Screening the habitat function of biochar-amended vineyard soils at field plot-scale, based on invertebrate avoidance behaviour

Abstract

There is an urge for rapid, cost-effective and ecologically representative tools that inform on possible changes in habitat function of biochar-amended soils, at representative spatial and temporal scales. We employed a battery of invertebrate avoidance behaviour tests to screen and biomonitor a vineyard soil amended with a premium grade mixed-wood chip biochar (applied alone or mixed with compost) at plot–scale, at 4 or 40 t ha−1, over 12 months. The assays combined representative organisms with complementary ecological functions in agroecosystems, i.e. earthworms (Eisenia andrei), collembolans (Folsomia candida) and isopods (Porcellionides pruinosus). In all treatments, soil habitat function was within the recommended limits for the selected invertebrate groups, by the corresponding soil quality guideline or protocol. However, collembolans exhibited significant avoidance behaviour from 6-month aged biochar treatments, coinciding with a strong peak in soil electrical conductivity (EC), suggestive of osmotic stress. Earthworms responded less sensitively than collembolans, with isopods being the least sensitive group to biochar amendments. Further, there was a preference by isopods for freshly-amended soil, whereas earthworms and collembolans preferred 12-month aged biochar amended soil, both of which can be explained, at least partly, by nutrient inputs. Overall, results show that invertebrate avoidance behaviour, based on multiple test groups, can be used to screen and complement site-specific biochar risk assessment strategies, for early decision-making and management. For screening batteries of mixed wood biochars, this study further supports the combined use of collembolans and earthworms, with isopods as a complementary test group.