Trees support functional soils in a dryland agricultural area

Trees provide multiple ecosystem services such as carbon sequestration, hydrological regulation and habitat for arboreal animals. However, they are often removed to support agricultural enterprises. Despite the importance of tree remnants, we know relatively little about how soils differ across sites of varying condition. Here, we describe a study where we examined the relative effects of trees, compared with unvegetated interspaces, on soil functions in remnant patches at sites in good and poor condition in two eucalypt communities in an irrigation area in eastern Australia. We found that, in general, carbon and nutrient cycling were relatively greater beneath trees, and in surface soils, but there were no clear trends in relation to site condition. The values of most soil attributes (e.g., soluble and exchangeable cations, nitrogen, phosphorus) were greater beneath trees, indicating strong fertile island effects in both communities. Overall, our study confirms the importance of trees in remnant patches in agricultural landscapes, particularly those in sites of poor condition. It also suggests that soil processes may still be relatively intact, even in sites in poor condition. Our study reinforces the need to protect trees in remnant woodland reserves to maintain critical ecosystem functions related to nutrient retention. These remnants are important for achieving sustainable management of agricultural systems.