Graduate Thesis Or Dissertation
 

An Analysis of Nutrient Depletion in Douglas-fir Forests of the Oregon Coast Range

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/d791sp843

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  • Nutrient limitation constrains tree growth in many managed forests. Nitrogen (N) is the most common limiting nutrient, but high N supply can shift limitation to other nutrients, particularly phosphorus (P) and the base cations calcium (Ca), magnesium (Mg), and potassium (K). As different soil minerals have different capacities to supply P and base cations, soil mineralogy is a major factor that determines the likelihood of nutrient limitation. Forest harvest can also intensify nutrient limitation via the removal of nutrient-containing biomass and by accelerating rates of nutrient leaching. The influence of forest harvest on nutrient depletion can vary by harvest type and frequency (utilization intensity), though detection of harvest effects can be difficult due to their emergence over long time frames. To study these factors, a process-based simulation modelling approach was used. Process-based models allow for nutrient cycling to be dynamically represented. The biogeochemical model NutsFor was used to evaluate how soil N (low N vs. high N) and soil mineralogy (sedimentary vs. basaltic) interact to drive soil nutrient limitation across 4 Douglas-fir forests in the Oregon Coast Range. I further examined interactions between harvest type (bole-only vs. whole-tree-harvest) and rotation length (40-year vs. 80-year) at these sites over 500 years of growth and harvest. I found that low N forests on both sedimentary and basaltic bedrock were mainly N limited, but that whole-tree harvest also led to K limitation at low N basalt sites. I also found that high N sites were limited by both Ca and K and that bedrock type led to primary Ca limitation in sedimentary sites and K limitation in basalt sites. Tree growth at high N sites responded negatively to all kinds of harvest. Overall, the findings suggest that historically productive high N sites may be particularly sensitive to nutrient depletion and reduced tree growth in as few as one or two rotations. The simulated interactions of site N status and mineralogy on nutrient limitation also provide a set of testable predictions to guide monitoring and changes in management aimed at sustaining long-term forest productivity across a broad range of site conditions.
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  • Pending Publication
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  • 2021-09-17 to 2023-10-18

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file details SiahKaveh2021.pdf 2021-09-17 Público Descargar