BOX 2-2 Site-Specific Forestry Management
Modern forestry practices require extensive harvest planning to maximize or optimize harvesting while maintaining yields from forests over many decades. Forest management today must consider forest ascetics and scenic vistas, historic and archeological sites, competing uses for recreation, grazing, and other extractive uses like harvesting for mushrooms, medicinal plants, ornamentals, and mining of mineral deposits.
Many forestry companies have adopted the use of models within a GIS to aid in site-specific management of forest resources. The economic value of forest products is sufficiently high to justify extensive use of site-specific technologies.
Management plans include decisions about modes of logging, such as by helicopter, tower, line, or chain, which depend on topography, stand condition, and distance to roads. GPS is used by timber cruisers to identify specific trees for harvest and locations of harvested trees are entered into the GIS database. GIS is used to predict the potential for soil erosion after logging, especially if the site is close to a stream, and to develop mitigation strategies. This allows erosion models based on actual soil characteristics, topography, and site conditions (i.e., cover type) to be used in developing spatially explicit erosion hazard estimates over the site rather than arbitrary rules like distance to roads or streams.
Evaluation of off-site nutrient and herbicide transport are other concerns. Fire hazard is another risk factor that can be minimized using spatially explicit models for site management and mitigation. Fire risk and fire hazard models require a digital terrain model, information about the fuel load and its vertical and horizontal distribution, and weather information. Foresters may also use site-specific forest mensuration models to predict tree growth that consider site-specific soil fertility and moisture
remaining in the soil after a crop is harvested. This works best for less mobile soil chemical properties such as phosphorus and potassium concentrations or pH. Nitrogen is more mobile and requires more frequent sampling to assess the appropriate credit levels. Nitrogen remaining in the soil after harvest may be available to the next crop, unless temperature and rainfall conditions result in leaching or volatilization. More accurate crediting of residuals can reduce costs and environmental load where overapplications would have occurred, and can improve yields for locations that would have been undertreated. Second, precision management of soil nutrients allows the producer to set variable yield goals for fields that do not have a uniform productive potential. With variable yield goals, inputs for a