I have no idea about Colorado.
There are several books that will introduce the science of ecology to you. I'm guessing you want a first-year undergraduate ecology textbook. You're probably looking for a copy of
Essentials of Ecology by Colin R. Townsend, Michael Begon and John L. Harper. If you fancy being more ambitious, try for
Ecology: From Individuals to Ecosystems by Michael Begon, Colin R. Townsend and John L. Harper. With luck you'll find a student selling textbooks.
If you want to understand
agroecosystems, from a
practical permaculture perspective, I recommend
Agroecology: the Ecology of Sustainable Food Systems by Stephen Gliessman. Review at some point in the next week or so, I hope. I've already reviewed one of his books from the standpoint of learning to do research:
https://permies.com/t/56250/books/Field-Laboratory-Investigations-Agroecology-Stephen
On a related note,
Practical Field Ecology: A Project Guide by C. Philip Wheater, James R. Bell and Penny A. Cook teaches what it says on the cover.