Environmental And Biological Controls On Water And Energy Exchange In Florida Scrub Oak And Pine Flatwoods Ecosystems

  • Sites: US-KL2, US-KS1
  • Bracho, R., Powell, T. L., Dore, S., Li, J., Hinkle, C. R., Drake, B. G. (2008/06) Environmental And Biological Controls On Water And Energy Exchange In Florida Scrub Oak And Pine Flatwoods Ecosystems, Journal Of Geophysical Research: Biogeosciences, 113(G2), n/a-n/a. https://doi.org/10.1029/2007JG000469
  • Funding Agency: U.S. Department of Energy (ER619930000313); National Research Council

  • Scrub oak and pine flatwoods are two contrasting ecosystems common to the humid
    subtropical climate of Florida. Scrub oak forests are short in stature (<2 m) and occur on
    well-drained sandy soils, and pine flatwoods are much taller and occur in areas with
    poorly drained soils. Eddy covariance measurements were made from January 2001 to
    February 2003 over a scrub oak forest and from January 2002 to February 2003 over an
    adjacent pine flatwoods located on in central Florida, USA, and exposed to similar
    atmospheric conditions to evaluate how the dynamics of latent heat (lE) and sensible heat
    (H) exchanges are affected by environmental and biological variables. Annual
    evapotranspiration (Et) for the scrub oak was 737 and 713 mm in 2001 and 2002,
    respectively. Et was comparatively higher, 812 mm, in 2002 at the pine flatwoods due to
    higher soil moisture and leaf area. In both ecosystems, springtime increases in lE
    coincided with increasing leaf area and evaporative demand. However, H was the main
    energy-dissipating component in the spring due to the seasonal decrease in soil water
    content in the upper soil profile. In the spring, mean weekly Bowen ratio (b, i.e. H/lE)
    values reached 1.6 and 1.2 in the scrub oak and pine flatwoods, respectively. With the
    onset of the summertime rainy season, lE became the dominant energy flux and b fells to
    < 0.4. In both ecosystems, b was strongly controlled by the interaction between leaf area
    and soil moisture. The lowest values of the decoupling coefficient (W, 0.2 and 0.25 scrub
    oak and pine flatwoods, respectively) also occurred during the dry springtime period
    indicating that surface conductance (gs) was the mechanism controlling energy
    partitioning causing high b in both ecosystems. Et increases in the spring, when water in
    the upper soil profile was scarce and strongly retained by soil particles, indicated that
    plants in both ecosystems obtained water from deeper sources. The results from this
    research elucidate how energy partitioning differs and is regulated in contrasting
    ecosystems within the Florida landscape, which is important for refining regional
    hydrological and climate models.