TEMPORAL CHANGE OF SPATIALLY AUTOCORRELATED SOIL PROPERTIES - OPTIMAL ESTIMATION BY COKRIGING

Data on temporal changes of soil properties are required to appraise and to mitigate man-made changes in ecosystems. The spatial distribution of a soil property at any one time may be considered to be a realization of a separate random process. On this assumption change can be estimated 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 made at identical points on two or more occasions, and experimental cross variograms between times cannot be computed in the usual way. These problems can be overcome by using pseudo cross variograms. Although the stationarity condition required for the existence of the pseudo cross variogram is theoretically more general than second order stationarity, the practical application of this function remains nonetheless limited to second order stationary random processes. The equations for describing temporal change from destructive sampling are derived, and the kriging system with the pseudo cross variogram is given.