Volume I: TREES (Timber Resource Economic Estimation System), a forest management and harvest scheduling model, is comprehensively described in the first of a four-volume series. Even- or uneven-aged forest inventories form basic resource units (BRUs), entered by age class or size and diameter classes; stocking level; and management intensity. Management assumptions for each grouped resource unit (GRU), a collection of BRUs, specify species type; site class; inventory shifts; changes in management intensity, land base, and utilization standard; and options for thinning, regeneration, cultural treatment, and growth. Harvest assumptions for each allowable cut unit (ACU), a collection of GRUs, comprise information on seven harvest scheduling methods, financial accounting options, and harvest-priority selection. Inventory, harvest, regeneration/cultural treatment, and total harvest/economic reports are available. Computer operating instructions for TREES are included. Volume II: The mathematical relations implicit in TREES (Timber Resource Economic Estimation System), a forest management and harvest scheduling model, are explained in this second of a four-volume series. Algorithm steps for applying fixed harvest scheduling methods (absolute amount, percent of inventory, and area control) are outlined and effects on harvest policy considered. Algorithms for the more complex variable methods (even-flow of volume, even-flow of a function of volume, present net benefit, and present net worth) are detailed; solution feasibility, optimality, and stability evaluated; and effects on harvest policy again considered. Growth options for even-aged stands (standard yield and approach-to-normal growth or volume) and uneven-aged stands (mortality, diameter growth, and ingrowth and upgrowth) are described. Appendices connect algorithms for the variable methods to their computer implementation and present supporting routines for performing quadratic interpolation and setting equation limits. Volume III:Understanding TREES (Timber Resource Economic Estimation System), a forest management and harvest scheduling model, is further aided by detailed examination of eight sample runs in the third of a four-volume series. In the first seven examples, each of seven harvest scheduling methods-three fixed (absolute amount, percent of inventory, and area control) and four variable (even-flow of volume, even-flow of a function of volume, present net benefit, and present net worth)-is applied to an even-aged inventory. The eighth example illustrates switching from a fixed (absolute amount) to a variable (even-flow of volume) harvest scheduling method for an uneven-aged inventory. Complete input specifications for all required files are provided. Portions of requested reports, including the optimization detail and allowable cut and cut-proportion tables, are illustrated via sample output for all eight examples. Inventory, harvest, regeneration/cultural treatment, and total harvest/economic reports are presented for the first and last examples. Volume IV:The FORTRAN code implementing TREES (Timber Resource Economic Estimation System), a forest management and harvest scheduling model, is annotated in this set of organized references, which forms the fourth of a four-volume series, for exploration by computer analysts or experienced users. System organization is depicted in a series of flowcharts, with accompanying discussion. Reference lists provide the location and description for each computer variable in COMMON, the interrelationships of subprograms and their use of COMMON variables and formal parameters, and the input and output operations performed. Special features of the Control Data Corporation CYBER 73 version of FORTRAN IV are briefly noted and miscellaneous features of TREES, including built-in limitations and diagnostic output requests, described.
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