Samuel M. Simkin

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Atmospheric deposition has long been recognized as an important source of pollutants and nutrients to ecosystems. The need for reliable, spatially explicit estimates of total atmospheric deposition (wet + dry + cloud) is central, not only to air pollution effects researchers, but also for calculation of input-output budgets, and to decision makers faced(More)
Atmospheric nitrogen (N) deposition has been shown to decrease plant species richness along regional deposition gradients in Europe and in experimental manipulations. However, the general response of species richness to N deposition across different vegetation types, soil conditions, and climates remains largely unknown even though responses may be(More)
Combined optical and radio images of galaxies can provide new insights into the sizes, masses, and possible evolution of these objects. Deep optical and neutral hydrogen images of Markarian 348, a type 2 Seyfert galaxy, show that it is a gigantic spiral (perhaps the largest known non-cluster galaxy). Measurements of the neutral hydrogen velocity field and(More)
Plant diversity in groundwater-fed wetland ecosystems is typically extraordinarily high, yet the biogeochemical controls of this diversity are still incompletely understood. We hypothesized that fine-scale variation in sulfide would influence plant community composition via direct phytotoxicity and indirect mediation of phosphorus release from iron, coupled(More)
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