Jacques Hebert

Modeling recent bark stripping by red deer (Cervus elaphus) in South Belgium coniferous stands

Abstract• ContextOver the past few decades, the impact of large herbivorous ungulates on forest vegetation has been clearly highlighted. Among those impacts, bark stripping of coniferous trees is one of the most damaging. Bark stripping leads to rot development, inducing serious loss of timber value.• AimsThe present study aimed firstly at evidencing the factors explaining the variations observed in fresh bark peeling rate for spruce and Douglas-fir in southern Belgium and secondly at identifying the key factors to consider when setting up a deer management plan.• MethodFresh bark peeling rate was recorded with a systematic sampling survey from 2004 to 2007. The covered territory was then divided into 63 distinct hunting zones of area ranging from 1,000 to 25,000xa0ha. About 5,000 plots were monitored annually. Each zone was characterized with a large number of explanatory variables. The explanatory variables were integrated firstly into fixed linear models using a stepwise procedure, and then into a mixed model.• ResultsThe significant variables included in the model (R2u2009=u200944xa0%) are (by decreasing order of importance) red deer densities, proportion of coniferous stands and agricultural areas, snow cover, distance to urban habitats, and species diversity in the understory.• ConclusionThe models revealed the impacts of several factors on bark peeling: deer density, deer-carrying capacity of the territory, landscape structure, and severity of winter conditions. The adjusted model allowed subtracting the impact of winter conditions in order to produce a relevant indicator for hunting management. In addition, the model was used to assess the sensitivity of a forested area to bark peeling based on its environmental characteristics.

A Silvicultural Decision Support System to Compare Forest Management Scenarios for Larch Stands on a Multicriteria Basis.

In forest resource planning choosing a silvicultural scenario is becoming a complex problem especially due to the multiplicity of goals and wide-ranging criteria that forest managers have to consider in any decision making process (Diaz-Balteiro & Romero, 2008; Kangas & Kangas, 2005; Maness & Farrell, 2004). For a long time, research focussed on growth modelling aimed at describing stand evolution through the construction of growth models for even or uneven-aged stands. These tools are useful for predicting and analysing stand evolution over time but they are not designed to compare and help to select appropriate silvicultural scenarios. With reference to that, DSS (Decision Support System) is a computer application typically designed to address the multi-faceted nature of management questions. Every decision can affect criteria of various kinds like: environmental issues (e.g., biodiversity conservation, carbon sequestration,..), economic issues (e.g., timber, wood quality, source of energy, ..) or social issues (e.g,. recreation, employment,..). Considering the increasing complexity of new challenges in forestry such systems are very useful in a wide range of fields, especially in sustainable natural resource management, business planning, transportation, timber harvest scheduling, ... (Gordon et al., 2004 ; Reynolds, 2005). In this paper we propose a silvicultural decision support system (SDSS) which is an extension of this concept. It consists in the selection of a silvicultural treatment that fits the best to the objectives assigned to pure even-aged stands which are, in this case, larch plantations. This SDSS has been developed to predict the influence of silvicultural alternatives on larch stand evolution and help forest managers choose scenarios according to preset goals. It is made of three interconnected modules designed for (i) growth prediction based on initial stand density, thinning regime and site index (scenario building), (ii) assessment of a set of indicators defining scenarios, and (iii) comparison of scenarios according to appropriate indicators using a Multi-Criteria Decision-Making – MCDM approach (Pauwels et al., 2007). Financial, technico-economic and ecological or environmental indicators are calculated in order to characterize wood production both qualitatively and quantitatively at the stand level. The SDSS is integrated into a user-friendly software package called “MGC_Larch (Make Good Choice for Larch)”. It has been developed for pure and even-aged larch stands