Field Methods
Sampling sites were randomly selected throughout both the burned and un-burned habitats within 4 km of Porkchop Lake (Figure 1). In total, 20 sites were placed in the burned habitat and 20 in the forested habitat (Figure 1). Several of the unburned sites occurred within the burn perimeter, having escaped the fire. At each sampling site plant samples were collected from all species that were considered potential browse species of moose, based on field observations of browsed plants at all the sites and previous experience from tame animal observations and browsing studies in the region. At each sampling location, three samples of the dominant browse species were collected in order to capture the spatial and individual variation in plant chemistry and nutritional quality across the burned and unburned habitats. Samples were placed into coin envelopes or zip lock bags and frozen immediately on dry ice. Sampling was done in mid-June, mid-July, and mid-August in the summer of 2018, and again in mid-June and mid-August in the summer of 2019 to capture the seasonal variation and yearly variation in nutritional quality of the plants.
During August of 2019, we also quantified canopy cover and available bites of forage at each sampling site using randomly placed point intercept transects in both habitat types. At each sample point, a point-cover transect was established to measure canopy cover of each browse species and the relative frequency of bites available to moose. Transects were 50 meters in length and oriented along a randomly selected bearing. At each meter, all species that intercepted meter marks on the tape measure were recorded, including ground cover and any overstory species (Elzinga et al. 1998). For species that could appear in a moose’s diets, we also recorded the number and size of the potential bites that intercepted the point this was used to as a metric for bite frequency available in the burned/disturbed and forest sites. Interceptions of potential bites were indicated with the use of a plumb bob or a periscope.
Winter sampling was done at the same field sampling locations during March of 2019, as well as new locations accessible by helicopter. Current annual growth (CYG) of available browse species was clipped and placed into a zip lock bag and frozen immediately. We also measured the diameter at the point of browsing for each species consumed by moose in winter using Bluetooth calipers that were paired with a mobile de-vice. These measurements guided our subsequent nutritional analyses of the winter twigs (Shipley and Spalinger 1995, Shipley et al. 1999).