SOIL MOISTURE MEASUREMENT


 Soil moisture readings were taken using a TH20 soil moisture meter. Readings of
 soil moisture were taken at each sampling point along the major and minor transects.
 Three outputs are possible with the TH20 meter: direct output voltage, organic moisture,
 and mineral moisture. Direct probe output was used because of greater ease of calibration
 for specific soils.

 Calibration curves for specific soils are based on the relationship between the
 dielectric constant (s) sensed by the probe and the water content (0). Specific calibration
 curves for each hummock soil type can be created. Soil moisture was calculated from the
 voltage read by the probe. Voltage (V) was related to s by the following equation:

 'ls = 1.07 + 6.4V 6.4V2 + 4.7V3 [4]
 &s = square root of dielectric constant
 V = voltage

 The actual soil moisture was then calculated from the following equation
 (coefficients described in user manual):

 0 = [Is ao] / al [5]
 0 = volumetric water content (m3/m3)
 ao = dry soil coefficient
 a, = wet soil coefficient

 A generalized curve for 0 versus V is provided in the user manual and provides a
 typical error of 0.05 m3/m3. The coefficients for wet and dry soil are based on these
 curves. Perfect calibration decreases error to 0.02 m3/m3. Calibration was not done for
 this project because the trends seen in water content are more important to the hummock
 comparison than true values. The tendency of soils to compact and shift in the new
 wetlands changing the pore spaces prohibits accurate calibration. Water contents were
 taken on a bi-monthly basis throughout the growing season.


 TREE MEASUREMENT

 Tree heights were measured with a standard tape measure. Heights were taken
from the base of the tree to the highest point of the tallest branch. Heights were taken to
the nearest 0.3cm. Basal diameter was measured using standard calipers. Diameters were
taken to the nearest millimeter. Tree measurements were taken for 18 trees of each type
planted on the hummocks in the Agrifos wetland. Nine trees of the same species off the
hummock were originally supposed to be sampled to compare growth and survivorship
with on hummock trees. However, only five ash trees were ever found off the hummocks,
and no sweet bay trees were ever seen. These trees were measured at the beginning and
end of the growing season. Due to the late construction of the Cargill wetland, only initial


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