To find books at UMass only, use the Five Colleges Library Catalog and select the UMass link (top right).
To cast a wider net, search all Five Colleges at once.
Try specific terms first,
then try more general ones.
Searching specific terms may miss a book about the broader topic with just a chapter on your topic.
Use both scientific and common names for organisms, connected with or, as above.
Try using truncation (forest* will find forest, forests and forestry) and variant spellings so you won't miss important titles.