Soil Properties Related to Forest Cover Type and Productivity on the Lee Forest, Snohomish County, Washington

Forristall, Floyd F.; Gessel, S. P.

Soil Properties Related to Forest Cover Type and Productivity on the Lee Forest, Snohomish County, Washington

1955

Forristall, Floyd F. | Gessel, S. P.

Five one-tenth acre plots were established on Lee Forest to investigate forest site and type and soil relationships. One plot was in each of the following types and sites: western hemlock-Douglas fir, site class III; Douglas fir, site class II; Douglas fir, site class III; western red cedar, site class III; red alder, site class I. Soils were sampled on these plots and the following data taken: effective depth, bulk density, texture, moisture equivalent, reaction, total nitrogen, and cation exchange capacity. In addition, weight and nitrogen content of the forest floor were determined and soil moisture followed throughout the 1953 growing season. Depth to a hardpan layer was an important criterion for productivity rating. High bulk densities impeded root growth and determined effective soil depth. The critical density differed for the different tree species. Total soil nitrogen and total cation exchange capacity were much greater in the more productive forest soils. The western red cedar and the red alder plots had shallow soils with excess soil moisture during a considerable portion of the year. Low soil moisture did not appear to be a factor in tree growth on any of the plots in the 1953 growing season although the soil on the red alder plot did become quite dry in late August and early September. The dominating influence in determining forest type seemed to be poor soil drainage.

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