Manitoba Alvars

 Alvars are globally rare ecosystems that occur along the edges of the Canadian Shield in Canada. This ecosystem is characterized by sparse tree cover and thin soils over a limestone bedrock that makes it a harsher environment. Only drought and flood tolerant species can survive here which makes it a very interesting ecosystem to study for plants. I have had the pleasure of completing my masters research in the Interlake region of Manitoba studying the plants that live on alvars.

 Hoary Puccoon - Lithospermum canescens

 In the spring, flowers such as Lithospermum canescens and Cyprepedium parviflorum attract pollinators with bright yellow flowers. Later in the season when the spring flowers are finished, Gaillardia aristata speckles the field again with yellow-orange flowers.

Lesser Yellow Lady Slipper - Cyprepedium parviflorum

Blanketflower - Gaillardia aristata

  Often the first things to colonize an area of open rock are lichens and mosses. These are very common on alvars since ecological processes maintain the openness and allow them to thrive.

Granite Erratic With Moss and Lichens

 They grow on both rock and tree bark often covering most of the rock or trees surface as seen above and below. These organisms often grow quite slowly indicating that these habitats remain open for long periods of time.

Bur Oak With Lichens

 Unfortunately not all alvars remain pristine. Here you can see nicer green alvar vegetation fading into a field of encroaching Poa pratensis. This invasive grass is commonly found in pastures and since alvars are so barren grazing usually requires providing cattle with hay bails that introduce invasive species to the area.

Poa pratensis Encroaching On Alvar Vegetation

Even admist the disturbances of grazing many alvar species can still find small pockets where the soil is to thin to support invasives. Myosurus minimus is a rare species to find in Manitoba since it reaches it most northern tip of its range here. On the alvars in Manitoba, Myosurus minimus is restricted to lower lying depressions on bare limestone pavement with extremely thin soils.

Tiny Mousetail - Myosurus minimus

Introduction to Manitoba Alvars

Habitat shot of an alvar in Manitoba

Alvars are a globally rare ecosystems characterized by thin soil and sparse tree cover over limestone bedrocks. These were first discovered in Sweden by Carl Linnaeus and were given the name alvar for their barren appearance.  The openness of alvars is maintained by ecological processes such as erosion, flooding, fire, drought, frost heaving and grazing. These dynamic ecosystems are home to many rare and unusual species which are adapted to these disturbances. Alvars are under threats from garbage dumping, off-road vehicle use, mining, over-grazing, development and road building.

Recently, alvars were first discovered in the Interlake region of Manitoba and the Nature Conservancy of Canada and Manitoba conservation formed the Manitoba Alvar Initiative in order to study and preserve these unique ecosystems. 

Map of confirmed alvar areas in Manitoba (Manitoba Alvar Initiative, 2012)

Work done by the Manitoba Alvar Initiative (2012) represents only a “first approximation of alvar types” in Manitoba and the authors recommend that a “quantitative data-based classification scheme be developed to refine the conservation status of alvar types, establish site-condition metrics, recommend compatible land-management activities and advance conservation activities”. 

Table of the various alvar types and parameters used to define them

 My current Masters project aims to build on previous work by completing a comprehensive vegetation survey in order to form a quantitative classification scheme that will verify the alvar types (grassland, wet grassland, jack pine savannah, oak savannah, spruce savannah, boreal shrubland, prairie shrubland, intermediate shrubland) proposed by the Manitoba Alvar Initiative (2012). Additional goals of the project are to make preliminary observations on how disturbances, such as fire and grazing, affect the various alvar types. 

This season, species diversity, abundance and environmental data were collected for 103 plots (10mX10m) from June till August.  Locations of rare species, such as Gastonyi’s Cliffbrake (Pellaea gastonyi) which only occurs on exposed limestone ridges and tabletops, were recorded. The information collected from plots will be used to separate alvars into alvar types allowing for species lists and mapping to be completed for each of the 20 sites on crown land. The completion of this project will give us a better understanding of a complex, dynamic and unusual ecosystem so that we can properly manage and conserve its biodiversity. 

Cliffbrake growing on exposed limestone ridge