Impacts of eucalypt plantation management on soil faunal communities and nutrient bioavailability: trading function for dependence?

Short-rotation forestry systems provide a range of ecosystem goods and services, yet the effects of intensive management on soil invertebrate community composition and ecosystem functioning are relatively unknown. Using an established eucalypt plantation study system, we investigated the effects of irrigation and inorganic fertilisation, and a dual fertilisation and irrigation treatment, on soil invertebrate abundance and community composition. Additionally, plant root simulator probes were used to estimate the effect of these interactions on nutrient bioavailability as a proxy for ecosystem functioning. Fertilisation reduced soil mite and nematode abundance when applied with irrigation, likely due to the increased solubilisation of inorganic fertilisers in water-limited soils. However, differences in soil invertebrate abundances were not associated with changes in plant nutrient bioavailability. Our findings suggest that high input systems can maintain productivity at the expense of shifts in the soil faunal community, which creates a lock-in, whereby there is a continuous need for artificial inputs in order to maintain productivity. Reliance on artificial inputs may reduce the soil's intrinsic capacity to maintain natural ecosystem function in the longer term and should therefore be considered in plantation planning and management.