For every management activity, there are potential 

 impacts on each of the resource outputs and associated 

 environmental effects. These will vary with the charac- 

 teristics of the land on which the activity is applied. 

 This diagram is misleadingly simple from the perspec- 

 tive of a national assessment. The variations in land 

 capability, existing resource conditions, and poten- 

 tial management practices combine to form many 

 thousands of potential output combinations even at 

 a highly aggregated level of analysis. 



Quantifying Multiple Resource Interactions 



It is necessary that these multiple resource inter- 

 actions be quantified to determine whether the 

 Nation's forest and range lands can meet projected 

 resource demands at reasonable costs, both monetary 

 and environmental. A recently developed computer- 

 ized analytical model has the potential of quantifying 

 resource interactions at the regional level. ^ This model 

 was developed in response to the need for a syste- 

 matic way to measure the impact of changes in the 

 level of any one or any combination of outputs or 

 services on the ability of the forest and range land 

 system to produce the remaining outputs or services. 



In this model, the degree of interaction among the 

 the various resources is measured by the impact 

 that increasing one output has on the costs of pro- 

 ducing the remaining products. Using timber and 

 range, for example, the model will aggregate for a 

 region those areas where increasing the region's soft- 

 wood timber supply raises the cost of producing 

 an increment of range grazing (in circumstances where 

 the two resources are competitive); it will also aggre- 

 gate those areas where increasing the timber supply 

 lowers the cost of providing an increment of grazing 

 (in circumstances where the two resources are com- 

 plementary). For purposes of this Assessment, the 

 model considers the interactions between changes in 

 softwood timber, hardwood timber, range grazing 

 of domestic animals, dispersed recreation, wild rumi- 

 nant grazing, water yield, sediment, and storm runoff. 



For use of this model, the forest and range land 

 base was divided into approximately 5,000 resource 

 units. Resource units are a means of categorizing 

 land by its potential natural community, ownership 

 (four classes), productivity (four classes), and stocking 

 condition (four classes). For each resource unit, a 

 set of management levels was identified by combining 

 specific activities from a list of 53 management prac- 

 tices. Different management levels emphasize dif- 



^ Ashton, Peter, James Pickens, Coryell Ohlander and Bruce 

 Benninghoff — Many resources, many uses: a system analysis 

 approach to current and future renewable resource development. 

 Paper presented at the 15th Annual Conference of the American 

 Water Resources Association, Las Vegas, Nevada. September 

 24-28, 1979. 



ferent management objectives and give preference to 

 different resource outputs. 



In the absence of research studies which could be 

 used to estimate the outputs from all appropriate 

 management levels applied to each resource unit, 

 the best current information was gathered from 

 knowledgeable professionals. The basic premise of 

 this data collection effort was that such people with 

 strong backgrounds in appHed research and resource 

 management could jointly specify production coeffi- 

 cients of the land base to form a consistent data base 

 suitable for evaluating natural resource use potential 

 at a national level. 



Thirteen output measures from the process were 

 used in the analysis: 



1. Herbage and browse production mea- 

 sured in pounds/ acre/ year; 



2. Net wood growth measured in cubic 

 feet/ acre/ year; 



3. Wood harvested measured in cubic 

 feet/ acre/ year; 



4. Domestic livestock grazing measured in 

 animal unit months (AUM)/acre/year; 



5. Wild ruminant grazing measured in ani- 

 mal unit months (AUM)/ acre/ year; 



6. Dispersed recreation use measured in 

 visitor-days/ acre/ year; 



7. Water yield measured in inches/ year; 



8. Storm runoff measured in inches/ year; 



9. Sediment yield measured in tons/ acre/ 

 year; 



10. Life form-water measured by percent of 

 area; 



1 1 . Life form-ground measured by percent 

 of area; 



1 2. Life form-shrubs measured by percent of 

 area; 



13. Life form-trees measured by percent of 

 area. 



For the analysis which follows, output and cost 

 estimates were converted to reflect the average output 

 and costs over a 50-year management period. This 

 conversion reflected the transition of lands to new 

 condition classes over this period of time. 



This information was used as input to a linear 

 programming model to determine the level of manage- 

 ment for each resource unit that would minimize the 

 cost of producing targeted levels of outputs of timber 

 and range products while maintaining levels of other 

 goods and services. 



Implications of Meeting Projected Regional 

 Timber and Range Grazing Demands 



To illustrate the usefulness of this interaction 

 model, this section discusses the implications of 



322 



