Senecio sylvaticus is a northern European adventive which has adapted well to a short term dominance at the beginning of secondary succession on slash—burned class—cuts in the Douglas—fir region. The species time—space niche is related to its copious production of small pappus—borne cypselas, low competitive ability, and apparent high soil—fertility requirements associated with the release of minerals directly following slash burning.
Seed of yellow foxtail(Setaria lutescens(Weigel) Hubb.) biotypes collected in Connecticut, Iowa, Massachusetts, Pennsylvania, and California were grown under field conditions at Davis and Woodland, California. Three biotypes collected in California alfalfa(Medicago sativaL.) fields all exhibited only a prostrate growth habit; the biotypes from the eastern United States all had an upright growth habit. The California biotypes were always glaucous; those collected in the east were not glaucous. Ratio of culm height to culm length were near unity for the eastern biotypes but averaged 1.5 to 1.7 for the California biotypes. Variations existed between biotypes in days from planting to heading, number of nodes per culm, leaf shape and size, and in final dry weight per plant.
Rodent caching is a significant factor in the establishment of Purshia tridentata in central Oregon pine forest. The pattern of cache placement is strongly influenced by pine litter patterns. As litter accumulates because of fire exclusion, desirable litter—free sites are becoming less abundant. As a result, a decline in Purshia populations may be expected.
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