28 May 2015
For hundreds of thousands of years, trees have provided all kinds of benefits to humanity. Millions of us use wood as fuel, we rely on their fruits and oils, and our houses are wood-framed. We climb them as children, and sit in their shade to escape the heat. But in the past few decades, our focus has increasingly shifted to the importance of trees in regulating regional hydrology1, global climate2 and the global carbon cycle3 as we continue to pump greenhouse gases into the atmosphere. Studies published in this issue (page 441) and the past six months in Nature Geoscience4, 5, 6, 7, 8 highlight that some of the environmental factors thought to control forest dynamics and productivity act in ways quite different than we might have expected, or sometimes not at all.
Terrestrial ecosystems store about three times as much carbon as resides in the atmosphere, and forests are the largest terrestrial carbon sink3. Understanding what regulates the carbon dynamics of forests brings us into the complex, knotty realm of ecology. A tangle of different factors control the growth of a plant and the dynamics of a plant community: the availability of nutrients such as nitrogen or iron, temperature, ozone and CO2 concentrations, water availability, competition and herbivory, and the biodiversity present in a community.