For example, you may want to establish cool-season grasses in tame pastures to use in early spring or fall when these species are most nutritious. Livestock can rotate to pastures with warm-season species during late spring and summer. If you use crested wheatgrass, Russian wildrye, bromegrass, or winter wheat for early-season pastures, move animals to native rangelands during late spring and summer. Because of cooler temperatures in the mountains and shorter growing seasons, cool-season species adapt best to these conditions. Range ecologists and physiologists have found that as grazing increases, grass productivity typically declines.
Frequency can be more important than intensity.
A plant that is harvested often has more photosynthetic tissue removed and little opportunity for regrowth. These plants may enter a period when soil moisture, temperature and growth stage limit regrowth and little leaf area remains for photosynthesis. Thus, their ability to replenish reserves or produce additional new tillers is restricted. Figure 3 shows what can happen to carbohydrate reserves and growth if a plant is defoliated once. If a plant experiences several defoliations, reserve levels and forage production might decline further.