Impracticable sampling requirements to monitor Blackfeet Nation carbon related soil health indicators

Abstract

Before the effects of grazing management on soil health can be assessed, a baseline analysis of soil conditions needs to be completed. This study, conducted across the Blackfeet Nation in Northwest Montana, explores patterns and variability of volumetric soil organic carbon (SOCv), using catena-based sampling and co-located holes to account for local soil variability. The research also conducts power analyses, a statistical test to determine the needed sample size to have a high likelihood of detecting a real effect, by examining key soil health indicators variability to assess the feasibility of detecting changes in SOCv. My findings indicate that detecting small shifts in SOCv requires potentially hundreds of thousands of samples per site due to the high local soil heterogeneity of these semiarid rangeland soils. These findings are supported by others in the literature. SOCv stocks were partly influenced by soil-forming factors such as vegetation and climate. However, other factors, such as rangeland management and hyperlocal conditions, may have a greater effect on explaining SOCv stocks and hillslope variability than soil-forming factors, although a copious number of samples will be needed to confirm this. These findings highlight the importance of integrating current and historical land use into SOCv models. Future research should explore SOCv changes after rangeland management changes while factoring in sample size and developing methods to extrapolate better SOCv and other soil health data across large rangeland landscapes.