Long-term warming restructures Arctic tundra without changing net soil carbon storage

Sistla, Seeta A.; Moore, John C.; Simpson, Robert G.; Gough, Laura; Shaver, Gaius R.; Schimel, Joshua P.

doi:10.1038/nature12129

Cited by 385 publications

(386 citation statements)

References 36 publications

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“…In line with our findings, many experimental warming studies showed increased aboveground productivity (Rustad et al 2001;Hudson, Henry & Cornwell 2011;Melillo et al 2011;Sistla et al 2013). However, only very few studies report effects on biomass partitioning between shoots and roots, and even less is known about the partitioning of recent C assimilates.…”

Section: Discussionsupporting

confidence: 77%

“…for almost one growing season. In the longer term, warming effects on C dynamics will also depend on factors we did not investigate, including aboveground biomass turnover and changes in vegetation composition (Walker et al 2006;Myers-Smith et al 2011;Sistla et al 2013;Hagedorn et al 2014). Our experiment suggests that rhizodeposition did not increase with warming, despite increased net 14 C assimilation.…”

Section: Discussionmentioning

confidence: 62%

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Experimental soil warming and cooling alters the partitioning of recent assimilates: evidence from a 14C-labelling study at the alpine treeline

2015

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Despite concerns about climate change-effects on ecosystems functioning, only little is known on how plant assimilate partitioning changes with temperature. Particularly large temperature-effects might occur in cold ecosystems where critical processes are at their temperature limit. In this study, we tested temperature effects on carbon (C) assimilate partitioning in a field experiment at the alpine treeline. We warmed and cooled soils of microcosms planted with Pinus mugo or Leucanthemopsis alpina, achieving daily mean soil temperatures (3-10 cm depth) around 5.8, 12.7 and 19.2°C in cooled, control and warmed soils. We pulse-labelled these systems with 14CO2 for one photoperiod and traced 14C over the successive four days. Plant net 14C uptake increased steadily with soil temperature. However, 14C amounts in fungal hyphae, soil microbial biomass, soil organic matter, and soil respiration showed a non-linear response to temperature. This non-linear pattern was particularly pronounced in P. mugo, with five times higher 14C activities in cooled compared to control soils, but no difference between warmed and control soil. Autoradiographic analysis of the spatial distribution of 14C in soils indicated that temperature effects on the vertical label distribution within soils depended on plant species. Our results show that plant growth, in particular root metabolism, is limited by low soil temperature. As a consequence, positive temperature effects on net C uptake may not be paralleled by similar changes in rhizodeposition. This has important implications for predictions of soil C storage, because rhizodeposits and plant biomass strongly vary in their residence time. AbstractDespite concerns about climate change-effects on ecosystems functioning, only little is known on how plant assimilate partitioning changes with temperature. Particularly large temperature-effects might occur in cold ecosystems where critical processes are at their temperature limit. In this study, we tested temperature effects on carbon (C) assimilate partitioning in a field experiment at the alpine treeline. We warmed and cooled soils of microcosms planted with Pinus mugo or Leucanthemopsis alpina, achieving daily mean soil temperatures (3-10 cm depth) around 5.8, 12.7 and 19.2°C in cooled, control and warmed soils. We pulse-labelled these systems with 14 CO 2 for one photoperiod and traced 14 C over the successive four days. Plant net 14 C uptake increased steadily with soil temperature. However, 14 C amounts in fungal hyphae, soil microbial biomass, soil organic matter, and soil respiration showed a non-linear response to temperature. This nonlinear pattern was particularly pronounced in P. mugo, with five times higher 14 C activities in cooled compared to control soils, but no difference between warmed and control soil.Autoradiographic analysis of the spatial distribution of 14 C in soils indicated that temperature effects on the vertical label distribution within soils depended on plant species. Our results show that plant growth, ...

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Section: Discussionsupporting

confidence: 77%

Section: Discussionmentioning

confidence: 62%

Experimental soil warming and cooling alters the partitioning of recent assimilates: evidence from a 14C-labelling study at the alpine treeline

2015

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“…Laboratory experiments offer precise control but lack the in situ nature of field manipulations (Sistla et al, 2013), raising uncertainties as to what degree their results can be extrapolated. Soils isolated during incubation may, for example, underestimate temperature sensitivity of respiration (Podrebarac et al, 2016) or exhibit lag effects .…”

Section: Limitations and Weaknessesmentioning

confidence: 99%

“…Most previous studies have focused on surface soils or permafrost soils, neglecting deep active-layer soils that were identified as subject to strong effects from a 2-decade warming experiment in the Alaskan Arctic (Sistla et al, 2013). Such deeper soils have particular characteristics distinguishing them from both shallow active-layer soils and underlying permafrost: they are most affected by interannual variability in thaw depth, potentially flipping the C source-sink status of entire ecosystems (Goulden et al, 1998;Harden et al, 2012); they are subject to distinctive freeze-thaw, cryoturbation, and microbial dynamics, which are likely to change their sensitivity to climate change and feedback potential (Schuur et al, 2008); and they are known to pose particular problems for accurate modeling of high-latitude carbon dynamics (Nicolsky et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Temperature and moisture effects on greenhouse gas emissions from deep active-layer boreal soils

2016

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Abstract. Rapid climatic changes, rising air temperatures, and increased fires are expected to drive permafrost degradation and alter soil carbon (C) cycling in many high-latitude ecosystems. How these soils will respond to changes in their temperature, moisture, and overlying vegetation is uncertain but critical to understand given the large soil C stocks in these regions. We used a laboratory experiment to examine how temperature and moisture control CO 2 and CH 4 emissions from mineral soils sampled from the bottom of the annual active layer, i.e., directly above permafrost, in an Alaskan boreal forest. Gas emissions from 30 cores, subjected to two temperatures and either field moisture conditions or experimental drought, were tracked over a 100-day incubation; we also measured a variety of physical and chemical characteristics of the cores. Gravimetric water content was 0.31 ± 0.12 (unitless) at the beginning of the incubation; cores at field moisture were unchanged at the end, but drought cores had declined to 0.06 ± 0.04. Daily CO 2 fluxes were positively correlated with incubation chamber temperature, core water content, and percent soil nitrogen. They also had a temperature sensitivity (Q 10 ) of 1.3 and 1.9 for the field moisture and drought treatments, respectively. Daily CH 4 emissions were most strongly correlated with percent nitrogen, but neither temperature nor water content was a significant first-order predictor of CH 4 fluxes. The cumulative production of C from CO 2 was over 6 orders of magnitude higher than that from CH 4 ; cumulative CO 2 was correlated with incubation temperature and moisture treatment, with drought cores producing 52-73 % lower C. Cumulative CH 4 production was unaffected by any treatment. These results suggest that deep active-layer soils may be sensitive to changes in soil moisture under aerobic conditions, a critical factor as discontinuous permafrost thaws in interior Alaska. Deep but unfrozen high-latitude soils have been shown to be strongly affected by long-term experimental warming, and these results provide insight into their future dynamics and feedback potential with future climate change.

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“…Longer growing seasons, elevated CO2, and increased nutrients released from decomposing organic carbon may all stimulate plant growth [74] to increase C assimilation. Temperature-driven increases in soil respiration would likely be pronounced in the drained mid-boreal uplands where Q 10 values are the largest.…”

Section: Implicatiuons Of Changing Climatementioning

confidence: 99%

Surface CO2 Exchange Dynamics across a Climatic Gradient in McKenzie Valley: Effect of Landforms, Climate and Permafrost

Startsev

Bhatti

Jassal

2016

Forests

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Abstract:Northern regions are experiencing considerable climate change affecting the state of permafrost, peat accumulation rates, and the large pool of carbon (C) stored in soil, thereby emphasizing the importance of monitoring surface C fluxes in different landform sites along a climate gradient. We studied surface net C exchange (NCE) and ecosystem respiration (ER) across different landforms (upland, peat plateau, collapse scar) in mid-boreal to high subarctic ecoregions in the Mackenzie Valley of northwestern Canada for three years. NCE and ER were measured using automatic CO 2 chambers (ADC, Bioscientific LTD., Herts, England), and soil respiration (SR) was measured with solid state infrared CO 2 sensors (Carbocaps, Vaisala, Vantaa, Finland) using the concentration gradient technique. Both NCE and ER were primarily controlled by soil temperature in the upper horizons. In upland forest locations, ER varied from 583 to 214 g C·m −2 ·year −1 from mid-boreal to high subarctic zones, respectively. For the bog and peat plateau areas, ER was less than half that at the upland locations. Of SR, nearly 75% was generated in the upper 5 cm layer composed of live bryophytes and actively decomposing fibric material. Our results suggest that for the upland and bog locations, ER significantly exceeded NCE. Bryophyte NCE was greatest in continuously waterlogged collapsed areas and was negligible in other locations. Overall, upland forest sites were sources of CO 2 (from 64 g·C·m −2 ·year −1 in the high subarctic to 588 g C·m −2 ·year −1 in mid-boreal zone); collapsed areas were sinks of C, especially in high subarctic (from 27 g· C· m −2 year −1 in mid-boreal to 86 g·C·m −2 ·year −1 in high subarctic) and peat plateaus were minor sources (from 153 g· C· m −2 · year −1 in mid-boreal to 6 g·C·m −2 ·year −1 in high subarctic). The results are important in understanding how different landforms are responding to climate change and would be useful in modeling the effect of future climate change on the soil C balance in the northern regions.

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Long-term warming restructures Arctic tundra without changing net soil carbon storage

Cited by 385 publications

References 36 publications

Experimental soil warming and cooling alters the partitioning of recent assimilates: evidence from a 14C-labelling study at the alpine treeline

Experimental soil warming and cooling alters the partitioning of recent assimilates: evidence from a 14C-labelling study at the alpine treeline

Temperature and moisture effects on greenhouse gas emissions from deep active-layer boreal soils

Surface CO2 Exchange Dynamics across a Climatic Gradient in McKenzie Valley: Effect of Landforms, Climate and Permafrost

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