Research Feature: OSU research on the role of northwest forests in the global carbon cycle

Carbon Cycle Basics

The global carbon cycle describes the movement of carbon between the atmosphere, the ocean, fossil fuels and land plants and soils.  Understanding the carbon cycle is an important issue in global change science since carbon is a component of carbon dioxide and methane - two greenhouse gases that trap heat near the surface of the earth. 

Terrestrial ecosystems both produce and remove carbon dioxide from the atmosphere.  Plants take up carbon dioxide during photosynthesis and plants and soils produce it during respiration and decay.  Plant and animal biomass also stores carbon.  Changes in land use, for example burning or planting a forest, can add carbon to or remove it from the atmosphere.  

Bev Law’s group studies both the details of how forests and soils take up and produce carbon dioxide and the big picture of how carbon storage and flux can be measured for whole terrestrial ecosystems.

Posted: July 9, 2009

Bev Law is the OSU Professor of Global Change Forest Science. She and her research group, TERRA-PNW, study how northwest forests store and exchange carbon with the atmosphere, and respond to climate and disturbance. In this short Web interview, Bev describes some of the group's primary research questions and how their studies relate to understanding and responding to climate change.

Your research group is called the Terrestrial Ecosystem Research and Regional Analysis group (TERRA-PNW) – what do you study?

We primarily do carbon-cycle science with a focus on terrestrial ecosystems.  We are looking for the effect of climate and disturbance, by fire or management, on the net carbon dioxide, water and energy exchange from forests.  We work at a variety of scales, from site-level experiments on plant and soil processes to regional studies that use data from satellites and field observations in biogeochemistry models to map the carbon balance of the Pacific Northwest.

I am also the science chair for the AmeriFlux network. It is a consortium of 90 sites across the U.S. where scientists are taking continuous observations of ecosystem level exchanges of carbon dioxide (CO2), water, and energy.  There are three AmeriFlux sites in Oregon – one in a Douglas-fir forest and two in ponderosa pine forests, one mature and one young. 

In my role with AmeriFlux, one of the challenges I’m always thinking about is the standardization and establishment of national and international observation networks.  Some of the techniques we use are fairly new, they have been developed in the past 20 years, and we need to do a better job pulling together so that methods are standardized and data are comparable globally.

How do your studies relate to soil microbial processes?

Carbon dioxide produced by root respiration and soil microbial decomposition (soil CO2 efflux) is a major portion of the total ecosystem respiration, so we need to dig into understanding the mechanisms controlling it. We are working to develop better mechanistic models of how these below ground processes work.  It’s sort of a holy grail – something that is very hard to do.  Because there are tradeoffs, if you get too complex, you are not going to be able to get the observations that you need to drive a process model and you might end up making the model too site specific when what you are looking for is something that is broadly applicable.

Ideally we are trying to develop a mechanistic model that is that is the right level of complexity for broad scale applications.  A lot of the work that we are doing right now in carbon-cycle science is at the landscape to continental level.  We are trying to understand how disturbance and climate are affecting terrestrial ecosystems and what the feedbacks are to climate and to carbon dioxide and methane in the atmosphere.

How does your data feed into climate change models?

The coupled climate-carbon models are interested in what is the net source or sink of carbon to the atmosphere.  They are trying to get more of the land surface feedback into the models.  There is a new suite of these coupled climate-carbon models that are being used in the next Intergovernmental Panel on Climate Change assessment report.  The models are using some of our measurements – like energy, heat flux, carbon dioxide flux and our derived estimates of gross photosynthesis over many years of data – to see how well they are modeling the exchange of carbon dioxide between landscapes and the atmosphere seasonally and from year to year.

Are there opportunities for researchers interested in the subsurface biosphere to work with your group?

We have welcomed students to work with us.  Ideally they should have an experiment that runs for several years to capture responses, because often there is a period of ecosystem adjustment to treatments, and it can take several years to see the changes.

I’d also encourage people who are designing curiosity driven studies to think about the big picture and where there are information needs.  We need a process level understanding of soil processes that is scalable so that we can do national level estimates of how these systems are reacting to climate change and disturbance and management.

Bev Law

Are there publications from your research group that you would like to highlight?

In 2005, I edited a volume of Biogeochemistry that focused on the below-ground carbon cycle.  Mike Ryan (USDA Forest Service) and I wrote an introductory article for that volume that summarizes key science issues related to soil respiration.

I also recommend several papers by James Irvine; he did a lot of cutting edge work while he was here as a research associate.  We also just had an article come out in Ecological Applications that looks at the carbon storage potential of Northwest forests.

The publications page on our TERRA-PNW website has PDFs of many of our group's journal articles. The rest of the site is also a good source of information about our research group and projects.