Tussock Regrowth after Grazing: Intercalary Meristem and Axillary Bud Activity of Tillers of Agropyron desertorum

Regrowth of the C3 Eurasian tussock grass, Agropyron desertorum, after grazing by cattle was investigated in a cold-desert steppe during the spring and early summer periods of 1983-1985. Relative growth rates and population dynamics of tillers were used as indicators of tussock performance. On tussocks grazed before internode (culm) elongation, tiller relative growth rates were usually greater than on ungrazed tussocks, for up to three weeks. Grazing during culm elongation usually reduced tiller relative growth rates, but stimulated the growth of axillary tillers. Axillary tiller production reached a maximum two to three weeks after defoliation. Grazing after the completion of internode elongation decreased tiller relative growth rates and did not stimulate axillary tiller production. Spring tillering may ameliorate some of the long-term effects of grazing during or after culm elongation when regrowth of grazed tillers is limited by the lack of intercalary meristem activity. Only once, very early in spring 1985, did tussocks appear to overcompensate for grazing. This response lasted less than a month.