Germinable seeds and periodicity of germination in annual grasslands

Young, James A.; Evans, Raymond A.; Raguse, C. A.; Larson, Jeanne R.

doi:10.3733/hilg.v49n02p037

Cited by 86 publications

(58 citation statements)

References 25 publications

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“…Where fire can be better controlled, our results suggest the possibility that seed banks in CSS and adjacent grassland areas might be amenable to direct manipulation by management activities such as prescribed burning (Keddy et al 1989;van der Valk and Pederson 1989;Chambers and MacMahon 1994). Indeed, prescribed spring burning has been applied successfully to eliminate grass seeds before shattering occurs and is still the most logistically feasible burning treatment (Young et al 1981;Meyer and Schiffman 1999;Gillespie and Allen 2004;DiTomaso et al 2006). Nevertheless even when burning is unplanned, such as the fall wildfire in this study, the first growing season following the wildfire is a window of opportunity for increasing native diversity at a time when the exotic grass seed bank has been reduced.…”

Section: Discussionmentioning

confidence: 77%

Composition of soil seed banks in southern California coastal sage scrub and adjacent exotic grassland

Cox

Allen

2007

Plant Ecol

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Soil seed banks are important to many plant communities and are recognized as an important component of management plans. Understanding seed bank composition and density is especially important when communities have been invaded by exotic species and must be managed to promote desirable species. We examined germinable soil seed banks in southern California coastal sage scrub (CSS) that is heavily invaded by exotic grasses and in adjacent exotic grassland. Soils from both communities had similar seed banks, dominated by high densities of exotic grass and forb species. Up to 4,000 exotic grass seeds and at least 400 exotic forb seeds/m 2 were found in most soils, regardless of aboveground vegetation type. Native forbs averaged 400 seeds/m 2 in grass-dominated areas and about 800 in shrub-dominated soils. Shrub seed density was \1 and \10 seeds/m 2 in grass-and shrub-dominated areas, respectively, indicating that the shrub seed bank is not persistent compared to annuals. We also compared pre-and post-burn soil seed banks from one location that burned in October 2003. Late-season burning in both grass-and CSS-dominated areas disproportionately reduced exotic grass seed densities relative to native seed densities. The similarity of the seed banks in adjacent grass and shrub communities suggests that without intervention, areas currently dominated by CSS may become more similar to grass-dominated areas in terms of aboveground vegetation. In such areas, the first growing season following a wildfire is a window of opportunity for increasing native diversity at a time when density of exotic grass seeds is low.

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Section: Discussionmentioning

confidence: 77%

Composition of soil seed banks in southern California coastal sage scrub and adjacent exotic grassland

Cox

Allen

2007

Plant Ecol

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“…Year-to-year weather variations are one explanation for this tenuous coexistence. The majority of exotic annual grasses seeds are thought to germinate every year, while many forbs form persistent seed banks, germinating only under favorable conditions (Young et al 1981, Rice 1989. Cued germination could allow forbs to take advantage of temporal refuges and allow replenishment of seed banks in years where competition with exotic grasses is reduced (Levine and Rees 2004).…”

Section: Introductionmentioning

confidence: 99%

Temporal variability and nestedness in California grassland species composition

Elmendorf

Harrison

2009

Ecology

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Abstract. Nestedness occurs when species-poor assemblages contain a subset of the species that occur in more species-rich communities and is a commonly observed pattern in spatial data sets. Examination of nested distribution patterns across time rather than space are rarely conducted, even though they may have important implications for species coexistence. Nested temporal assemblages can occur when most species respond similarly to interannual variation in conditions. In contrast, assemblages might be non-nested when different sets of species occur in different years, either because of different resource requirements or as a result of competitive exclusion. Using eight years of plant occurrence data at 71 sites in California grasslands, we found strong signals of temporal nestedness with most species favored by similar conditions. High-quality years enabled the expansion of both grasses and forbs into locales where they were not found during poor-quality years. Native annual forb, exotic annual forb, and exotic annual grass species richness were all greatest in cool, wet years following hot, dry years. Together, these analyses support the hypothesis that, in the absence of community members that specialize on poor-quality years, interannual environmental variation can cause communities to form nested subsets across time much as they do across space.

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“…Allenrolfea occidentalis seeds were detected in seed banks were found in the nest of saline harvester ants Pogonomyrmex salinus (Young et al, 1995). In the Great Basin desert, plant communities with numerous annuals have seed banks that fluctuate much like those of the hot deserts as a result of the variable productivity of annuals (Young et al, 1981;Young et al, 1995). However some Great Basin communities have seed banks with a much greater proportion of seeds of perennials species than do the hot deserts, and the soil seed densities of these species are less variable than those of annual species (Parmenter & MacMahon, 1983).…”

Section: Introductionmentioning

confidence: 99%