Influence of the Value of Relascopic Coefficients on the Accuracy of Determining the Stand Basal Area

Abstract

When conducting angle-count sampling in the forests of Ukraine, the most common is the use of factor gauge with a relascopic coefficient of 1. According to the standards, the recommended value of this coefficient depends on the approximate stocking and mean diameter of the stand and can be 0.5, 1, 2, 3, and 4. Proceeding from the fact that in Ukraine there are no tools for relascopic measurations that would allow making measurements using the 5 values of the relascopic coefficient provided for in the standards, the authors of this paper developed and tested an original model of the factor gauge “Crab”. The purpose of this paper is to investigate the accuracy of determining the stand basal area of stands using relascopic coefficients of various values depending on the mean diameter and stand density. By comparing the data on fixed-area plots with a radius of 17.85 m with the data of angle-count sampling, it was discovered that no systematic errors were found that underestimated or overestimated the results of angle-count sampling. It is determined that deviations of the stand basal area from the true values slightly depend on the value of the relascopic coefficient, as well as on the stocking and mean diameter of the stand. According to the authors, the accuracy of the results of determining the stand basal area during angle-count sampling directly depends on the representation of the tree selection zone within the circular sample. This is completely random when using any relascopic coefficient. It is established that in mixed forest plantations, the greatest accuracy in determining the sum of cross-sectional areas of individual forest elements is provided by small coefficients (1, 0.5, and 2). In pure stands, it is advisable to use larger relascopic coefficients (2-4). This implies a corresponding increase in the number of measurements that can better cover stands and increase the accuracy of the results obtained

Keywords

• angle-count sampling
• fixed-area plots
• factor gauge
• mean diameter
• stocking