An empirical approach for better estimating soil organic carbon and bulk density using a fixed-volume sampling method.

摘要

Bulk density is necessary to characterize the magnitudes of organic carbon and soil nutrients, but both scale and sampling methods influence bulk density measurements in rocky soils. Fixed-volume core sampling is advantageous for collecting many samples across large areas, but rocky soils necessitate the use of power samplers, which often compact the soil. Our objectives are to improve soil organic carbon pool estimation in Ozark forest soils and to develop a modeling methodology to permit accurate bulk density estimation for samples extracted with a two-person power auger. Samples were taken in soils mapped as loamy-skeletal, siliceous, mesic typic fragiudults, and the widest possible range of rock contents was sampled using a qualitative stratification of low, medium, and high rock contents based on landform characteristics. Associations between coarse fragments and organic carbon concentrations were also evaluated. Preliminary results suggest that the parameters of core-hole depth, soil water, and texture may provide better density estimates for surface horizons than a proportional volume adjustment based on observed core length and hole depth alone. After coarse fragment adjustment, unadjusted mean densities in the surface 30cm ranged from .63 to 1.48 Mg/m3, and with volume adjustment mean densities ranged from.59 to 1.28 Mg/m3 . There was no evidence of a positive association between coarse fragments and organic carbon concentrations. Temporal carbon variability was not statistically significant in a one-year data set, but concatenation with the year two data set is needed for a robust interpretation of the data.