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Harvard Forest REU Symposium Abstract 2006

  • Title: Below Ground Root Biomass Response to Soil Warming
  • Author: ()
  • Abstract:

    The Intergovernmental Panel of Climate Change predicts soil temperatures to increase between 1.5°C and 5.8°C for the New England Region by the end of the century, due to the rapidly increasing levels of greenhouse gases. Soil dynamics such as root respiration and microbial activity are important in understanding climate change because soil is the largest terrestrial carbon pool. To better understand the implications of increased soil temperatures, a large scale soil warming experiment was begun at the Barre Woods experimental site at Harvard Forest in 2003. This experimental site consists of two “megaplots,” one control and one heated, each 30m x 30m. The heated plot contains heating cables buried 10cm deep and 20cm apart that heat the soil 5°C above ambient soil temperatures. These plots, which are large enough to contain entire tree and herbaceous root networks, enable us to investigate whether increased nitrogen availability, due to warming alters carbon allocation between above ground and below ground biomass. To address this question, an estimate of the live fine roots, which are responsible for obtaining nutrients from the soil and respiring, were extracted from the organic layer of soil cores by flotation. Roots were then sorted into <1mm, 1-2mm, 2-3mm, and >3mm, size categories and dead or alive. After 24 hours at 105°C in a drying oven, each sample was weighed. Samples processed in June suggested the heated plot contained significantly fewer live roots than the control. However, samples collected in July had no significant difference between the two treatments and an overall lower root biomass than observed in June (Figure 1). These findings correlate with other studies in which root biomass varied throughout the growing season. Therefore, sampling for an entire growing season will enable us to obtain a more accurate estimate of the live fine roots and thus a greater understanding of increased soil temperatures on root biomass.

  • Research Category: Large Experiments and Permanent Plot Studies; Soil Carbon and Nitrogen Dynamics