Comparative Water and Nutrient Use in Eucalyptus benthamii and Pinus taeda Plantations

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Understanding the biology of Eucalyptus to examine the species as a biofuel crop alternative in the Southeast

´┐╝Study objective

The Southeast Partnership for Integrated Biomass Supply Systems (IBSS) is supported by the Agriculture and Food Research Initiative from the US Department of Agriculture National Institute of Food and Agriculture. The overall IBSS goal is to demonstrate real world solutions to economically and environmentally sustainable production and conversion of biomass to biofuel in the southeast United States.

We work with the USDA Forest Service to focus on understanding the biology of Eucalyptus to examine the species as a biofuel crop alternative in the region. Eucalyptus is grown in other regions of the world and can be very productive however it has been associated with high water consumption. Water requirements for Eucalyptus plantations in the SE US are largely unknown. Generally, then, our objective is to quantify water as well as nutrient use for Eucalyptus benthamii.

More specifically our objectives are to:

  1. Quantify stand water use, water use efficiency (WUE), nutrient use, nutrient use efficiency and tree growth for nine year old stands of E. benthamii and Pinus taeda.
  2. Define mechanisms for regulating stand water use. Mechanisms examined will be physiological (photosynthesis, stomatal conductance), morphological (leaf area, specific leaf area, crown shape), and structural (biomass allocation, rooting depth)
  3. Parameterize the 3-PG process model for E. benthamii in the US.

Treatments and experimental design

We are working at the MWV Ravenel Nursery Site where adjacent nine-year-old E. benthamii (Figure 1) and P. taeda stands are planted. Twelve trees of each species were instrumented 

Current status

Trees were instrumented in January 2013 and meteorological equipment was installed in April 2013. A destructive harvest was completed on adjacent trees to quantify above and below ground biomass and rooting depth in April 2014. Probe calibration was completed in Summer 2014 for both species (Figure 2). Our site is an installation in the RAFES network which is described in a separate report. Monitoring and maintenance of the study continues.


Probe calibration deviated substantially from published equations. Monthly transpiration on a ground area basis was higher for E. benthamii than for P. taeda in 2013 especially in late summer and fall (months 9 and 10) (Figure 3). Annual water use in 2013 was 27% greater in E. benthamii than P. taeda (Figure 4). Annual stem increment was correlated with water use however E. benthamii had 21% greater WUE than P. taeda (Figure 5). Eucalyptus benthamii had higher leaf scale transpiration and less strict stomatal regulation than P. taeda. Annual water use as a fraction of precipitation was 0.92 and 0.67 for E. benthamii and P. taeda, respectively. Although the same age, E. benthamii was at a later stand development stage (growth was slowing). A freeze in 2014 killed all E. benthamii foliage but more leaves were produced in spring.

Future plans

We monitored E. benthamii foliage recovery in 2014 after the freeze. We plan similar work on a younger stand of eucalyptus and pine to quantify how these traits vary during the rotation. Nutrient determinations will be completed on tissue samples from the biomass harvest.


The IBSS Partnership is supported by AFRI Competitive Grant #2011-68005-30410 from USDA NIFA.

MWV has provided access to the stands and additional support to complete the research

The USDA Forest Service provides support for the RAFES study. 

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