Organic matter and chemical element dynamics in an aspen woodland soil

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Abstract
Temporal and spatial dynamics of organic matter and mineral elements were studied in an aspen woodland floor in southwestern Alberta, Canada. The average depths of the layers comprising the organic horizon were as follows: L, 0–2 cm; F, 2–4 cm; H, 4–7 cm; and Ah, 7–8 cm. The average annual amounts of organic matter in the soil layers were the following: L, 10.3 × 103 kg ha−1 (range 8.0–16.4); F, 18.2 × 103 kg ha−1 (13.2–24.5); H, 31.5 × 103 kg ha−1 (24.0–40.4); and Ah, 4.2 × 103 kg ha−1 (3.8–5.0); the total weight of soil organic matter was 64.2 × 103 kg ha−1 (49.0–86.3). The H layer accounted for 50% of the soil organic matter; total soil organic matter, to a depth of 8 cm, constituted about 0.30 of the total living above-ground plant biomass. There were no evident statistically significant seasonal fluctuations of organic matter in any of the organic layers; the turnover rate of the soil organic matter was 0.08 year−1 and the mean residence time was 12.5 years.The concentrations of Ca, Mg, P, and N generally decreased with profile depth, while K, Fe, Mn, and Na increased in concentration. Zinc concentrations showed no obvious trend but it did appear that Zn might be concentrated in the F and Ah layers. The orders of abundance of elements in the soil layers were as follows: L, Ca > N > K > Mg > P > Fe > Zn > Mn > Na > Cu; F, Ca > N > Mg > K > Fe > P > Zn > Mn > Na > Cu; H, Ca > N > Fe > K > Mg > P> Na > Mn > Zn > Cu; Ah, Fe > N > K > Ca > Na > Mg > P > Mn > Zn > Cu; total, Ca > N > Fe > K > Mg > Na > P > Mn > Zn > Cu. Maximum weights of Ca, N, Mg, and P were found in the H layer, whereas K, Fe, Zn, Mn, Na, and Cu were most abundant in the Ah. There was some indication that the amounts of some elements fluctuated positively or negatively with rainfall and (or) soil moisture levels. Based on limited input data for the elements, turnover times were calculated and compared with literature values.