One of the most common problems students (and faculty!) have when trying to find information is only using one term, or only one term for each idea. For example, take a look at the search history in the screenshot below. If you are interested in biodiversity, you are probably going to want to use it as one of your terms. However, if you limit yourself to only that term, you will be missing out on research that discusses community composition. Sure, there will be some overlap between the two, which is understandable since they are related terms, but you will be missing a lot of potentially good information by not expanding your search and including similar terms.
Do your best to identify different keywords for all your topic concepts. If you have trouble coming up with additional terms, reach out to one of your subject librarians.
This series of short videos will show you a few useful techniques you can use to improve your literature searches.
If you need a quick introduction to a database, check out these videos from you librarians at Miami.