Learning about Ligules

September 24th, 2010 | by | 4 Comments
Published in Berry Go Round, Botany, Dunes, Grass, Introduced Species, Landscapes
Tags: , , , , , , , , , ,

I’m out on the west coast of Vancouver Island this weekend finding out more about Parks Canada’s dune restoration program in Pacific Rim National Park Reserve.

European Beachgrass (Ammophila arenaria)

European Beachgrass (Ammophila arenaria) creates a wall at the edge of the dunes that prevents sand movement.

Sand dunes up and down the west coast of North America are being choked with introduced grasses, in particular European Beachgrass (Ammophila arenaria) and American Beachgrass (Ammophila breviligulata). These species do a very good job of preventing sand movement (which is why they were introduced in the first place). Unfortunately, most of the native species of plants that can be found in coastal dune ecosystems depend, and even thrive in conditions that are dynamic and changing with a lot of sand movement.

American Beachgrass (Ammophila breviligulata)

American Beachgrass (Ammophila breviligulata) forms dense clumps in sand dunes.

Grasses are fairly challenging to identify but with a little effort both of these “awful ammophilas” can be separated from the native Dune Grass (Elymus mollis). To do so, one must learn a little about ligules.

European Beachgrass (Ammophila arenaria) ligules

The ligules of European Beachgrass (Ammophila arenaria) look a little like rabbit ears.

The ligule is a small membranous flap that occurs where the sheath of the blades of grass joins the stem of the plant. In the case of European Beachgrass, the ligule is very pronounced, looking a little like a pair of up-right ears. In contrast, American Beachgrass has a very blunt ligule with some fringing.

American Beachgrass (Ammophila breviligulata) ligule

The ligules of American Beachgrass (Ammophila brevilligulata) are blunt and sometimes fringed.

Visually there are some other differences as well. European Beachgrass tends to have a thinner leaf (2-4 mm wide) than American Beachgrass (4 – 8 mm wide). In addition, European Beachgrass has a bit of a papery sheath appearance to the base of the stalk of grass while American Beachgrass usually has reddish markings at the base of the leaves.


All of these characteristics require some close examination of the grass itself. A superficial look at the wall of grass marking the top of the beach and the beginning of the dunes might lead one to assume that it is all European Beachgrass. While European Beachgrass is the dominant species, American Beachgrass grows here as well. The native Dune Grass looks quite different in that its leaves are a bluish green in colour and fairly wide (6 – 15 mm wide). Dune Grass has short ligules as well so some care must be taken to separate it from the American Beachgrass since there is some overlap in leaf width. Dune Grass tends to grow in more isolated patches and doesn’t form the thick networks of vegetation that is typical with both species of Ammophila.

Three Grasses

All three grasses are shown here - left and right foreground is Dune Grass (Elymus mollis), middle foreground is American Beachgrass (A. breviligulata), and European Beachgrass (A. arenaria) in the background.

This winter Parks Canada is working to remove substantial sections of Ammophila from the edge of the dunes to encourage sand movement from the beach deeper into the dunes.

In previous years, small scale removal of beachgrass by hand and excavator has resulted in dramatic changes in plant communities in the dunes, restoring the natural sand dune ecosystem. An ongoing larger scale project involving two backhoes began this fall. Large sections of beachgrass have been removed and while it looks a little messy right now, winter storms, wind and waves will finish the work by redistributing the sand and reshaping the dunes. It will be interesting to see the results in the spring!

As you’re visiting the beaches and dunes on the west coast of British Columbia and the United States look for these two species of grass. They are invasive and can radically change a sand dune ecosystem. Check with your local national, provincial, or state parks to find out what is being done to restore the dunes to their natural state.

Further Reading

More botanical delights can be found at Berry Go Round, this month hosted by Bora over at Blog Around the Clock.


Responses

  1. Josie says:

    September 25th, 2010 at 12:50 pm (#)

    Great post, Dave. I was on Denman Island last week participating in a Spartina monitoring program, and spent part of my time on a Washington State/USDA boat which has no name but its skipper affectionately calls the Hairy Ligule. Spartina (cordgrass) indeed has a hairy ligule! In fact, there’s some nice dense patches of Spartina patens right on the Courtenay estuary near you…
    I’ve now looked at many ligules and feel confident in my Spartina abilities…let me know when you want to go Spartina watching on the Tofino Mudflats!

  2. Dave says:

    September 25th, 2010 at 12:56 pm (#)

    I’ll be back and forth between the Comox Valley and Ucluelet over the next couple of months while working on a Wickaninnish Beach sand dunes project so will let you know when I’m next out in Ukee. Will keep and eye on the tides and try to plan the trip for a good low tide day!

  3. Berry Go Round #31 | A Blog Around The Clock says:

    September 29th, 2010 at 7:38 am (#)

    [...] Dave Ingram of the Dave Ingram’s Natural History Blog explains how identification of native vs. introduced grasses requires some Learning about Ligules. [...]

  4. Dave Ingram's Natural History Blog :: Sand Patterns says:

    October 29th, 2010 at 8:54 pm (#)

    [...] much more extensive further south along Wickaninnish Beach. With the “armoured” wall of beach grass (Ammophila sp.) preventing sand movement into the dunes, sand is moved along the beach creating these beautiful [...]

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