Summary Salsola australis, like other agricultural weed species of the Salsola genus, produces a mobile seedbank. Aspects of this mobile seedbank were investigated in three field trials, including total seed production, rate of seed shedding, rate at which seeds lose germinability and the distance and directionality of plant movement. Total seed production was highly variable (ranging from 138 to 7734 seeds per plant), but was directly related to aboveground plant biomass at maturity. Following senescence, mature plants broke free of their root system and the wind driven plants moved considerable distances (1.6–1247.2 m). Half of the mobile plants moved <100 m, as they became entangled with other S. australis plants within the stand. Seed shedding commenced before the plants became mobile and increased with movement, but was also related to the aging and weathering processes experienced by stationary or mobile plants. All plants retained a proportion of their seed in spite of movement, weathering and ageing of the plants, although germinability of retained seed dropped to <2% after 2 months. Salsola australis engages in broad scale seed dispersal similar to that observed in other species of the Salsola genus, allowing this species to maintain a high rate of invasion and range expansion.
Summary Salsola australis is a widespread annual weed of broad‐scale cropping and pasture systems throughout Australia, and is of concern in the wheat belt of Western Australia. The population dynamics of S. australis was monitored at four sites in the Lake Grace district of Western Australia. At all sites, two to three cohorts emerged in summer and autumn or winter. While initial seedling density varied, density‐dependent mortality ensured that the total number of senesced plants at each site was not significantly different. Estimated seed production ranged from 95 to 19 596 seeds per plant, although seed viability was low (approximately 9% for seeds that were shed and 15% for seeds that were retained on the mature plants). Total annual seed production per unit area was highly variable within sites but was not significantly different between sites. These data will facilitate the development of improved control strategies for S. australis.
Summary A matrix model of the life cycle of Salsola australis was constructed, based on population ecology data collected from the district of Lake Grace, Western Australia. The model was used to assess potential control strategies for this summer annual weed within the Western Australian broad acre grain cropping system. The population growth rate (λ) of S. australis in the absence of weed control strategies was 1.49 and was virtually unaffected by the dormant seedbank. However, λ increased to 8.21 if it was assumed that a constant number of seed immigrated into the area in question from neighbouring populations of S. australis, through farm‐scale seed dispersal. As a result, effective weed management depended on reducing seed dispersal. The model determined that burning all senesced, mobile plants in late autumn, combined with herbicide control of the largest cohorts of S. australis in summer and autumn, reduced population growth rate to 0.79. This control strategy resulted in a 66.1% chance of the population becoming extinct over 25 years. Management strategies are proposed based on the results of the models and further research is required to validate their effectiveness and practicality in the field.
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