Assessing Forage Value and Using Distance Sampling to Estimate Abundance of Pedicularis spp. in Northern Alaska
Abstract
Caribou in Northern Alaska require specific forages during summer to support newborn calves and to build fat and nutrient reserves for the long winter. Caribou have clear preferences for specific shrubs, graminoids, and forbs because of their high nutritional value and low content of secondary compounds, but easily digestible forbs, specifically Pedicularis spp., are highly desirable. Compared to the nearly continuous cover of shrubs and graminoids on the North Slope, forb abundance is more heterogenous and abundance estimates are rare. We used distance sampling to estimate abundance of Pedicularis spp. on a transect from the foothills of the Brooks Range to the coastal plain. Rather than estimating abundance from quadrats, distance sampling allowed us to sample a larger area and capture lower density populations that are not uniform on the landscape. We sampled eight sites along a transect from the foothills to the coastal plain. At each sample point, four 100-m transects were sampled in the primary cardinal directions from a random point (two in June, and two in July). Additionally, five Pedicularis spp. individuals were collected each week for 10 weeks from a pre-determined location in the vicinity of Toolik Field Station, located north of the Brooks Range. Samples were oven dried at 60˚C for 72 hours, ground to pass a 1-mm mesh sieve, and analyzed for digestibility by quantifying neutral and acid detergent fiber, and lignin and cutin content. A subsample was further ground to a fine powder in a tissue homogenizer, loaded into tin capsules, and combusted in an elemental analyzer to determine carbon and nitrogen content. Distance sampling yielded an abundance estimate of 269.42 individuals/hectare in June and 1,737.76 in July. For a rough biomass estimate, 5 individuals were collected at each point, weighed to determine an average mass, and multiplied by the estimated July abundance for the point. Average July dry biomass for eight points was 915.52 g/hectare. Variance in biomass between points was likely due to the differences in dominant Pedicularis species at each point. Also, we found abundance to be greatest in the central North Slope with the forb existing in lower densities in the shrub-dominated foothills of the Brooks Range, and in low densities on the sedge-dominated coastal plains.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B24F..07P
- Keywords:
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- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCES