Plant succession and Sediment Cells? Lesson Objectives Understand what plant succession is and how it stabilises depositional features 2. 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

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)

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

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

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.

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.

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.