The responses of soil and rhizosphere respiration to simulated climatic changes vary by season

Department of Forestry and Natural Resources, Purdue University, West Lafayette, Indiana 47907, USA.
Ecology (Impact Factor: 4.66). 03/2013; 94(2):403-413. DOI: 10.2307/23435987


Responses of soil respiration (Rs) to anthropogenic climate change will affect terrestrial carbon storage and, thus, feed back to warming. To provide insight into how warming and changes in precipitation regimes affect the rate and temperature sensitivity of Rs and rhizosphere respiration (Rr) across the year, we subjected a New England old-field ecosystem to four levels of warming and three levels of precipitation (ambient, drought, and wet treatments). We measured Rs and heterotrophic respiration (Rh) monthly (in areas of the plots with and without plants, respectively) and estimated Rr by calculating the difference in respiration between Rs and Rh. Even in this mesic ecosystem, Rs and Rr responded strongly to the precipitation treatments. Drought reduced Rs and Rr, both annually and during the
growing season. Annual cumulative Rs responded nonlinearly to precipitation treatments; both drought and supplemental precipitation suppressed Rs compared to the ambient treatment. Warming increased Rs and Rr in spring and winter when soil moisture was optimal but decreased these rates in summer when moisture was limiting. Cumulative winter Rr increased by about 200% in the high warming (;3.58C) treatment. The effect of climate treatments on the temperature sensitivity of Rs depended on the season. In the fall, the drought treatment decreased apparent Q10 relative to the other precipitation treatments. The responses of Rs to warming and altered precipitation were largely driven by changes in Rr.We emphasize the importance of incorporating realistic soil moisture responses into simulations of soil carbon fluxes; the long-term effects of warming on carbon–climate feedback will depend on future precipitation regimes. Our results highlight the nonlinear responses of soil respiration to soil moisture and, to our knowledge, quantify for the first time the loss of carbon through winter rhizosphere respiration due to warming. While this additional loss is small relative to the cumulative annual flux in this system, such increases in rhizosphere respiration during the non-growing season could have greater consequences in ecosystems where they offset or reduce subsequent warming-induced gains in plant growth.

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    • "Previous results have shown that R plant was more temperature sensitive than R h (Chen et al., 2015b;Lin et al., 2011), and therefore warming was more likely to have more positive effects on autotrophs than heterotrophs. If one were to extrapolate the results showing positive response of the R plant /R eco to warming (Fig. 3), eventually R eco would become dominated by R plant , and if that were to occur R eco might then increase in response to warming (Hicks Pries et al., 2015;Peng et al., 2014;Suseela and Dukes, 2013). These changes indicate that shifts in the contributions of the components of R eco caused by warming would potentially alter the ecosystem's carbon balance, and this possibility should be explicitly considered when modeling the carbon-climate feed backs. "
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    ABSTRACT: Global warming is anticipated to have profound effects on terrestrial carbon fluxes and thus feed backs to future climate change. Ecosystem respiration (Reco) is one of the dominant components of biosphere CO2 fluxes, but the effects of warming on Reco are still unclear. A field warming experiment using open top chambers (OTCs) was conducted in a meadow grassland on the Tibetan Plateau to study the effects of warming on the components of Reco. Warming significantly enhanced above-ground plant respiration (Ragb) and total autotrophic plant respiration (Rplant) by 28.7% and 19.9%, respectively, but reduced heterotrophic respiration (Rh) by 10.4%. These different responses resulted in the insensitive responses of Reco and soil respiration (Rs) to the experimental warming. The warming treatment also increased Rplant/Reco and Ragb/Reco by 8.4% and 17.3%, respectively, while decreasing Rh/Reco by 19.0%, suggesting that warming could eventually cause Reco to be dominated by Rplant. Enhancements in Rplant and Ragb were related to the warming-induced increases in aboveground biomass (AGB) while reduced Rh was closely coupled with warming-induced decrease of microbial biomass carbon. Our results highlight that the differential responses of the components of Reco to different environmental physics under warming scenarios should be taken into consideration to project the future carbon-climate feed backs.
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    • "Warming heightened the sensitivity of aboveground biomass to precipitation; aboveground plant growth increased under warmer and wetter climate conditions, and decreased under warmer and drier conditions (Hoeppner & Dukes, 2012). However, soil respiration also became more sensitive to precipitation with warming (e.g. Suseela & Dukes, 2013). As a result, net ecosystem exchange over the growing season did not respond more strongly to precipitation in the warmed treatments. "

    No preview · Article · Feb 2016 · New Phytologist
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    • "The site has a loamy topsoil and gravelly sandy loam subsoil. Warming treatments were administered using different wattage infrared heaters (200 W for low, 600 W for medium and 1000 W for high warming) installed at the four corners of each plot (Auyeung et al., 2013; Suseela & Dukes, 2013). Precipitation treatments were achieved using rain out shelters, sprinkler systems and storage tanks. "
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    ABSTRACT: The process of nutrient retranslocation from plant leaves during senescence subsequently affects both plant growth and soil nutrient cycling; changes in either of these could potentially feed back to climate change. Although elemental nutrient resorption has been shown to respond modestly to temperature and precipitation, we know remarkably little about the influence of increasing intensities of drought and warming on the resorption of different classes of plant metabolites. We studied the effect of warming and altered precipitation on the production and resorption of metabolites in Quercus rubra. The combination of warming and drought produced a higher abundance of compounds that can help to mitigate climatic stress by functioning as osmoregulators and antioxidants, including important intermediaries of the tricarboxylic acid cycle, amino acids including proline and citrulline, and polyamines such as putrescene. Resorption efficiencies (RE) of extractable metabolites surprisingly had opposite responses to drought and warming; drought treatments generally increased RE of metabolites compared to ambient and wet treatments, while warming decreased RE. However, RE of total N differed markedly from that of extractable metabolites such as amino acids; for instance, droughted plants resorbed very little N from their leaves; a smaller fraction than plants exposed to the ambient control. In contrast, plants in drought treatment resorbed amino acids more efficiently (> 90%) than those in ambient (65-77%) or wet (42-58%) treatments. Across the climate treatments the RE of elemental N correlated negatively with tissue tannin concentration, indicating that polyphenols produced in leaves under climatic stress could interfere with N resorption. Thus, senesced leaves from drier conditions might have a lower nutritive value to soil heterotrophs during the initial stages of litter decomposition despite a higher elemental N content of these tissues. Our results suggest that N resorption may be controlled not only by plant demand, but also by climatic influences on the production and resorption of plant metabolites. As climate-carbon models incorporate increasingly sophisticated nutrient cycles, these results highlight the need to adequately understand plant physiological responses to climatic variables. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
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