Reciprocal Influences of Long-Term Beaver Occupancy on Landscape Factors and Forest Structure (Adirondack Mountains, NY) Dr. John Stella Anna Harrison 19 th September 2011

2 Question 1: What landscape factors maintain suitable habitat for beaver in the long-term?

3 3 Potential site influences on long-term occupancy Maintenance Cost Dam Volume Number of Dams Cross Valley Slope Landscape Capacity Down Valley Slope Forage Area Pond Area Positive Negative Beaver Occupancy Duration Resource Quality & Quantity Hardwood basal area Softwood basal area Total basal area Expected Relationships

Huntington Wildlife Forest 30-year beaver occupancy dataset 14 sites stratified by occupancy rate: 1.Located on stream reach or wetland 2.Open-canopy wetlands 3.Evidence of dam 4.One active colony only 5.Sites are discrete land areas 4 4

5 Forage Area Pond Area Dams and Dam Volume Upland Forest Vegetation – 5-m wide belt transects – Inventory of tree community 5 Field Sampling

Landscape Capacity 6 6

Can calculate total beaver habitat area from pond area

Resource quantity and quality 8 8

Conceptual Model Summary: Strongest relationships with long-term occupancy 9 Landscape Capacity Pond Area Forage Area Down Valley Slope Cross Valley Slope Maintenance Cost Positive Negative Highly Significant Beaver Occupancy Hardwood basal area Softwood basal area Resource Quality & Quantity Total basal area Cross Valley Slope Down Valley Slope Forage Area Hardwood basal area Beaver Occupancy 30 year dataset Forage Area Hardwood basal area Number of Dams Dam Volume Pond Area

10 Question 2: How do forest impacts by beaver vary with distance from the pond?

Known selection processes and beaver preferences 11 Variety of documented forage preferences – Aspen, willow, cottonwood, and alder (Denny 1952) Preferred sizes: <10cm diameter (Pinkowski 1983, Haarberg & Rosell 2006 Raffel et al. 2009) – Allows for multiple uses (Barnes and Mallik 1997) Increase selectivity with increased distance from pond (Raffel et al 2009) Josh Cousins Photo: Josh Cousins

Species selectivity by stem and basal area 12 Selectivity = cut / cut + live (Gallant et al. 2004, Raffel 2009)

Size selectivity along a gradient

Multi-stemmed growth habit

Large area + concentrated impact on forest communities

Potential landscape area impacted by beaver at HWF

Implications 18 Broad landscape controls on beaver behavior Fine-scale foraging impacts of beaver Results in changes to forest composition and abiotic environment Extensive areas with intense foraging could alter forest composition