Predicting long-term effects of silvicultural practices on forest site productivity

We describe a system for predicting long-term consequences ofsilvicultural practices, especially those that may decrease long-termforest productivity. The system requires: (1) conceptual models thatincorporate current understanding of interactions among ecosystemprocesses; (2) process studies that, guided by the conceptual models,allow us to establish equations for the transfer of material and energyamong ecosystem components and to refine the conceptual models; (3) amanagement-oriented simulation model, developed from the conceptual model,used to predict long-term consequences of silvicultural practices; and(4) validation studies that test those predictions. Conceptual modelsmust account for interactions among processes as well as for all materialflow. Process studies should clarify the relations between processes andtheir controlling factors; operational trials should duplicate silvicul-tural practices to determine their effectiveness. In general, processstudies should be replicated at each site, operational trials across manysites. Experimental treatments selected for process studies need notadhere to standard silvicultural practice. Development of a management-oriented simulation model must be a high priority. FORCYTE, developed byJ. P. Kimmins and K. A. Scoullar, may offer the best starting point forforesters and researchers in the Pacific Northwest. Operational trialsshould validate the simulation model rather than merely provide informa-tion for specific sites, species, and treatments.