Browsing by Author "Schimpf, David J."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Did Cryptic Invasion of North America by Common Reed Change Exposure to Pollen Allergens?
    (2011-02-24) Schimpf, David J.; White, Natalie A.
    Common reed, Phragmites australis (reed), is a very tall grass that spread greatly to occupy large areas near many eastern North American cities over the past century. Its aerially dispersed pollen is known to incite allergic reactions, and possibly asthma, in some persons, but is not distinguished from that of any other grass in routine pollen monitoring. We hypothesize that this regional expansion by reed has increased late-season exposure to grass-pollen allergens in parts of these metropolitan areas. The information available indicates that reed's geographic location, high abundance, small pollen size, release of pollen relatively far above ground, substantial pollen productivity, pollen allergen composition, and late season of pollen release all point to its potential importance for a large number of persons whose health may be degraded by grass pollen. If the other common late-flowering grasses in the same area have larger pollen grains, it may be possible to visually distinguish reed pollen captured by monitoring devices. If not, ratios of stable isotopes of carbon in the pollen may permit differentiation. Otherwise, analytical techniques based on molecular differences need further development in order to estimate local population exposure to allergens from reed. Some 90 million North Americans may live close enough to large tracts of reed to be exposed to substantial concentrations of its pollen, so much more attention to this situation seems warranted. If reed pollen were found to be a health hazard for a particular metropolitan area, removal of the pollen sources may be more feasible than is the case for many other species.
  • Thumbnail Image
    Item
    Persistent Effects of Herbaceous Species on the Infectious Lethality of Soil for Conifer Seedlings
    (2014-01-06) Schimpf, David J.; Garske, Steven C.; Regal, Ronald R
    Seeds of the coniferous trees Abies balsamea, Picea mariana, and Pinus strobus were sown in the laboratory in two soils taken from ground‐layer patches differing in species composition, one of which was dominated by Aegopodium podagraria (goutweed). This permitted inference whether herbaceous species may affect the favorableness of the soil for establishment of these trees. Weibull distributions were fitted to the time course of aggregate seedling emergence and post-emergence mortality, enabling seedling lifespan to be inferred without monitoring of each individual. A higher percentage of Abies seeds developed into emerged seedlings in the goutweed soil, likely because of less preemergence mortality incited by pathogens. Picea and Pinus emergence percentages were similar in both soils. Most emerged seedlings died within weeks, with symptoms of diseases incited by soil‐ or seed‐borne fungi. Although the timing of seedling emergence did not differ between soils, seedlings died more quickly on the goutweed soil, largely because of a faster development of post‐emergence damping‐off. Total post-emergence mortality of Picea and Pinus was greater on the goutweed soil. The relative frequencies of the several symptoms exhibited by dying seedlings varied between the two soils, suggesting that the ground‐layer species differentially affected the microbial community’s composition or interactions with the seedlings. Symptom frequencies differed among tree species. Local spatial variation in herbaceous species composition appeared to produce patchy infectious lethality of soil for tree seedlings, an indirect effect that was observed after the herbaceous plants had been removed.