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Title: Litters of photosynthetically divergent grasses exhibit differential metabolic responses to warming and elevated CO2

Author
item SUSELLA, V - Clemson University
item TRIEBWASSER, D - Clemson University
item LINSCHED, N - Clemson University
item MORGAN, JACK - Retired ARS Employee
item THARAYIL, N - Clemson University

Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2014
Publication Date: 9/19/2014
Publication URL: http://handle.nal.usda.gov/10113/59712
Citation: Susella, V., Triebwasser, D., Linsched, N., Morgan, J., Tharayil, N. 2014. Litters of photosynthetically divergent grasses exhibit differential metabolic responses to warming and elevated CO2. Ecosphere. 5(9):106. http//dx.doi.org/10.1890/ES14-00028.1.

Interpretive Summary: The continued accumulation of greenhouse gases in Earth’s atmosphere is motivating society to understand the causes of these changes in gas concentrations to better manage their release into the atmosphere. This experiment, which exposes a native grassland to higher temperatures and concentrations of carbon dioxide (CO2) expected in the second half of this century evaluated the impact of these environmental changes on plant metabolites. These metabolites can sufficiently alter plant chemistry to affect the cycling of soil carbon, and eventually its release back into the atmosphere as CO2. The results indicated that warming and higher ambient CO2 can induce significant changes in plant metabolites that will ultimately affect the digestibility and decomposability of their tissues, and that these changes may be different in different plant species. Understanding the potential magnitude of these responses will be important in determining the degree to which we can predict future emissions of greenhouse gases like CO2 from terrestrial ecosystems into the atmosphere.

Technical Abstract: Climatic stress induced by warming can alter plant metabolism, leading to changes in litter chemistry that can affect soil carbon cycling. Elevated CO2 could partly mitigate warming induced moisture stress, and the degree of this mitigation may vary with plant functional types. We hypothesized that, although C3 and C4 functional types would respond similarly to unfavorable climates, due to the inherent variation in their tolerance to warming and CO2, these functional types will exhibit metabolite responses under different climatic conditions. We studied the composition of non-structural and structural metabolites in senesced tissues of Bouteloua gracilis (C4) and Pascopyrum smithii (C3) at the Prairie Heating and CO2 Enrichment experiment, Wyoming, USA. In B. gracilis, warming increased the presence of structural components such as lignin, cuticular-matrix, and cell wall-bound phenolics that reduce water loss, and polar metabolites that exhibit osmoregulatory functions. Conversely, P. smithii showed weak metabolite changes when exposed to warming alone, whereas warming combined with CO2 enrichment resulted in a higher abundance of both structural and osmoregulatory compounds, possibly due to the partial alleviation of moisture stress. Influenced by plant functional type responses, similar climates could produce litter with different chemical composition that could potentially alter carbon cycling in grass-land ecosystems.