Soil Carbon in
Jay S. Gregg
Wednesday, November 12, 2006
meter-deep hole was dug in
show a general decreasing increasing trend in density with depth. There was a decreasing trend in porosity and
total carbon content with depth. Cubic
spline fitting was used to interpolate data at the millimeter increments of
depth, and the carbon weight per cubic meter was estimated by integrating
across the spline function. Multiplying
this by the area yielded a estimate of 5500 tonnes of carbon in the soil at
Water content also decreased with depth, yet increased again at about 70 cm, where the soil was more clay. The 13C/12C ratio increased with depth as there was less organic material which tends to have higher concentrations of 12C carbon. However, as with mass and total carbon percent, the soil at 50 cm was anomalous to the trend. The soil at 50 cm had less density, greater porosity, greater carbon concentration, and a lower 13C/12C ratio than the soil at 30 cm and 70 cm. This suggests there may be evidence of past agricultural activities, but there is not enough data to be sure. Another possibility is organic matter from roots is contained in this layer.
The soil samples were collected in only one location, due to cost, permission, and time constraints. A more systematic sampling method across the entire park could answer these questions more thoroughly as well as give some understanding of the spatial variability of soils within the park.