Harvard Forest Research

Effect of Warming and Nitrogen Additions on Microbial Community and Soil Organic Matter Dynamics

Principal Investigator: Serita Frey
University of New Hampshire: Oct 01 2005 - Jun 01 2010:

Abstract:
The purpose of this project is to examine how warming and N additions interact to influence microbial metabolism and community dynamics, soil C and N cycling, and soil CO2 flux. This experiment, installed adjacent to the existing soil warming plots on Prospect Hill, has four treatments (control, heated +N, heated –N, +N only) and six replicates in a randomized block design. Average soil temperature in the heated plots is elevated 5ºC above ambient by the use of buried heating cables placed at 10 cm depth in the soil and spaced 20 cm apart. The heating cables are controlled by a data logger that monitors thermistors (5 per plot) every 10 min. Plots automatically turn on and off to maintain a 5ºC temperature difference between the heated and control plots. The N addition plots (heated +N, +N only) are fertilized following the protocol of the Harvard Forest Chronic N Addition Study. An aqueous solution of NH4NO3 is applied at a rate equivalent to the low N plots at the chronic N study (5 g m-2 yr-1). Fertilizer is applied in equal monthly doses during the growing season (Apr-Oct). The control plots and unfertilized, heated plots (heated –N) receive water only.

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