The objective of this study was to examine the variation among ammonia-oxidizing and denitrifying communities in soils of a natural Fennoscandian boreal forest and of a forest with a long history of fertilization with different levels of nitrogen (N), and to examine whether there are any changes in the microbial...
Application of N fertilizer is a common forest management practice in the Pacific
Northwest, yet the long-term influence of fertilization on forest soil properties is not well known. Although elevated N often increases mineralization of C and N from labile organic matter, negative effects have been documented in recalcitrant organic...
The optimum goal of forest management is to foster long-term productivity and ecological integrity while maintaining or increasing short-term growth and yield through sustainable practices. Understory vegetation plays a definite role in forest functions through nutrient cycling and habitat provisions. The objective of this study was to determine how salal,...
Soil organic carbon (SOC, kg C m-2) is an important component in evaluating global C stores. The nitrogen (TN, kg N m"2) cycle is closely linked to C and understanding its role is also important. Contents and distributions of SOC and TN in soil profiles, to 1-meter depth, were estimated...
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1.3. The soilnitrogen cycle of a coniferous forest ecosystem ................5
2.1. Old-growth
The mechanisms governing short- and long-term belowground carbon dynamics need to be understood. As part of a larger project developed to assess the effect of quantity and quality of litter inputs on the rate of soil organic matter (SOM) formation, I examined SOM in the H. J. Andrews Detritus Input...
The objectives of this thesis were to examine the links between soil microbial community composition and function using the nitrogen (N) cycle as a model for these interactions and to assess the impact of environmental factors such as microclimate, vegetation type, and nutrient availability on microbial diversity and N transformations...
Nitrification and denitrification are major biological processes transforming nitrogen (N) in soils to plant available N, highly leachable nitrate (NO₃⁻) and gaseous N oxides. Although many studies in the past have studied N cycling communities, the effect of increased N inputs on ammonia-oxidizer and denitrifier population dynamics is still under...
Silvicultural canopy gaps are emerging as an alternative management tool to accelerate development of complex forest structure in young, even-aged forests of the Pacific Northwest. I investigated patterns of nitrogen (N) availability along transects through 0.1 and 0.4 ha silvicultural gaps in three 50-70 year old Douglas-fir forests of western...
Understanding how N availability influences base cation stores is critical for long-term ecosystem sustainability. Indices of nitrogen (N) availability and the distribution of nutrients in plant biomass, soil, and soil water were examined across ten young, unpolluted Douglas-fir (Pseudotsuga menziesii) stands in the Oregon Coast Range spanning a three-fold soil...
Ecosystem nitrogen (N) supply strongly influences the availability and cycling of other essential nutrients in temperate forests, especially calcium (Ca). Short-term additions of N that exceed ecosystem demands often increase dissolved nitrate fluxes and decrease soil pH, which can stimulate soil Ca loss. However, the long-term effects of high N...