Research Projects

Quantifying biogenic volatile organic compound (BVOC) emissions is critical in the development of effective ozone and fine particle control strategies in certain of California's air sheds. However, because of the diversity and complexity of California's vegetation (e.g. more than 6000 plant species), as well as the large areal extent of its airsheds, additional field data are needed to produce reliable gridded, speciated BVOC emission inventories from current and future ARB modeling efforts. The principal objectives of this field-based research project were to generate data needed to further develop predictive methods for BVOC emissions and leafmass for the large number of plant species relevant to California, and to further validate the vegetation landcover maps currently in use. To meet these objectives, we surveyed total BVOC emissions for more than 200 plant species not previously measured, using a photoionization detection system to identify emitters vs. non-emitters of BVOC for important California plant species; developed and tested methods for estimating leafmass, leaf area index, and leafmass densities for urban trees; conducted biomass sampling in a blue oak savanna to test leaf mass and leaf area index allometric relationships for this high-emitting species; conducted quantitative field-based analysis of the GAP GIS landcover vegetation database for the San Joaquin Valley; and continued to work collaboratively with ARB staff to further develop a state-of-the-science methodology for the generation of a quantitative statewide BVOC emission inventory for California. Among our principal findings were that plant taxonomy provided a useful framework for categorizing emitting plant species, genera, and families; the volumetric method for estimating leafmasses, and corresponding leaf area indices, gave good agreement with field measurements, including whole-tree harvests for urban trees and oaks; mean leafmass densities for urban trees and a natural stand of blue oak trees were higher and lower, respectively, than values for eastern deciduous forests; and the GAP GIS database for the Central Valley, while showing substantial agreement with species found in the field, exhibited enough discrepancies between GAP listings and our field surveys to imply the need for a careful review of the utility of GAP for BVOC inventory development in California. The detailed data and predictive methods resulting from this field program will be directly useful in testing and improving current BVOC emissions models being developed by ARB, including the statewide BEIGIS model.