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Continental Diversity of Chenopodium album Seedling Recruitment

Chenopodium album seedling emergence studies were conducted at nine European and two North American locations comparing local populations with a common population from Denmark. It is hypothesized that C. album seedling recruitment timing and magnitude have adapted to environmental and cropping system practices of a locality. Limitations in the habitat (filter 1) were reflected in local C. album population recruitment season length. Generally, the duration of seedling recruitment of both populations (local; DEN-COM) increased with decreasing latitude, north-to-south. In general, compared to the local population, DEN-COM recruitment at locations north of Denmark was longer and south of Denmark was shorter, and ended sooner. Generally, the local cropping system disturbances (CSD) period increased with decreasing latitude. The total duration of the CSD period was over twice as long in the south as that in the north. Recruitment at each locality possessed seasonal structure (time, number) consisting of 2-4 discrete seasonal cohorts. This may be an adaptive means by which C. album searches for, and exploits, recruitment opportunity just prior to, and after, predictable disturbances. The control of C. album seedling emergence is contained in the heteroblastic traits of its locally adapted seeds, and is stimulated by a complex interaction of light, heat, water, nitrate and oxygen signals inherent in the local environment. Our observations of complex recruitment patterns occurring at critical cropping times is strong evidence that C. album possesses a flexible and sensitive germination regulation system adaptable to opportunity in many different Eurasian and North American agricultural habitats.