Local and regional tree species-soils relationships in old-growth forersts of Oregon Coast Range.
Cross, Alison*,1, Perakis, Steven1, 2, 1 Oregon State University, Corvallis, OR2 USGS Forest and Rangeland Ecosystem Science Center, Corvallis, OR
ABSTRACT- Many field studies of tree species effects on soils examine plant-soil relationships across relatively few sites, typically one to several stands, which makes it difficult to draw inferences of relationships in other areas or across larger spatial scales. As part of an investigation of tree species controls on soil nutrient dynamics, we sought to determine whether relationships of tree species to soil characteristics are scale-dependent. Are local (within-stand) relationships similar to regional (between-stand) relationships? Soils were collected beneath four tree species (Douglas-fir, western hemlock, bigleaf maple, and western redcedar) in eight old-growth forest stands across the central Oregon Coast Range. While pH, bulk density, and plant-available phosphorus differed frequently among species in univariate analyses at the local scale, we found that total % soil carbon and nitrogen best distinguished species in discriminant analyses at both scales. At the regional scale, soils beneath maple, cedar, and hemlock were mutually distinct. In contrast, Douglas-fir soils were highly variable, distinct from some species in some stands yet overlapping in others. This suggests a degree of malleability in plant-soil relationships for Douglas-fir that is absent in the other late-successional tree species of the Pacific Northwest. Overall, for the species we studied, we conclude that locally observed tree species-soil relationships are not necessarily indicative of general patterns across stands or at larger regional scales. Qualitatively significant variations in underlying site characteristics (e.g., soil parent material, fire history) across our study sites may contribute to differences in species-soils relationships that exist at the regional scale.
Key words: plant-soil relationships, spatial scales, Pacific Northwest forests
All materials copyright The Ecological Society of America (ESA), and may not be used without written permission.