The diagram above clearly shows the plant zonation pattern across the wetland.
At the northern-most end of the transect, species which
prefer drier land predominate. This includes species such as Nettles, Brambles,
Rhododendron, Silver Birch and Scots Pine. The Rhododendron which used to dominate this
area prior to restoration (Historical Background) still
dominates this marginal dry land zone (6-21m mark). The marsh area adjoining the dry land
zone prevents the Rhododendron from encroaching further, but it is easy to see that if the
wetland were allowed to silt up to any extent, the Rhododendron would once more rapidly
cover the area. The trunks of Rhododendron can stretch virtually horizontally, above
ground level, for many metres. It is therefore possible for the roots and main trunk of
the plant to be on acceptably dry land, while the rest of the plant canopy reaches well
out into adjacent marshy areas. This means Rhododendron plants are capable of extending
their zone of dominance well beyond suitable ground conditions.
The dry land zone grades into the marsh area beyond
the Rhododendron (22metre mark). The marsh zone is characterised by water-logged sediments
and levels of standing water which vary with the topography of the zone. Dips and hollows
fill with water, while higher mounds are dry. It must be stressed that the water
levels marked on the diagram above were correct at the time of the survey. However, they
will fluctuate according to the amount of rainfall and stream water which is entering the
The marsh area closest to the dry land zone
(22m-30m) has many small Rhododendron and Silver Birch seedlings. The area is too wet for
them to compete successfully here. Soft Rush is also common in this region.
Further into the marsh area (approximately 31m -
46m), species such as Yellow Iris, Water Mint, Marsh Bedstraw, Willow, Wood Clubrush,
Branched Bur-reed and Reedmace predominate. As the water becomes deeper, most of these
species begin to die out, leaving Yellow Iris, small Water Mint plants and Branched
Bur-reed to dominate.
With increasing water depth, only the Branched
Bur-reed is left from the marsh flora (56m mark) and open water species such as Duckweed
and Canadian Pondweed begin to occur. These are the main species to be found in the open
The continuous line transect is valuable in that it
does pick up most of the species present in the transect area (29 species in this case).
However, the great number of plants which have to be diagrammatically represented along
the line makes the illustration quite difficult to look at and extract information from.
There is a great deal of 'clutter' taking the eye away from general patterns of
In contrast, the interrupted line transect (Transect Diagram) where records were taken every metre very clearly
shows the patterns of plant zonation. This is because a lot of the less dominant species
have been removed from the picture. The disadvantage with this line transect is that it is
likely to underestimate the range of each species. This is the total region through which
the species can be found. As records are only being taken at every metre mark, plants will
only be recorded if they happen to touch the line at the right point.
The range of a number of the more important plant species
distributed along the North/South line transect is shown here.
This diagram was derived from the continuous line transect data, for the reason noted just
Why use line transects? - the
merits of different types of line transect.
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