In this study, biological and chemical characteristics were determined for two high-elevation meadow-to-forest transitions located in the Central Oregon Cascades. The chloroform fumigation incubation method (CFIM) was used to determine microbial biomass C(MBC) and the N flush due to fumigation (NF), and meadow values were compared to forest values for each. Meadow and forest MBC values were also compared for estimates of MBC determined with microscopy and these values were compared to CFIM estimates. Net N mineralization and C mineralization were determined for an 85-d incubation period and used as a measure of labile C and N. Microbial biomass C and NF were then compared to these labile pools in order to investigate the relationship between the amount of each nutrient stored in biomass and the magnitude of the respective labile nutrient pool for each. Long-term and short-term net N mineralization rates and C/N ratios were also compared for meadow and forest soils, and the relationship between these two characteristics was examined. In general, microbial biomass estimates made with the CFIM method did not show any significant differences between meadow and forest soils. Mean MBC for both sites as determined by CFIM was estimated to be 369 and 406 μg C g⁻¹ soil in meadow and forest soils, respectively. Mean NF was estimated to be 37 and 56 μg N g⁻¹ soil in meadow and forest soils, respectively. MBC estimates made using microscopy showed biomass C to be greater in the forest than in the meadow. Mean MBC as determined by microscopy was estimated to be 529 and 1846 μg C g⁻¹ soil in meadow and forest soils, respectively. The NF measured as a percentage of the net N mineralized over 85 d was significantly greater in the forest than in the meadow soils, but was a substantial percentage in both. The means of these values were 30 and 166% in meadow and forest soils, respectively. This led to the conclusion that biomass N may be a very important pool of stored labile N in this ecosystem. Net N mineralization rates were almost always greater in the meadow than in the forest soils. Net N mineralization for the 10-d incubations averaged 21 μg N g⁻¹ soil in the meadow and 8 μg N g⁻¹ soil in the forest Rates for long-term N mineralization averaged 126 μg N g⁻¹ soil in the meadow and 52 μg N g⁻¹ soil in the forest. Net N mineralization rates were correlated with C/N ratios for both short-term and long-term incubations. / Graduation date: 2002

The abundance and spatial heterogeneity of coarse woody debris (CWD) on the forest floor is a prominent feature of Pacific Northwest (PNW) forest ecosystems. The effect of CWD on soil solution chemistry, nutrient cycling and availability, soil physical structure and formation of soil organic matter, however, remains unknown. Therefore, studies on the spatial and temporal imprint of CWD on forest soils are timely and can fill critical gaps in our understanding of the role of CWD in PNW forest ecosystems. I investigated the effect of CWD on soils and soil solution at the H.J. Andrews Experimental Forest in a two-part study. Mineral soils were sampled beneath CWD to a depth of 60 cm. The top 15 cm of soil was also repeatedly sampled for seasonal differences. Control leachate, CWD leachate and soil solution from control soils and from under CWD were collected from the fall of 1999 until the spring of 2001. Results indicated that CWD leachates were much more acidic than water leaching from the forest floor without CWD. Intermediate stages of CWD decomposition had the highest concentrations of hydrophobic compounds and polyphenols of all stages of decay. Correspondingly, surface soils sampled from under well-decayed CWD were more acidic and had more exchangeable acidity and aluminum, and a lower percent base saturation than soils under the forest floor. Nutrient pools were not different under CWD, although nitrogen fluxes were slower under CWD. Although we had hypothesized that the spatial variability of CWD inputs may affect forest soils under CWD, we found that the spatial variability is much more temporal than I had hypothesized and is limited to the top five centimeters of the underlying soil. / Graduation date: 2002

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 114-131). Also available on the World Wide Web.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2002. / Abstract inserted. Appendix reprints four papers and manuscripts co-authored with others. Includes bibliographical references. Also partially issued electronically via World Wide Web in PDF format; online version lacks appendix.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 69-72). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 79-86). Also available on the World Wide Web.

High-elevation spruce-fir forests in the southern Appalachians may potentially be in a state of decline as a result of either natural or anthropogenic causes. Soils were investigated in areas representative of 117 permanent intensive field plots established to evaluate changes in forest composition that may be influenced by the deposition of atmospheric pollutants. A total of 35 pedons were described, sampled, and characterized. Over 75% of the soils studied were classified in the field as either Typic or Pachic Haplumbrepts, but weakly developed spodic horizons were identified in 13 of the soils by chemical determinations in the laboratory. A high degree of morphological similarity exists between soils in these areas despite widespread differences in parent material and local geology. This similarity is the result of physical mixing of these soils by climatically-driven slope processes. A considerable amount of chemical variability exists in these soils which is not expressed in morphological characteristics. Multiple discriminant analysis established that physical and morphological properties used to separate and classify these soils in the field were not significantly different between study areas. Parent material differences, however, expressed in both soil chemical and mineralogical properties, were sufficiently different between study areas to result in the clear separation of soils into distinct groups. The importance of nutrient cycling in these spruce-fir forests is underscored by high levels of exchangeable bases in surface horizons relative to lower in the profile. This suggests that disturbances to the forest floor resulting from fire, overgrazing, logging, or erosion could have a major impact on ecosystem resilience during stress. / Master of Science

Graduation date: 1994

Thesis (M.S.)--Oregon State University, 1984. / Typescript (photocopy). Includes bibliographical references (leaves 104-107). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.