The diagram above clearly shows the plant zonation patterns across the wetland.
There is a very narrow dry land zone on the eastern section
of this transect (1-6m mark). The plant species here are those which prefer drier
conditions. They include species such as Brambles, Silver Birch, Ivy and Rhododendron. The
Rhododendron, which originally covered the entire area, still occurs in a narrow band down
both the East and West sides of the wetland and on the northern margins. It is prevented
from encroaching further by the wet, marsh conditions in the adjacent areas.
The dry land areas grade very quickly into marsh
(6-28m). 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 wetland.
The marsh zone is characterised by species such as
Willow, Wood Clubrush, Marsh Willowherb, Greater Tussock Sedge, Reedmace, Yellow Iris,
Marsh Bedstraw, Water Mint and Branched Bur-reed. The Silver Birch at the 16m mark was on
a mound raised above the general level of the marsh. It was therefore dry enough at this
point for the Silver Birch to survive.
As the water level begins to rise (29m mark), the
marsh plants begin to die out. Water Mint and Reedmace are the last to die out. As the
marsh plants disappear, swamp plants such as Bog Bean, Greater Spearwort and Water
Plantain take over (29-37m). As the water depth increases, only the Bog Bean is left.
The swamp ends adjacent to the incoming stream
channel. The western bank of the stream very abruptly marks the end of the deep water zone
(38m). The west bank of the stream is raised and Willow and Alder trees have grown up
here. Marsh species predominate to the west of this region. The species here are slightly
different to the marsh species in the centre of the wetland. Soft Rush, Pendulous Sedge,
Monkey Flower (a non-native species), Water Plantain and Lesser Spearwort are all common
species in this area.
The continuous line transect is valuable in that it
does pick up most of the species present in the transect area (36 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
Patterns of zonation are somewhat clearer in the
interrupted line transect (Transect Diagram) where records were
taken every metre. This is because a lot of the less dominant species have been removed
from the picture. However, this transect diagram does not show the patterns of zonation as
clearly as the corresponding transect diagram for the N/S transect.
This is because the 1m transect interval in this E/W transect picks up only about half of
the species present (19, as opposed to 36 for the continuous line transect). In other
words, rather too much 'clutter' has been removed.
There is an added disadvantage with this line
transect in 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
The range of a number of the more important plant species
distributed along the East/West 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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