TEMPORAL CHANGE OF SPATIALLY AUTOCORRELATED SOIL PROPERTIES - OPTIMALESTIMATION BY COKRIGING

Data on temporal changes of soil properties are required to appraise a nd to mitigate man-made changes in ecosystems. The spatial distributio n of a soil property at any one time may be considered to be a realiza tion of a separate random process. On this assumption change can be es timated optimally by kriging. This results in a set of equations with close resemblance to a bivariate cokriging system. Difficulties arise where soil sampling is destructive, for then measurements cannot be ma de at identical points on two or more occasions, and experimental cros s variograms between times cannot be computed in the usual way. These problems can be overcome by using pseudo cross variograms. Although th e stationarity condition required for the existence of the pseudo cros s variogram is theoretically more general than second order stationari ty, the practical application of this function remains nonetheless lim ited to second order stationary random processes. The equations for de scribing temporal change from destructive sampling are derived, and th e kriging system with the pseudo cross variogram is given.