About This Project

The current drought in California is causing widespread impacts in many ecosystems throughout the state, but the extent of drought effects on redwood trees and forests is uncertain. We want to evaluate how the drought is impacting southern redwood forests in order to help understand and predict how this unique ecosystem might respond to a future changing climate.

Ask the Scientists

What is the context of this research?

California's coast redwood is widely known as the Earth's tallest tree. However, we know very little about how drought affects redwood trees and forests.

California is currently suffering a record-breaking drought, and more severe droughts are predicted in the future. Drought can reduce tree growth rates, increase tree susceptibility to insects and disease, decrease seedling establishment, and may even lead to tree death.

In October 2014 we made preliminary measurements to examine drought effects on coast redwood, Douglas fir and California bay laurel trees at two sites with contrasting site conditions.

Now in the 4th consecutive year of the drought, we want to expand this research project by examining tree water status, leaf integrated physiology, and trunk growth responses to the drought.

What is the significance of this project?

Redwoods once grew throughout the entire Northern Hemisphere. Today, redwoods only naturally occur along a narrow coastal strip in northwest California and in southwest Oregon where temperatures are mild and precipitation is abundant.

In 2014 we revealed that redwood trees in our two study sites were more water-stressed than those we have measured in other locations during non-drought years. We expect tree water stress to be even worse in 2015, so hope to obtain more measurements and samples.

Results will show us how redwoods in the southern part of the range are responding to the current drought. We plan to share this information with the State and National Parks and other landowners to help develop effective conservation and management strategies for redwood forests in a changing climate.

What are the goals of the project?

We want to improve our understanding of how drought impacts coast redwoods and other important tree species in two forests at the southern end of the redwood range near Santa Cruz, California.

In the summer of 2015 we will measure soil moisture content, canopy temperature and humidity, and treetop leaf water potential. We will also collect leaf samples for analysis of their stable carbon isotope composition. We will compare the 2015 data to 2014 to evaluate how the extended drought has impacted the trees.

At the end of the 2015 growing season we will collect tree-ring cores from a sub-set of trees to analyze historical patterns of tree growth. This will help us evaluate how the last 4 years of drought have impacted tree growth relative to prior non-drought years.

Thank you for your support!