A method of land evaluation including year to year weather variability

Land evaluation is sensitive to the effects of annual variability in weather. A method to incorporate this variability into land evaluation systems is proposed, using the land capability system for Scotland as a case study. Land capability classes were found to be sensitive to the climate reference period from which data are taken. Individual stations rarely occupy their long-term land capability class. In addition, the relative position of stations in the land classification alters from year to year, indicating variations with time in spatial correlation structures. Markov chain analysis was used in a risk assessment approach to estimate the mean return time to a land capability category for individual stations and for areas of land. The main conclusions were: that land evaluation systems should not be applied using data from a different period to the baseline weather period used to establish the classification; there is a need to establish whether groups of stations tend to behave in similar ways over space and through time; mapping zones of risk could provide a means of formally incorporating weather variability into land evaluation.