Biomass of Desert Winter Annual Plant Populations in Southern Nevada

Biomass of mature desert winter annual populations was measured during three growing seasons, which included the possible extremes in length, in 68 Mojave and Great Basin Desert communities. Precipitation was measured concurrently. Biomass was highly variable from site to site, and season to season. Its site variability was related primarily to local edaphic variables and was usually not correlated with the shrub dominants of the site; seasonal variations were related, directly or indirectly, to the rainfall regimes. Values ranged from 0 to 616 kg/ha on sites with undisturbed soils, and seasonally were 2 to 5 times higher on burned sites than on comparable unburned sites in the same area. Maximum site value was 753 kg/ha, obtained on a burned site where most of the weight was due to high density of Bromus rubens L., an introduced grass species. Although in two of the three years averaged site values were similar, the biomass was overall the greatest in the 38 Mojave Desert communities, least in the 10 Great Basin Desert communities, and intermediate (if large contributions of Bromus on about half the sites are excluded) in the 20 communities considered transitional between the two desert regions. Pe3IoMe