Optimizing cattle and timber production in the Black Hills
BROOKINGS — About 16 percent of all grazed land area in the United States is forested.
“While cattle producers have grazed livestock on forested lands since the settlement era, relationships between livestock and timber management practices and resource condition are not well understood,” said Kurt Chowanski, graduate student completing a Ph.D. in biological Sciences at South Dakota State University.
Chowanski focused his Ph.D. research on practices that could be implemented in the Black Hills of South Dakota to sustainably maximize economic returns from livestock and timber production.
With the cooperation of the Black Hills National Forest, Chowanski surveyed grazed meadow and forest sites in 44 pastures over a two-year span.
The survey looked at cattle stocking rates, grazing pressure index identified from 16 years of cattle grazing history and 45 years of timber harvest history.
The survey yielded the following best management practices:
• Animal unit days: Plant diversity was maximized with grazing pressure index between 18 and 27 animal unit days per ton of forage production. Plant diversity was lowest in ungrazed pastures.
This is less than the suggested 35 animal unit days which sustainably maximizes economic returns in a tallgrass prairie.
• Basal Areas: “Open tree spacing in pine forests promotes timber growth and forage production, providing economic opportunities for simultaneous timber and livestock production,” Chowanski said.
Herbaceous forage and livestock production decrease with increasing tree canopy cover.
Economic returns from combined timber and livestock production are maximized at tree basal areas between 30 and 60-square feet per acre.
A similar basal area also minimizes risk of timber loss associated with mountain pine beetle infestation.
• Forest Density Maps: Forest density maps are an important tool that can inform management decisions.
These maps are developed using high-resolution satellite imagery to calibrate lower resolution satellite imagery.
Today, cattle producers have access to temporal series of forest density maps covering the Black Hills from 1999 to 2015.
Chowanski used forest density maps in combination with soil and climate information to estimate forage production in the Black Hills.