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Infrared heater system for warming tropical forest understory plants and soils

January 15, 2018

The response of tropical forests to global warming is one of the largest uncertainties
in predicting the future carbon balance of Earth. To determine the likely effects of elevated
temperatures on tropical forest understory plants and soils, as well as other
ecosystems, an infrared (IR) heater system was developed to provide in situ warming
for the Tropical Responses to Altered Climate Experiment (TRACE) in the Luquillo
Experimental Forest in Puerto Rico. Three replicate heated 4-m-
plots were
warmed to maintain a 4°C increase in understory vegetation compared to three unheated
control plots, as sensed by IR thermometers. The equipment was larger than
any used previously and was subjected to challenges different from those of many
temperate ecosystem warming systems, including frequent power surges and outages,
high humidity, heavy rains, hurricanes, saturated clayey soils, and steep slopes. The
system was able to maintain the target 4.0°C increase in hourly average vegetation
temperatures to within ± 0.1°C. The vegetation was heterogeneous and on a 21°
slope, which decreased uniformity of the warming treatment on the plots; yet, the
green leaves were fairly uniformly warmed, and there was little difference among
0–10 cm depth soil temperatures at the plot centers, edges, and midway between. Soil
temperatures at the 40–50 cm depth increased about 3°C compared to the controls
after a month of warming. As expected, the soil in the heated plots dried faster than
that of the control plots, but the average soil moisture remained adequate for the
plants. The TRACE heating system produced an adequately uniform warming precisely
controlled down to at least 50-cm
soil depth, thereby creating a treatment that allows
for assessing mechanistic responses of tropical plants and soil to warming, with applicability
to other ecosystems. No physical obstacles to scaling the approach to taller
vegetation (i.e., trees) and larger plots were observed.

Publication Year 2018
Title Infrared heater system for warming tropical forest understory plants and soils
DOI 10.1002/ece3.3780
Authors Bruce A. Kimball, Aura M. Alonso-Rodríguez, Molly A. Cavaleri, Sasha C. Reed, Grizelle González, Tana E. Wood
Publication Type Article
Publication Subtype Journal Article
Series Title Ecology and Evolution
Index ID 70198089
Record Source USGS Publications Warehouse
USGS Organization Southwest Biological Science Center