Elemental and isotopic compositions of New Zealand regional soils identifies human and climate-induced effects

Abstract

A regional soil study of 61 sites from the Wairau and Awatere Valleys, Marlborough region, New Zealand characterised the geochemical baselines of different land-use types. The study used three stable isotopes (δ13C, δ15N, δ34S) and 65 elements to describe the influence of parent-rock geology, human and climate-induced effects and natural transport processes on the soil quality and soil health of this region. The temperate Marlborough region produces high quality wine and the elemental and isotopic composition of a subset of vineyard soils are examined in more detail to identify soil characteristics specific to this agriculturally productive region. Higher levels of Cd, K, N, P, S and Zn were found in vineyard soils compared to forested and rural soils, indicative of anthropogenic agricultural inputs. Stable isotopes in vineyard soils had higher δ13C and δ15N values and lower δ34S values than forested and rural soils, typical of more highly cultivated soils. The natural geogenic inputs from the ultra-mafic mountains enclosing the Wairau and Awatere Valleys were geochemically distinct from localised anthropogenic contaminants. Comparisons with a further 240 New Zealand urban (Dunedin) and rural (Southland-Otago region) soils suggests the elemental contaminants found in the Marlborough vineyard soils may be specific to high-yielding agricultural zones across New Zealand.