The effective hydrological neighborhood: A new concept to formulate harvest area constraints

Forest managers have struggled to develop several measures to mitigate the impacts of logging operations on soil erosion. Two measures have consisted in considering slope restrictions and limiting the size of clearcut harvest areas in timber harvest scheduling models by means of adjacency constraints. However, these constraints build on an externally predefined limit on harvest area valid to all stands regardless of their topographic features. Thus, we present a methodology to formulate maximum harvest area constraints for each stand on the basis of its topographic features and hydrological connectivity. Using a grid-based digital elevation model, we first introduce the concept of the “Effective Hydrological Neighborhood” and propose a method to compute it through the analyses of water flow directions and the LS topographic factor of the USLE. Then, we develop a recursive procedure to compute for each stand the maximum harvest area in any single period and in consecutive periods of the planning horizon. Finally, we formulate a set of maximum harvest area constraints for each stand. The methodology is applied to a eucalyptus plantation in northwestern Spain. The constraints can then be considered in strategic timber harvest scheduling models along with other constraints. In this way, the harvest plans derived at this planning level can be compatible with later solutions considering hydrological connectivity concerns at the tactical level.