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The article discusses the acetylene reduction in relaxation to levels of phosphate and fixed nitrogen in Green Bay. This paper reports data collected during the summer of 1971 in the southern part of Green Bay of Lake Michigan. This study undertook to characterize acetylene reduction and nutrient levels throughout the summer. Water samples were collected. Phytoplankton characteristically increase rapidly in the spring. A high soluble phosphate concentration in the water preceded all major increases in the population of heterocystous, nitrogen-fixing blue-green algae.

• The evolutionary impact of crop-to-wild gene flow depends on the fitness of hybrids under natural, competitive conditions. Here, we measured the performance of third-generation (F3) radish hybrids ( Raphanus raphanistrum ×  Raphanus sativus) and weedy R. raphanistrum to understand how competitive interactions affect life history and relative fecundity. • Three wild and three F1 crop-wild hybrid radish populations were established in semi-natural, agricultural conditions in Michigan, USA. The effects of competition on life-history traits and fecundity of F3 progeny were measured 2 yr later in a common garden experiment. • Third-generation hybrid plants generally produced fewer seeds per fruit and set fewer fruits per flower than wild plants, resulting in lower lifetime fecundity. With increasing competition, age at reproduction was delayed, the relative number of seeds per fruit was reduced in wild plants and differences between hybrid and wild fecundity diminished. • Competition may enhance the fecundity of advanced-generation hybrids relative to wild plants by reducing differences in life history, potentially promoting the introgression of crop alleles into weed populations. [ABSTRACT FROM AUTHOR]

Fine root demography was quantified in response to patches of increased water and nitrogen availability in a natural, second-growth, mixed hardwood forest in northern Michigan, USA. As expected, the addition of water and water plus nitrogen resulted in a significant overall increase in the production of new fine foots. New root production was much greater in response to water plus nitrogen when compared with water alone, and the duration of new root production was related to the length of resource addition in the water plus nitrogen treatments; the average difference in new root length between the 20 vs 40 d additions of water plus nitrogen amounted to almost 600%. Roots produced in response to the additions of water and water plus nitrogen lived longer than roots in the control treatments. Thus, additions of water and water plus nitrogen lived longer than roots in the control treatments. Thus, additions of water and water plus nitrogen influenced both the proliferation of new roots and their longevity, with both proliferation and longevity related to the type and duration of resource supply. Results suggest that root longevity and mortality may be plastic in response to changes in soil resource availability, as is well known for root proliferation. [ABSTRACT FROM AUTHOR]