The Influence of Two Tree Species and the Synoptic Meteorological Setting on the Dry Deposition of Calcium and Magnesium to a Mixed Eastern Kansas Deciduous Canopy.

The primary objective of this research was to investigate what factors influenced the dry deposition of calcium and magnesium to selected deciduous trees. As part of the overall research plan, data necessary to address (a) the depositional rate similarity between two tree species and (b) the influence of synoptic meteorology on the overall depositional process were collected and analyzed. This research represents the findings for data collected during the 1988 and 1989 growing seasons. Two tree species (red oak, Quercus rubra; shagbark hickory, Carya ovata) were selected for sampling during periods absent of precipitation. Leaves were collected from three individual canopies at similar geometric locations for each species at approximately three day intervals. Leaves were then washed using distilled, deionized water and the leaf areas were measured. Concentrations of calcium and magnesium were determined using atomic absorption; a mass per unit leaf area were subsequently calculated. The rate of dry deposition was calculated by dividing the mass per unit area difference between two sequential dry segment collections by the time difference. During all dry segments, the synoptic meteorological setting was determined. This was accomplished using on -site meteorological and upper air measurements. Each dry segment was subsequently analyzed using both numerical and subjective classification schemes. Rate data collected for the oak and hickory were compared and found to show significant differences in rate magnitude. The temporal and spatial trend of deposition was similar. Depositional rates were also compared with the synoptic meteorological setting using correlation matrices and multiple linear regression. Two synoptic variables, absolute humidity and relative humidity, typically showed the highest association with calcium and magnesium depositional rates. These variables in addition to other standard synoptic variables were used to generate a series of depositional models. In general these models predicted deposition in both trend and magnitude reasonably well.