|The diagram below shows the ranges of
eleven of the most important species occurring in the wetland, along the N/S transect
line. The range is the total area in which the species is found.
The diagram was drawn from data taken from the continuous
line transect survey, which noted every plant to touch the line along its entire length.
Data was not used from the interrupted line transects, which recorded plants touching the
line at either 1 or 2 metre intervals. This is because this type of transect will tend to
underestimate the range of species. They are only recorded as being present if they happen
to touch the line at the right point and are otherwise missed.
The blue bars at the bottom of the chart represent
the changes in water depth along the line.
The chart clearly illustrates the plant zonation
patterns in the wetland. It also illustrates how the boundaries of zones become blurred
where certain species overlap and occur in more than one zone. Only three plants of the
plants illustrated (Alder, Wood Clubrush and Marsh Bedstraw) were confined to one zone.
The rest overlap and it becomes difficult to draw a distinct boundary between zones.
Increasing water depths, together with comparisons of the overall composition of the flora
are the most reliable indicators of changes in zone.
Rhododendron is a species which prefers dry
conditions. It is found in the northernmost region of the wetland where there is no
standing water, but extends a little way into the marsh region. Plants such as Alder and
Soft Rush are characteristic of the wetter conditions where dry land grades into marsh.
Soft Rush occurs at the edge of the marsh zone and
also in the wetter woodland areas of the dry land zone. It does not extend far into the
marsh region because plants such as Wood Clubrush, Marsh Bedstraw, Reedmace, Yellow Iris,
Branched Bur-reed and Water Mint dominate this area.
As water depths begin to increase, the marsh species
noted above begin to die out, except for Branched Bur-reed. This continues well into the
swamp zone, where it is joined by floating Duckweed and Canadian Pondweed. Canadian
Pondweed continues into the open water zone.