Redwood forest ecosystem of northern California depends on fog during rainless summers

Science Daily: As the mercury rises outdoors, it's a fitting time to consider the effects of summertime droughts and global warming on ecosystems. Complex interactions among temperature, water cycling, and plant communities create a tangled web of questions that need to be answered as we face a rapidly changing climate.

Drs. Emily Limm and Todd Dawson (University of California, Berkeley) recently tackled one aspect of the challenging question of how climate change can impact plant communities that obtain water from fog. Their results are published in the July issue of the American Journal of Botany.

Fog is an important source of water to ecosystems around the world, because fog allows plants to stay hydrated even during times without rain. Fog may condense and drip to the soil, where it can be taken up by roots. Alternatively, some plants are able to absorb the water from fog through their leaves, allowing these plants to immediately benefit from the atmospheric moisture that may never reach the forest floor. The fern Polystichum munitum covers the forest floors of the redwood forests in northern California. Limm and Dawson examined variation in the ability of the leaves of P. munitum to absorb the water from fog.

The researchers found that the quantity of water the plants absorbed varied in the different regions of the redwood forest. "Today, summertime drought conditions are greater in the southern end of the redwood forest ecosystem of Northern California, and this reduces P. munitum abundance and plant size. These smaller ferns in the south are less able to capture fog water that drips to the forest floor during the summer, and they may therefore suffer more drought stress than ferns in the northern end of the redwood forest ecosystem," Limm stated.

This has important implications for the structure of plant communities. Limm explained, "If climate change causes further shrinkage of these ferns, this will change how fog water is distributed on the forest floor and may lead to dramatic changes in how the redwood understory functions."…

Fog in Redwood National Park, shot by Scott Catron, Wikimedia Commons, under the Creative Commons Attribution ShareAlike 3.0 License