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Honors Biology Laboratory INVESTIGATING FOREST SUCCESSION Introduction: In nature, communities of organisms experience frequent change. Sometimes, existing plants create environmental conditions in an ecosystem that promote the growth of a new and different community of producers. The replacement of a community by another is called “ecological succession.” Many different factors initiate succession in forest ecosystems. And many different environmental variables influence the types of trees that grow to replace an existing forest. Nevertheless, by studying a forest one can infer much about the history of the ecosystem. And by analyzing the age structure of different species, one can also predict how the forest will change over time. In this investigation you will learn to “read” the dynamics of a forest community. Materials: Masking tape Pen/pencil String Meter sticks (2-4 per group) Plastic bag for collection of leaves Graph paper- for drawing of “plot” made by group Field guide to local trees Lab books for data collection Data Collection: Working in groups of 5-6, you will study an area in the forest that is approximately 5meters by 5meters. To approximate your “grid” you will use the meter sticks and string provided to mark off your area of study. Within the 5x5meter area, you will identify and count numbers of species of every tree. It is critical not to skip trees. If you are having trouble identifying a species because it is so tall or otherwise challenging, seek help from other students or the teacher. Also every identified tree must be categorized by an estimate of its age. Tree ages will be estimated using their diameter at breast height (DBH). These are the categories: Sapling Young Adult Mature Old Over mature Less than 1 cm @DBH 1 to 7.5 cm 7.6 to 12.5 cm 12.6 to 22.5 cm 22.5 to 37.5 cm Greater than 37.5 cm Jobs: Data keeper- has their lab notebook to record data Grid drawer- uses graph paper to draw out their “plot” Measure width of tree- corresponding to number of tree (see below) Leaf collection- everyone in group other than data keeper. Collect and tag, using masking tape, according to the # of tree on plot (example below) If you can’t reach the leaf, make a drawing of your leaf and “tag” it. You will determine the genus and species name in laboratory later after data collection. 3 1 2 4 5 Data analysis: 1. 2. 3. Lab groups will pool data to come up with class totals. (Why is this a good idea?) Devise a system with other students to do this efficiently. (Wiki anyone?) Calculations- using class data a. Total tree density (total of all trees/square meter) b. Density for each species (total of each species/square meter) c. For each species, percentage at each age. Graphs- using class totals a. Choose 5 of the species that yielded the most data. For, each, graph the distribution by age b. Graph the distribution of all species by density Lab Write-up: (in lab notebook) 1. 2. 3. 4. An introduction: Explain, discuss the concepts of the lab (such as ecological succession) Procedure followed Data- spreadsheet, calculation results, graphs Analysis and conclusions a. Discuss and explain your results b. Refer to data in your explanations c. Address the following in your conclusion: i. What was this forest like (in terms of species composition, species densities) 50 to 100 years ago? ii. Predict what the forest will be like in the future iii. Why is the forest changing? iv. How confident are you about the data? Sample Date Table: __________________________________________________ Species Saplings Young Adult Mature Old Over-mature Ex : Maple Acer saccharum 7 4 2 1 1 0