Predicting Elk Nutritional Resources and Habitat Use Across Large Landscapes: the Westside Model

Transcription

1 Predicting Elk Nutritional Resources and Habitat Use Across Large Landscapes: the Westside Model

2 Topics: Background of Westside elk modeling project Development of elk nutrition model Modeling methods for elk habitat use Results of model selection and model validation Example management applications and utility

3 Modeling Background

4 Why new elk models? Earlier models still in use, but many components unvalidated. Data from many radiotelemetry studies now available for use with new modeling approaches. More recent data collected on elk nutritional resources for modeling at landscape scales.

5 Project Objectives 1. Build a nutrition model that predicts dietary digestible energy for elk across all landscape conditions during summer 2. Build and evaluate a set of plausible, competing habitat use models that predict the relative probability of elk use at landscape extents 3. Include nutrition model predictions as a covariate in habitat use models

6 Project Objectives 4. Include additional human disturbance and abiotic covariates that potentially affect or account for the probability of elk use of nutritional resources 5. Use data from multiple study areas (diverse environments & land ownerships) to construct, select, and validate McCorquodale

7 The Westside elk models Apply to summer range (June 1 August 31) Regional landscapes (>10,000 ha), multiple landowners, integrated management Female elk Hunted populations Management-focused, mechanistic models

8 Methods to model nutrition

9 Nooksack S.A. NUTRITION MODEL Willapa Hills S.A. Springfield S.A.

10 Development of nutrition equations Based on stand and overstory forest conditions Separate equations for more mesic Pacific silver fir/mt. hemlock vs. western hemlock potential natural vegetation communities

11 Development of nutrition equations Different equations for each of 3 study areas Two final nutrition models Forage biomass Elk dietary digestible energy (DDE), predicted from biomass Input variables: PNV zone, % canopy cover, hardwoods

12 Scaling up of field data to Westside landscapes Mapped predicted nutrition across Westside region Used readily available, coarse-scale spatial data Found excellent agreement between predicted DDE and elk locations

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14 Methods to Model Habitat Use

15 HABITAT USE MODEL Study areas & years: 7 Study Areas, 21 Years Study area sizes: 13,400 to 98,000 ha Average 57,000 ha

16 Covariate reduction Nutrition Human Disturbance Vegetation Physical/ Other DDE (continuous) DDE (categorical) Accepted Biomass (AB) Distance to: High DDE Mod DDE Percent area in M to H DDE Quadratic, Cubic forms Density of & Distance to: Open Roads Closed Road High Traffic Roads Low Traffic Roads Public Use Roads Administrative Use Only Motorized Use Trails Quadratic, Cubic forms Overstory CC Dominant CC Cover-Forage Ratio Habitat Effectiveness of size/spacing of Cov & For Cover Quality Distance to: Forage Cover Cover-Forage Edge Optimal Cover Thermal Cover Hiding Cover Slope (continuous) Slope (categorical) Percent Area in: Flat to Gentle Slope Mod to Steep Slope Very Steep Slope Aspect Convexity Curvature Soil Depth Solar Radiation Distance to Water Land Ownership

17 Modeling methods 1. Model the probability of elk use for each model set and for combined models within each study area 2. Evaluate models using a model selection approach 3. Develop a regional model of elk use for western OR and WA using a meta-analysis approach

18 Model Selection Results

19 Best models Best of best Used top model from each model set Evaluated 7 models within each of 5 study areas Selected best model based on lowest summed rank across all model training study areas

20 The best model included: Dietary digestible energy Distance to open roads Distance to cover/forage edge Slope

21 Nutrition Model Elk Habitat Use Model % Canopy cover % Hardwoods Potential veg. zone Dietary Digestible Energy (DDE) DDE Dist. to public roads % Slope Dist. to edge Predicted Level of Elk Use

22 Model Validation Results

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24 Summary The best model was the top performer in all 5 study areas Marginal plots showed consistent relationships between predicted use by elk and each of the covariates in this model Validation with spatially independent data sets showed a good fit for the regional model across a wide spectrum of conditions

25 Model Application

26 Elk Forage Analysis Area (8,170 ha) Thinning Unit Analysis Area (7,570 ha) 243 ha 500 ha

27 Nutrition Summary % Area in Good or Better Nutrition Percent Existing Alt. 1 Alt. 2 0 Region Elk Forage Areas Thinning

28 % Change in Predicted Use from Baseline % change Opt1 Opt2 Opt Region Elk Forage Area Thin Units A Thin Units B Analysis Area

29 Management utility Readily adaptable to land management planning at multiple scales across land ownerships Landscapes can be characterized by nutritional condition (e.g., poor, meeting baseline needs) Probability of elk use can be estimated and mapped by nutritional condition

30 Management utility Human disturbance factors can be managed to influence elk use Region 6 (FS) and OR-WA (BLM) formally adopted as best available science User guidelines and technical support available: earch/elk/ Rachel Cook

31 Significance of work Focus on mechanistic, management-focused models Scaling up of nutrition to landscape levels Modeled predictions of elk use directly link landscape choices by elk to nutrition-based measures of population health Spatial inference many years of data and elk locations from disparate data sources larger inference space than typical for elk habitat models