Current Research Projects

Collaborative Proposal: MRA: Seasonality of photosynthesis of temperate and boreal conifer forests across North America
Dr. David Bowling, Professor of Biology, University of Utah Dr. Christian Frankenberg, Associate Professor, Caltech Dr. Barry Logan, Professor, Bowdoin College Dr. John Gamon, Professor, University of Nebraska-Lincoln

Overview The timing and magnitude of terrestrial photosynthesis is changing at an alarming rate for ecosystems across the globe, making it difficult to predict how carbon feedbacks will alter future climate. Deciduous forests across North America have generally responded to climate change by extending their growing season, thereby enhancing gross CO2 uptake. In contrast, the actual outcome of the changing seasonality of evergreen coniferous ecosystems remains an open question, with multiple factors likely affecting the timing, magnitude, and feedbacks of ecosystem functioning. This is largely because coniferous forests pose several challenges to quantifying changes in the seasonality of photosynthesis: 1) The remote and inaccessible nature of these ecosystems has restricted the ability to collect highly resolved data in both space and time; 2) Evergreen forests retain their foliage throughout the season, making it difficult to detect changes in timing of carbon uptake using traditional remote sensing techniques ; 3) We lack a mechanistic understanding of the relationship between remotely sensed indices sensitive to dynamic changes in photosynthesis (solar-induced fluorescence, chlorophyll:carotenoid index) and physiological functioning of coniferous forests. As such, we propose to link observations of vegetation reflectance and fluorescence with high temporal and spatial resolution (tower-based spectroscopy) to carbon fluxes, needle-level photosynthesis and needle pigments across the NEON domain. The basis for our approach lies in the premise that pigment-based thermal dissipation of excess sunlight is an integrative general property of evergreen plant response to environmental conditions, ultimately controlling the fate of photons that drive photosynthesis.

The overall objective for this application is to quantify spatial and temporal variability in forest photosynthetic capacity of conifer forests across North America. Our approach to achieve this is:

  1. Determine variation in light energy dissipation mechanisms affecting seasonality of forest photosynthetic capacity across temperate and boreal North America.
  1. Refine and test models of forest photosynthetic capacity with data from NEON and other flux tower sites.
  2. Develop the tools to launch a continental-scale observational framework that will quantify photosynthetic response to climate change over the 30-year NEON lifetime.

 

Intellectual Merit This project will provide crucial information on how plant physiological processes scale in both time and space. Climate change has altered the traditional seasonal concepts of "spring", "growing season", and "fall". Northern hemisphere vegetation is responding to longer growing seasons with increased photosynthesis, but the response of the vast conifer forests in this region is highly uncertain. By combining fundamental theory of plant physiological ecology with a diverse combination of observations at scales from conifer needle to flux tower to satellite, we will provide fundamental knowledge on the environmental and physiological controls on the seasonality of conifer photosynthesis across North America.

Broader Impacts This project will benefit the continental -scale ecological scientific community by providing a through investigation of the potential for new techniques in satellite remote sensing to quantify seasonality of conifer photosynthesis across North America. All data collected will be made publicly available. We will develop and disseminate teaching materials that merge plant physiology and remote sensing that bridge often disparate research communities. We will actively focus on STEM training and diversity. We will conduct two science outreach efforts with the Natural History Museum of Utah to provide interactive resources to help visitors connect changes observed in their backyard to similar ecosystems across the continent. Finally, we will train three postdoctoral scientists, two graduate students and several undergraduates.