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Harvard Forest Symposium Abstract 2016

  • Title: Terrestrial Silica Cycling - Harvard Forest as a Model System
  • Primary Author: Robinson W. Fulweiler (Boston University)
  • Abstract:

    The biological component of the global silica cycle is arguably the most well-known and best described for ocean diatoms. But diatoms are not the only biological force altering the global silica cycle. On land, vegetation can also sequester significant amounts of silica. In fact, silica is considered a “quasi-essential” nutrient for plants. Plants readily absorb dissolved silica (DSi), also known as silicic acid (H4SiO4), the dominant form of silica in soil solutions. DSi is taken up with water and carried in the transpiration stream where, with the evaporation of water, it becomes supersaturated and precipitated as biogenic Si (BSi) or phytoliths. Silica is found throughout plants, from their roots to their shoots, but peak concentrations are generally observed at the transpiration termini. In fact, silica can compose 10% or more of the dry weight, exceeding those concentrations of well-known macronutrients such as nitrogen and potassium. We have strong, indirect evidence that silica uptake by trees alters in-stream silica concentrations and thus watershed export of silica to downstream receiving waters. However, to date there are limited studies, and in fact none that I could find in the peer-reviewed literature, that provide direct evidence. Additionally, we know little about how climate change may alter silica uptake by forests nor how the terrestrial silica cycle has changed over time. This research has the following three goals: 1) to determine the rate and timing of silica uptake in dominant tree species in Harvard Forest, 2) quantify how foliar silica concentrations change over the growing season and link this to changes in leaf-out phenology, and 3) calculate historic and future estimates of New England forest silica uptake rates.

  • Research Category: Historical and Retrospective Studies
    Watershed Ecology