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Figure 5. Left Yellow Flag Iris In Bloom, Right Some of the Iris, Active State
Figure 6. After a Few Days Hard Work, Some pond areas maintained and a couple Truck
Loads of Iris to dispose of.
Disposal of Iris pseudacorus involved the use of Oak Bay’s waste management services,
where organic matter is hot composted to kill viable seeds/plant material. The hot
composting of the plant material ensures that it will not be spread.
Results and Interpretation
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The results of the bathymetric analysis (Fig. 7) and core samples reveal that some areas
of the pond can be reached by light weight machinery to assist in the mechanical removal
of Iris pseudacorus. In other areas, partial draining of the pond may be required to ensure
safe use of machinery within the pond. The cores revealed a clay matrix, which indicates
that the machinery will not sink into the ground.
Figure 7. Bathymetric Map of Ravenshill Pond (Photo obtained from Sannich GIS, 2012)
Ground cover analysis indicated that study site ground cover is mainly, salal, kindbergia,
trailing blackberry, Oregon grape and bracken fern, with patches of invasive St. John
Wort. Salal had a frequency of 50%, St. Johns wort of 25%, oregon grape of 50%,
bracken fern of 25%, trailing blackberry of 37.5 %, and beaked moss of 12.5%
(Appendix A, Table 1). Results indicate that the invasive St. Johns Wort needs to be
contained and controlled.
The aquatic and terrestrial plant species inventory (Appendix A: Table 5,6.) indicate that
there is a wide assortment of native species, however, there are also some invasive
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species that may require attention in the future, namely ivy, holy, creeping buttercup, and
Scottish broom, at present there numbers/abundance appear to be very low, but that can
change quickly.
Some Iris patches have been removed (Fig.8), and others controlled by seed head
removal, however, active patches still remain and require attention.
Figure 8.Location of Iris pseudacorus within Ravenshill Pond. (Photo obtained from
Sannich GIS, 2012)
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The native cattail species Typha latifolia was planted to promote native species within the
pond, and potentially prevent reestablishment of Iris pseudacorus.
Figure 9. Iris pseudacorus seed heads
Figure 9 above depicts the Iris pseudacorus seed heads which float, and can hide. It is
important to be thorough when plants are removed and no traces can be left behind
because of the high potential of re-colonization by the plant.
Figure 10. Iris pseudacorus Left showing the roots, Right, floating mat hauled
in
Figure 10 shows Iris pseudacorus roots that will form rhizomes and mats that
will infiltrate areas of the aquatic ecosystem, with the potential to displace
native species.
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Ecosystem typing/site series of CwFd-Kindbergia (Western-Red Cedar, Douglas
fir) was revealed through digging soil pits (Fig. 2). The reason soil pits were
dug was to confirm that the pond was manmade, the soil matrix of areas
adjacent to the pond shore reveal that the pond was in fact man made.
Water tests obtained a dissolved oxygen rating of 6ppm for surface and 2-3ppm
for 1m deep, pH was 6.5 at surface and 6.2 at 1m deep, TDS 42 at surface and
46 at 1m deep (Appendix A: Table 3).
Discussion
The ecological restoration of Ravenshill pond involved the assessment of the aquatic
invasive species Iris pseudacorus. To slow its spread the removal of some of the plant
patches was carried out along with the cutting/removal of seed heads. Also a bathymetric
analysis of Ravenshill pond took place in conjunction with ecosystem typing,
aquatic/terrestrial plant survey, pond cores, water data collection, and dam inspection to
assist in the development of a long term invasive Iris eradication/control program.
Bathymetric analysis revealed that the pond is quite shallow, meaning that it has a high
potential for invasive plant invasion, and also native aquatic species clogging. The
analysis suggests that potential dredging of the pond may be necessary to maintain a
diverse habitat for native aquatic waterfowl.
Although the ecological restoration of Ravenshill pond helped remove some of the
invasive iris impacts there are still numerous active patches of iris that need to be
removed/controlled. This is a timely and thus costly endeavor, if funds could be obtained
to hire machinery to assist in the removal, it may prevent further ecological damage to the
area by preventing its spread to nearby areas. Leung et al. (2002) point out that if you
can contain/maintain an invasive species before it gets out of control it is much more cost
effective to deal with. In lines with that train of thought, are Keller et al. that suggest the
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risks of invasive species be assessed in order to delineate solutions that will have less
economic and environmental impacts.
The core analysis revealed a clay matrix, which is important if machinery will be used to
assist in ecological restoration. This observation suggests that if machinery is available it
can be used to assist in some removal of invasive iris because the stable ground matrix
will keep machinery from sinking.
Data gathered on water qualities depicted what is typical of pond water, the slightly
acidic pH reading suggests that the pond is not receiving significant contamination from
human activities, since a negative pH is what would be expected in that particular
ecosystem.
It is important to mention that some of the data collection may not be perfect because of
my human error, and the potential that can be attributed to the instruments used for
analysis. That being said, further research, mapping, and analysis of the area should be
carried out.
Maintenance and monitoring should be a huge part of any ecological restoration.
Monitoring is required to assess the effectiveness of any implemented restoration
activities, if it appears that restoration efforts are not being effective than more
maintenance is required. Hopfensperger et al. (2007) suggest that feasibility studies be
carried out in order to assess whether or not ecological restoration projects should be
conducted in the first place. The reason being is that if the funds or the people (labor) are
not there to support the project, it will just fail, thus compromising the ecological
integrity.
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Conclusions & Recommendations
Ravenshill pond is a unique area and provides great habitat for native species,
unfortunately there are also invasive species present that need to be maintained and
controlled.
Recommendations
Source funding for complete removal of Iris pseudacorus
Machinery should be hired to assist in the control/eradication of Iris pseudacorus.
Tree frog populations estimate: in order to see if species are declining
Conduct Bull frog population estimate
Control/removal of St. Johns Wort & keep a watchful eye on other noted
invasives
References
Ecosytems Working Group, Terrestrial Ecosystems Task Force, and Resources Inventory
Committee. 1998. Standard for Terrestrial Ecosystem Mapping in British Columbia.
Retrieved July 2012 from: www.for.gov.bc.ca/ric
Green,R &Klinka,K. 1994. A field Guide for Site Identification and Interpretation for the
Vancouver Forest Region. Resource Branch, BC. Retrieved July 2012 from:
http://www.for.gov.bc.ca/hfd/pubs/docs/lmh/lmh28.htm
Hopfensperger, K. N., Engelhardt, K. A. M., & Seagle, S. W. (2007). Ecological
feasibility studies in restoration decision making. Environmental Management, 39(6),
843-852.
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Invasive Plant Council of British Columbia (IPCBC). Retrieved July 2012 from:
http://www.thinksalmon.com/reports/Aquatic_Invasive_Plants_Action_Plan_%28Feb_28
_2010%29.pdf
Keller, R. P., Lodge, D. M., & Finnoff, D. C. (2007). Risk assessment for invasive
species produces net bioeconomic benefits. Proceedings of the National Academy of
Sciences of the United States of America, 104(1), 203-207.
Leung, B., Lodge, D. M., Finnoff, D., Shogren, J. F., Lewis, M. A., & Lamberti, G.
(2002). An ounce of prevention or a pound of cure: Bioeconomic risk analysis of
invasive species. Proceedings of the Royal Society of London Series B-Biological
Sciences, 269(1508), 2407-2413.
Meidinger, D., and J. Pojar (1991) Ecosystems of British Columbia. British Columbia
Ministry of Forests, Victoria, British Columbia, Canada.
Pojar, J,& MacKinnon,A. (1994) Plants of Coastal British Columbia, Victoria:British
Columbia Forest Service; Vancouver, Lone Pine Publishing.
Nuszdorfer F.C., Klinka, K. And Demarchi D.A. 1991. Chapter 5 Coastal Douglas-fir
Zone. Ecosystems of British Columbia. BC Ministry of Forests.
Sutherland, W. J. (1990). Iris-pseudoacorus L. Journal of Ecology, 78(3), 833-848.
University of Florida. (2008). Iris pseudacorus: Center for Aquatic and Invasive Plants.
Retrieved July 2012 from: Center for Aquatic and Invasive Plants:
"http://aquat1.ifas.ufl.edu/node/205" http://aquat1.ifas.ufl.edu/node/205
Ward-Harris, J. 1979. Creature Comforts. Toronto: Collins.
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Appendix A
Table 1. Ground Cover Assessment: Eight 1m x 1m Quadrats, July 2012
Presence Frequency Average Coverage
Species (#quadrats) (%) in respective quadrats
(%)
Gaultheria shallon(Salal) 4 50 80
Hypericum perforatum
(St. Johns Wort) 2 25 80
Mahonia aquifolium
(Oregon grape) 4 50 5
Pteridium aquilinum
(Bracken Fern) 2 25 5
Rubus ursinus
(Trailing Blackberry) 3 37.5 5
Kindbergia oregano
(Beaked moss) 1 12.5 100
Table 2. GPS Coordinates of Iris pseuacorus patches, size,type, and status _
Approx.Size Type Status
GPS Cooridinates (m2)
N48° 30.092’
W123°26.695’ <1 shore removed
N48° 30.094’
W123°26.698’ <1 shore removed
N48° 30.100’ floating removed
W123°26.692’ 1 mat
N48° 30.096’ floating
W123°26.678’ 1 mat removed
N48° 30.094’
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W123°26.683’ 4 f/m removed
N48° 30.078’
W123°26.689’ 5 f/m seed heads cut
N48° 30.076’
W123°26.689’ 8 f/m seed heads cut
N48° 30.072’
W123°26.693’ 2 f/m seed heads cut
N48° 30.061’
W123°26.705’ 3 f/m active
N48° 30.058’
W123°26.706’ 3 f/m active
N48° 30.055’
W123°26.711’ <1 f/m active
N48° 30.55’
W123°26.713’ 5 f/m active
N48° 30.055’
W123°26.713’ 4 f/m active
N48° 30.056’
W123°26.712’ 1 f/m active
N48° 30.058’
W123°26.711’ 2 f/m active
N48° 30.061’
W123°26.709’ 4 f/m active
N48° 30.061’ <1 f/m active
W123°26.711’
N48° 30.062’
W123°26.716’ <1 shore active
N48° 30.061’
W123°26.718’ 4 f/m active
N48° 30.049’
W123°26.718’ 8 f/m active adjacent to willow Islands
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N48° 30.048’
W123°26.718’ 2 f/m active adjacent to willow Islands
N48° 30.054’
W123°26.720’ 5 f/m active adjacent to willow Islands,
decomposing canada goose
egg seen
N48° 30.052’
W123°26.723’ <1 f/m active adjacent to willow Islands
Table 3. Ravenshill Pond pH, TDS, and Temperature____________________
Status
Depth Disolved Oxygen pH TDS Temperature
(m) (ppm) (ppm) (C°)
0 6 6.5 42 22.3*, 18.9**
1 3 6.2 46 19.5*
Notes on temperature: *In sun, **In Shade
Table 4. Wildlife Observed On Within Study Sited, July 2012___________________
Eagle
Hawk
Red Squirrel
Dragon Fly(many species)
Numerous Birds
Raven
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Table 5. Teresterial Plant Species Inventory of Ravenshill Study Site, July2012
Latin Name Common name
Thuja plicata Western Red Cedar
Pseudotsuga menziesii Douglas Fir
Alnus rubra Red Alder
Lonicera involucrate Twin Berry
Spiraea douglasii Hardhack
Pteridium aquilinum Bracken Fern
Gaultheria shallon Salal
Rubus ursinus Trailing Blackberry
Cornus sericea Red Osier Dogwood
Fragaria vesca Woodland strawberry
Rubus spectabilis Salmon berry
Trientalis latifolia Western Star Flower
Holodiscus discolor Ocean spray
Mahonia aquifolium Oregon grape
Rosa nutkana Nootka Rose
Monotropa uniflora Indian pipe
Physocarpus capitatus Pacific nine bark
Polystichum munitum Swordfern
Malus fusca Pacific Crab Apple
Ranunculus occidentalis Western Buttercup
Prunella vulgaris Heal-all
Leucanthemum vulgare Oxeye daisy
Digitalis purpurea Foxglove
Salix scouleriana Scoulers Willow
Lonicera ciliosa Honey Suckle
Acer macrophyllum Big Leaf Maple
Populus tremuloides Trembling Aspen
Lysichiton americanus Skunk Cabbage
Vaccinium parvifolium Red Huckleberry
Galium aparine Cleavers
Juncus effusus Common Rush
Brodiaea elegans Harvest Lily
Fritillaria affinis Chocolate Lily
Quercus garryana Garry Oak
Amelanchier alnifolia Saskatoon berry
Salix cordata Furry Willow
Claytonia sibirica Siberian miners lettuce
Oenanthe sarmentosa Water Parsley
Salix lucida Pacific Willow
Kindbergia oregano Beaked moss
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Oemleria cerasiformis Indian Plum
Tsuga heterophylla W. Hemlock
Betula papyrifera Paper Birch
Ilex aquifolium L.* Holly
Hypericum perforatum* St. Johns Wort
Hedera helix* English Ivy
Cytisus scoparius* Scottish Broom
Cirsium arvense* Canada Thistle
Ranumculus occidentalis Western Buttercup
Ranumculus repens* Creeping Buttercup
Notes: *Invasive species
Table 6.Aquatic Species Inventory of Ravenshill Pond Study Site, July 2012
Latin Name Common name
Nuphar polysepalum Yellow Pond Lily
Potamogeton natans Floating-Leaved Pondweed
Lemna minor Common Duckweed
Myriophyllum spicatumz Water-Milfoil
Iris pseudacorus Yellow Flag Iris
Appendix B
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Figure 11. Earth Dam Inspection Path (Cut July,2012)
Figure 12. Evidence of Beaver ecosystem modification (engineering), purported to be
invasive