GEOG 302 Lecture Notes - Lecture 8: Wicken Fen, Peucedanum Palustre, The Broads

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23 Jul 2016
Department
Course
- Environmental management: understanding autecology (dynamics of species population and how
they interact with the envr)
Island Biogeography is the study of the distribution of species or ecosystem(s) over a geographic area over a
geological time. It attempts to explain how isolation and habitat size affects probable mixes of species through
species influx/migration/extinction (Ex. Debate over what is better: a large habitat, or smaller, fragmented
habitats.
Natural environment and succession of Wicken Fen
Succession is the process by which ecological communities undergo changes following a disturbance. There is
- Primary succession (what happens from a massively disturbed area, like a post-tsunami ecosystem.
New growth on disturbed substrate
- Secondary succession is something that happens recurrently, or on previously existing substrate,
from smaller disturbances. Example:
o Fireweed jack pine spruce tree
Getting more and more fire vulnerable (Disaster complex)
Succession in a wetland is HYDROSERE. Often, areas of freshwater eventually dry out to become woodland.
Over this time, marshes and swamps will succeed each other. Wicken Fen has been flooded many times before
(once part of the ocean). But succession can be arrested- for example, through the harvesting of reed and sedge.
This displaces the species such as birds, insects, and diseases (mosquitoes carrying malaria). The change that
took place was the rise of WINDMILLS, due to demand for land. The area was drained, which caused 3 main
problems:
o As water levels in drainage basins fell, the surrounding land became drier. Air became
trapped in the land, oxidation occurred, and there was an increase in microorganism activity
and decomposition.
o Wind erosion on land
o Riverbanks dropped due to compression
In all, this was a vicious cycle- the more the land declined, the greater the need to pump out the water. As
digging around the drainage basin continued, the land began to collapse.
The range of the butterfly was up to 1/3 of England, but the drainage of the fen fragmented the landscape. By
1950, the butterfly was only in Norfolk Broads (network of navigable rivers) and Wicken Fen. Attempts were
made to conserve the butterfly, such as introducing it from other areas to the fen, but it did not work. When
looking at the autecology, they finally saw the connection with milk parsley. We know now that the swallowtail
butterfly has an obligate relationship with milk parsley- it only lays its eggs on it.
o Morphometric change:
The more fragmentation, the more high mobility is a disadvantage (wind blows
them away). Looking back at old butterfly collections, butterflies began to adapt by
becoming smaller and smaller in size (selective pressure). The butterflies introduced
from Norfolk Broads was simply too large to be sustained at Wicken Fen.
o Habitat distribution:
Within Wicken Fen, there was a matrix of habitat types. Some were forested areas
with no plants. Areas with plants (including the milk parsley) were not homogenous,
but patchily distributed. Thus, the ‘habitat’ for the butterfly was not simply all of the
fen- it was only in certain parts.
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