Are point measurements in a bog representative of their surrounding area

Abstract

Descriptions of abiotic properties in bogs are often based on point measurements. To assess whether these point measurements are representative of their surrounding area, depth to water table (DTW), soil moisture, pH, electrical conductivity (EC), the degree of peat humification and ash content were measured at 25 points in a 4 m × 4 m study site. The gravimetric moisture content of the peat samples varied little (coefficient of variation (CV): 2–4 %), while the volumetric moisture content (CV: 11 %) and DTW (CV: 48 %) were more variable. Pore water pH also varied little throughout the study site (CV: 1 %), but pore water EC was more variable (CV: 84 %). The degree of humification was generally within 1–2 points on the von Post scale. Ash content was fairly variable (CV: 61–100 %). Plant species composition varied across the study site in relation to microtopography and was, not surprisingly, most strongly influenced by DTW and near-surface soil moisture. Some point measurements in bogs (e.g. pH, gravimetric moisture content) are likely to be representative for an area of at least several square metres, while other variables (e.g. EC, volumetric moisture content, degree of humification, ash content) may need to be measured at more than one point to obtain a representative average.