Soil Source, Seed Source, and Organic‐Matter Content Effects on Douglas‐Fir Seedling Growth

Abstract

Douglas‐fir [Pseudotsuga menziesii var. glauca (Beissn.) Franco] seedling success on harvested areas in northern Idaho is often limited on harsh sites because of moisture and nutrient stress. This study was conducted to determine the importance of soil source, seed source, and organic matter on seedling growth and nutrition. Soil and seed were taken from both high‐ and low‐elevation sites at the Priest River Experimental Forest, Priest River, ID. In a greenhouse, seed was sown in both home‐source soil (taken from local seed‐collection zone) and nonsource soil (taken from opposite seed‐collection zone) mixes. Soil mixes included 100% organic, 50% organic/50% mineral, or 100% mineral soil. Seedlings were measured for height, bud length, root collar diameter, dry root and shoot weight, total N, total P, K, and number of ectomycorrhizal roots tips g−1 of dry root. Both soil and seed sources had similar nutrient and growth characteristics for each of the three soil mixes. One hundred percent organic soils, after only one growing season, produced seedlings that were significantly taller and had greater bud length, root collar diameter, and biomass than those growing in either mineral soil or the organic/mineral mix. Total N and P uptake was greater in the organic soil than in the mineral soil or the mix, but K uptake was greater in pure mineral soil. Low‐elevation seed‐source trees were always taller than their high‐elevation counterparts, an apparent result of adaptation to longer growing seasons. The best ectomy‐corrhizal colonization took place in the mineral soil mix. Ectomy‐corrhizae were most prolific on seedlings grown in nonsource soil when compared with those grown in home‐source soil. Regeneration success in the Inland Northwest will be substantially improved by maintaining the integrity of organic horizons on harvested areas and by adhering closely to seed‐transfer‐zone guidelines.

Effectiveness of Road Ripping in Restoring Infiltration Capacity of Forest Roads

“…In mining and rangeland rehabilitation, endeavors similar to road rehabilitation, soil amendments are commonly used to increase soil organic content. Several studies (Skujins & Richardson 1984;Page-Dumroese et al 1990;Aguilar 1992;Sidle et al 1993;Hudson 1994) highlight the importance of organic matter content for soil productivity, structure, and erosion protection. In those studies, organic matter was amended as topsoil, sludge, or surface mulch that later decomposed.…”

Species-mediated soil moisture availability and patchy establishment of Pseudotsuga menziesii in chaparral

“…We suggest four hypotheses for future investigation that could explain strong species-mediated soil moisture resource patchiness. (1) Soil moisture may be retained better under A. glandulosa than under A. fasciculatum due to reduced evaporation of moisture from the soil surface as a result of a thicker litter layer (e.g., Page-Dumroese et al 1990). A. glandulosa, with leaves of about 2±3 cm width and 2±5 cm length, produces a litter layer that can be many centimeters deep, unlike A. fasciculatum, a shrub with tiny needle-like leaves that produces little or no litter (personal observation).…”

Soil processes related to organic matter modifications following Douglas-fir mature reforestation

“…The study area is dominated by European chestnut (Castanea sativa Mill.) forests, and in 1963-1964, about 3.5 ha was reforested with Douglas-fir, characterized by high productivity and timber quality (Tarrant and Miller 1963;Whiteside et al 1977;Page-Dumroese et al 1990;Marshall and Curtis 2005). The age of the Douglas-fir trees was confirmed by collecting drill cores from six plants using a Pressler borer.…”