Kriging Direct and Indirect Estimates of Sulfate Deposition: A Comparison

Abstract

Due to logistical and cost constraints, acidic deposition is rarely measured at forest research or sampling locations. A crucial first step to assessing the effects of acid rain on forests is an accurate estimate of acidic deposition at forest sample sites. We examine two methods (direct and indirect) for estimating sulfate deposition at atmospherically unmonitored forest sites. The direct method only uses directly measured deposition data, while the indirect method additionally incorporates precipitation measurements from a spatially denser network of monitoring sites. Sulfate deposition values were estimated by point kriging using both the direct and indirect methods. By using the supplemental data from the precipitation monitoring network, estimates of sulfate deposition improved substantially, particularly at sitesthatare relatively isolated to the acid deposition monitoring network. Cross-validation procedures indicate that by using the indirect method, a reduction of approximately 20 to 25 percent in the predicted error sum of squares occurred.

Citation

Reams, Gregory A.; Huso, Manuela M.P.; Vong, Richard J.; McCollum, Joseph M. 1997. Kriging Direct and Indirect Estimates of Sulfate Deposition: A Comparison. Res. Pap. SRS-7.Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 10 p.