Research Projects

Project at a Glance

Title: Determination of variability in leaf biomass densities of conifers & mixed conifers under different environmental conditions in the San Joaquin Valley Air Basin.

Principal Investigator / Author(s): Temple, Patrick J.

Contractor: UC Riverside

Contract Number: 92-303


Research Program Area: Emissions Monitoring & Control, Atmospheric Processes

Topic Areas: Agriculture


Abstract:

Biogenic emissions of reactive hydrocarbons from vegetation constitute a significant, but as yet undefined, fraction of total hydrocarbon emissions in the San Joaquin Valley Air Basin (SJV AB). Uncertainties in the amounts of reactive hydrocarbons emitted by vegetation have contributed to uncertainties in models of regional ozone formation in the SJV AB. The objective of this research was to provide accurate estimates of foliar biomass per unit area, and the variability associated with those estimates, for the dominant native vegetation of the western slopes of the Sierra Nevada portion of the SJV AB. Biomass sampling plots were established at 29 locations within the dominant vegetation zones of the study area. All of the trees on each 500 m2 plot were measured for stem and canopy dimensions and branch samples were collected from representative trees. Measurements of intercepted light and soil samples were collected at each plot. Estimates of foliar biomass were made for each plot by three independent methods: 1) regression of tree diameter with leaf biomass; 2) light interception relative to leaf area index; 3) scaling from branch leaf area and biomass to whole canopy leaf area and biomass. Multivariate regression analysis was used to relate these foliar biomass estimates for oak and for conifer plots to a suite of independent predictor variables, including elevation, slope, aspect, temperature, precipitation, and soil chemical characteristics. Results of the regression analyses showed that elevation was the single most useful parameter to predict foliar biomass of conifer-dominated plots. Regression equations for oak plots were generally not significant, possibly because of lack of variability among the oak plots. Based on these results, GIS techniques were employed to calculate foliar biomass of conifer and mixed conifer forest types in 2 x 2 km grid cells across elevational gradients along the western slopes of the Sierras.


 

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