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: 5). 03/2013; 94(2):403-413. DOI: 10.2307/23435987

ABSTRACT 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.

  • Source
    Dataset: GCB 2012
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The response of soil respiration (Rs) and its components (autotrophic [Ra] and heterotrophic respiration [Rh]) to climate warming is one of the uncertainties in ecosystem carbon (C) models. Here we conducted a warming experiment in an alpine meadow dominated by Koresbia in the permafrost region of the Qinghai-Tibet Plateau (QTP) to examine effects of warming on Rs and its components. Infrared heaters were used to simulate a 2°C warming of the surface soil temperature. Deep collars (50 cm to exclude root growth) were inserted into soil to measure Rh: Ra, which was calculated by subtracting Rh from Rs. Average Rs and its components (Ra and Rh) were significantly stimulated by 21.5, 27 and 15.6%, respectively, in warmed plots from January 2011 to October 2013. The contribution of Rh to Rs decreased in the warmed plots because of the smaller relative increase in Rh than in Ra. Annual soil C release increased by 263 and 247 g C m−2 in 2011 and 2012, respectively. Stimulation in Ra and Rh was related to the significant increase in root biomass (0–50 cm) and in labile soil C in the deeper layer (40–50 cm). The temperature sensitivities (Q10) of Rs and its components all increased with larger values in Ra, followed by Rs and Rh. Our results suggest a positive feedback between soil C release and climatic warming in the permafrost region of the QTP.
    European Journal of Soil Science 10/2014; 66(1). DOI:10.1111/ejss.12187 · 2.39 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Warming generally accelerates the decomposition of plant litter. However, changes in precipitation could alter the sensitivity of litter decomposition to warming, thereby affecting the formation of litter-derived soil organic matter. As grassland soils store ∼20% of Earth's soil carbon, understanding the effect of climatic changes on the decomposition dynamics of grasses is important. However, little is known about how projected changes in climate would affect litter microbial communities and enzyme activities, and the consequences of these changes for the mass loss and compound-specific degradation of grass litter that possess complex lignocellulosic chemistry. Over a period of two years, using litter of the grass Poa trivialis, we studied how mass loss, microbial enzyme activity and fine-level litter chemistry responded to a factorial combination of 4 levels of warming (up to ambient +∼4 °C) and three levels of precipitation [ambient, wet (+50%) and dry (−50%)] at the Boston-Area Climate Experiment (BACE), in Massachusetts, USA. After 393 days of decomposition, supplemental precipitation accelerated mass loss compared to the dry treatment, as a consequence of faster loss of hydroxycinnamates, which protect carbohydrates through cross-linkages with lignins. Only a third as much of the cell wall-bound ferulic and p-coumaric acids remained in litter from the supplemental precipitation treatment compared to the ambient controls. In contrast, the warming treatments did not affect mass loss until later, after 740 days, when the litter in the warmest treatment (+∼4 °C) had lost the most mass. Although warming significantly affected mass loss after 740 days, there was also a trend in the warmest treatments toward greater mass loss in the wet (78% mass loss) and ambient (68%) plots compared to dry plots (61%), possibly due to the higher activity of β-glucosidase. Though mass loss at this final time point varied with both warming and precipitation treatments, the compound-specific degradation of litter captured by diffuse reflectance infra-red Fourier transform (DRIFT) and 13C Nuclear Magnetic Resonance (NMR) spectroscopy revealed that only the precipitation treatments significantly altered the chemistry of carbon compounds in the decomposed tissue. Litter that decomposed in the dry treatment had a higher proportion of carbohydrates remaining than litter in the wet and ambient treatments. Similarly, although ergosterol content and potential activity of phenol oxidase decreased in the warmer treatments, the consequences of this response were not observed in the degradation of specific compounds in litter, which varied only with precipitation treatments. Our results suggests that mass loss and enzyme activities may not accurately capture the complexity of compound-specific degradation of litter during decomposition. Our results also identified non-linear responses of β-glucosidase and N-acetyl-β-D-glucosaminidase (NAG) activities to warming. These results thus emphasize the complexities of litter decomposition and suggest that similar changes in decomposition across other grass species could alter the carbon budget of grasslands.
    Soil Biology and Biochemistry 08/2014; 75:102–112. DOI:10.1016/j.soilbio.2014.03.022 · 4.41 Impact Factor