Psammosere, dune succession in Umbra Nature Reserve

Question 1

Dunes are formed by

Answer 1

deposition of sand on the landward side of wide beaches

Question 2

Waves and onshore winds carry material above the tide line…

Answer 2

…where it may be trapped behind small obstacles forming small embryo dunes

Question 3

these small embryo dunes, often less than a metre in height…

Answer 3

…can provide a home for a group of specialist pioneer plants, including sand couch grass. These species can tolerate the low nutrient saline and windswept conditions

Question 4

Root systems of pioneer plants can help stabilize dunes…

Answer 4

…trapping more sand and the dunes grow. Marram grass is the most important plant species here; it thrives on burial by sand, forming a complex rhizome root network which binds the dune in place

Question 5

Over time a series of ridges can be created parallel to the shoreline…

Answer 5

…nearest the sea are embryo dunes, then foredunes, then yellow and grey dunes. Between these ridges lie low sheltered areas termed dune slacks.

Question 6

In dune slacks the conditions may be wet or dry but are always more sheltered…

Answer 6

…and provide a habitat for plants, insects and animals less suited to the dune ridges.

Question 7

A walk inland from a beach through dunes is essentially a walk through time…

Answer 7

…starting with the initial colonization of the embryo dunes to the final stage in the sere - the climax vegetation community

Question 8

Expected changes in characteristics moving inland:

Answer 8

Proportion of bare sand decreases as more species invade and conditions improve.
Proportion of soil that is organic in origin from plants and animals increases.
pH decreases from salty alkaline environment of shore as decomposing dead plant material adds organic material.

Question 9

Expected changes in characteristics moving inland:

Answer 9

Ability of soil to retain water improves as organic material is added.
Range of plant, insect and animal species increases, although pioneer species are replaced.
The height and stability of both the dunes and vegetation increases.

Question 10

Magilligan, 32km squared of land is Ireland’s largest area of coastal deposition… the psammosere studied is:

Answer 10

Umbra Nature Reserve Dunes

Question 11

Umbra: youngest embryo dunes - hostile environment for plant life…

Answer 11

…very dry, salty and lacks humus; alkaline pH of 8-9 partly due to shell fragments. Pioneer plant - sand couch grass - stores water in succulent leaves. Helps slow and collect sand blown from beach. Vegetation cover sparse; 80% of dune is exposed sand.

Question 12

Umbra: Foredunes - first seral stage of pioneer community..;.

Answer 12

…older slightly higher foredunes - sometimes referred to as yellow dunes because of high proportion (over 20%) of visible sand. Mobile dunes, collecting sand and growing in height. Marram grass dominates. well adapted to dry conditions(rolled leaves, waxy surface). Long rhizomes which grow laterally and vertically. Long tap roots reach groundwater deep below the surface and help stabilize the dunes, allowing other plant species to colonise.

Question 13

Umbra: Dune slacks - between dune ridges. Often near or below water table. More sheltered environments, plant range:

Answer 13

wild strawberries, buttercups, violets

Question 14

Umbra: Grey dunes - older, fixed dunes at later seral stage of succession…

Answer 14

…gradually conditions for plant growth improves with distance from beach. pH of grey or mature dunes is reduced (6.5-7.5 - slightly acidic or alkaline). More shelter, less salt. Better conditions - number and diversity of plant species increases, covering the sand surface. Less than 10% of dunes now visible sand. Plants die and decay - thin layer of humus develops, hence name grey dunes. Moisture and nutrients present in humus help colonization of this part of the dune system.

Question 15

Umbra: grey dunes - plants grow in rosettes, helping to maintain moisture:

Answer 15

dandelions, plantains, ragwort.
Plants with leafy stems - bird’s foot trefoil, clover.
Fescue and meadow grass replace marram.
Further inland, burnet rose and sea buckthorn

Question 16

Umbra: dune scrub/woodland - final seral stage of climatic climax - climax vegetation in Umbra dune ecosystem is a deciduous forest - with willow, hazel, birch and oak. At rear of dunes, under tree canopy…

Answer 16

…undergrowth and ground surface is rich in insect and plant life: wood anemones, wood sorrel, ivy and mosses. In many parts of Umbra dune system the climax vegetation has been replaced, including by planting coniferous woodland.

Question 17

Management of Umbra dunes - a plagioclimax vegetation -

Answer 17

• much of dune system at Magilligan would have developed into forest were it not for introduction of rabbits. Through grazing, the rabbits preserved the dune vegetation by preventing encroachment of trees and bushes. As such, this is an excellent example of a plagioclimax vegetation community.

Question 18

As a result of myxomatosis, rabbit numbers have declined sharply…

Answer 18

…but in some areas of the dunes, including Umbra, grazing cattle have been introduced to retain the plagioclimax vegetation. These animals are placed on the dunes in the winter months to restrict the invasion of forest plants into the dunes. The aim is to retain the distinctive rich assemblage of plant species found on the older dune ridges and in the damper dune slacks where rare orchid species thrive in the summer.

Question 19

Recreational use of dunes impacts severely on the vegetation. marram grass has little resistance to trampling and, when damaged, its binding properties are lost. When bare sand is exposed to the wind without roots to secure it, a blow-out can form.

Answer 19

This is a concave area of exposed sand on the face of a dune. In order to protect the Umbra dunes from such environmental damage, fencing is used to restrict pedestrian access.