Temperate subhumid grasslands are simple in structure, composed of tussock grasses with scattered forbs, with few isolated trees and shrubs. Cold winters with occasional to frequent snow and frost limit the growing season, but hot dry summers create water stress. Nonetheless, fertile soils enable high productivity after rains, supporting a complex foodweb of invertebrates, ground-nesting birds, burrowing mammals, large herbivores, reptiles and predators. Large herbivores graze heavily, range widely, and are important in maintaining coexistence of plant species and nutrient cycling, as are periodic fires.