The Influence of Western Hemlock and Western Redcedar on Soil Properties

Soils beneath very old western hemlock ( Tsuga heterophylla (Raf.) Sarg.) and western redcedar ( Thuja plicata Donn) trees at three sites in Washington and Idaho were compared. The sites differed in climate and parent materials, but were similar to the extent that western hemlock and western redcedar dominated the overstory. The A2‐B2 sequences were generally more strongly developed under hemlock than under cedar. At two of the three sites considerable mixing of the organic and mineral soil horizons had occurred under cedar, but much less so under hemlock. Below the top 15 cm of mineral soil no large morphological differences were observed between profiles under cedar and hemlock. Soil pH, “exchangeable” Ca, cation‐exchange capacity, base saturation, and the total weight of organic horizons were greater under cedar than under hemlock. Soil N, C, Mg, and K were generally higher under cedar than under hemlock but the differences were not large. The differences between soil properties under hemlock and cedar, as well as the depth to which these differences occurred, varied from one property to another, and from site to site.