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Harvard Forest Symposium Abstract 2013

• Title: Soil freezing effects on nitrogen uptake by trees in a mixed temperate forest
• Primary Author: Pamela Templer (Boston University)
• Additional Authors: Ana Castillo (Columbia University in the City of New York); Andrew Reinmann (Boston University); Rebecca Sanders-DeMott (Boston University)
• Abstract:

  Climate models project warming for the northeast United States that will lead to reduced winter snowpack depth and duration, and an increased frequency of soil freeze and thaw cycles. Soil freezing in winter causes root damage and may reduce the nutrient uptake capacity of fine roots in the following growing season in mixed temperate forests. A snowpack removal experiment was conducted at Harvard Forest, Petersham, MA in the winters 2010-2011 and 2011-2012 to simulate delayed onset of snowpack and to induce soil freezing. Due to the low rates of snowfall in winter 2011-2012, soil freezing occurred in both treatment and reference plots. In August 2012, root uptake of ammonium (NH4+) and nitrate (NO3-) were measured using the excised root method. Roots from both treatment and reference plots took up significantly more NH4+ than NO3- (p < 0.01). There was no significant difference in uptake of NO3- between snow removal and reference plots. Uptake of NH4+ tended to be higher in snow removal plots than in reference plots and this relationship was significant when an outlier was excluded from analysis (p = 0.04). The relationship between snow removal treatment and N uptake found in August 2012 may suggest a delayed effect on fine roots resulting from the soil freezing treatment that was successfully induced in winter 2010-2011.

• Research Category: Large Experiments and Permanent Plot Studies
  Physiological Ecology, Population Dynamics, and Species Interactions
  Soil Carbon and Nitrogen Dynamics