VEGETATIVE RESPONSE IN DORRY CANYON TO PACK CREEK WILDFIRE
Natural Resources/Aquaculture
Cory Farnsworth
Extension Assistant Professor, Agriculture and Natural Resources
Utah State University Extension
Moab
Abstract
The Pack Creek Wildfire began in June of 2021 and burned approximately 8,952 acres of the La Sal National Forest, including the Dorry Canyon Pasture. Data was collected in August of 2022 to determine how many Animal Unit Months (AUM’s) the pasture could support in 2023. An AUM is a measurement for how many cow/calf pairs can feed for one month on the available forage. Forage supply was estimated using the hoop toss method. A hoop measuring the area of 4.8’ and a circumference of 92.2” was thrown randomly 10 times within the pasture. The plants rooted within the hoop were clipped, placed in a tared bag, dried completely, and weighed to determine grams of dry matter per sample. The sample weights were averaged together and multiplied by 20 to achieve pounds of dry matter per acre. A 50% utilization factor was used to determine the amount of available dry matter. The number of acres to be grazed was measured using a GPS and multiplied by the amount of available dry matter. Forage supply was converted to AUM’s based off of a 1,000 lb. cow. The number of cows the rancher planned to run was factored into the AUM’s to determine the number of days that number of cattle may be on the pasture. The data collected showed a forage production of 484 lbs/acre which would allow 119 cow/calf pairs to be grazed on 360 acres of the Dorry Canyon Pasture for 22 days. With hay prices at $225/ton, grazing this pasture could save over $10,000 in feed costs, or provide several weeks of relief to other pastures, resulting in better rangeland health. While gathering samples, it was also determined that grass had only regrown in the area of the pasture that had been chained and reseeded in the 1960’s. No grass grew outside of the chaining due to Pinyon and Juniper encroachment before the fire and soil sterilizing temperatures during the fire. This finding reiterates the importance of mechanical thinning of pinyon juniper pre-wildfire and reseeding native species post-wildfire.
Authors: Cory Farnsworth
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Cory Farnsworth Horticulture and Natural Resource Agent, Utah State University Cooperative Extension, Utah, 84532