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United States Department of Agriculture

Agricultural Research Service

Research Project: Predicting Impacts of Climate Change on Agricultural Systems and Developing Potentials for Adaptation

Location: Plant Physiology and Genetics Research

Title: Microclimate and ecological threshold responses in a warming and wetting experiment following whole-tree harvest

Authors
item Mcdaniel, M -
item Wagner, R -
item Rollinson, C -
item Kimball, Bruce
item Kaye, M -
item Kaye, J -

Submitted to: Journal of Theoretical and Applied Climatology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 30, 2013
Publication Date: June 19, 2013
Citation: Mcdaniel, M.D., Wagner, R.J., Rollinson, C.R., Kimball, B.A., Kaye, M.W., Kaye, J.P. 2013. Microclimate and ecological threshold responses in a warming and wetting experiment following whole-tree harvest. Journal of Theoretical and Applied Climatology. 116:287-299.

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, and arrays of such heaters have recently been developed. However, the effects of the warming on other important climate-driven thresholds within a vegetation canopy had not been determined. Therefore, an infrared warming experiment was performed near State College, PA on canopies of tree saplings. Warmed plots had fewer soil freeze-thaw events, and soil temperatures did not drop below freezing, in contrast to unheated control plots. The warming treatment also increased the number of growing-degree-days, the number of frost-free days, and number of day’s leaf temperatures spent in optimal photosynthetic range, so generally the warming treatment improved the growing conditions at this presently temperate climate site. This research will benefit all consumers of food and fiber.

Technical Abstract: Ecosystem climate manipulation experiments (ECMEs) are a key tool for predicting the effects of climate on ecosystems. However, the strength of inferences drawn from these experiments depends on whether the manipulated conditions mimic future climate changes. While ECMEs have examined mean temperature and moisture conditions, ecosystem processes may respond more to microclimatic thresholds (e.g. freeze-thaw events). We reported mean and microclimatic thresholds from a post-clearcutECME in a temperate, mixed-deciduous forest. Target treatments were ambient, warmed (+ ~2 °C), wetted (+ ~20% precipitation), and warmed+wetted. Wetted treatments increased mean monthly precipitation by 23%, but did not change the amount of time the soil water potential was below permanent wilting point. Relative to ambient, warmed treatments increased mean temperatures of the surface and soil by 1.8 and 2.5 °C, respectively. Warming decreased the number of soil freeze-thaw events, and increased the number of growing degree days, frost-free days, and the amount of time leaf surface temperatures were in optimal photosynthetic range. Our results showed that even when ECMEs mimic mean predicted climate conditions, their effect on microclimatic thresholds can be variable. We suggest that measuring these, and other, microclimatic thresholds will be essential for interpreting ECME results and assessing their value in predicting ecosystem responses to future climate change.

Last Modified: 9/23/2014
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