A couple of years ago I wrote a feature for Oxford Today about the climate change research that Earthwatch carries out in Wytham Woods, just outside Oxford. Wytham Woods is actually a reasonably large (by today's standards) patch of wood, with an intriguing history and an amazing track record in ecological research, to the extent that there is now an entire book about it:
Peter Savill, Christopher Perrins, Keith Kirby, and Nigel Fisher:
Wytham Woods: Oxford's Ecological Laboratory
Oxford University Press 2010
Publisher's page with link to pdf of first chapter
When I visited the Earthwatch project in Wytham Woods, it was run as a corporate partnership, recruiting volunteers only among the employees of the relevant company. From next year, however, the project appears in the generall Earthwatch programme, so everybody can join the fun, jug the trees and weigh the voles:
Full details of the Earthwatch project.