were enhanced by incorporating moving average smoothing (MA model) as a data filter to

reduce cyclical and seasonal variations found in the datasets for a number of the indicators

affected by climate (Platt and Denman 1975; Kumar et al. 2001; Ittig, 2004). The trend analysis

was followed by loglo data transformations where necessary to stabilize variances prior to

analysis. Partial Canonical Correspondence Analysis with multivariate regression (proc

CANCORR) was used to determine the relative contributions of the different variables to the

relationship (SAS, 2002; Fortin and Dale, 2005).

 Results

Soil Types, Soil Organic Matter, and Soil pH

 All three reference sites contained taxonomically equivalent soil types. All of the soils

had similar soil properties (sandy, acidic, thermic, aquic). The soils were also found to be

functionally equivalent even when compared by drainage class (Table 3-1). Soil organic matter

content (SOM) was found to increase from 1% to 4.5% as gravimetric soil moisture increased

from 20% to 60% of soil weight (Figure 3-1). Soil pH decreased from a pH of 5.0 to 4.0 as SOM

increased from 1% to 4.5% (Figure 3-2). The plant-available phosphorus tests produced too

many non-detectable samples for any meaningful results (Table 3-2).

Net Nitrogen Mineralization

 Net nitrogen mineralization rates (Nmin) increased during the young age class, peaked

during the mid-age class, and then decreased after 60 years (Figure 3-3). Mean Nmin rates were

12 mg N / kg soil / month for the young age stands, 14 mg N / kg soil / month during the mid-

aged class, and 8 mg N / kg soil / month during the mature age class for the reference sites (table

3-2). The pattern for Nmin rates followed microbial biomass levels (Cmb) over the 110-year

chronosequence (Figure 3-4). Nmin rates increased from 5 mg N / kg soil / month to 20 mg N /

kg soil / month as Cmb inCTreSed from 100 mg-l C / kg soil to 1000 mg-l C / kg soil (Figure 3-5).