Texture effects on carbon stabilisation and storage in New Zealand soils containing predominantly 2 : 1 clays

Developing strategies to sequester carbon (C) in soils requires an understanding of the key factors that influence C stabilisation. Although fine mineral particles, especially clay, play a key role in stabilising soil organic matter (SOM), the relationship between SOM and texture is often not strong. We examined the role of the fine mineral fraction in C storage in sedimentary soils in New Zealand. Soils, representing two soil Orders (Brown and Recent) and different land use histories (total of 58 soils; 0-15 cm depth) were sampled. The concentration of C (and N) in four particle size fractions (50 µm) was determined (soils fractionated after dispersion by sonication). The soils had a wide range of textures and SOM; the mass proportion of clay (0.05) between the C concentration in whole soil and clay content. The concentration of C in the clay fraction, which varied over a wide range (35 to 135 g [kg.sup.-1] clay), decreased as the mass proportion of clay increased. A similar trend in C concentration was observed for the fine (5-20 µm) silt fraction. Because of this inverse relationship between the mass of the fine fractions and their C concentration, there was little change in amount of stable C (defined as C in the Additional keywords: C stabilisation by mineral particles, extractable Al & Fe, organic matter fractions.
Introduction Soils play an important role in the global C cycle. Management practices that enhance soil C storage are frequently advocated as possible mitigation options to offset C[O.sub.2] emissions from [...]