The nutrients stored in the roots will jump-start plant growth the following spring. This banking system is especially important for tallgrass species, which, favoring higher temperatures, sprout later in the spring than their shortgrass competition. Since the shortgrass can draw first on nutrients in the soil, the nutrients stored by the plants themselves may be the only resource left for the tallgrass. But if cattle mow the grass stalks all summer, little green material is left to fill the nutrient reservoirs before winter, and the tallgrass will be at a disadvantage come spring. Tests show that grazing in winter and spring is most effective in maintaining the tallgrass, said Seastedt.
Cattle eat the shortgrass and weeds and are moved to new pastures before the tallgrass sprouts.
However, this year, cattle grazed along South Boulder Creek all summer. We ll have to wait and see if it recovers. Occasional summer grazing won t destroy the tallgrass, he noted, but chronic grazing can slowly convert a tallgrass area to shortgrass. And, he added, the South Boulder Creek parcel is a particularly fine example of tallgrass. But a long-term lease until 2006 means that city land managers can keep cows off only one meadow in this tract each year, according to Riedel.