Evaluating Kriging as a Tool to Improve Moderate Resolution Maps of Forest Biomass |
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Authors: | Elizabeth A Freeman Gretchen G Moisen |
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Institution: | (1) U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Forestry Sciences Laboratory, 507 25th Street, Ogden, UT 84401, USA |
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Abstract: | The USDA Forest Service, Forest Inventory and Analysis program (FIA) recently produced a nationwide map of forest biomass
by modeling biomass collected on forest inventory plots as nonparametric functions of moderate resolution satellite data and
other environmental variables using Cubist software. Efforts are underway to develop methods to enhance this initial map.
We explored the possibility of modeling spatial structure to make such improvements. Spatial structure in the field biomass
data as well as in residuals from the map was investigated across 18 ecological zones in the Interior Western U.S. Exploratory
tools included directional graphs of summary statistics, three dimensional maps, Moran’s I correlograms, and variograms. Where
spatial pattern was present, field and residual biomass were kriged, and predictions made for an independent test set were
evaluated for improvement over predictions in the initial biomass map. While kriging has some potential benefit when analyzing
the field data and exploring spatial structure, kriging residuals resulted in little or no improvement in the initial biomass
map developed using Cubist software. Stationarity assumptions, variogram behavior, and appropriate model fitting strategies
are discussed. |
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Keywords: | Biomass Correlograms Forest Inventory and Analysis Kriging Moran's I Variograms |
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