Bunchgrasses in California and the Desert Southwest

The myth of the California grasslands (i.e., that they were originally a sea of perennial “bunchgrass” tufts, spaced far enough apart to give the landscape a lumpy, freckled appearance and to allow for small flowering plants between, and that “overgrazing” by introduced livestock rapidly killed off the bunchgrasses and led to their replacement by low-quality Mediterranean annual grasses) seems to have arisen by analogy with the story of the desert grasslands of the American southwest. The grasslands of the desert and semidesert lands of Arizona, New Mexico, West Texas, Southeastern California, etc. are, for the most part, very different from those of “our” California. In both regions the original grass biomass was divided between perennial and annual species, with the former generally predominating, and in both regions there has been a dramatic recent shift. In nearly all other respects, however, and in the ecological processes involved in the change, the two regions differ.

It is easy to imagine the easily uprooted desert bunchgrasses being cleared away wholesale by hungry livestock over a relatively short period. Although easily reestablishing themselves from seed, if the grazing pressure is continued relentlessly enough and drought stress is severe and prolonged enough, the desert bunchgrasses are vulnerable to being replaced by either fast-growing annual grasses (red brome, cheat, etc.) or by deep-rooted woody plants like mesquite (Prosopis spp.) and [Opuntia?].

Both of these kinds of type-conversion have replaced the productive native grasslands on a very large scale in different parts of the southwest.

In California, however, wrong assumptions about:

1) original flora of the “grasslands”

2) intrinsic ecological diversity

3) ecological factors involved in the ultimate type-conversion and therefore

4) the best Rx for California grassland “restoration” and management