Organic matter and major elements of the forest floors and soils in subalpine balsam fir forests

Abstract

Forest floors, fallen branches and fallen tree boles were sampled in 13 balsam fir (Abiesbalsamea (L.) Mill.) stands in the subalpine zone (1220–1450 m) of the White Mountains in New Hampshire, U.S.A. These 13 stands were distributed in three sites of contrasting exposure, slope, and rockiness. Soil pits were excavated in three of the stands representing each of the three sites. The ash-free dry weights and major elemental contents of the forest floor and dead wood were compared along chronosequences following natural disturbances, between sites, and with other forest types. No significant trends in these components were found along chronosequence comparisons. For sites that are dissimilar in terms of physical position on the landscape and in the appearance of the trees, compensating biotic and abiotic factors apparently underlie the convergence in forest floor and soil characteristics, thereby eliminating site differences as well. The forest floor is massive; ash-free dry weight averages 92 200 kg•ha⁻¹. Total soil profile ash-free weight is 323 600 kg•ha⁻¹. The forest floor and mineral soil horizons are unusually rich in nitrogen and phosphorus, with weighted average ash-free nitrogen and phosphorus concentrations of 2.42 and 0.23%, respectively, in the forest floor. Total nitrogen and phosphorus contents of the forest floor are 2300 and 217 kg•ha⁻¹, respectively. The weight and nitrogen and phorphorus contents of the fir forest floor are greater than that found in other regional forests and coniferous forests in general.