Abstract
AbstractIt is commonly accepted that an estimated soil variogram can be transferred to another similar area for deriving the tolerable spacing of a sampling grid or, more generally, the sample size, given a requirement on the quality of the soil property map of the recipient area. The quality of the derived tolerable grid spacing depends on how similar the population variograms of the donor area and recipient area are. In practice we are uncertain about the variograms of both areas due to sampling errors. Ideally, the uncertainty about the variogram of the donor area is accounted for in deriving the tolerable grid spacing. To assess the transferability, we should also account for uncertainty in the estimated variogram of the recipient area. In this study the transferability of variograms of soil pH, P, Mg and K is analysed for three grassland fields in Ireland, which are similar in soil‐forming factors. One field served as donor area, the other two as recipient area. For all three fields and for each soil property, 500 variograms were sampled from the posterior distribution of the variogram parameters. Results showed that the estimated variogram parameters of the recipient fields differed largely from those of the transferred variograms. The ranges of estimated mean kriging variance values for the various grid spacings, as obtained with the two sets of variograms (one set of the donor field, one set of the recipient field), did not overlap. Even after scaling the transferred variogram with an estimate of the variance of the recipient field, the transferred variogram was of no use for determining the tolerable grid spacing. The difference in the variograms can possibly be explained by the difference in historical land use.Highlights Transferability of variograms to derive tolerable grid spacing for mapping grassland fields is assessed Transferability should be based on the uncertainty distributions of the tolerable grid spacings Due to difference in historical land use, local and transferred variograms differed largely Transferability of a variogram is very poor, even after scaling the transferred variogram
Highlights
Highlights Transferability of variograms to derive tolerable grid spacing for mapping grassland fields is assessed Transferability should be based on the uncertainty distributions of the tolerable grid spacing
To transfer a variogram of a donor field to derive a tolerable grid spacing for mapping of a recipient field by ordinary kriging, we propose the following procedure
This study demonstrates that the transferability of a variogram to derive tolerable grid spacings for another similar field can be very limited, even after scaling the the three grasslands of our case study are similar in major soil-forming factors, that is, parent material, climate, topography and land use, they were under different soil use and management
Summary
Three grassland fields in Ireland were intensively sampled on a square grid (Figure 1). To transfer a variogram of a donor field to derive a tolerable grid spacing for mapping of a recipient field by ordinary kriging, we propose the following procedure. 2 Use the estimated kappa value to draw a large number of triplets of Matérn variogram model parameters from the multivariate posterior distribution, using Markov Chain Monte Carlo (MCMC) and all sample data of the donor field in computing the likelihood (Minasny, Vrugt, & McBratney, 2011). This results in as many transferred tolerable grid spacings as we have sampled variograms in the donor field. We used the geoR package (Ribeiro Jr. & Diggle, 2001) for R 3.3.3 (R Core Team, 2016) for REML estimation of the variogram, and package DREAM (Vrugt et al, 2009) for MCMC sampling with the DREAM algorithm
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
