The use of the natural range of variability for identifying biodiversity values at risk when implementing a forest management strategy

The Natural Range of Variability is a concept used under the ecosystem management paradigm that means understanding the disturbance-driven spatial and temporal variability of the ecological systems and mimicking them in management strategies. With this project, we developed a framework that permitted addressing biodiversity issues under the lens of the Natural Range of Variability (NRV) for a managed public forest in central-west Alberta. To do so, we brought together a spatial harvest scheduler, a fire and succession landscape simulator, and a toolbox of biodiversity indicator models. Indicator models, that encompass landscape configuration, ecosystem diversity, stand internal habitat features and speciesspecific habitat supply models, were applied on the outputs of the landscape dynamics simulator to define the NRV. The risk of losing biodiversity values in applying the forest management strategy was addressed by comparing indicators outputs over the simulation horizon with their respective NRV. Results demonstrate that no forest-age-related indicator evaluated on the harvest scheduler output shows an important deviation from the NRV. However, in regards to forest cover types there is obviously a loss in ecosystem diversity, as a direct effect of the stand composition control of the silvicultural strategies. We found that patch size distribution is generally compliant with the NRV, although we observed more large patches and better connectivity for old growth patches under fire-driven landscapes. We also found that downed woody debris volume and many understory vegetation (ground lichen, herb and shrub) covers were at risk. Over the seventeen wildlife species, we detected nine species that could be jeopardized by important loss of habitats. Back-tracking bottleneck forest conditions that put these biodiversity values at risk has allowed development of recommendations with regards to landscape design and adapted practices. Key words: BAP toolbox, fire-driven landscape, natural disturbance regime, ecosystem diversity, landscape configuration, wildlife habitat models, risk analysis

Implementation of mid-scale fire regime condition class mapping

We used mid-scale Fire Regime Condition Class (FRCC) mapping to provide Hawthorne Army Depot in the Mount Grant area of Nevada, USA, with data layers to plan fuels restoration projects to meet resource management goals. FRCC mapping computes an index of the departure of existing conditions from the natural range of variability, and consists of five primary steps: (1) mapping the Potential Natural Vegetation Types (PNVT) based on interpretation of a soil survey; (2) refining PNVTs based on additional information; (3) modelling the natural range of variability (NRV) per PNVT; (4) using field verification, calculation and mapping of departure of current distribution of structural vegetation classes interpreted by remote sensing (IKONOS 4-m resolution satellite imagery) from the NRV; and (5) mapping structural vegetation classes that differ from reference conditions. Pinyon–juniper and mountain mahogany woodlands were found within the NRV, whereas departure increased from moderate for low and big sagebrush PNVTs and mixed desert shrub to high for riparian mountain meadow. Several PNVTs showed departures that were close to FRCC class limits. The common recommendation to reach the NRV was to decrease the percentage of late-development closed and cheatgrass-dominant classes, thus increasing the percentage of early and mid-development classes.