Desert grasslands and grasses

Desert grasslands experience hot, dry, sunny climates, and have one of the lowest levels of primary production and rates of solar energy conversion of North American grassland types. Peak growth occurs later than in these other grassland types, coincident with the rainfall maximum during June-September. Reflecting this late-season growth the proportion of C4 grasses is greater than that found in other grasslands of this continent. Shrubs and trees can be abundant but the relative proportion of grasses and shrubs has changed greatly during this century. Habitat fragmentation and the impact of introduced species are the major human environmental impacts. Members of the grass family (Poaceae) are important because of their morphological and physiological adaptations to withstand constant defoliation; regrowth ability depends on severity and season of grazing. Recruitment is from seeds, rhizomes or stolons. Desert grasses are relatively short-lived, though maximum longevity can be several decades; the influence of weather and defoliation varies among species.