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In 2008, the five cattle can be assumed to have again consumed a total of 15 AUM's of forage, <br />which is about 3.7 AUM (435 lb /ac) beyond what might be optimal. The single event of grazing <br />beyond 11.3 AUM's in 2008 is not likely to have inflicted long -term damage to the productivity <br />of the stand by itself. It is also important to note that bond release measurements made in 2008 <br />had occurred before any of the grazing. <br />The grazing system that has been used in this Irrigated Pasture reference area since its <br />establishment in 2007 is apparently simply summer grazing (the three months of July, August, <br />and September) followed by total rest. Given the dominance by cool season grasses (Bromus <br />biebersteinii, Schedonorus phoenix (aka Festuca arundinacea), S. pratensis, and Poa pratensis ) <br />whose primary growing periods are in spring and fall, the summer grazing regime allows active <br />growth to proceed without defoliation. All these grasses are bred to be very responsive to <br />irrigation and fertilization and tolerant of periodic heavy harvest. Because of this, use of as <br />much as 80% of maximum (likely produced by June) is feasible without damage to the viability <br />of the grass stand (see USDA 2003). By comparison, un- irrigated native upland vegetation <br />would almost surely deteriorate rapidly at such high usage levels (proper levels are usually in the <br />range of 40 to 50% or sometimes less there). <br />David Bucker <br />Senior Plant Ecologist and Owner, ESCO Associates Inc. <br />Boulder, Colorado <br />Dr. Buckner has forty -one years of professional experience in the areas of applied plant ecology, <br />plant taxonomy, reclamation, soils, and statistics. Project experience includes the design and <br />execution of baseline vegetation and soils studies, evaluation of long -term natural and <br />reconstructed plant community dynamics, development of reclamation plans for mine permit <br />applications and hazardous waste covers, and analysis and reconstruction of wetlands. His <br />projects have been performed in the states of Colorado, Wyoming, Montana, Utah, Arizona, New <br />Mexico <br />{00058185.1 <br />