U.S. Department of Energy, Office of Science

Program for Ecosystem Research

Research Project   Physiological, demographic, competitive, and biogeochemical controls on the response of California's ecosystems to environmental change

Principal investigator:   Michael L. Goulden

Southern California transects and research sites

Project research sites that traverse a wide range of ecosystem types located along a Santa Ana Mountains--San Jacinto Mountains transect.

Project goal

Understand how a change in climate (precipitation) might affect Southern California's ecosystems.

Ecosystem being studied

Two types of research sites are being established: (1) Natural Gradient Sites in grassland, coastal sage, chaparral, evergreen hardwood forest, pine forest, pinyon pine woodland, and creosote bush desert and (2) Experimental Sites in grassland, coastal sage, pine forest, and creosote bush desert. All of the field sites will be located along a 150-km climate transect that traverses the Santa Ana Mountains and San Jacinto Mountains.


Experimental and monitoring systems have been deployed in the study ecosystems.

Why this is important

The focus is on high value ecosystems in a region where climatic change is expected to have a major impact. Four considerations underscore the importance and relevance of this research. (1) Southern California provides an excellent natural laboratory for understanding how climate controls ecosystem structure and functioning. (2) Southern California's location at the edge of the mean winter storm track and exposure to climatic variability associated with the El-Nino and Pacific Decadal Oscillations increase the likelihood of pronounced future climatic changes. (3) Southern California's semiarid climate and steep climatic and vegetational gradients increase the likelihood that a change in climate will have a major effect on California's ecosystems. (4) The tight link between climate, ecosystem structure and functioning, and natural disasters (e.g., wildfire, insect outbreaks, and mudslides) in Southern California increases the likelihood that climatic change will result in significant socioeconomic impacts.


Interannual comparisons within the Natural Gradient Sites will be used to understand how short-term (year-to-year) variation in precipitation and temperature controls ecosystem physiology and functioning. Spatial comparisons between the Natural Gradient Sites will be used to understand how long-term (decadal, century, and longer) variation in precipitation and temperature determines ecosystem structure and functioning. Measurements at the Natural Gradient Sites will include net primary production (NPP), litterfall, leaf area index (LAI), community composition, nitrogen mineralization, plant water status, and the fluxes of CO2, energy, and water vapor.

Manipulations of water input at the Experimental Sites (i.e., an experimental doubling or halving of ambient precipitation) will be used to more mechanistically understand how a change in moisture balance affects ecosystem functioning. Manipulations of fire, nitrogen deposition, and seed input at two of the experimental sites (coastal sage and grassland) will be used to understand how multiple environmental changes interact to control ecosystem structural and functional changes. Measurements at the Experimental Sites will include NPP, plant community composition, nutrient cycling, and plant water use.

Further information is available at Prof. Goulden's website.


Michael L. Goulden, University of California, Irvine

Katharine N. Suding, University of California, Irvine

Funding period:   May 2005 to present