Sylvain Caurla

Large-scale dynamics of a heterogeneous forest resource are driven jointly by geographically varying growth conditions, tree species composition and stand structure

Abstract• ContextForest resource projections are required as part of an appropriate framework for sustainable forest management. Suitable large-scale projection models are usually based on national forest inventory (NFI) data. However, sound projections are difficult to make for heterogeneous resources as they vary greatly with respect to the factors that are assumed to drive forest dynamics on a large spatial scale, e.g. geographically varying growth conditions (here represented by NFI regions), tree species composition (here broadleaf-dominated, conifer-dominated and broadleaf-conifer mixed stands) and stand structure (here high forest, coppice forest and high-coppice forest mixture).• Question and objectiveOur question was how does the variance of forest dynamics parameters (i.e. growth, felling and mortality, and recruitment processes) and that of 20-year forest resource projections partition between these factors (NFI region, tree species composition and stand structure), including their interactions. Our objective was to capitalise on the suitability of an existing multi-strata, diameter class matrix model for the purposes of making projections for the highly heterogeneous French forest resource.• MethodsThe model was newly calibrated for the entire territory of metropolitan France based on most recent NFI data, i.e. for years 2006–2008. The forest resource was divided into strata by crossing the factors NFI region, tree species composition and stand structure. The variance partitioning of the parameters and projections was assessed based on a model sensitivity analysis.• ResultsGrowth, felling and mortality varied mainly with NFI region and species composition. Recruitment varied mainly with NFI region and stand structure. All three factors caused variations in resource projections, but with unequal intensities. Factor impacts included first order and interaction effects.• ConclusionsWe found, by considering both first order and interaction effects, that NFI region, species composition and stand structure are ecologically relevant factors that jointly drive the dynamics of a heterogeneous forest resource. Their impacts, in our study, varied depending on the forest dynamics process under consideration. Recruitment would appear to have a particularly great impact on resource changes over time.

Accounting for Active Management and Risk Attitude in Forest Sector Models

Given the importance of anthropogenic determinants in forest ecosystems within Europe, the objective of this paper is to link the evidence arising from biological models to socio-economic determinants, where the expected returns of forest investments represent the main driver. A micro-economic area allocation module is therefore coupled with an inventory-based forest dynamics module and a partial-equilibrium market module in a national-level forest sector model for France (FFSM++). Running long-term scenarios (until 2100), we show the implication of an active management policy on forest composition: when the most profitable option drives forest investments, coniferous forests are generally preferred over broadleaved ones. This result is, however, reappraised when the risk aversion of forest owners is explicitly considered in the model, given the higher risk associated with the former. We further show the strong stability of forest ecosystems that, due to the very long cycles, undergoes very small variations in volume stocks, even in scenarios where the initial forest regeneration is strongly influenced.

Fuelwood Consumption, Restrictions about Resource Availability and Public Policies: Impacts on the French Forest Sector

In the context of climate change and of increasing energy prices, the share of fuelwood in primary energy consumption may increase, especially in countries with large forest endowments. However, larger fuelwood consumption may have non-negligible impacts on forest sectors. This paper assesses those impacts for France using a new model of the French forest sector, and comparing four different policy options to boost fuelwood demand. First, supply- and demand-side policies yield very different outcomes, with a trade-off between trade balance and harvest intensity. Second, even a modest increase in fuelwood consumption leads to tensions over forest stock over time under pessimistic views about resource availability.