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Harvard Forest REU Symposium Abstract 2006

  • Title: High watering frequency of leaf litter causes a relative loss of carbon available to decomposition.
  • Author: ()
  • Abstract:

    Recently fallen leaf litter composes the top layer of the soil column and is important to the carbon budget of forest ecosystems. Temperature and moisture have been shown to have important effects on respiration (CO2 production) from the O horizon of the soil. In this experiment, we show that frequency, and less importantly, size of precipitation events affects respiration and loss of easily decomposable carbon in leaf litter. Six groups of four samples each were given irrigation treatments of varying frequency and size over a period of 8 weeks, and periodically measured for carbon dioxide increase. Dry weights for the leaf litter were obtained at the beginning and end of the experiment and compared to determine total carbon loss over the course of the experiment. An additional experiment was conducted to investigate the effect of temperature on leaf litter respiration. Over a temperature range of 13 to 36 o C, CO2 production increased exponentially with temperature. The Q10 for CO2 production decreased from 3.66 at a leaf litter moisture content of 39 % to 2.04 at a moisture content of 266 %. Using these relationships, we were able to correct our respiration measurements with respect to an air temperature of 25 o C. Leaf litter respiration usually followed a Michaelis-Menten relationship with respiration increasing more slowly with moisture content as moisture content increased. Unlike the infrequently irrigated samples, the frequently irrigated samples respired more slowly at high water contents at the end of the experiment than during earlier measurements, implying that the pool of easily decomposable carbon had been diminished relative to other treatments. Our results show that precipitation changes in the future may affect carbon cycling between leaf litter and the atmosphere.

  • Research Category: Forest-Atmosphere Exchange