Estimating surrogates, utility graphs and indicator sets for soil capacity and security assessments using legacy data

Abstract

Context Legacy data from prior studies enable preliminary analysis for soil security assessment which will inform future research questions. Aims This study aims to utilise the soil security assessment framework (SSAF) to evaluate the capacity of soil in fulfilling various roles and understand the underlying drivers. Methods The framework entails: (1) defining a combination of role(s) × dimension(s) and identifying a target indicator (a soil property that can be used to evaluate a particular role × dimension combination) or a surrogate indicator (an alternative indicator when there is not a clear target indicator); (2) transforming the indicator into a unitless score (ranging from 0 to 1) using a utility graph based on expert knowledge; (3) fitting the remaining soil properties (potential indicators) into utility graphs and weighing them using (a) ordination and (b) regression method. The application of this framework is demonstrated in evaluating two soil roles: nutrient storage and habitat for biodiversity (with pH and microbial DNA Shannon’s diversity index as surrogates, respectively) for an area in the lower Hunter Valley region, New South Wales, Australia. Key results The regression model provides utility estimates that were similar to those obtained from surrogates, in comparison to the utility derived from the ordination model. Conclusions This study provides a methodological pathway to examine the capacity and drivers of fulfilling different soil roles. The standardisation of this method opens the door to a complete quantification under the SSAF. Implications Indicators derived from a legacy dataset can be used for soil security assessment.