At Horseshoe Bay, Bermuda, the visible stages of dune succession are limited due to beach grooming (raking) which disrupts natural development. However, a partial dune succession sequence can still be observed, especially at the posted coordinates in the back dune area. Your task will be to answer the following questions:
- What stage of dune succession do you observe at the posted coordinates?
- What is the elevation at the posted coordinates?
- Do you see evidence of human impact on the dunes and, if so, describe what you see?
- How does plant growth protect the dunes?
- In your log, please post a photo of yourself or a personal item with the dunes in the background.
You may go ahead and log your find, but answers must be received and photo posted within 10-14 days or your log will be deleted.
How Are Dunes Formed?
The sand dunes at Horseshoe Bay are formed through a combination sediment supply, wind patterns, and vegetation. Initially, sediment is transported landward from the beach face by wind, particularly during periods of strong onshore winds. This sediment is often trapped by vegetation that colonizes the area just landward from the limit of storm wave action, leading to the development of embryo dunes.
Depending on the sediment availability and wind conditions, anything from a single embryo dune to an extensive dune field may develop. The dunes can evolve over time, potentially becoming larger. The presence of vegetation is critical in the formation and stabilization of dunes. Vegetation acts as a natural barrier, reducing wind speed and causing sand particles to settle and accumulate. As the dunes grow, they can become colonized by more vegetation, further stabilizing the dune system.
Stages of Sand Dune Succession
Source: Alex C G Cooper, slideshare.com
Sand dune succession refers to the process by which different parts of a sand dune system represent various stages of ecological development over time. It begins with the establishment of pioneer species on the bare sand, which gradually leads to the formation of a stable ecosystem with a diverse range of flora and fauna.
The stages of sand dune succession typically include:
- Embryo Dunes: These are the first dunes formed by the accumulation of sand trapped by shoreline debris and pioneer plants such as marram grass that can withstand the harsh coastal conditions. However, these are often removed on commercial beaches like Horseshoe Bay due to raking.
- Yellow Dunes: As vegetation becomes more established, the dunes become less mobile. The death and decay of vegetation add organic matter to the soil, improving its quality and allowing for a wider range of plant species to thrive.
- Grey Dunes: At this stage, the vegetation cover is continuous, with only a few patches of bare sand. The soil is deeper, with higher moisture and humus content, and the daily temperature range is smaller than in earlier stages.
- Climax Community: In the final stage of dune succession, the ecosystem reaches a stable state known as the climax community. Woody species dominate, forming a maritime forest.
In summary, Horseshoe Bay Beach in Bermuda is not only a beautiful natural attraction but also an important site for the study of dune succession. Dune succession at Horseshoe Bay is a dynamic ecological process in which coastal sand dunes evolve over time through distinct stages, driven by interactions between physical factors like wind and waves, and biological factors such as plant colonization.
Sources:
https://www.biology-fieldwork.org/a-level/succession/sand-dunes/
https://www.field-studies-council.org