Valentine Lafond

Reconciling Biodiversity Conservation and Timber Production in Mixed Uneven-Aged Mountain Forests: Identification of Ecological Intensification Pathways

Mixed uneven-aged forests are considered favorable to the provision of multiple ecosystem services and to the conciliation of timber production and biodiversity conservation. However, some forest managers now plan to increase the intensity of thinning and harvesting operations in these forests. Retention measures or gap creation are considered to compensate potential negative impacts on biodiversity. Our objectives were to assess the effect of these management practices on timber production and biodiversity conservation and identify potential compensating effects between these practices, using the concept of ecological intensification as a framework. We performed a simulation study coupling Samsara2, a simulation model designed for spruce-fir uneven-aged mountain forests, an uneven-aged silviculture algorithm, and biodiversity models. We analyzed the effect of parameters related to uneven-aged management practices on timber production, biodiversity, and sustainability indicators. Our study confirmed that the indicators responded differently to management practices, leading to trade-offs situations. Increasing management intensity had negative impacts on several biodiversity indicators, which could be partly compensated by the positive effect of retention measures targeting large trees, non-dominant species, and deadwood. The impact of gap creation was more mitigated, with a positive effect on the diversity of tree sizes and deadwood but a negative impact on the spruce-fir mixing balance and on the diversity of the understory layer. Through the analysis of compensating effects, we finally revealed the existence of possible ecological intensification pathways, i.e., the possibility to increase management intensity while maintaining biodiversity through the promotion of nature-based management principles (gap creation and retention measures).

Reconstructing harvesting diameter distribution from aggregate data

Abstract• ContextDistribution of removed trees among species and diameter classes is usually used to characterize selection harvesting. This information is, however, rarely available when analysing past time series. The challenge is then to determine the minimal level of information required to characterize harvests.• AimsWe tested in this work whether an algorithm based on the total number of trees and volume to be removed enabled the reconstruction of harvesting diameter distributions, when combined with stand diameter distribution before harvest.• MethodsWe tested the algorithm against empirical data in the case of selection system, comparing distributions by χ² tests, and extended its evaluation to more diversified theoretical situations.• ResultsObserved harvesting distributions were well-reconstructed in most empirical cases, with better results when considering mean simulated distributions. The algorithm was also effective for other thinning and harvesting strategies: low thinning, thinning of dominants, and mechanical thinning, whatever the structure of the stand before being cut.• ConclusionTotal number of trees and volume harvested appeared thus sufficient to reconstruct DBH distribution of removed trees in diverse situations, provided that the distribution before harvest was known. This algorithm, therefore, enables the simulation of complex harvesting operations with minimal information.

Trade-offs and synergies between ecosystem services in uneven-aged mountain forests: evidences using Pareto fronts

Uneven-aged mountain forests are considered favourable for the continuous provisioning of multiple ecosystem services (ES). These ES may however exhibit trade-offs or synergies that can be modulated by forest management. Yet, our knowledge remains poor on both the relationships between ES and the way management practices can optimise and reconcile them. In this study, we aimed at (1) characterising trade-offs and synergies between timber production, biodiversity conservation and protection against natural hazards; (2) identifying efficient (i.e. Pareto-optimal) management scenarios for the joint provisioning of these ES; and (3) comparing them to “reference” management scenarios. Using a simulation framework that couples a forest dynamics model, a silviculture algorithm and linker functions relating ES indicators to stand structure, we predicted the response of different ES indicators to various uneven-aged management practices in the Western Alps. With a metamodeling approach and Pareto front techniques, we intensively explored and analysed relationships between ES indicators and found trade-offs between timber production and other ES, but synergies between protection and biodiversity. “Pareto-optimal” management scenarios were characterised by low thinning and harvesting intensities but exhibited gradients of total removals and deadwood and large tree retention along the Pareto front. They greatly differed from our set of production and biodiversity oriented reference scenarios, thus emphasising the strong impact of considering additional ES in scenario optimisation processes. This study highlighted the strengths and weaknesses of Pareto front techniques for both the analysis of trade-offs and synergies between ES and the identification of efficient management practices.

Determining sectoral and regional sensitivity to climate and socio-economic change in Europe using impact response surfaces

Responses to future changes in climatic and socio-economic conditions can be expected to vary between sectors and regions, reflecting differential sensitivity to these highly uncertain factors. A sensitivity analysis was conducted using a suite of impact models (for health, agriculture, biodiversity, land use, floods and forestry) across Europe with respect to changes in key climate and socio-economic variables. Depending on the indicators, aggregated grid or indicative site results are reported for eight rectangular sub-regions that together span Europe from northern Finland to southern Spain and from western Ireland to the Baltic States and eastern Mediterranean, each plotted as scenario-neutral impact response surfaces (IRSs). These depict the modelled behaviour of an impact variable in response to changes in two key explanatory variables. To our knowledge, this is the first time the IRS approach has been applied to changes in socio-economic drivers and over such large regions. The British Isles region showed the smallest sensitivity to both temperature and precipitation, whereas Central Europe showed the strongest responses to temperature and Eastern Europe to precipitation. Across the regions, sensitivity to temperature was lowest for the two indicators of river discharge and highest for Norway spruce productivity. Sensitivity to precipitation was lowest for intensive agricultural land use, maize and potato yields and Scots pine productivity, and highest for Norway spruce productivity. Under future climate projections, North-eastern Europe showed increases in yields of all crops and productivity of all tree species, whereas Central and East Europe showed declines. River discharge indicators and forest productivity (except Holm oak) were projected to decline over southern European regions. Responses were more sensitive to socio-economic than to climate drivers for some impact indicators, as demonstrated for heat-related mortality, coastal flooding and land use.