Improved large-area forest increment information in Europe through harmonisation of National Forest Inventories

Abstract

Consistent knowledge about the increment in European forests gained amplified importance in European policies and decision processes related to forest-based bioeconomy, carbon sequestration, sustainable forest management and environmental changes. Until now, large-area increment information from European countries was lacking international comparability. In this study we present a harmonisation framework in accordance with the principles and the approach established for harmonisation of National Forest Inventories (NFIs) in Europe. 11 European NFIs, representing a broad range of increment measurement and estimation methods, developed unified reference definitions and methods that were subsequently implemented to provide harmonised increments by NUTS regions (classification system of the European Union: Nomenclature of territorial units for statistics), forest type and tree species groups, and to rate the impact of harmonisation measures. The main emphasis was on Gross annual increment (GAI), however, also Annual natural losses (ANL) and Net annual increment (NAI) were estimated. The data from the latest available NFI cycles were processed. The participating countries represent a forest area of about 130 million ha, and 82% of the European Unions’ (EU) forest area, respectively. The increments were estimated in terms of volume (m³ year-1, m³ ha-1 year-1) and above-ground biomass (t year-1, t ha-1 year-1). The harmonised GAI volumes deviate in a range of +12.3 % to -26.5 % from the results according to the national definitions and estimation methods. Within the study area, the harmonised results show a considerable range over the NUTS regions for GAI, from 0.6 to 12.3 m³ ha-1 year-1, and 0.8 to 6.4 t ha-1 year-1, of volume and above-ground biomass, respectively. The largest increment is found in Central Europe and gradually decreases towards the North, South, West and East. In most countries coniferous forests produce larger increments per hectare than broadleaved forests while mixed forests are at an intermediate level. However, in some instances, the differences were small or mixed forests revealed the largest increment. The most important tree species groups in the study area are Pinus spp. and Picea spp., contributing 29% and 26% of the total GAI volume, respectively. The shares of the prevalent broadleaved species are smaller with contributions of 9%, 7% and 6% by Quercus spp., Fagus sylvatica and Betula spp. The results underline the importance of harmonisation in international forest statistics. Looking ahead, harmonised large-area increment estimation is pivotal for accurate monitoring and evidence-based policy decisions in the changing context of future forest ecosystems dynamics, management strategies and wood availability.JRC.D.1 - Forests and Bio-Econom