General Ecology–Structure — Abstract of Paper


Leaf Area Index, Leaf Mass Density, and Allometric Relationships Derived From Harvest of Blue Oaks in a California Oak Savanna
John F. Karlik¹ and Alistair H. McKay¹


Given the key role played by biogenic volatile organic compounds (BVOC) in tropospheric chemistry and regional air quality, it is critical to generate accurate BVOC emission inventories. Because oak species found in California often have high BVOC emission rates, and are often of large stature with corresponding large leaf masses, oaks may be the most important genus of woody plants for BVOC emissions modeling in California airsheds. Accordingly, reference data for leaf mass and leaf area for a stand of native blue oaks were obtained through harvest of 14 trees located in the Sierra Nevada foothills. In addition, leaf mass estimation methods based on a volumetric method and allometric relationships were evaluated for these trees. Leaf mass density (leaf mass per surface area of land) was 310 g m^-2 for the site, but consideration of the surrounding grassland devoid of trees would result in a value of about 150 g m^-2, less than half of reported values for eastern U.S. oak woodlands, but close to a reported value for oaks found in an Italian site, which like California has a Mediterranean climate. The mean value for leaf area index (LAI) for the 14 individual trees at this oak site was 4.4 m² m^-2. LAI for the site was 1.8 m² m^-2, but this value was appropriate for the oak grove only; including the surrounding open grassland would result in an overall LAI value of 0.9 m² m^-2 or less. A volumetric method worked well for estimating the leaf mass of the oak trees. Among allometric relationships investigated, trunk circumference, mean crown radius, and crown projection were well correlated with leaf mass. BVOC estimates based on data obtained at the study site indicate blue oaks may be significant contributors of BVOC to California airsheds where this species is plentiful.