Models are great to use to make a concept easier to understand, to visualize a process or outcome, and also to allow a scientist to test selected variables. IMOLD is a great model of leaf decomposition, because it allows the students to interact with two variables affecting decomposition rates, and test those variables in many more ways than they could at their own local research site. The fact that IMOLD uses real data collected over many years to populate the data points of the graphing activity highlights the fact that data collected for one experiment has uses to other groups in different ways. It is important that students design and carry out their own hands-on experiments with litter decomposition, but this model will help them understand the concepts behind decomposition better, and also give them ideas for multiple questions they can pursue on their own.
Plant litter decomposes at different rates depending upon many factors. Two such variables are the chemical composition of the litter itself, and the type of climate it is in. IMOLD applies knowledge learned in three animations and then allows the student to test the decomposition rates of various litter types with different chemical compositions in different environments, or test rates of decomposition of different litter types in one environment.
In this model, students can decide upon a question to investigate, choose the variables they are testing, and learn very directly how chemical composition of the litter and climate can affect decomposition rates. They can also choose to look at the effects of soil temperature and soil moisture on the decomposition rates. Finally, students can choose among 25 different types of vegetation, and seven different ecosystems. In the process, they will be learning about different climate regions in the US, and also about the representative plant species from these ecosystems.
The chemical compositions of the leaf litters in this model come from the NSF-sponsored program called LIDET (Long-Term Inter-site Decomposition Experiment Team) of the Oregon State University and the Andrews Forest LTER (Long Term Ecological Research) Site. http://andrewsforest.oregonstate.edu/research/intersite/lidet.htm The LIDET project itself is worthy of study; a painstaking, 10 year, 28 site experiment to gather data about factors affecting long term decomposition and nitrogen accumulation of leaf litters. The information about their methods, the biomes involved, and the plant species themselves, all available through the IMOLD website, are a treasure trove of data that an inquisitive student could use to pose further questions of their own.
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