Northern Forest Ecosystem Experiment: Aspen Regeneration and Carbon Cycling

Research Background

The U.S. Forest Service’s Institute for Applied Ecosystem Studies (IAES) collaborated closely with Michigan Technological University to conduct the highly successful, world-class Aspen FACE Experiment for 11 years. Following a final analytical harvest in 2009, residual stands were clear-cut to simulate the silvicultural treatment typically applied in aspen forest management.

The harvested stands of Aspen FACE were allowed to naturally regenerate during the 2010 growing season: aspen by root suckering and birch and maple by stump sprouting,  thus inaugurating the Northern Forest Ecosystem Experiment as a large-scale, long-term field experiment in which harvested forests regenerate in atmospheres with enhanced concentrations of carbon dioxide (CO₂), ozone (O₃) or both gasses combined for one year followed by normal atmospheric conditions.

Research Issue

Effects of elevated carbon dioxide and ozone on long term growth and development of pure and mixed trembling aspen stands were well studied and documented at Aspen FACE  but effects on natural regeneration of pure and mixed trembling aspen forests following complete harvest are unknown.  It is important to understand these effects, because forests of the future will be affected by continued changes in global climate, driven by increased concentrations of greenhouse gasses.  It is unequivocal that increases in the concentrations of carbon dioxide and tropospheric ozone affect functioning of forest ecosystems:  carbon dioxide stimulates forest productivity, and ozone pollution in the troposphere inhibits it. As climate and atmospheric composition change, forests will adapt to the new growing conditions.  An understanding of what these adaptations might be will inform management and policy decision making. 

Our Research

Armed with highly detailed information on the entire life history of each stand, the new regenerating forest will provide the IAES and its collaborators a unique and invaluable research platform to address many critical issues of regenerating aspen forest response to global change conditions. Our research focus will be to:

1. Determine the regeneration success of aspen genotypes using DNA fingerprints of the five aspen genotypes of Aspen FACE and aspen, birch, and maple mixed species, providing insight into how forests adapt to global change conditions.
   
2. Quantify the use of stored carbon reserves that support regeneration and the acquisition and storage of new carbon as the new forest grows using the unique ¹²C/¹³C carbon ratio inherent in plant biomass produced at Aspen FACE. 
3. Determine how altered growth under increasing CO₂ and ozone might interact with the availability of nitrogen following the introduction of ¹⁵N tracer in 2006. 

Expected Outcomes

We will determine the regeneration success of the aspen genotypes and mixed stands of aspen, birch, and maple species, providing insight into how forests adapt to global change conditions. Further, we will determine the use of stored carbon reserves versus acquisition and storage of new carbon in the framework of regeneration success.

Research Results

Preliminary observations of aspen regeneration suggest vigorous response overall but higher numbers and higher survival rates by late summer under ambient conditions and least under elevated ozone conditions. Analysis of genotypic links to regeneration success will be conducted from 2011 sampling.

Darbah, J.N.T., W.S. Jones, A.J. Burton, J. Nagy, and M.E. Kubiske. 2011. Acute O3 damage on first year coppice sprouts of aspen and maple spouts in an open-air experiment. Journal of Environmental Monitoring 13:2436-2442

Research Participants

Principal Investigator

• Mark E. Kubiske, U.S. Forest Service- Northern Research Station Plant Physiologist, NFEE co-director

Research Partners

• Andrew J. Burton, Michigan Technological University, NFEE co-director
  
• Joseph N.T. Darbah, Michigan Technological University
  
• Kurt S. Pregitzer, University of Idaho (steering committee member)
  
• Donald R. Zak, University of Michigan (steering committee member)
  
• Richard Lindroth, University of Wisconsin (steering committee member)