A potential loss of carbon associated with greater plant growth in the European Arctic

Hartley, Iain P.; Garnett, Mark H.; Sommerkorn, Martin; Hopkins, D. W.; Fletcher, Benjamin J.; Sloan, V. L.; Phoenix, Gareth K.; Wookey, Philip A.

doi:10.1038/nclimate1575

Cited by 206 publications

(290 citation statements)

References 32 publications

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“…A persistent challenge, however, is detecting the amount and type of C respired by soil microbes. At Willow Creek, it appears that recent photosynthates are an important substrate for microbial respiration, but in systems with large pools of old soil C, summer microbial activity may utilize much older C as well (Hartley et al, 2012). Going forward, our study and others suggest more complexity involved in partitioning root and microbial respiration with 14 CO 2 than was previously appreciated, as both end-members appear to be highly dynamic.…”

Section: Utility and Limitations Of 14 Co 2 For Understanding Soil Mementioning

confidence: 44%

“…Repeated measurements through the growing season of respired 14 CO 2 could be partitioned into present year and previous C sources using a two end-member mixing model. Such an approach may not be appropriate in all ecosystems, for example, if summer root inputs stimulate priming of old soil C pools (Hartley et al, 2012).…”

Section: Utility and Limitations Of 14 Co 2 For Understanding Soil Mementioning

confidence: 99%

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Biological and physical influences on soil 14CO2 seasonal dynamics in a temperate hardwood forest

et al. 2013

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Abstract. While radiocarbon ( 14 C) abundances in standing stocks of soil carbon have been used to evaluate rates of soil carbon turnover on timescales of several years to centuries, soil-respired 14 CO 2 measurements are an important tool for identifying more immediate responses to disturbance and climate change. Soil 14 CO 2 data, however, are often temporally sparse and could be interpreted better with more context for typical seasonal ranges and trends. We report on a semi-high-frequency sampling campaign to distinguish physical and biological drivers of soil 14 CO 2 at a temperate forest site in northern Wisconsin, USA. We sampled 14 CO 2 profiles every three weeks during snow-free months through 2012 in three intact plots and one trenched plot that excluded roots. Respired 14 CO 2 declined through the summer in intact plots, shifting from an older C composition that contained more bomb 14 C to a younger composition more closely resembling present 14 C levels in the atmosphere. In the trenched plot, respired 14 CO 2 was variable but remained comparatively higher than in intact plots, reflecting older bomb-enriched 14 C sources. Although respired 14 CO 2 from intact plots correlated with soil moisture, related analyses did not support a clear cause-and-effect relationship with moisture. The initial decrease in 14 CO 2 from spring to midsummer could be explained by increases in 14 Cdeplete root respiration; however, 14 CO 2 continued to decline in late summer after root activity decreased. We also investigated whether soil moisture impacted vertical partitioning of CO 2 production, but found this had little effect on respired 14 CO 2 because CO 2 contained modern bomb C at depth, even in the trenched plot. This surprising result contrasted with decades to centuries-old pre-bomb CO 2 produced in lab incubations of the same soils. Our results suggest that root-derived C and other recent C sources had dominant impacts on respired 14 CO 2 in situ, even at depth. We propose that 14 CO 2 may have declined through late summer in intact plots because of continued microbial turnover of root-derived C, following declines in root respiration. Our results agree with other studies showing declines in the 14 C content of soil respiration over the growing season, and suggest inputs of new photosynthates through roots are an important driver.

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Section: Utility and Limitations Of 14 Co 2 For Understanding Soil Mementioning

confidence: 44%

Section: Utility and Limitations Of 14 Co 2 For Understanding Soil Mementioning

confidence: 99%

Biological and physical influences on soil 14CO2 seasonal dynamics in a temperate hardwood forest

et al. 2013

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“…Climate changes, in particular regional warming and drying, cause vegetation stress (Ju and Masek, 2016;Barber et al, 2000) and increased mortality. Conversely, increasing plant productivity in some regions can stimulate the decomposition of older SOC (Hartley et al, 2012). Climate also drives fire regime changes, and ecosystem disruption is particularly likely after intense fires (Johnstone et al, 2010;Genet et al, 2013).…”

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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“…Major CO 2 sinks include photosynthetic uptake, stabilization in soils, and the dissolution of CO 2 from soil and rock mineral weathering and calcium carbonate formation in the ocean. There is great uncertainty in identifying and quantifying the feedbacks between enhanced atmospheric CO 2 concentrations and whether the response of vegetation and soil microbes provide sources or sinks for this additional atmospheric carbon source (Hartley et al, 2012;Higgins and Harte, 2012;Van Huisstden and Dolman, 2012;Krankina et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

Douglas

Jones

Hiemstra

et al. 2014

Elementa: Science of the Anthropocene

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Boreal ecosystems store large quantities of carbon but are increasingly vulnerable to carbon loss due to disturbance and climate warming. The boreal region in Alaska and Canada, largely underlain by discontinuous permafrost, presents a challenging landscape for itemizing carbon sources and sinks in soil and vegetation. The roles of fire, forest succession, and the presence (or absence) of permafrost on carbon cycle, vegetation, and hydrologic processes have been the focus of multidisciplinary research in boreal ecosystems for the past 20 years. However, projections of a warming future climate, an increase in fire severity and extent, and the potential degradation of permafrost could lead to major landscape and carbon cycle changes over the next 20 to 50 years. To assist land managers in interior Alaska in adapting and managing for potential changes in the carbon cycle we developed this review paper by incorporating an overview of the climate, ecosystem processes, vegetation, and soil regimes. Our objective is to provide a synthesis of the most current carbon storage estimates and measurements to guide policy and land management decisions on how to best manage carbon sources and sinks. We surveyed estimates of aboveground and belowground carbon stocks for interior Alaska boreal ecosystems and summarized methane and carbon dioxide f luxes. These data have been converted into similar units to facilitate comparison across ecosystem compartments. We identify potential changes in the carbon cycle with climate change and human disturbance. A novel research question is how compounding disturbances affect carbon sources and sinks associated with boreal ecosystem processes. Finally, we provide recommendations to address the challenges facing land managers in efforts to manage carbon cycle processes. The results of this study can be used for carbon cycle management in other locations within the boreal biome which encompasses a broad distribution from 45° to 83° north.

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A potential loss of carbon associated with greater plant growth in the European Arctic

Cited by 206 publications

References 32 publications

Biological and physical influences on soil <sup>14</sup>CO<sub>2</sub> seasonal dynamics in a temperate hardwood forest

Biological and physical influences on soil <sup>14</sup>CO<sub>2</sub> seasonal dynamics in a temperate hardwood forest

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

Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

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A potential loss of carbon associated with greater plant growth in the European Arctic

Cited by 206 publications

References 32 publications

Biological and physical influences on soil &lt;sup&gt;14&lt;/sup&gt;CO&lt;sub&gt;2&lt;/sub&gt; seasonal dynamics in a temperate hardwood forest

Biological and physical influences on soil &lt;sup&gt;14&lt;/sup&gt;CO&lt;sub&gt;2&lt;/sub&gt; seasonal dynamics in a temperate hardwood forest

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

Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

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Biological and physical influences on soil <sup>14</sup>CO<sub>2</sub> seasonal dynamics in a temperate hardwood forest

Biological and physical influences on soil <sup>14</sup>CO<sub>2</sub> seasonal dynamics in a temperate hardwood forest