Use of shallow samples to estimate the total carbon storage in pastoral soils

摘要

Using data from pastoral soils sampled by horizon at 56 locations across New Zealand, we conducted a meta-analysis. On average, the total depth sampled was 0.93±0.026 m (± SEM), and on a volumetric basis, the total C storage averaged 26.9±1.8, 13.9±0.6 and 9.2±1.4 kg C m~(?2) for allophanic ( n =12), non-allophanic ( n =40) and pumice soils ( n =4), respectively. We estimated the total C storage, and quantified the uncertainty, using the data for samples taken from the uppermost A-horizon whose depth averaged 0.1±0.003 m. For A-horizon samples of the allophanic soils, the mean C content was 108±6 g C kg~(?1) and the bulk density was 772±29 kg m~(?3), for non-allophanic soils they were 51±4 g C kg~(?1) and 1055±29 kg m~(?3), and for pumice soils they were 68±9 g C kg~(?1) and 715±45 kg m~(?3). The C density—a product of the C content and bulk density—of the A-horizon samples was proportional to their air-dried water content, a proxy measure for the mineral surface area. By linear regression with C density of the A-horizon, the total C storage could be estimated with a standard error of 3.1 kg C m~(?2), 19% of the overall mean.