FCBA – Forest inventory

Every year, the French NFI inventories the whole metropolitan forested area including poplar plantations. The NFI is carried out in public and private forests, irrespective of whether they are available for wood supply or not. Hedges and heathlands are also inventoried. FCBA uses these data and applies methodologies developed internally to correct the availability of wood numbers.

FCBA has also worked on the development of aerial stereoscopic image analysis (systematic cover over the forested area) and airborne laser data (experimental projects) that allow measuring young stand attributes and integrate them in resource projections, which is currently made impossible by the use of a 7.5 cm-diameter threshold for tree inventory.  The availability of such images also makes it possible to compare stand height measurements at different time periods. That would allow mapping stand growth dynamics and increase the accuracy of wood availability on the local scale. The use of periodic maps of forest attributes linked to the growing stock (e.g. stand height, basal area, volume) in a multi-source forest inventory design would contribute to improve the accuracy of NFI results at local level. Major improvements on the assessment of harvest conditions in wood resource projections are also expected in the near future. Cadastral (ownership) maps are currently fully digitized but not yet completely vectorized. As soon as this task is completed, integration of further attributes such as cadastral stands size and ownership size as stratification factors in the resource projections will be possible. Maps of harvest costs based on slope and distance to roads would also be useful to determine areas where additional harvests could be a problem because of economic constraints.

The second major issue of wood availability is the prediction of future resources. The typical temporal horizon for forest resource projections ranges between 10 and 30 years ahead. Typical spatial scales in forest resource projection refer to: i) a given tree species in a given area, ii) all the broadleaved/coniferous species in a given area, iii) a comprehensive approach on a regional or national domain. Fundamental target variables include the estimation of future growing stock (in quantity and quality), the availability of wood for different uses (sawnwood, pulpwood and fuelwood), and projections of forest carbon stocks and fluxes. In France, specific growth models are still missing for many wood species. And for the existing models (e.g. for abundant species such as sessile oak, beech or maritime pine), they are usually not appropriate for projections at the regional level, or even less at the national level. As a consequence, robust projections for the French forest resource, which is characterized by its diversity in forest types and ecological conditions, and its non-stationary state, have required the development of large-scale forest resource models and simulators, as well as a specific expertise based on forest inventory data. The description of the current forest resource (area, growing stock, etc. distributed by tree species etc.) and the parameters of forest dynamics processes (growth increment, natural mortality and recruitment) are also of interest of FCBA in order to be implemented in wood resource projections in France based on NFI data and statistics.

Typical models used for evaluation of wood availability are diameter-class and age-class distribution models. More elaborated models are needed, such as models taking into account the stratification of the forests and wood species according to different geographic region or a categorization of the study area based on biophysical classifications, models which consider different silvicultural scenarii for each stratum, since a stratum often aggregates stands differing in terms of ecological conditions, forest owner objectives (wood production, biodiversity, hunting, recreation, nothing, etc.) and forest management practices. These type of modelling is of major interest for R&D in this topic at FCBA.