The Jasper Ridge Global Change Experiment

Technical overview
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The Jasper Ridge Global Change Project examines the response of California grassland to four components of global change: elevated atmospheric carbon dioxide, elevated temperature, increased precipitation, and increased nitrogen deposition. Initially funded by a grant from the National Science Foundation to Professors Christopher Field and Harold Mooney, this is the first experimental study to address this broad suite of interacting global changes in the field. To incorporate climate warming and study all treatments in field plots, the experiment uses a new technology (FACE, or free-air CO2 enrichment) in which the level of CO2 is increased by emitting concentrated CO2 from distribution tubing that encircles the two-meter diameter study plots. Temperature is raised with infrared heaters, precipitation is augmented by overhead sprinklers, and nitrogen is added as calcium nitrate (in both dissolved and slow-release forms). For each of the four variables, there are two levels of treatment: ambient (unaltered) and elevated.

The experimental design includes 8 replicate quarter-circle plots for all possible combinations of the four treatments (128 total) and an additional 8 sampling sites that control for the effects of project infrastructure. Studies focus on four integrated components of ecosystem response to the treatments: plant primary production, soil carbon storage, soil nutrient availability, and species or functional-group composition. The combination of a complete factorial design for the treatments together with measurements on multiple, related response variables, provides a test of the experiment's null hypothesis that responses to warming and elevated CO2 in combination are essentially additive, i.e. the sum of the responses to the individual factors.

The JRGCE is currently funded by grants from the David and Lucile Packard Foundation and from NSF.