Temperature Sensitivity of Soil Carbon Decomposition and Feedbacks to Climate Change

The Woods Hole Research Center, PO Box 296, Woods Hole, Massachusetts 02543, USA.
Nature (Impact Factor: 41.46). 04/2006; 440(7081):165-73. DOI: 10.1038/nature04514
Source: PubMed

ABSTRACT Significantly more carbon is stored in the world's soils--including peatlands, wetlands and permafrost--than is present in the atmosphere. Disagreement exists, however, regarding the effects of climate change on global soil carbon stocks. If carbon stored belowground is transferred to the atmosphere by a warming-induced acceleration of its decomposition, a positive feedback to climate change would occur. Conversely, if increases of plant-derived carbon inputs to soils exceed increases in decomposition, the feedback would be negative. Despite much research, a consensus has not yet emerged on the temperature sensitivity of soil carbon decomposition. Unravelling the feedback effect is particularly difficult, because the diverse soil organic compounds exhibit a wide range of kinetic properties, which determine the intrinsic temperature sensitivity of their decomposition. Moreover, several environmental constraints obscure the intrinsic temperature sensitivity of substrate decomposition, causing lower observed 'apparent' temperature sensitivity, and these constraints may, themselves, be sensitive to climate.

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Available from: Ivan A. Janssens, Jun 11, 2015
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    • "In contrast to N lab , gross rate of N rec mineralization increased with WFPS (Table 2). Under higher moisture, microbes become more active as indicated by higher respiration (Fig. 4) and in turn more efficiently decompose the recalcitrant SOM, which is more energy and moisture consumption than the labile SOM (Davidson and Janssens, 2006; Chavez-Vergara et al., 2014). Total gross NH 4 þ immobilization rate (I NH4-Nlab þ I NH4-Nrec ) varied with a similar pattern to total mineralization in response to changing moisture regimes, but was about 1.3 times higher than the later (Fig. 3). "
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    ABSTRACT: Future climate change is predicted to influence soil moisture regime, a key factor regulating soil nitrogen (N) cycling. To elucidate how soil moisture affects gross N transformation in a cultivated black soil, a 15N tracing study was conducted at 30%, 50% and 70% water-filled pore space (WFPS). While gross mineralization rate of recalcitrant organic N (Nrec) increased from 0.56 to 2.47 mg N kg−1 d−1, the rate of labile organic N mineralization declined from 4.23 to 2.41 mg N kg−1 d−1 with a WFPS increase from 30% to 70%. Similar to total mineralization, no distinct moisture effect was found on total immobilization of ammonium, which primarily entered the Nrec pool. Nitrate (NO3−) was mainly produced via autotrophic nitrification, which was significantly stimulated by increasing WFPS. Unexpectedly, heterotrophic nitrification was observed, with the highest rate of 1.06 mg N kg−1 d−1 at 30% WFPS, contributing 31.8% to total NO3− production, and decreased with WFPS. Dissimilatory nitrate reduction to ammonium (DNRA) increased from near zero (30% WFPS) to 0.26 mg N kg−1 d−1 (70% WFPS), amounting to 16.7–92.9% of NO3− consumption. A literature synthetic analysis from global multiple ecosystems showed that the rates of heterotrophic nitrification and DNRA in test soil were comparative to the forest and grassland ecosystems, and that heterotrophic nitrification was positively correlated with precipitation, soil organic carbon (SOC) and C/N, but negatively with pH and bulk density, while DNRA showed positive relationships with precipitation, clay, SOC, C/NO3− and WFPS. We suggested that low pH and bulk density and high SOC and C/N in test soil might favor heterotrophic nitrification, and that C and NO3− availability together with anaerobic condition were crucial for DNRA. Overall, our study highlights the role of moisture in regulating gross N turnover and the importance of heterotrophic nitrification for NO3− production under low moisture and DNRA for NO3− retention under high moisture in cropland.
    Soil Biology and Biochemistry 12/2015; 91:65-75. DOI:10.1016/j.soilbio.2015.08.026 · 3.93 Impact Factor
    • "However, a slight decrease was observed near the glacier, probably due to glacial melting. The soil CO 2 -C emissions from most global soil environments are considered a measure of both microbial respiration and root respiration (Davidson and Janssens, 2006; La Scala et al., 2010; Mendonça et al., 2010; Kuzyakov and Gavrichkova, 2010; Cannone et al., 2012). Root and aerial parts of plants can greatly contribute to the total soil respiration (Mendonça et al., 2010; Cannone et al., 2012). "
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    ABSTRACT: Soil organic matter (SOM) plays an important role for soil quality and productivity maintenance, acting as energy source, promoting biological diversity, enhancing terrestrial ecosystems composition. This study assessed the effects of long-term weed control and cover crops between coffee rows on SOM quality in a very clayey (80 dag kg−1 of clay) Typic Haplorthox (Dystroferric Red Latosol) from State of Paraná, Southern Brazil. Seven weed control and cover crops were assessed between coffee rows: (i) hand weeding—HAWE; (ii) portable mechanical mower—PMOW; (iii) pré + post-emergence herbicides—HERB; (iv) peanut horse (Arachis hypogeae) cover crop—GMAY; (v) dwarf mucuna (Mucuna deeringiana) cover crop—GMMA; (vi) no-weed control between coffee row—SCAP; (vii) weed check—CONT. Soil samples were collected in the center of the inter-rows between coffee trees at four depths: 0–10 cm, 10–20 cm, 20–30 cm, and 30–40 cm. SOM quality assessment included total soil organic carbon (SOC) content and organic matter humification degree (HFIL) by laser-induced fluorescence spectroscopy (LIFS). C content was up to 26% higher for SCAP and CONT samples, compared to the other field conditions, denoting influence of plant material accumulation at top soil (0–10 cm). Higher HFIL results (up to 47%) were observed at deeper layers, inferring incidence of less humified/labile structures at top soil, and condensed/recalcitrant character for organic matter at depth, regardless of cover crops and weed control method considered. In terms of weed density it was observed a higher negative impact on weed growth in areas under GMMA cover crop (decrease of 90.8% in weed density). The behavior may be attributed to the chemical composition of the species, ultimately leading to possible occurrence of allelopathic phenomenon.
    Soil and Tillage Research 11/2015; 153. DOI:10.1016/j.still.2015.06.005 · 2.62 Impact Factor
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    • "Because of such multifactorial control, no general mechanism of the temperature effect on OC decomposition has become widely accepted (Reichstein et al., 2005; Agren and Wetterstedt, 2007; Allison et al., 2010; Sierra, 2012). According to kinetic theory, the temperature sensitivity of OC decomposition is a function of OC quality (Knorr et al., 2005; Davidson and Janssens, 2006; Conant et al., 2008). The lower the OC quality, the higher is the temperature sensitivity as the decomposition of low quality OC requires more energy. "
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    Soil Biology and Biochemistry 11/2015; 90:19-29. DOI:10.1016/j.soilbio.2015.07.013 · 3.93 Impact Factor
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