THE NUMBER OF REPETITIONS DURING OF THE SOIL ORGANIC CARBON CONTENT MONITORING IN THE FOREST REVISITED

Abstract

Using the example of data from the article by E.A. Dmitriev et al., the estimation of the required number of soil samples to assess the SOC content in the forest biogeocenosis during monitoring studies is considered. Primary data on SOC content were obtained in the spruce forest at 166 points in layers 0-10, 10-20, and 20-30 cm af er removal of the litter. T e sampling was carried out at the nodes of a regular grid of equilateral triangles with 1 m side within a regular hexagon with a side of 7 m. T e SOC content was determined by the Tyurin method. T e original article presents statistics for three zones - near-stem, under-crown and inter-crown space. Spatial variation in all zones and at all depths is high, the coef cients of variation are about 50%. It is shown that the number of replicates required for estimating the average SOC content at a 95% conf dence level in the 0-10 cm layer is hundreds of samples and decreases to tens of samples in the 20-30 cm layer. Since the number of repetitions for testing hypotheses about the equality of means depends not only on the conf dence level, but also on the power of the criterion used, the required number of repetitions increases several times. Sampling with samples taken from the entire vertical layer of 0-30 cm and forming mixed samples from them reduces the number of required repetitions, however, careful observance of sample preparation, including primary mixing of samples, is required.