L-ACER
Lichens, Acidification, and CutEdge Response
Research goal
The overarching goal of this multi-year research project is to understand how forest clearcutting and habitat acidification affects the composition of at-risk lichens in forested wetlands of Nova Scotia, Canada.
Our objectives are :
(i) To determine how at-risk lichen communities change in relation to the distance from a forest edge, how far this influence extends into forested wetlands, and to compare the edge influence on lichens in natural vs. harvested areas.
(ii) To determine how at-risk lichen community composition relates to varying bark acidity levels.
In the past, we have also focused on the impact that non-native slugs have on cyanolichens.
Our objectives are :
(i) To determine how at-risk lichen communities change in relation to the distance from a forest edge, how far this influence extends into forested wetlands, and to compare the edge influence on lichens in natural vs. harvested areas.
(ii) To determine how at-risk lichen community composition relates to varying bark acidity levels.
In the past, we have also focused on the impact that non-native slugs have on cyanolichens.
The locations of L-ACER study sites (green stars) within Nova Scotia, Canada (source: H. Medeiros).
What are forest edges and why do we study them？
Edge studies have been an important part of the history of forest science research since early studies on agricultural edges. Boundaries have become a focus of ecological research because of their high diversity. Estimating and predicting transition widths and their dynamics are important for understanding effects of management activities on forest ecosystems, predicting impacts of climate change, and identifying priority areas for conservation.
Forest edges
Forest edges, which are the interfaces between forested and non forested areas, are integral components of forested landscape, particularly those fragmented by anthropogenic disturbance such as tree harvesting or agricultural development.
Forest edges are classified as natural if they were created by a natural phenomenon or were adjacent to an inherent natural ecosystem and had been unaffected by human activity for at least five decades prior to data collection. Consequently, forest edges adjacent to areas grazed by domestic animals or forest edges maintained by fires intentionally ignited by humans were not considered natural edges.
Forest edges are classified as natural if they were created by a natural phenomenon or were adjacent to an inherent natural ecosystem and had been unaffected by human activity for at least five decades prior to data collection. Consequently, forest edges adjacent to areas grazed by domestic animals or forest edges maintained by fires intentionally ignited by humans were not considered natural edges.
Anthropogenic edges
Anthropogenic edges are the boundaries between natural habitats and human-modified or -created habitats, such as agricultural fields, urban areas, roads, or logging sites. Anthropogenic edges can affect ecosystems in various ways, depending on the type, size, shape, and contrast of the edge.
Forested wetlands in Nova Scotia
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A wetland is a place where water covers the soil or is near the surface for most or all of the year. Wetlands can be found in different parts of the world, and they have different types of plants and animals that live in them. Wetlands are important for the environment, because they help clean the water, store the water, protect the land, and support many living things. Some examples of wetlands are marshes, swamps, bogs, fens, and estuaries.
In this study, the standard was a depth to water table of ≤ 50 cm |
Sphagnum sp.
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Cyanolichens
A lichen is a fascinating organism that is not a single species, but a symbiotic association of algae or cyanobacteria and fungi. The algae or cyanobacteria provide photosynthesis, while the fungi provide protection and structure. Together, they form a unique body called a thallus, which can have different shapes and colors depending on the species involved.
What is a cyanolichen?
Cyanolichens are a type of lichens that have cyanobacteria as their photosynthetic partner. Cyanobacteria are also known as blue-green algae, and they can use sunlight and water to make food and fix nitrogen. Cyanolichens can be found in many different habitats, such as deserts, forests, or mountains. They are important for the ecosystem, because they produce oxygen, recycle nutrients, provide food and shelter for animals, and indicate air quality.
Green algae are one of the partners that can form lichens with fungi. They provide food for the fungi by using sunlight and water to make sugar. They are green because they have a substance called chlorophyll that helps them capture light. They can be found in many places, such as ponds, oceans, or rocks. They can be very small or very big, and have different shapes and forms. Some lichens that have green algae are Flavoparmelia caperata and Letharia vulpina.
Cyanobacteria are another type of partner that can form lichens with fungi. They also provide food for the fungi by using sunlight and water to make sugar. They are blue-green because they have a substance called phycocyanin that gives them color. They are usually found in fresh water, but can also live in other places, such as soil, or ice. They are always very small, but can join together to make bigger groups or strings. Some cyanobacteria can make things that can hurt people or animals if they eat them or touch them. Some lichens that have cyanobacteria are Peltigera rufescens and Collema tenax.
Green algae are one of the partners that can form lichens with fungi. They provide food for the fungi by using sunlight and water to make sugar. They are green because they have a substance called chlorophyll that helps them capture light. They can be found in many places, such as ponds, oceans, or rocks. They can be very small or very big, and have different shapes and forms. Some lichens that have green algae are Flavoparmelia caperata and Letharia vulpina.
Cyanobacteria are another type of partner that can form lichens with fungi. They also provide food for the fungi by using sunlight and water to make sugar. They are blue-green because they have a substance called phycocyanin that gives them color. They are usually found in fresh water, but can also live in other places, such as soil, or ice. They are always very small, but can join together to make bigger groups or strings. Some cyanobacteria can make things that can hurt people or animals if they eat them or touch them. Some lichens that have cyanobacteria are Peltigera rufescens and Collema tenax.
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Cylindrospermum sp , a blue-green algae species
Under magnification at the Adelaide laboratories of CSIRO Land and Water, 1993. |
Some lichens can have both green algae and cyanobacteria as their photobionts, meaning that they can use both types of organisms to produce food through photosynthesis. These lichens are called tripartite lichens, because they have three partners: a fungus, a green alga, and a cyanobacterium. Tripartite lichens are relatively rare, and only about 50 species are known. Some examples of tripartite lichens are Lobaria pulmonaria, Peltigera aphthosa, and Sticta fuliginosa.
These lichens can benefit from having both green algae and cyanobacteria, because they can use different light wavelengths, fix nitrogen, and tolerate different environmental conditions. However, they may also face some challenges, such as maintaining the balance between the two photobionts, avoiding competition or antagonism, and coping with the toxicity of some cyanobacteria. Tripartite lichens are fascinating examples of complex symbiotic relationships in nature.
These lichens can benefit from having both green algae and cyanobacteria, because they can use different light wavelengths, fix nitrogen, and tolerate different environmental conditions. However, they may also face some challenges, such as maintaining the balance between the two photobionts, avoiding competition or antagonism, and coping with the toxicity of some cyanobacteria. Tripartite lichens are fascinating examples of complex symbiotic relationships in nature.
Why cyanolichens are important?
Cyanolichens are often used as indicators of environmental quality and habitat continuity, as they reflect the long-term effects of environmental changes on their communities.
· Nitrogen Fixation in Cyanobacteria
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Nitrogen fixation is the process of converting nitrogen gas from the air into a form that can be used by living organisms. Cyanolichens can perform nitrogen fixation on behalf of the lichen community.
Nitrogenase is the enzyme that catalyzes the reaction of nitrogen gas and hydrogen to form ammonia, which can then be converted into other nitrogen compounds. Cyanolichens are important for the ecosystem, because they provide nitrogen for themselves and other plants and animals, especially in nutrient-poor environments. |
Nitrogen Fixation in Cyanobacteria
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A lichen's response to nutrient enrichment depends on not only on species and environmental factors but also partially on thallus concentrations of nutrients such as nitrogen and phosphorus.
When a lichenized algal cell is nitrogen limited, the addition of nitrogen caused the growth of algal cells. Under nitrogen limiting condition, chlorophyll concentration was positively correlated with the growth of algal cells indicating that should the concentration of chlorophyll increase, the photobiont population will also increase. As lichens absorb nitrogen through fixation, it will have a very strong negative reaction if the nitrogen availability changes, indicating its sensitivity to environmental changes.
General pollution of climate that is indicated by the concentration of nitrogen oxides can also affect the growth of lichen. When compared to bryophyte (non-vascular land plant), which is also sensitive to nitrogen fertilizer, lichen showed a much stronger response.
When a lichenized algal cell is nitrogen limited, the addition of nitrogen caused the growth of algal cells. Under nitrogen limiting condition, chlorophyll concentration was positively correlated with the growth of algal cells indicating that should the concentration of chlorophyll increase, the photobiont population will also increase. As lichens absorb nitrogen through fixation, it will have a very strong negative reaction if the nitrogen availability changes, indicating its sensitivity to environmental changes.
General pollution of climate that is indicated by the concentration of nitrogen oxides can also affect the growth of lichen. When compared to bryophyte (non-vascular land plant), which is also sensitive to nitrogen fertilizer, lichen showed a much stronger response.
· Desiccation tolerance of cyanolichens
Lichens are amazing organisms that can survive extreme dryness by entering a state of suspended animation. They can lose almost all of their water content and still revive when they get wet again.
This ability is called desiccation tolerance, and it allows lichens to live in places where most plants and animals cannot. Lichens are made of a fungus and an alga or a cyanobacterium that work together in a symbiotic relationship. The fungus provides protection and structure, while the alga or cyanobacterium provides food through photosynthesis.
This ability is called desiccation tolerance, and it allows lichens to live in places where most plants and animals cannot. Lichens are made of a fungus and an alga or a cyanobacterium that work together in a symbiotic relationship. The fungus provides protection and structure, while the alga or cyanobacterium provides food through photosynthesis.
Gasulla, F.; del Campo, E.M.; Casano, L.M.; Guéra, A. Advances in Understanding of Desiccation Tolerance of Lichens and Lichen-Forming Algae. Plants 2021, 10, 807.
They have different mechanisms to cope with desiccation, such as producing antioxidants, sugars, proteins, and lipids that protect their cells from damage. Some lichens can also change their shape or color to reduce water loss or reflect sunlight.
Why are so many cyanolichens at risk in Nova Scotia?
In Nova Scotia, the cool temperate and hemi-boreal rainforests and their associated wetlands host a diverse community of lichens including several rare species and a high abundance and richness of cyanolichens.
Habitat loss and degradation has impacted lichens in Nova Scotia; seven species （including six cyanolichens） are considered at-risk and federally protected. Logging is one of the principal causes of the decline of these lichens.
Logging has effects beyond just the removal of the host trees. It also changes the climate. Climatic changes associated with logging may extend as far as 240m into the adjacent forest via edge influence, and clearcut edges do have a negative effect on cyanolichens in Nova Scotia.
Habitat loss and degradation has impacted lichens in Nova Scotia; seven species （including six cyanolichens） are considered at-risk and federally protected. Logging is one of the principal causes of the decline of these lichens.
Logging has effects beyond just the removal of the host trees. It also changes the climate. Climatic changes associated with logging may extend as far as 240m into the adjacent forest via edge influence, and clearcut edges do have a negative effect on cyanolichens in Nova Scotia.
Cyanolichens of forested wetlands
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Leptogium corticola
Interesting facts
Slate-gray when dry; black to olive and jelly-like when wet Distinctive Features Wrinkled and blistered slate-gray thallus with apothecia Lobaria pulmonaria
Interesting facts
Tan to gray-green when dry,bright green when wet; underside orange-brown and fuzzy with paler bare patches Distinctive Features Large,loosely attached lobes with lobes with ridges and depressions like lung tissue; bright green when wet Lobaria quercizans
Interesting facts
Green-gray when dry;blue-green when wet Distinctive Features Flat, red-brown apothecia on a smooth and wrinkled thallus Nephroma bellum
Interesting facts
Brown with a white medulla; lower surface light brown Distinctive Features Thallus dull, lower surface light brown almost always smooth and perfectly naked. Apothecia usually abundant and conspicuous Pannaria conoplea
Interesting facts
Blue-gray to pale brown; often with a dark blue, felt-like margin around the thallus (hypothallus) Distinctive Features Blue-gray, small lobes with dense granular soredia on the margins, often surrounded by a dark, felt-like fungal mat (hypothallus) Pseudocyphellaria holarctica
Interesting facts
Tan or brownish thallus, round patches of bright yellow soredia. The middle layer of the thallus is mostly white, with some shades of yellow in spots Distinctive Features On the ends of the lobes of mature specimens, round patches of bright yellow soredia can be found. The lower surface has a somewhat furry appearance, with occasional small, yellow pores scattered about. Apothecia are rarely seen |
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Other lichens of forested wetlands
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Menegazzia subsimilis
Interesting facts
Green to pale gray; lower surface black Distinctive Features Lobes perforated on the upper surface and hollow; granular soredia in irregular mounds with holes in the center Parmelia squarrosa
Interesting facts
Whitish or greenish gray upper surface, sometimes brown at the edges; black below Distinctive Features Isidia on the upper surface combined with squarrose, black rhizines below |
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Usnea spp
Description
Usnea spp. is a lichen, composed of algae and fungus functioning together in symbiosis, growing epiphytically on a host tree. Punctelia rudecta
Interesting facts
Green-gray, often looking bleached our exceot foe the outer thallus edges; lower surface pale to light brown, occasionally with orange patches Distinctive Features Green-gray, isidiate thallus covered with white speckles, pale-brown lower surface |
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Slugs
Non-native slugs, such as Arion, are becoming a concern for land managers in Nova Scotia, Canada, particularly in forested wetlands. They appear to have a highly diverse diet and may pose a particular risk to native slug species and to rare or at-risk lichens.
In Nova Scotia, Canada, non-native slugs are generally thought to increase grazing pressure on rare and at-risk lichens such as the Endangered Atlantic population of Boreal Felt Lichen .However, the prevalence and severity of slug grazing on lichen communities have not been well documented in North America.
In Nova Scotia, Canada, non-native slugs are generally thought to increase grazing pressure on rare and at-risk lichens such as the Endangered Atlantic population of Boreal Felt Lichen .However, the prevalence and severity of slug grazing on lichen communities have not been well documented in North America.