Germination of Freshly Harvested Seed of Some Western Range Species

Abstract

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Ecotypic Variation in Medusahead, an Introduced Annual Grass

“…mainder of the locations ranged from 55 to 76%. In previous work medusahead seed was found to have approximately a 3-month dormancy period; Laude ( 1956) also found a dormancy period. Such large differences in germination, however, cannot be explained by differences in dormancy since the seed used was mature by July, collected in August, and not germinated until November.…”

Annual grassland ecosystem model

“…Water is lost from the soil layers through bare-soil evaporation and transpiration. Bare-soil evaporation is assumed to occur in the top three soil layers, 10 ern in depth (this may vary with soil type, from 2 to 15 ern (Lemon, 1956)); it decreases rapidly as those layers become dry. Bare-soil evaporation from each of the top three layers is a function of PE, soil-water content of each layer, average soil-water potential in the top Parton, 1978 three soil layers (weighted by a water-loss coefficient for each layer, the assumed fraction of bare-soil evaporation coming from each layer), the biomass of live shoots, and •the biomass of the standing crop.…”

“…Germination can occur in the model only if the average soil water potential of the top two layers of soil (5 cm) is greater than -12 bars (Young et aI., 1970). No germination can occur during or' following the flowering and fruiting stages of growth (phenophases 5 and 6), thus preventing any germination of seeds produced in the current model-year (Laude, 1956).…”

Seed Bank Depletion: The Key to Long-Term Downy Brome ( Bromus tectorum L.) Management

“…Temperatures (soil and air) often exceed 60 F in late June into July when seeds are first shed and the after-ripening period provides an ecological advantage to downy brome by avoiding precocious germination shortly after dispersal and subsequent seedling desiccation and death during hot, dry summer conditions. Laude (1956) observed delayed germination of downy brome over time. He found, under controlled greenhouse conditions, that downy brome germination steadily increased over a 5-month period from 0 to 81%.…”