The effects of tree girdling on soil and bole respiration in big tooth aspen trees (Populus grandidentata)

Abstract

Much attention has been given to the effects of anthropogenic activities on the global carbon cycle. Deforestation and the burning of fossil fuels has added vast amounts of carbon to the atmosphere, while at the same time reducing the number of carbon sinks that are available to sequester the carbon. The focus of this study was to determine the effects of a selected disturbance (tree girdling) on a forest’s ability to remain a carbon sink, or transform into a carbon source. A field experiment was conducted on the site of the University of Michigan Biological Station in Pellston, Michigan. Six plots containing Aspen trees were set-up in a block design. All of the trees in the experimental plots were girdled. The soil respiration and bole respiration rates were measured at designated time interval over a period of 26 days. A strong efflux decline trend was observed in the soil of plots where the trees were girdled. However, when a paired t-test was performed only one time interval provide a p value that was significant (p=0.014). Trees that were girdled in March-June of 2007 and July 2006 were included in the bole respiration data. It was found that in all but one of the trees, the area above the girdled area had the highest efflux value; followed by the area below the girdled area and finally the girdled area with the lowest efflux value. It was also found that the trees that were girdled prior to July 2007 had a substantially higher average efflux above the girdled area when compared to the trees that were girdled in July 2007 (9.86 μmol/m2/sec and 4.67 μmol/m2/sec, respectively).