ARS | Publication request: Comment on the Comment by Amthor et al. on “Appropriate Experimental Ecosystem Warming Methods” by Aronson and McNulty

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 29, 2010
Publication Date: March 15, 2011
Citation: Kimball, B.A., 2011. Comment on the Comment by Amthor et al. on “Appropriate experimental ecosystem warming methods” by Aronson and McNulty. Agricultural and Forest Meteorology. 151:420-424.

Interpretive Summary: In order to study the likely effects of global warming on future ecosystems, including agricultural fields, a method for applying a heating treatment to open-field plant canopies [i.e., a temperature free-air controlled enhancement (T-FACE) system] is needed which will warm vegetation as expected by the future climate. One method which shows promise is infrared heating, which heats the vegetation directly but not the air. However, because global warming is generally associated with warming the air, confusion exists in the scientific community about how this infrared warming of vegetation can be used to produce an experimental treatment equivalent to the expected future air warming. By means of a simple diagram and resistance model, this commentary seeks to clarify the situation. This research will benefit all consumers of food and fiber.

Technical Abstract: In a recent comment on the paper by Aronson and McNulty (2009) about “Appropriate experimental ecosystem warming methods by ecosystem, objective, and practicality”, Amthor et al. (2010) state that infrared lamps do not warm open-field plots by the mechanism expected with global warming. While this statement is correct, in the aftermath of their comment, confusion exists about how warming with infrared heaters can be related to global warming. This comment illustrates how infrared heating at “constant temperature rise” relates in a quantitative way to anticipated global warming. Amthor et al. (2010) also state that changes in vapor pressure gradient from leaf to atmosphere are an issue with infrared heating, but this problem can be minimized with supplemental irrigations in controlled amounts. Therefore, “constant temperature rise” infrared warming experiments with supplemental irrigations are a viable T-FACE (temperature free-air controlled enhancement) that can be used in combination with CO2-FACE to produce conditions more representative future open-fields than can be done with chambers with their many known artifacts.