| The diagram below shows the ranges of
twelve of the most important species occurring in the wetland, along the E/W 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 two of the plants
illustrated (Greater Spearwort and Bog Bean) were confined to one zone. The rest overlap
and it becomes difficult to draw a distinct boundary between the zones. Increasing water
depths, together with comparisons of the overall composition of the flora are the most
reliable indicators of changes in zone.
The greater part of this transect runs through
marsh, with a short stretch of dry land on the eastern edge. Here species such as Silver
Birch and Willow are found. The Silver Birch does not extend into the marsh area as it is
too wet, although it did occur at one point in the marsh. Here, one plant grew on a raised
mound, which lifted it above the general water level. Willow however, is found right
across the marsh zone, as it prefers the wetter conditions. Alder is another tree species
which is tolerant of high soil water levels. This species occurred where water depth was
less than 5 cms.
Water Mint, Yellow Iris, Marsh Bedstraw, Wood
Clubrush, Reedmace and Branched Bur-reed all extended over most of the marsh zone.
Reedmace was the last marsh species to die out in the swamp zone, as the water depth
increased.
Greater Spearwort, Water Plantain and Bog Bean all
grew in the swamp area, occurring in all but the deepest water of the stream channel. |