Coupled Nitrogen and Calcium Cycles in Forest Ecosystems: New Insights from Multiple Stable Isotopes

Oregon State University, Corvallis OR

Investigators

Abstract

Nitrogen is a key essential nutrient that regulates plant productivity and the cycling of calcium in temperate forest ecosystems. Increases in nitrogen availability beyond the threshold of plant and ecosystem needs may drive fundamental, non-linear changes in forests that include excess nitrate leaching and potential calcium depletion from soils. These changes expose forests to unprecedented nitrogen-rich, calcium-poor conditions that can impact long-term forest health and sustainability. This interdisciplinary research will take advantage of a wide gradient in nitrogen status for coastal Douglas-fir forests of the Pacific Northwest as a way to examine couplings between cycles of nitrogen and calcium. Natural abundance and enriched stable isotope studies of calcium, strontium, and nitrogen will be used to examine: 1) the relative importance of atmospheric vs. weathering sources of calcium to forests growing across a gradient in soil nitrogen; 2) how ecosystem nitrogen and calcium status influences the retention of new calcium inputs, and; 3 the utility of strontium as a tracer for calcium in plant-soil-mycorrhizal systems. Results from this work will contribute to the sound management of forests of the Pacific Northwest, and will refine broader-scale predictions of how temperate forests in general will function in an increasingly nitrogen-rich world.