Biogeochemical impacts of wildfires over four millennia in a<scp>R</scp>ocky<scp>M</scp>ountain subalpine watershed

Dunnette, Paul V.; Higuera, Philip E.; McLauchlan, Kendra K.; Derr, Kelly; Briles, Christy E.; Keefe, Margaret H.

doi:10.1111/nph.12828

Cited by 84 publications

(153 citation statements)

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“…Briefly, the 4500-year record has an average sample resolution of 4 years and a chronology constrained by 13 210 Pb dates spanning the upper 20 cm and 25 accelerator mass spectrometry 14 C dates for deeper sediments. Pollen analysis indicates that the site was continuously dominated by lodgepole pine for the duration of the record presented here, with successional changes following inferred fire events (Dunnette et al, 2014). The persistence of subalpine forest over the past 4500 years is also supported by nearby pollen records in Rocky Mountain National Park (Caffrey and Doerner, 2012;Higuera et al, 2014).…”

Section: Study Sitesmentioning

confidence: 57%

“…Detailed methods for the collection and analysis of the Chickaree Lake sediment record are found in Dunnette et al (2014). Briefly, the 4500-year record has an average sample resolution of 4 years and a chronology constrained by 13 210 Pb dates spanning the upper 20 cm and 25 accelerator mass spectrometry 14 C dates for deeper sediments.…”

Section: Study Sitesmentioning

confidence: 99%

“…We studied the biogeochemical consequences of fire-regime variability by informing the DayCent model with fire history data derived from sedimentary charcoal preserved in Chickaree Lake, Colorado (Dunnette et al, 2014). Chickaree Lake (40.334 • N, 105.841 • W; 2796 m above sea level) is a small, deep lake (ca.…”

Section: Study Sitesmentioning

confidence: 99%

“…While the immediate impacts of disturbance can be dramatic, the longevity of these impacts is less clear. In ecosystems where disturbance is historically prevalent, vegetation and biogeochemical properties typically return to predisturbance conditions over years to decades (Dunnette et al, 2014;McLauchlan et al, 2014), motivating the concept of "biogeochemical resilience" (Smithwick, 2011). Characterizing biogeochemical resilience emphasizes understanding pool sizes and changes to inputs or outputs of key elements Smithwick, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Here, we pair a paleoecological record of vegetation and wildfire activity in a subalpine forest (Dunnette et al, 2014) with an ecosystem model to evaluate the sensitivity of forest ecosystem processes to fire-regime variability over a 4500-year period. Our paleoecological record reveals the timing and severity of past wildfire activity within a subalpine forest watershed that was consistently dominated by lodgepole pine (Pinus contorta).…”

Section: Introductionmentioning

confidence: 99%

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Fire-regime variability impacts forest carbon dynamics for centuries to millennia

2017

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Abstract. Wildfire is a dominant disturbance agent in forest ecosystems, shaping important biogeochemical processes including net carbon (C) balance. Long-term monitoring and chronosequence studies highlight a resilience of biogeochemical properties to large, stand-replacing, high-severity fire events. In contrast, the consequences of repeated fires or temporal variability in a fire regime (e.g., the characteristic timing or severity of fire) are largely unknown, yet theory suggests that such variability could strongly influence forest C trajectories (i.e., future states or directions) for millennia. Here we combine a 4500-year paleoecological record of fire activity with ecosystem modeling to investigate how fire-regime variability impacts soil C and net ecosystem carbon balance. We found that C trajectories in a paleo-informed scenario differed significantly from an equilibrium scenario (with a constant fire return interval), largely due to variability in the timing and severity of past fires. Paleo-informed scenarios contained multi-century periods of positive and negative net ecosystem C balance, with magnitudes significantly larger than observed under the equilibrium scenario. Further, this variability created legacies in soil C trajectories that lasted for millennia. Our results imply that fire-regime variability is a major driver of C trajectories in stand-replacing fire regimes. Predicting carbon balance in these systems, therefore, will depend strongly on the ability of ecosystem models to represent a realistic range of fire-regime variability over the past several centuries to millennia.

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Section: Study Sitesmentioning

confidence: 57%

Section: Study Sitesmentioning

confidence: 99%

Section: Study Sitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fire-regime variability impacts forest carbon dynamics for centuries to millennia

2017

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The differing biogeochemical and microbial signatures of glaciers and rock glaciers

et al. 2016

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Glaciers and rock glaciers supply water and bioavailable nutrients to headwater mountain lakes and streams across all regions of the American West. Here we present a comparative study of the metal, nutrient, and microbial characteristics of glacial and rock glacial influence on headwater ecosystems in three mountain ranges of the contiguous U.S.: the Cascade Mountains, Rocky Mountains, and Sierra Nevada. Several meltwater characteristics (water temperature, conductivity, pH, metals, nutrients, complexity of dissolved organic matter (DOM), and bacterial richness and diversity) differed significantly between glacier and rock glacier meltwaters, while other characteristics (Ca 2+ , Fe 3+ , SiO 2 concentrations, reactive nitrogen, and microbial processing of DOM) showed distinct trends between mountain ranges regardless of meltwater source. Some characteristics were affected both by glacier type and mountain range (e.g., temperature, ammonium (NH 4 + ) and nitrate (NO 3 À ) concentrations, and bacterial diversity). Due to the ubiquity of rock glaciers and the accelerating loss of the low-latitude glaciers, our results point to the important and changing influence that these frozen features place on headwater ecosystems.

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Linkages Among Climate, Fire, and Thermoerosion in Alaskan Tundra Over the Past Three Millennia

Chipman

2017

JGR Biogeosciences

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Amplified Arctic warming may facilitate novel tundra disturbance regimes, as suggested by recent increases in the rate and extent of thermoerosion and fires in some tundra areas. Thermoerosion and wildfire can exacerbate warming by releasing large permafrost carbon stocks, and interactions between disturbance regimes can lead to complex ecosystem feedbacks. We conducted geochemical and charcoal analyses of lake sediments from an Alaskan lake to identify thermoerosion and fire events over the past 3,000 years. Thermoerosion was inferred from lake sediments in the context of modern soil data from retrogressive thaw slumps (RTS). Magnetic susceptibility (MS), Ca:K, and Ca:Sr increased with depth in modern RTS soils and were higher on recently exposed than older slump surfaces. Peaks in bulk density, % CaCO3, Ca:K, Ca:Sr, and MS values in the sediments suggest at least 18 thermoerosion events in the Loon Lake watershed over the past 3,000 years. Charcoal analysis identifies 22 fires over the same period at this site. Temporal variability in these records suggests climate‐driven responses of both thermoerosion and fire disturbance regimes, with fewer RTS episodes and fire events during the Little Ice Age than the Medieval Climate Anomaly. Moreover, RTS activity lagged behind catchment fires by 20–30 years (>90% confidence interval), implying that fires facilitated thermoerosion on decadal time scales, possibly because of prolonged active‐layer deepening following fire and postfire proliferation of insulative shrub cover. These results highlight the potential for complex interactions between climate, vegetation, and tundra disturbance in response to ongoing warming.

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Biogeochemical impacts of wildfires over four millennia in aRockyMountain subalpine watershed

Cited by 84 publications

References 84 publications

Fire-regime variability impacts forest carbon dynamics for centuries to millennia

Fire-regime variability impacts forest carbon dynamics for centuries to millennia

The differing biogeochemical and microbial signatures of glaciers and rock glaciers

Linkages Among Climate, Fire, and Thermoerosion in Alaskan Tundra Over the Past Three Millennia

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