Organic matter and mineral distribution in an old-growth Acer saccharum forest near the northern limit of its range

Two sites, both supporting old-growth Acersaccharum Marsh, dominated forest on rugged topography in central northern Ontario, were compared in terms of organic matter and N, P, K, Ca, Mg, S, Fe, Mn, Zn, and Cu content in the tree- and field-layer phytomass, the forest floor, and the mineral soil. One site was on a shallow, low-base, Precambrian-derived till, and the other was on a till of somewhat higher base status. Gross and net growth of the overstory tree layer were also determined. Total phytomass values for the two stands at the beginning of the study period were 245 000 and 210 000 kg•ha −1 , respectively. Gross growth was largely offset by mortality in both stands, producing a rough equilibrium with regard to net increment. Growth before mortality was on the order of 2.4–2.5 m 3 •ha −1 •year −1 in terms of gross total wood volume or 3700–3900 kg•ha −1 •year −1 in terms of phytomass, and it was slightly greater in percent terms on the higher base site. In addition to that in the phytomass, organic matter in the forest floor and mineral soil to a depth of 1 m also contributed to the total organic matter content of 638 000–642 000 kg•ha −1 (equivalent to 34 8000–353 000 kg•ha −1 of C) on both sites and was distributed as follows: 29–34% in phytomass, 5% in the forest floor, and 61–66% in mineral soil. The order of abundance of elements in the phytomass was similar on both sites: Ca > N > K > Mg > S > Mn > P > Fe > Zn > Cu, with accumulation in the phytomass in rough proportion to occurrence in the soil. A more base-rich parent material would appear to be the origin of 1452 kg•ha −1 of Ca estimated to be in the phytomass and forest floor on the higher base soil, compared with 1250 kg•ha −1 in the phytomass and forest floor on the lower base soil.