Heavy Seasonal Grazing on Central Arizona Piñon–Juniper Rangeland: Risky Business?

Abstract

As a rangeland extension specialist, I see the land outside my windshield as I drive across the countryside differently than most. Things such as body condition of animals, what plants are greening up, who got a rain, or how much water is in the creek catches my eye. I am also always on the lookout for “teachable moments”; events or experiences that occur out on rangelands that I can turn into a study, presentation, or pub- lication to share with others. So it is not too surprising that one day in late June of 2012, I noticed that heavy (greater than 60%) grazing utilization1 had occurred on a 520-acre

piñon–juniper (approximately 5,000-foot elevation) pasture in the Mogollon Rim country of central Arizona (Fig. 1). It turns out that grazing by cattle (approximately 350 cow–calf pairs) had occurred 2 weeks earlier. The pasture is long and narrow, running northwest to southeast and has one water source (earthen tank) at the southeast end. This area had re- ceived 2.83 inches of precipitation from January to April and no measurable rain in May and June (Table 1). The most recent 10-year averages for these periods measured by a rain gauge approximately 3 miles northeast are 6.85 ± 1.5 and 0.49 ± 0.21 inches respectively (Table 1). This general area of the state was in the severe drought category at the time.2 Due to the drought conditions, I wanted to observe and docu- ment perennial range grass regrowth in this pasture. Because our Arizona summer monsoon precipitation is often highly variable in space and time, I also wanted to assess the poten- tial risk to near-term forage production caused by a one-time heavy grazing event in this piñon–juniper rangeland.

DOI: 10.2458/azu_rangelands_v36i3_tolleson