Nutrient availability in the bog.
We deployed ion-exchange resins across hummock-hollow microtopography in two locations in each SPRUCE experimental plot. Resins are retrieved every 28 days during the growing season to assess plant-available NH4-N, NO3-N, and PO4 throughout the peat profile, and to track changes in plant-available nutrients in response to warming and elevated [CO2].
Thus far, warming—combined with a longer frost-free period—has increased the amount of NH4-N and PO4-P adsorbed to ion-exchange resins in the warmest treatment enclosures. However, the increase in nutrients was initially much greater below the rooting zone, potentially indicating plant uptake in surface peat (i.e., greater competition for nutrients). In recent years, we have observed large spikes in resin-available nutrients in the shallow peat of the warmest enclosures, likely due to the death and decay of Sphagnum mosses.
Iversen CM, Latimer J, Burnham A, Brice DJ, Childs J, Vander Stel HM. 2017. SPRUCE plant-available nutrients assessed with ion-exchange resins in experimental plots, beginning in 2013. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A.