Cooperative Ecosystem Studies Unit, Pacific Northwest CESU

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The USGS Forest and Rangeland Ecosystem Science Center (FRESC) is offering a funding opportunity to a CESU partner for research to develop new information on factors that influence nutrient supply to forests of the Oregon Coast Range. Two key questions that shape the sustainability of forest nutrition in this region are: (1) what are current rates of nitrogen input from biological nitrogen fixation by red alder trees? and (2) how does nitrogen in soils influence mineral weathering to release of other essential nutrients? Both nitrogen fixation and mineral weathering provide nutrient inputs to soils that are essential for sustaining soil fertility and tree growth, but current rates of nutrient input and their relative amounts are poorly described, making it difficult to set forest nutrition guidelines. Perakis and Pett-Ridge (2019) recently demonstrated that nitrogen-fixing red alder trees can preferentially access nutrients directly from mineral weathering, thus providing a potential link of inputs of nitrogen from fixation and other nutrients from mineral weathering. These combined processes could sustain supplies of multiple nutrients required for forest growth. What is needed to apply this finding is data on how nitrogen fixing red alder trees stimulate mineral weathering, and how this scales across landscapes. This missing information can be used to parameterize forest growth and watershed nutrient flux models that have direct economic, ecological, and societal importance in forested watersheds of the Oregon Coast Range.

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