The emergence of Sorghum bicolor seedlings and the dormancy status and survival of S. bicolor seeds buried in soil in the midwestern United States were studied from 1992 to 1995. Possible causes of seed mortality were also investigated. Emergence of seedlings from seeds buried in November averaged less than 2%, compared with 28% from seeds buried in March. Seeds showed little ability to survive winter, with more than 80% dying between November and March and virtually none surviving a second winter. Many seeds exhibited signs of cold damage. Further evidence of the effect of cold was the decreased mortality of seeds protected somewhat from the cold. The decline in the viability of seeds was modeled well by negative exponential curves with an exponent of between 0.011 and 0.016.

Conservation managers need to be able to assess and prioritize issues that may affect their target habitats and species. In the Baie de Somme, France, conservation issues affecting overwintering shorebirds include hunting pressure, cockle fishing, recreational disturbance, Spartina encroachment, and changing sediment levels. We used an individual-based model to predict the effect of these issues on the survival of three shorebird species: dunlin Calidris alpina, oystercatcher Haematopus ostralegus and curlew Numenius arquata. In the model, removing hunting from the mudflats in the eastern part of the estuary had the greatest positive effect on shorebird survival. Oystercatcher survival decreased markedly when stocks of large cockles were reduced to <250 m-2 or numbers of fishermen per day were doubled. Short-term disturbance events, such as walkers, had more effect on shorebird survival than long-term events, such as fishermen. Dunlin, as a protected species, were able to feed outside the Réserve Naturelle and were unaffected by disturbance within the Réserve. Oystercatcher survival decreased when the number of disturbance events within the Réserve exceeded one h-1, and curlew survival when disturbance events exceeded six h-1. Spartina encroachment caused dunlin survival to decline steadily as feeding habitat was lost. Dunlin were also the species most affected by changes in sediment levels, likely to occur through either sedimentation or sea level rise.

Abuscular mycorrhizal fungi are thought to survive adverse environmental conditions primarily as spores. Extraradical mycelia of two Glomus species were produced in fine mesh pouches which excluded roots but not hyphae. The mycelia in these pouches were exposed to freezing conditions, either in the field or in a controlled-temperature chamber. Bioassay plants were grown directly in the pouches and mycorrhizal colonization was assessed after 1 month. The mycelia remained infective in frozen soil over winter. This survival was not dependent on either the presence of root pieces or on the connection of mycelia to roots. Spores were not an effective inoculum in these bioassays. Overwinter survival of mycelia would enable plants to become incorporated into functional mycorrhizal associations early in spring.