PARENT SESSION
Oral Session #8: Restoration Ecology: Grasslands, wetlands, aquatic. Presiding: G. Noe.
Monday, August 6, 2001. 8:00 AM to 12:15 PM. Hall of Ideas H.
Spatial distribution of seeds in desert grasslands and their potential vulnerability to prescribed burning.
Stromberg, Juliet1, Ortiz-Barney, Elena1, 1
ABSTRACT- Over the last 100 years, large areas of desert grasslands in the US Southwest have shifted to shrublands. Land managers are experimenting with the use of prescribed burning to restore these areas to grasslands. The regeneration potential of the herbaceous community will be determined in large part by the availability of seed and its location within the landscape. In this study, I assessed the diversity of the soil seed bank and its spatial distribution. I collected soil and litter samples from three microsites at sixteen locations within two grassland preserves in southern Arizona. Approximately 60 species of warm-season plants were identified using the seedling emergence method. The majority of seeds were found in the litter layer (157±45 seeds per square meter) rather than the soil (60±16 seeds per square meter). As expected there were more species of annual forbs (about 30 sp.), than of perennial grasses (3 sp.) Of the grass seeds present, eighty-nine percent belonged to one of two perennial species, one native and one exotic. The seed bank appears to only contain a small subset of the dominant perennial grasses. Due to their location, the few seeds available will most likely be exposed to lethal temperatures during a fire. These results indicate that prescribed burning as the sole restoration tool will not produce the desired results.
KEY WORDS: seed bank, desert grassland, prescribed burning, restoration