Earth's Climate System: The Biosphere & Ecosystems
The online Encyclopedia of Earth provides nice summaries of fundamental basic topics, but of course bazillions of other good sources exist. For related sources, see Ecosystems.
The Biosphere (Encyclopedia of Earth)
Ecosystems (Encyclopedia of Earth)
Ecology (Encyclopedia of Earth)
The Millenium Ecosystem Assessment: From 2001 to 2005, over 1,300 international experts produced this state-of-the-art scientific appraisal of the world’s ecosystems and the services they provide, plus the scientific basis for conservation and sustainable use. Key sections include Biodiversity, Desertification, and Wetlands and Water.
Biosphere: How Life Alters Climate: Long chapter from Spencer Weart's fine book The Discovery of Global Warming (rev. 2008).