Ecosystem Carbon Remains Low for Three Decades Following Fire and Constrains Soil CO2 Responses to Precipitation in Southwestern Ponderosa Pine Forests

Ross, Christopher S.; Kaye, Jason P.; Kaye, Margot W.; Kurth, Valerie J.; Brimmer, Rachel; Hart, Stephen C.; Fulé, Peter Z.

doi:10.1007/s10021-012-9541-3

Cited by 13 publications

(8 citation statements)

References 45 publications

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“…The seasonal variations in pCO 2 and soil moisture (Figs. S5 and S6) observed in this study are consistent with patterns reported elsewhere (Piñol et al, 1995;Risk et al, 2002;Schulz et al, 2011;Ross et al, 2012). The fall pCO 2 peak is not as large as the peak in June, presumably because lower temperatures limit biological activity (i.e., CO 2 production).…”

Section: Seasonal Patterns Of Soil Pcosupporting

confidence: 94%

“…While previous work has extensively examined seasonal (Solomon and Cerling, 1987;Burton and Beauchamp, 1994;Schulz et al, 2011;Ross et al, 2012), diurnal (Tang et al, 2003, geographic (Schulz et al, 2011), climatic (Oh and Richter, 2004), depth (Fisher et al, 1985;Benstead and Lloyd, 1996;Fierer et al, 2005), and vegetative (Buyanovsky and Wagner, 1983;Kaye and Hart, 1998) controls on CO 2 concentrations and fluxes, to our knowledge topographic controls on pCO 2 have been characterized at only two locations. In northeastern Spain, the variability in soil pCO 2 between two topographic positions within a single small catchment was as large as differences observed in two different mountain ranges (Piñol et al, 1995).…”

Section: Introductionmentioning

confidence: 96%

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Topographic controls on the depth distribution of soil CO2 in a small temperate watershed

Hasenmueller

Jin

Stinchcomb

et al. 2015

Applied Geochemistry

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a b s t r a c tAccurate measurements of soil CO 2 concentrations (pCO 2 ) are important for understanding carbonic acid reaction pathways for continental weathering and the global carbon (C) cycle. While there have been many studies of soil pCO 2 , most sample or model only one, or at most a few, landscape positions and therefore do not account for complex topography. Here, we test the hypothesis that soil pCO 2 distribution can predictably vary with topographic position. We measured soil pCO 2 at the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO), Pennsylvania, where controls on soil pCO 2 (e.g., depth, texture, porosity, and moisture) vary from ridge tops down to the valley floor, between planar slopes and slopes with convergent flow (i.e., swales), and between north and south-facing aspects. We quantified pCO 2 generally at 0.1e0.2 m depth intervals down to bedrock from 2008 to 2010 and in 2013. Of the variables tested, topographic position along catenas was the best predictor of soil pCO 2 because it controls soil depth, texture, porosity, and moisture, which govern soil CO 2 diffusive fluxes. The highest pCO 2 values were observed in the valley floor and swales where soils are deep (!0.7 m) and wet, resulting in low CO 2 diffusion through soil profiles. In contrast, the ridge top and planar slope soils have lower pCO 2 because they are shallower ( 0.6 m) and drier, resulting in high CO 2 diffusion through soil profiles. Aspect was a minor predictor of soil pCO 2 : the north (i.e., south-facing) swale generally had lower soil moisture content and pCO 2 than its south (i.e., north-facing) counterpart. Seasonally, we observed that while the timing of peak soil pCO 2 was similar across the watershed, the amplitude of the pCO 2 peak was higher in the deep soils due to more variable moisture content. The high pCO 2 observed in the deeper, wetter topographic positions could lower soil porewater pH by up to 1 pH unit compared to porewaters equilibrated with atmospheric CO 2 alone. CO 2 is generally the dominant acid driving weathering in soils: based on our observations, models of chemical weathering and CO 2 dynamics would be improved by including landscape controls on soil pCO 2 .

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Section: Seasonal Patterns Of Soil Pcosupporting

confidence: 94%

Section: Introductionmentioning

confidence: 96%

Topographic controls on the depth distribution of soil CO2 in a small temperate watershed

Hasenmueller

Jin

Stinchcomb

et al. 2015

Applied Geochemistry

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“…As a preliminary estimate of how infilling may have affected C accumulating in O horizons, we converted simulated changes forest floor fuels over the past century (using ECOSIM; Covington and Moore ) to C accumulation rates (by multiplying forest floor fuel mass by 0.48; Ross et al. ). Rates of C accumulation in forest floor fuels in forests with fire exclusion were ~0.25 Mg·ha −1 ·yr −1 between the late 1800s and 2000s.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, future analyses of ponderosa pine C budgets should take into account new research showing large C losses and very slow soil and plant C recovery following stand replacing fires (Ross et al. ) that are becoming more prevalent in this region.…”

Section: Discussionmentioning

confidence: 99%

“…We do not expect this pattern in the ecosystems we studied because thick O horizons that develop after infilling are not present when intercanopy spaces are dominated by bunchgrasses (Kaye and Hart 1998b), A horizons under these O horizons have higher C concentrations than A horizons in adjacent grass patches, and adjacent grass and forest patches have similar C concentrations in the B horizon (Kerns et al 2003). As a preliminary estimate of how infilling may have affected C accumulating in O horizons, we converted simulated changes forest floor fuels over the past century (using ECOSIM; Covington and Moore 1994) to C accumulation rates (by multiplying forest floor fuel mass by 0.48; Ross et al 2012). Rates of C accumulation in forest floor fuels in forests with fire exclusion were ~0.25 Mg·ha −1 ·yr −1 between the late 1800s and 2000s.…”

Section: Implications For Regional C Accountingmentioning

confidence: 99%

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Slow carbon and nutrient accumulation in trees established following fire exclusion in the southwestern United States

Kaye

Hart

et al. 2016

Ecological Applications

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Increasing tree density that followed fire exclusion after the 1880s in the southwestern United States may have also altered nutrient cycles and led to a carbon (C) sink that constitutes a significant component of the U.S. C budget. Yet, empirical data quantifying century-scale changes in C or nutrients due to fire exclusion are rare. We used tree-ring reconstructions of stand structure from five ponderosa pine-dominated sites from across northern Arizona to compare live tree C, nitrogen (N), and phosphorus (P) storage between the 1880s and 1990s. Live tree biomass in the 1990s contained up to three times more C, N, and P than in 1880s. However, the increase in C storage was smaller than values used in recent U.S. C budgets. Furthermore, trees that had established prior to the 1880s accounted for a large fraction (28-66%) of the C, N, and P stored in contemporary stands. Overall, our century-scale analysis revealed that forests of the 1880s were on a trajectory to accumulate C and nutrients in trees even in the absence of fire exclusion, either because growing conditions became more favorable after the 1880s or because forests in the 1880s included age or size cohorts poised for accelerated growth. These results may lead to a reduction in the C sink attributed to fire exclusion, and they refine our understanding of reference conditions for restoration management of fire-prone forests.

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High‐severity wildfire leads to multi‐decadal impacts on soil biogeochemistry in mixed‐conifer forests

Dove

Safford

Bohlman

et al. 2020

Ecological Applications

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During the past century, systematic wildfire suppression has decreased fire frequency and increased fire severity in the western United States of America. While this has resulted in large ecological changes aboveground such as altered tree species composition and increased forest density, little is known about the long-term, belowground implications of altered, ecologically novel, fire regimes, especially on soil biological processes. To better understand the long-term implications of ecologically novel, high-severity fire, we used a 44-yr highseverity fire chronosequence in the Sierra Nevada where forests were historically adapted to frequent, low-severity fire, but were fire suppressed for at least 70 yr. High-severity fire in the Sierra Nevada resulted in a long-term (44 +yr) decrease (>50%, P < 0.05) in soil extracellular enzyme activities, basal microbial respiration (56-72%, P < 0.05), and organic carbon (>50%, P < 0.05) in the upper 5 cm compared to sites that had not been burned for at least 115 yr. However, nitrogen (N) processes were only affected in the most recent fire site (4 yr post-fire). Net nitrification increased by over 600% in the most recent fire site (P < 0.001), but returned to similar levels as the unburned control in the 13-yr site. Contrary to previous studies, we did not find a consistent effect of plant cover type on soil biogeochemical processes in mid-successional (10-50 yr) forest soils. Rather, the 44-yr reduction in soil organic carbon (C) quantity correlated positively with dampened C cycling processes. Our results show the drastic and long-term implication of ecologically novel, high-severity fire on soil biogeochemistry and underscore the need for long-term fire ecological experiments.

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Ecosystem Carbon Remains Low for Three Decades Following Fire and Constrains Soil CO2 Responses to Precipitation in Southwestern Ponderosa Pine Forests

Cited by 13 publications

References 45 publications

Topographic controls on the depth distribution of soil CO2 in a small temperate watershed

Topographic controls on the depth distribution of soil CO2 in a small temperate watershed

Slow carbon and nutrient accumulation in trees established following fire exclusion in the southwestern United States

High‐severity wildfire leads to multi‐decadal impacts on soil biogeochemistry in mixed‐conifer forests

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