1. Plant succession and Sediment Cells?
Lesson Objectives
Understand what plant succession is and how it stabilises
depositional features
Understand sediment cells as a system
Skills
Complete Chi-squared analysis on quadrant data collected in the field
Key Words:
Pioneer species
Succession
Climatic climax community
Halophytes

2. Stabilising depositional features
Many depositional features consist of sand and shingle and are therefore loose and
unstable and easily eroded and transported.
Sand dunes are made of wind blown sand and are stabilised by a process called
Plant Succession.
1. Bare ground is gradually colonised by plants called pioneer species.
2. Pioneer species modify the environment by binding sand or mud with their roots
and add nutrient when they die and decay.
3. Creeping plants, with leaves, help keep moisture in the sand/mud. These changes
allow other species to colonise.
4. The new invaders modify the environment by providing shade and improve the soil.
5. As the environment changes, different species colonise until it becomes stable.
6. The final community to colonise is the climatic climax community (trees)

4. Sand Dune Plant succession
Task: annotate your diagram to explain what plant succession is.
Marram grass!

5. Salt Marsh succession Salt Marshes are areas of flat,
Some of plants are Halophytes –
plants that can tolerate saline
(salty) conditions.
Salt Marshes are areas of flat,
silty sediments that accumulate
around estuaries or lagoons.
They develop;
In sheltered areas where
deposition occurs
Where salt and fresh water meets
Where there are no strong tides
or currents to prevent deposition
or accumulation
As mud flats develop, salt tolerate plants (such
as eelgrass) begin to colonise and stabilise them.
Halophytes such as codrgrass, help slow down tidal
flow and trap more mud and silt.
As sediment accumulates, the surface becomes
drier and different plants colonise e.g. sea asters.
Creeks (created by water flowing across the estuary
At low tide) divide up the slat marshes

6. Plant succession field work
Results
This is a KITE DIAGRAM which show the species found and their richness along the transect from the shoreline at each site.
Methods of Data Collection
The quadrant is a 50cm x 50cm square.
From the shoreline, place the quadrant at regular
intervals, e.g. every 5m.
Count the number of different plant species that are within the quadrant (you may count the number of sub-squares that each species takes up within the quadrant).
Record the results in table.
Task: See the results table and calculate the significance of the data collected using the
Chi-squared statistical test.

7. Distance from the high water mark 10m 20m 30m 40m 50m 60m
total
Number of plants observed within a plant quadrant (O) 1 11 15 14 9 5 56
This table shows the number of Marram grass plants at various points in an area of sand dunes. This data is known
as observed (O), or actual numbers that exist when doing a Chi-squared test.
At first glance, it would seem as if the distance from the water mark is important in determining the number of
marram grass plants present. But how important? The Chi-squared test shows how clustered distributions are -
it compares how clustered a distribution is with how it might be if everything was evenly distributed.
1. Establish a hypothesis: There is no difference in the distribution of marram grass plants with increasing
distance from the high-water mark.
2. Decide what the hypothesis means. A total of 56 plants would be evenly distributed with 7 plants at each of
the 8 sampling sites. This is the expected (E) or theoretical numbers, which would exist if the marram grass were
evenly distrubuted to match the hypothesis.
3. Now compare the observed values (O) with the expected Values (E) and calculate the value known
as Chi-squared.
4. Chi squared or x2 is the final figure in the table. This figure means nothing by itself. It has to be referred to
significance tables.
5. degrees of freedom are arrived at by subtracting 1 from the number of categories tested, in this case 8.

8. This means that as the our
chi-squared total is greater than any
of these values at the 7 degrees of
freedom, then there is 0.01%
Probability of the value occurring
by chance ie one in 1000 occasions!
There for the hypothesis is rejected.
It means that chance alone is unlikely
to have caused the observed
distribution of marram grass, and
there is a 99.9% probability that
the observed differences are
statistically highly significant. In this
case the distribution of marram grass
is closely linked to the distance
from the high water mark.