Northern Research Station

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Forest Disturbance Processes

Water Use Efficiency of Poplars

Research Issue

[photo:] Poplar veneer logs.Successful deployment of poplars for bioenergy requires that genotypes be properly matched to site conditions. For example, poplars with high water use efficiency (WUE) have been observed to be less susceptible to water stress than genotypes with low WUE. Thus, poplars with high WUE can be identified and selected for the purpose of ensuring high biomass productivity on water-limited sites. Chemical analysis of stable isotope ratios in growth rings has proven useful in evaluating WUE in trees. Specifically, genotypes with higher WUE exhibit greater stomatal closure, which in turn affects carbon isotope ratios as heavier isotopes are absorbed at a higher rate when the stomata are closed. Thus, differences in WUE can be identified by differences in carbon isotope ratios in the trees, as previous research has demonstrated for various species, including poplars and their hybrids. However, such information is lacking for poplars grown in the United States.

Our Research

We are evaluating stable isotope ratios within the growth rings of seven poplar genotypes grown at three contrasting sites in the north-central USA, in order to identify genotypes with high WUE for future deployment on water-limited sites in the region. Because the seven clones represent three distinct genomic groups, we are also comparing these genetic groups to evaluate the extent to which different parent species may be contributing to WUE. Correlations between WUE, environmental conditions (e.g. climate and soils), and biomass productivity are also being examined, to further improve our understanding of how genotype-specific WUE interacts with site conditions to impact biomass yields.

Expected Outcomes

The results of this research are expected to be useful for selecting appropriate genotypes for water-limited sites and/or future climate scenarios with reduced water availability, thereby enhancing feedstock production for bioenergy applications and phytotechnologies. Researchers and resources managers will be able to make informed policy and management decisions, especially in the face of changing climates.

Research Participants

Principal Investigators

  • William L. Headlee, Iowa State University, Department of Natural Resource Ecology and Management, Ames, IA
  • Ronald S. Zalesny Jr., US Forest Service Northern Research Station- Team Leader, Research Plant Geneticist
  • Richard B. Hall, Iowa State University, Department of Natural Resource Ecology and Management, Ames, IA
  • Jesse A. Randall, Iowa State University, Department of Natural Resource Ecology and Management, Ames, IA

Research Partners

  • Edmund O. Bauer, US Forest Service Northern Research Station- Technician Emeritus
  • Adam H. Wiese, US Forest Service Northern Research Station- Forestry Technician
  • Bruce A. Birr, US Forest Service Northern Research Station- Laboratory Technician

Last Modified: October 4, 2016