Spongy Lake Field Trip

This is a virtual field trip to a UW property in Baden, ON known as Spongy Lake. The property contains multiple vegetation communities, from upland hardwood forest, to wetland and nutrient-poor fen. The purpose of this lab is to introduce you to the ecological functions and significance of this ecosystem, while considering the impact of our changing climate and potential disruption to ecological integrity of these systems. Further, anthropogenic land use surrounding the property will be examined.

Each stop is accompanied with narration that can alternatively be accessed as transcripts.

By the end of this lab, students will be able to:

1. Describe the defining characteristics of different types of wetland ecosystems and succession (i.e., wetland, fen, bog).
2. Identify specific glacial features and processes that formed this landscape (e.g., isostasy, kettle lakes, and kames) and understand more broadly the important role glaciation has played in shaping many North American landscapes.
3. Apply the succession concept (explored earlier in lecture and for different ecosystems) to a wetland environment, describing characteristic successional communities and transitions within wetland ecosystems.
4. Describe how organisms (predominantly plants) respond to gradients in environmental factors (e.g., elevation, moisture, nutrients, aerobic vs. anaerobic, light availability, pH and other growth limiting factors) and how these gradients can create corresponding gradients in vegetation characteristics.
5. Understand how climate change is impacting this and other wetland ecosystems, considering also the key role that wetlands play in carbon storage, greenhouse gas (GHG) emissions and potential feedback systems which may cause disruption.
6. Explain ways in which this ecosystem is impacted by human infrastructure and activity (e.g., limestone addition, agriculture, gas line, peat mining, trampling by students, etc.) and the difficult questions this may raise about the future management of this property and wetland ecosystems more broadly.
7. Understand the connectivity and balance between surficial hydrology, human influences, and groundwater recharge.

Spongy Lake property boundary

Spongy Lake Field trip stops

Spongy Lake is land locked so we travel along the edge of a farmer’s field. There is a rail line adjacent to the property, lined with limestone, and ongoing vegetation clearing maintenance. From the field looking south, you can see a high hill known locally as Baden Hill with a communications tower, this a geologic formation from the last ice age, known as a kame, a sand and gravel hill that was formed when a glacier was neither retreating nor advancing. Commercial extraction of gravel has been attempted several times but has been prevented due to public resistance.

Spongy Lake is a protected property under the Regional Municipality of Waterloo’s Environmentally Sensitive Protected Area (ESPA). It is "ESPA #14". There are several criteria that need to be met in order to deem ESPA protection status. It is protected due to its hydrological significance as a groundwater recharge area, geologic significance as a kettle lake, ecological significance for breeding habitat and migratory rest area, regionally rare plants and insects. The peat bog area hosts several unique Ericaceous plants (thrive in acidic, low nutrient conditions). 

Spongy Lake formed when glaciers created a depression through isostasy (the flexibility of the Earth’s surface under great pressure). The isostatic rebound of the surrounding area occurred, but a block of ice melted in-situ to create a depression, a kettle lake, which is Spongy Lake.

Wetland succession generally follows this order: pond — marsh — swamp — fen — bog. Currently, Spongy Lake is in the successional stages between a fen and a bog but more characteristic of a fen.

Note familiar trees in the area: white pine (Pinus strobus), staghorn sumac (Rhus typhina), black cherry (Prunus serotina), sugar maple (Acer saccharum), and American beech (Fagus grandifolia).

The forest floor is mainly comprised of native vegetation such as wild ginger (Asarum caudatum), white baneberry (Actaea pachypoda), red elderberry (sambucus racemosa), ferns, and sugar maple seedlings.

In the spring, the forest floor is full of spring ephemeral flowers. Ephemerals are plants that take advantage of the early spring sunlight by blooming before foliage appears on the trees and blocks sunlight from reaching the forest floor.

There is non-native invasic garlic mustard (Aliara petiolata) and European buckthorn (Rhamnus cathartica) along the edges of the forest boundary and path. Consider how human disturbance, invasive species, and edge effects all impact this ecologically sensitive area.

Historically, students have found scrap metal and glass dumped along the side of the path, remnants of a time when forested areas were used for disposal.

Key Questions and Review

Identify two features at Spongy Lake that occurred as a result of glacial processes.

A lagg is a sharp ecotone change in plant composition and soil type (mineral to organic in this case). It interfaces between the pH basic upland forest and the acidic fen environment, acting as a buffer between the two. As a result, soils here are comprised of both organic and mineral components.

Conditions such as seasonal inundation and water level fluctuations create less than ideal plant growth conditions for a diverse area, rather vegetation is adapted to these extreme conditions.

Note the different vegetation in this area: herbaceous plants such as jewelweed and clearweed grow in the middle of the lagg, while along the edge of the lagg you will find yellow birch (Betula alleghaniensis), silver maple (Acer saccarinum), cinnamon fern (Osmunda cinamomea) , and royal fern (Osmunda regalis).

Because of the plant composition and soil type, the lagg contains many species of ferns. Click the 'i' button in the upper corner of each photo to see what kind of ferns are found here!

Describe one difference between a bog and a fen. Discuss conditions that cause the change in vegetation community observed between the forest and the lagg zone

Conditions within both bogs and fens are considered anaerobic, meaning little or no disturbance and decomposition of organic matter (leaves, roots). This means organic material accumulates and slowly over time creates organic peat layers. Anaerobic conditions provide harsh plant growth environment as it is difficult to uptake nutrients and there is no aeration/oxygen. Spongy is currently a nutrient poor fen as there is a small stream flowing into Spongy Lake at the southwest boundary, creating some water movement. To compare a bog would not have inflow or outflow of water.

This site was formerly used for peat extraction on a small scale. Peat is sold in garden centres as an additive to garden soil mix, as it retains moisture. There’s an average depth of about 5 meters of peat at Spongy Lake, which is a substantial amount considering that it takes about 100 years to create just 20 centimeters of peat.

Slow vegetation decay due to anaerobic conditions means that the history of peatlands can be observed through cores. Pollen, insects, tree roots may be preserved and can be useful for researchers when gathering history of the landscape, historical evidence of climate fluctuations and plant and wildlife community composition.

The slow rate of decay also moderates the climate, creating a cooler microclimate in the summer, and a warmer microclimate in the winter that can reduce freezing and provide shelter to wildlife.

The anaerobic organic peat acts as a carbon sink, storing carbon. Any changes to water levels, trampling or disturbing the area can cause the area to become a carbon source, releasing carbon into the atmosphere. This property is sensitive to climate fluctuations, for example when peatlands dry out, organic material starts to decompose and release GHG like carbon and methane along with other gases such as hydrogen sulfide. Methane is especially harmful as it can ignite, starting ground fires. Smouldering peat fires can burn for hundreds of years and release large amounts of GHG's.

• What are anaerobic conditions?
• How can they contribute to research on historical climate and community composition?
• What role do wetlands play in moderating climate, both locally and globally?

At this stop in the tour, the ground has a buoyant quality. Students enjoy jumping on the peat mat and feeling it move up and down. They are walking on the water table, while keeping afloat with the peat mat and vegetative roots!

Here, growth limiting factors become more obvious.

• Water: despite being so close to the water, many plants residing here have water conservation characteristics similar to desert plants such as thick waxy or hairy leaves to reduce water loss, typical of ericaceous plants.
• Nutrients: this fen is nutrient-poor and vegetation has adapted to sourcing their nutrients in other ways. For example, Pitcher plants (Sarracenia purpurea) and sundew (Drosera sp.) get nitrogen and phosphorus by digesting insects that they trap in their leaves.
• Low pH: the low pH conditions persist in the fen through precipitation, acidic biomass such as coniferous needles and sphagnum peat moss, and the recycling of basic elements by the upland forest.
• Oxygen: plants adapt to low oxygen conditions with slow growth. The dwarf trees and the abundance of shrubs found on the peat are evidence of this slow growth. In addition, shallow root systems along the surface allow plants to access atmospheric oxygen.

All these conditions contribute to the unique ecosystem that can be observed in Spongy Lake. Ferns and plants such as Labrador tea (Ledum groenlandicum), buckbean (Menyanthes trifoliata), bog laurel (Kalmia polifolia), pitcher plant (Sarracenia purpurea), leatherleaf (Chamaedaphne calyculata), cranberry (Vaccinium macrocarpon), and blueberry (Cyanococcus sp.) that are all commonly found in acidic and nutrient-poor soils become more prevalent as we move further away from the lagg zone.

Pitcher plants, cranberry, blueberry, and sweet flag (Acorus calamus) can be observed along the water’s edge. Also note the leatherleaf, tamarack, and silver maple. In the water, water lilies (Nymphaea sp.), sedges (Carex sp.), and cattails (Typha sp.) grow. Cattails, which generally prefer more neutral soils, are potential evidence of a decrease in acidity in the fen and nutrient source. This may be due to runoff from the surrounding agricultural fields. Note the areas of invasive common reed grass (Phragmites australis) that has the potential to spread rapidly, impact water levels, choke out and dominate the vegetative landscape.

• Identify three growth limiting factors in Spongy Lake and ways that plants have adapted to overcome them.

• Sketch a transect that shows the gradient of vegetation zones at Spongy Lake based on what you observed.

Climate change has the potential to greatly impact this sensitive ecosystem in a variety of ways.

For example:

• Flooding would increase the open water zone and push back vegetation.
• Drought would expose the peat and thus increase decomposition rates and release nutrients and greenhouse gases. Plants that flourish in higher nutrient levels may begin to outcompete existing vegetation. Which plants would you expect to disappear from Spongy Lake?
• Change in climate patterns could bring in invasive flora and fauna.
• Dry peat could ignite, whether naturally or through anthropogenic influence, breaking up the fen and releasing GHG's.

Potential human impacts include:

• Runoff from the basic limestone along the railway which could increase the pH of the area.
• Runoff from agricultural activity which could cause shifts in the vegetative community by adding excess nutrients, sediment and pesticides.
• Human groundwater consumption which could result in the open water zone depleting and drying out the peat. Consider the combined effect of increased population growth and warmer climates on groundwater levels.
• Trampling and compaction of the fen due to field trips. The Ecology Lab has tried to reduce impact by installing a board walk or visiting when the ground is frozen.
• Snowmobiles and ATV’s could damage the landscape.
• A gas line was proposed in the past but did not occur due to concerns that the pipeline would sink and rupture.
• A subdivision was proposed in the mid-1960s but was denied for reasons of septic disposal and potential for runoff into this unique ecosystem.

Spongy Lake is a unique environment initially created by glacial action and requires the existence of specific conditions in order to perpetuate itself as a fen. These conditions include little inflow or outflow, an anaerobic environment with slow vegetative decay, and a moderate microclimate for southern Ontario.

Normal limiting factors to growth are partially overcome through vegetative adaptation that’s evident in the fen. Distinct zonation, each with its own unique characteristics, can be observed in the fen and adjacent upland forest, separated by the lagg zone.

Peat cores can be used to reconstruct the history of a fen. Natural and human-induced changes could cause the disappearance of the fen. Climate change may play an important role in the health of the fen.