This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. Wildl. Soc. Bull. 13:121-130, 1985 EVALUATINGPOPULATION-HABITAT MODELS USING ECOLOGICALTHEORY CURTIS H. FLATHER, U.S. Department of Agriculture,Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO 80526 THOMAS W. HOEKSTRA, U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO 80526 Passage of the Forestand Rangeland Re- CRITERIA FOR SELECTION newableResources Planning Act (P.L. 93-378) Populationmodels can be classifiedas either (RPA), as amended by the National Forest energy-flowmodels, population-parameter ManagementAct (P.L. 94-588), requiresthe models, or habitat-evaluationmodels. We U.S.D.A., ForestService (FS) to develop and analyzed these3 approacheswith respectto conductperiodic national assessments of re- theirpotential for meeting assessment goals. newable natural resources on forestsand Energy-flowmodels are restrictivebecause rangelands.Such assessmentsreport the cur- the data requirementsand knowledgeneces- rentand expectedstatus of naturalresources, sary to constructthem are not available for and proposealternative opportunities with as- most wildlifespecies. Population-parameter sociatedecological, economic, and social im- modelscurrently are limitedbecause data are pacts (Hoekstraet al. 1979). difficultto obtainand applicationsdo not ad- The appraisalsof wildliferesources require dress populationresponse to land manage- theability to forecastconsequences of human- ment actions.Habitat evaluations,however, induced environmentalchanges accurately, attemptto establisha directlink betweena relativeto bothnational and forest-levelman- populationand the habitatto be altered.In agement planning.Models relatingwildlife addition,existing habitat data bases will sup- populationsto habitathave been developed. portregional analyses. Thus, we chosehabitat- The FS must develop, modify,and recom- based modelingas a startingpoint for research mend assessmentmethods for wildlife,and on techniquesfor national assessments. needs a basis forevaluating these methods. A We then rated specifichabitat-evaluation synthesisof existingecological knowledge and modelsbased on objectivityand cost of data, theoryinto a frameworkfor evaluating these abilityto directlyestimate population levels modelscan functionas thatbasis. ratherthan habitat quality, and capabilityto In termsof FS assessmentgoals, a synthesis predictchanges in wildlifepopulations from should expedientlyidentify ecological weak- alternativeland-management activities. In ad- nessesand limitationsin modelsand provide ditionto PATREC, some of the othermodels a mechanismfor proposing recommendations considered (Hawkes et al. 1983) includedthose and researchhypotheses. Accordingly, this pa- developedby Willis(1975), Hawes and Hud- per reviewsand organizesecological theory son (1976), Boyce (1977), U.S. ArmyCorps of relevantto predictingchanges in wildlifepop- Engineers(1980), and U.S. Departmentof the ulations(see Flather1982), and illustratesthe Interior(1980b). PATREC best met the cri- utilityof thisframework in a case exampleby teriaand warrantedfurther consideration in evaluatingthe PatternRecognition Method termsof ecologicaltheory. (PATREC) (Williamset al. 1977). Specifically, PATTERN RECOGNITIONAND PATREC we definereasons for selecting PATREC, de- scribethe method,review ecological theory, Patternrecognition generally refers to a and evaluatePATREC's use. processwith the objectiveof assigningobser- 122 Wildl. Soc. Bull. 13(2) 1985 CONSTRUCT SPECIES constructingindividual species models by de- MODELS 1) Determineclassification termining: categories 2) Determinehabitat attributes 1. The population-levelclasses based on user 3) Determinequantitative objectives. the relationshipsbetween (Is userinterested in pre- habitat attributesand dictingpresence/absence, or relative pop- MODEL classification categories DEVELOPMENT ulationlevels?) 2. A listof habitatattributes believed to be importantin differentiatingthe popula- tion-levelclasses chosen. INDIVIDUAL SPECIES 3. Thequantitative relationship between hab- MODEL MODELS itatattributes and population-levelclasses APPLICATION (interpretedas a frequencyof occurrence ofeach habitatattribute within each pop- HABITAT INVENTORY PROBABILITY ulationclass). OF AREA STATEMENT Points2 and 3 are accomplishedthrough ex- HISTORICAL WEIGHTED POPULATION pertopinion, literature search, or empirical VERAGE TREND DATA investigation.Application involves the collec- tionof habitat data, which are compared with LONG-TERM DENSITY theinformation in the species model to make POTENTIAL a probabilitystatement about the ability of an areato supporta population.Population esti- Fig. 1. Diagramaticrepresentation of the PATREC matesare desirablefor process. nationalassessments; PATRECcan providesuch estimates by cal- culatingan expectedvalue (Spurr and Bonini 1973).Historical population trends are used to vationsto classesbased upon a set of common estimatethe average abundance characteristic attributes(Tou and Gonzalez 1974). PATREC ofeach population-level class. These values are is only 1 methodthat could be used in the multipliedby their associated probabilities and assignmentprocess. Application has focused summedto estimate the long-term density po- on classifyinglandscape patternsas wildlife tential(Kling 1980). habitat by examining relationshipsamong PATRECprovides a probability that an area population-levelclasses and habitatcharacter- can supportuser-defined population classes, istics(Williams et al. 1977, Seitz et al. 1982). whichcan be convertedto a long-termpop- Each class has a nonexclusivebut character- ulationaverage for comparisons among areas. isticset of habitatattributes that define a pat- A morecomprehensive review of PATREC tern.The attributescan be used to categorize can be foundin Williamset al. (1977) and additional unclassifiedunits. PATREC uses Kling(1980). Bayesianstatistical inference (an alternativeto classicalstatistical inference), which employs ECOLOGICALTHEORY IN bothobjective data fromsamples and the sci- EVALUATIONS entist'ssubjective judgment (Spurr and Bonini The ConceptualModel 1973) to categorizepatterns. The PATREC classificationprocess com- Theoryprovides a logicalframework for prises2 steps:model developmentand model analyzingproblems and improvingexisting application (Fig. 1). Development involves assessmenttechniques. Techniques for nation- ECOLOGICAL THEORY IN APPLIED MODELS * Flatherand Hoekstra 123 /~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ / I Succession | , I II ,' - I I S Species-Habitat - Interspecific A 1. Relationships Interactions I Habitat Space Niche Theory Competition and SelectionCoptin l w Biogeography Predation Ilk > /DISTRIBUTION Territoriality ABUNDANCE OF Oter ' CarryingCap. ~~~Pouato Growth__ Density Density - Direct relationshipto distribution and abundance _Depend. Independ. w Factors Factors tndirectI relationship to distribution and abundance thruspecified channel Fig. 2. Conceptualmodel relating distribution and abundanceto areasof ecologicaltheory. al wildlifeassessments must be able to with- spatialdistribution of a species,and is the standcritical evaluation based on ecological productof thebehavioral process of habitat theory;however, ecologists disagree which selection.Habitat selection principles assume theoriessupport evaluations of thistype. For thatit is adaptivefor an animalto selecta thisreason, the framework that we proposeis specificsite over another. Theoretically, nat- tentative.Our hypothesizedmodel depicts 5 uralselection favors those individuals that se- interrelatedareas of ecological thought lectbetter habitats, resulting in a correlation deemedimportant in evaluationsof habitat- betweenpreference for a givenpatch type and basedpopulation models (Fig. 2). fitnesswithin it (Pianka 1974:104).Conse- Species-HabitatRelationships.-The spe- quently,density decreases from areas of more cificareas of ecological theory that support the suitablehabitat to areas of less suitable habitat conceptof species-habitatrelationships in- (Andrewarthaand Birch1954, Wynne-Ed- cludehabitat space and selection,island bio- wards1962). Although this pattern appears to geography,territoriality, and carryingcapac- holdin general(Partridge 1978), the relation- ity. In addition,the principleof carryingship between density and habitatsuitability capacitymust be consideredtogether with life shouldbe examinedcarefully. VanHorne historystrategies, including the concept of r- (1983) suggestedconsideration be givento vs.K-selection (MacArthur and Wilson1967). seasonof criticalhabitat use (e.g., winter Habitatspace and habitatselection, al- range),time lags, and intraspecificinterac- thoughdifferent concepts, are inseparablein tionsthat temporarily may resultin higher our conceptualframework. Habitat space is densitiesin lowerquality habitat as subdom- describedempirically by thosestructural inantsare forcedout of optimal habitat. characteristicsofa landarea that relate to the Islandbiogeography also has implications to 124 Wildl.Soc. Bull. 13(2) 1985 species-habitatrelationships. This theoryfo- In contrast,populations of K-selectedor- cuses primarilyon communitydynamics and ganismsoccur at or near carryingcapacity. the influenceof island size, shape, and prox- Populationsize tendsto be constantover time imityon species richness.Application