|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 Alder. The Rhododendron which used to dominate this area prior to restoration (Historical Background) still dominates this marginal dry land zone
(7-21m 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) contains small Rhododendron and Silver Birch seedlings. However, the area is too
wet for them to compete successfully here. Soft Rush is common in this region.
Further into the marsh area (approximately 31m -
46m), species such as Willow, Yellow Iris, Water Mint, Wood Clubrush, Branched Bur-reed
and Reedmace predominate. As the water becomes deeper, most of these species begin to die
out, leaving Yellow Iris to dominate.
With increasing water depth, only the Branched
Bur-reed is left from the marsh flora (55m mark) and open water species such as Canadian
Pondweed begin to occur. This is the main species to be found in the open water zone.
The continuous line transect
is valuable in that it does pick up most of the species present in the transect area.
Twenty nine plant species were found on the continuous line transect, whereas only sixteen
were recorded on the every metre, interrupted N/S transect. However a great number of
plants have to be diagrammatically represented along the line for the continuous line
transect. This 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, this interrupted line transect 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 interval of one metre, is that it is likely to
underestimate the range of each species. (The range of a species is the total region
through which it occurs along the line.) It may, at times, even miss a fairly dominant
species entirely from a particular region (see Water Mint
on the E/W 1 metre interrupted line transect). 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
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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