Assessment of Growing Stock Components for Data Harmonization in International Reporting. Lithuanian Case Study

Abstract

One of the main goals of forest inventories is estimation of the growing stock volume. Practically all countries for this purpose use the same main parameters of trees – measured stem diameters at breast height (DBH) and the height or length of tree stems, i.e. the distance between root collar and terminal bud. At the same time growing stock volume estimates differ between countries and assessments. Sometimes they do not include stumps, tops, small size stems, while sometimes they include large branches. To unify the estimates of the growing stock volume, the most reasonable way is to follow the practice of forest inventory and to use the main inventory object, i.e. tree stem as the reference object during forest assessments. Assuming the traditions of various countries to use different national reference objects, it is suggested to estimate the volume of stumps, tops, small sized trees or large branches and to make adequate corrections in the national data. This study suggests a method of how using the data of national forest inventory and estimation models of stem volume and its separate parts to adjust national data in compliance with all European or global forest resources assessment data. Presented in the study are estimates of separate parts of stems or small sized stems that can be used as the default values for the harmonization of growing stock volume estimates in countries with similar climatic and soil conditions. The growing stock volume of Lithuanian forests, assessed using the national definition, overestimates volumes assessed using global forest resources definition by 8%, while using COST Action E43 definition – by 2%.