Physical Sciences and Mathematics Commons^™

A Nonparametric Method For Separating Photosynthesis And Respiration Components In Co2 Flux Measurements, Chuixiang Yi, Runze Li, Peter S. Backwin, Ankur Desai, Daniel M. Ricciuto, Sean P. Burns, Andrew A. Turnipseed, Steven C. Wofsy, J. William Munger, Kell Wilson, Russell K. Monson

Publications and Research

Future climate change is expected to affect ecosystem-atmosphere CO₂ exchange, particularly through the influence of temperature. To date, however, few studies have shown that differences in the response of net ecosystem CO₂ exchange (NEE) to temperature among ecosystems can be explained by differences in the photosynthetic and respiratory processes that compose NEE. Using a new nonparametric statistical model, we analyzed data from four forest ecosystems. We observed that differences among forests in their ability to assimilate CO₂ as a function of temperature were attributable to consistent differences in the temperature dependence of photosynthesis and respiration. This observation …

Relationships Between Needle Nitrogen Concentration And Photosynthetic Responses Of Douglas-Fir Seedlings To Elevated Co2 And Temperature, James D. Lewis, Melissa S. Lucash, David M. Olszyk, David T. Tingey

Environmental Science and Management Faculty Publications and Presentations

• Here we examined correlations between needle nitrogen concentration ([N]) and photosynthetic responses of Douglas-fir (Pseudotsuga menziesii) seedlings to growth in elevated temperatures and atmospheric carbon dioxide concentrations ([CO₂]).
• Seedlings were grown in sunlit, climate-controlled chambers at ambient or ambient+3.5^° C and ambient or ambient +180 μmol mol^-1 CO₂ in a full factorial design. Photosynthetic parameters and needle [N] were measured six times over a 21-month period.
• Needle [N] varied seasonally, and accounted for 30–50% of the variation in photosynthetic parameters. Across measurement periods, elevated temperature increased needle [N] by 26% and light-saturated …