Fire suppression and ecosystem carbon storage
TL;DR: A 35-year controlled burning experiment in Minnesota oak savanna showed that fire frequency had a great impact on ecosystem carbon (C) stores, with most carbon stored in woody biomass.
Abstract: A 35-year controlled burning experiment in Minnesota oak savanna showed that fire frequency had a great impact on ecosystem carbon (C) stores. Specifically, compared to the historical fire regime, fire suppression led to an average of 1.8 Mg·ha−1·yr−1 of C storage, with most carbon stored in woody biomass. Forest floor carbon stores were also significantly impacted by fire frequency, but there were no detectable effects of fire suppression on carbon in soil and fine roots combined, or in woody debris. Total ecosystem C stores averaged ∼110 Mg/ha in stands experiencing presettlement fire frequencies, but ∼220 Mg/ha in stands experiencing fire suppression. If comparable rates of C storage were to occur in other ecosystems in response to the current extent of fire suppression in the United States, fire suppression in the USA might account for 8–20% of missing global carbon.
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TL;DR: In this article, the authors separated soil organic matter into specific size/density fractions and determined the concentration of organic carbon and total nitrogen in these fractions and found that the mass proportions of free microaggregate and free silt+clay increased linearly with time following woody plant invasion of grassland.
Abstract: Woody plant invasion of grasslands is prevalent worldwide. In the Rio Grande Plains of Texas, subtropical thorn woodlands dominated by C3 trees/shrubs have been replacing C4 grasslands over the past 150 yr, resulting in increased soil organic carbon (SOC) storage and concomitant increases in soil total nitrogen (STN). To elucidate mechanisms of change in SOC and STN, we separated soil organic matter into specific size/density fractions and determined the concentration of C and N in these fractions. Soils were collected from remnant grasslands (Time 0) and woody plant stands (ages 10–130 yr). Rates of whole-soil C and N accrual in the upper 15 cm of the soil profile averaged 10–30 g C m−2 yr−1 and 1–3 g N m−2 yr−1, respectively, over the past 130 yr of woodland development. These rates of accumulation have increased soil C and N stocks in older wooded areas by 100–500% relative to remnant grasslands. Probable causes of these increased pool sizes include higher rates of organic matter production in wooded areas, greater inherent biochemical resistance of woody litter to decomposition, and protection of organic matter by stabilization within soil macro- and microaggregates. The mass proportions of the free light fraction ( 250 μm) increased linearly with time following woody plant invasion of grassland. Conversely, the mass proportions of free microaggregate (53–250 μm) and free silt+clay (
206 citations
Cites background from "Fire suppression and ecosystem carb..."
...In fact, it has been estimated that woody encroachment into grasslands may represent as much as 34% of the terrestrial C sink strength of the USA alone (Houghton et al., 1999; Tilman et al., 2000; Pacala et al., 2001)....
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TL;DR: In this paper, the effect of fire on nitrogen pools is studied and the amount of nitrogen lost during the burning of forest fuels is directly related to fuel consumption and ranges from 3 to 6 kg of fuel consumed, and the combined losses of N and other elements through harvesting and burning appear to exceed considerably the rate of replacement by natural processes.
202 citations
TL;DR: In this paper, the authors used a chronosequence approach to characterize soil organic carbon storage and dynamics in the Rio Grande Plains of southern Texas where C3 trees/shrubs have largely replaced C4 grasslands (d 13 C ¼� 14%) over the past 100-200 years.
Abstract: Soil physical structure causes differential accessibility of soil organic carbon (SOC) to decomposer organisms and is an important determinant of SOC storage and turnover. Techniques for physical fractionation of soil organic matter in conjunction with isotopic analyses (d 13 C, d 15 N) of those soil fractions have been used previously to (a) determine where organic C is stored relative to aggregate structure, (b) identify sources of SOC, (c) quantify turnover rates of SOC in specific soil fractions, and (d) evaluate organic matter quality. We used these two complementary approaches to characterize soil C storage and dynamics in the Rio Grande Plains of southern Texas where C3 trees/shrubs (d 13 C ¼� 27%) have largely replaced C4 grasslands (d 13 C ¼� 14%) over the past 100–200 years. Using a chronosequence approach, soils were collected from remnant grasslands (Time 0) and from woody plant stands ranging in age from 10 to 130 years. We separated soil organic matter into specific size/density fractions and determined their C and N concentrations and natural d 13 C and d 15 N values. Mean residence times (MRTs) of soil fractions were calculated based on changes in their d 13 C with time after woody encroachment. The shortest MRTs (average ¼ 30 years) were associated with all particulate organic matter (POM) fractions not protected within aggregates. Fine POM (53–250mm) within macro- and microaggregates was relatively more protected from decay, with an average MRT of 60 years. All silt+clay fractions had the longest MRTs (average ¼ 360 years) regardless of whether they were found inside or outside of aggregate structure. d 15 N values of soil physical fractions were positively correlated with MRTs of the same fractions, suggesting that higher d 15 N values reflect an increased degree of humification. Increased soil C and N pools in wooded areas were due to
200 citations
TL;DR: In this paper, the authors used 1-m soil cores to evaluate soil profile characteristics and carbon and nitrogen pools in 32 residential home lawns that differed by previous land use and age, but had similar soil types.
Abstract: Urban areas are growing in size and importance; however, we are only beginning to understand how the process of urbanization influences ecosystem dynamics. In particular, there have been few assessments of how the land-use history and age of residential soils influence carbon (C) and nitrogen (N) pools and fluxes, especially at depth. In this study, we used 1-m soil cores to evaluate soil profile characteristics and C and N pools in 32 residential home lawns that differed by previous land use and age, but had similar soil types. These were compared to soils from eight forested reference sites. Residential soils had significantly higher C and N densities than nearby forested soils of similar types (6.95 vs. 5.44 kg C/m2 and 552 vs. 403 g N/m2, P < 0.05). Results from our chronosequence suggest that soils at residential sites that were previously in agriculture have the potential to accumulate C (0.082 kg C/m2/y) and N (8.3 g N/m2/y) rapidly after residential development. Rates of N accumulation at these sites were similar in magnitude to estimated fertilizer N inputs, confirming a high capacity for N retention. Residential sites that were forested prior to development had higher C and N densities than present-day forests, but our chronosequence did not reveal a significant pattern of increasing C and N density over time in previously forested sites. These data suggest that soils in residential areas on former agricultural land have a significant capacity to sequester C and N. Given the large area of these soils, they are undoubtedly significant in regional C and N balances.
199 citations
TL;DR: In this paper, the effects of low and high-severity fire 14 months post-burn on key environmental variables typically limiting to microbial activity were quantified and the soil microbial community structure was characterized through ester-linked fatty acid analysis (EL-FAME).
Abstract: Most wildfires, even the most severe, burn at mixed intensities across a landscape, depending on local fuel loads, fuel moistures, and wind strength and direction. This heterogeneous patchwork of fire effects can influence the patterns of above- and belowground biotic recovery through altered environmental conditions, nutrient availability, and biotic sources for microbial and vegetative re-colonization. We quantified the effects of low- and high-severity fire 14 months post-burn on key environmental variables typically limiting to microbial activity. We characterized the soil microbial community structure through ester-linked fatty acid analysis (EL-FAME) and identified the soil environmental factors that best explain the pattern of microbial community profiles through canonical correspondence analysis (CCA). Low-severity burning caused no change in soil moisture, pH or temperature while high-severity burning caused an increase in soil moisture, temperature, and a decrease in pH levels, relative to the unburned sites. Soil respiration rates were significantly lower in both the low- and high-severity burn sites, relative to unburned sites, likely due to initial root and microbial death. Overall microbial biomass did not change with either low- or high-severity burning, but the microbial community ordination biplots showed separation of communities by fire, and slight separation by fire severity along three axes. This community separation was driven primarily by a decrease in fungal biomarkers (18:2ω6c, 18:3ω6c) with both low- and high-severity fire. Only 23% of the variation in the microbial community distribution could be explained by three environmental variables: soil pH, temperature, and carbon. These results suggest that the microbial communities in both the low- and high-severity burn sites are structurally different from the populations in the unburned sites.
193 citations
References
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06 Mar 1997
TL;DR: In this paper, the authors present a perspective of the global cycle of nitrogen and phosphorous, the global water cycle, and the global sulfur cycle from a global point of view.
Abstract: Part 1 Processes and reactions: origins the atmosphere the lithosphere the terrestrial biosphere biogeochemical cycling on land biogeochemistry in freshwater wetlands and lakes rivers and estuaries the sea. Part 2 Global cycles: the global water cycle the global carbon cycle the global cycle of nitrogen and phosphorous the global sulfur cycle a perspective.
3,871 citations
TL;DR: Slowing deforestation, combined with an increase in forestation and other management measures to improve forest ecosystem productivity, could conserve or sequester significant quantities of carbon.
Abstract: Forest systems cover more than 4.1 x 109 hectares of the Earth9s land area. Globally, forest vegetation and soils contain about 1146 petagrams of carbon, with approximately 37 percent of this carbon in low-latitude forests, 14 percent in mid-latitudes, and 49 percent at high latitudes. Over two-thirds of the carbon in forest ecosystems is contained in soils and associated peat deposits. In 1990, deforestation in the low latitudes emitted 1.6 ± 0.4 petagrams of carbon per year, whereas forest area expansion and growth in mid- and high-latitude forest sequestered 0.7 ± 0.2 petagrams of carbon per year, for a net flux to the atmosphere of 0.9 ± 0.4 petagrams of carbon per year. Slowing deforestation, combined with an increase in forestation and other management measures to improve forest ecosystem productivity, could conserve or sequester significant quantities of carbon. Future forest carbon cycling trends attributable to losses and regrowth associated with global climate and land-use change are uncertain. Model projections and some results suggest that forests could be carbon sinks or sources in the future.
3,175 citations
"Fire suppression and ecosystem carb..." refers background or methods in this paper
...…biomass creates ;20–25% of annual anthropogenic CO2 (Andreae 1991, Schimel 1995), modifications of fire frequency may significantly change regional and global C budgets (e.g., Fahenstock and Agee 1983, Andreae 1991, Stocks 1991, Dixon and Krankina 1993, Dixon et al. 1994, Sohngen and Haynes 1997)....
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...This work was supported by National Science Foundation Grant 9411972 and by the Andrew Mellon Foundation....
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...Our work supports the proposal that increased fire suppression and decreased anthropogenic burning of vegetation could significantly influence global carbon dynamics (Dixon et al. 1994, Sampson and Clark 1995, Sohngen and Haynes 1997, San Jose et al. 1998)....
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...Dixon et al. (1994) calculated that fire management in Russia could lead to long-term C storage of 0.6 3 1015 g C/yr....
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TL;DR: The terrestrial biosphere plays an important role in the global carbon cycle as mentioned in this paper, which is the fluxes of carbon among four main reservoirs: fossil carbon, the atmosphere, the oceans, and the terrestrial Biosphere.
Abstract: The terrestrial biosphere plays an important role in the global carbon cycle. In the 1994 Intergovernmental Panel Assessment on Climate Change (IPCC), an effort was made to improve the quantification of terrestrial exchanges and potential feedbacks from climate, changing CO2, and other factors; this paper presents the key results from that assessment, together with expanded discussion. The carbon cycle is the fluxes of carbon among four main reservoirs: fossil carbon, the atmosphere, the oceans, and the terrestrial biosphere. Emissions of fossil carbon during the 1980s averaged 5.5 Gt y−1. During the same period, the atmosphere gained 3.2 Gt C y−1 and the oceans are believed to have absorbed 2.0 Gt C y−1. The regrowing forests of the Northern Hemisphere may have absorbed 0.5 Gt C y−1 during this period. Meanwhile, tropical deforestation is thought to have released an average 1.6 Gt C y−1 over the 1980s. While the fluxes among the four pools should balance, the average 198Ds values lead to a ‘missing sink’ of 1.4 Gt C y−1 Several processes, including forest regrowth, CO2 fertilization of plant growth (c. 1.0 Gt C y−1), N deposition (c. 0.6 Gt C y−1), and their interactions, may account for the budget imbalance. However, it remains difficult to quantify the influences of these separate but interactive processes. Uncertainties in the individual numbers are large, and are themselves poorly quantified. This paper presents detail beyond the IPCC assessment on procedures used to approximate the flux uncertainties.
Lack of knowledge about positive and negative feedbacks from the biosphere is a major limiting factor to credible simulations of future atmospheric CO2 concentrations. Analyses of the atmospheric gradients of CO2 and 13 CO2 concentrations provide increasingly strong evidence for terrestrial sinks, potentially distributed between Northern Hemisphere and tropical regions, but conclusive detection in direct biomass and soil measurements remains elusive.
Current regional-to-global terrestrial ecosystem models with coupled carbon and nitrogen cycles represent the effects of CO2 fertilization differently, but all suggest longterm responses to CO2 that are substantially smaller than potential leaf- or laboratory whole plant-level responses. Analyses of emissions and biogeochemical fluxes consistent with eventual stabilization of atmospheric CO2 concentrations are sensitive to the way in which biospheric feedbacks are modeled by c. 15%. Decisions about land use can have effects of 100s of Gt C over the next few centuries, with similarly significant effects on the atmosphere.
Critical areas for future research are continued measurements and analyses of atmospheric data (CO2 and 13CO2) to serve as large-scale constraints, process studies of the scaling from the photosynthetic response to CO2 to whole-ecosystem carbon storage, and rigorous quantification of the effects of changing land use on carbon storage.
1,510 citations
"Fire suppression and ecosystem carb..." refers background or methods in this paper
...2680 Key words: carbon storage; fire suppression; missing carbon; oak savanna....
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...San Jose et al. (1998) calculated that fire suppression, by causing the transformation of the 2.8 3 107 ha Venezuelan Orinoco Llanos from grassland to semideciduous forest, could lead to a C sink of 0.08 3 1015 g C/yr....
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...Atmospheric CO2 is currently accumulating at ;3.2 3 1015 g C/yr (Schimel 1995)....
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...Dixon et al. (1994) calculated that fire management in Russia could lead to long-term C storage of 0.6 3 1015 g C/yr....
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...Because the burning of ecosystem biomass creates ;20–25% of annual anthropogenic CO2 (Andreae 1991, Schimel 1995), modifications of fire frequency may significantly change regional and global C budgets (e.g., Fahenstock and Agee 1983, Andreae 1991, Stocks 1991, Dixon and Krankina 1993, Dixon et al.…...
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TL;DR: The first edition of Schlesinger's Biogeochemistry in 1991 was an early entry in the field of Earth system science/global change, and has since gained sufficient popularity and demand to merit a second, extensively revised edition.
Abstract: Compared to the well-established disciplines, the field of Earth system science/global change has relatively few books from which to choose. Of the small subset of books dealing specifically with biogeochemical aspects of global change, the first edition of Schlesinger's Biogeochemistry in 1991 was an early entry. It has since gained sufficient popularity and demand to merit a second, extensively revised edition.
The first part of the book provides a general introduction to biogeochemistry and cycles, and to the origin of elements, our planet, and life on Earth. It then describes the functioning and biogeochemistry of the atmosphere, lithosphere, biosphere, and hydrosphere, including marine and freshwater systems. Although system function and features are stressed, the author begins to introduce global change topics, such as soil organic matter and global change in Chapter 5, and landscape and mass balance in Chapter 6.
1,075 citations
"Fire suppression and ecosystem carb..." refers background or methods in this paper
...This work was supported by National Science Foundation Grant 9411972 and by the Andrew Mellon Foundation....
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...Moreover, the immense global extent of tropical savanna and woodland, 2.45 3 109 ha (Schlesinger 1997), suggests that even moderate fire suppression in this ecosystem type could provide a globally significant C sink....
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TL;DR: The rates at which lands in the United States were cleared for agriculture, abandoned, harvested for wood, and burned were reconstructed from historical data for the period 1700-1990 and used in a terrestrial carbon model to calculate annual changes in the amount of carbon stored in terrestrial ecosystems, including wood products.
Abstract: The rates at which lands in the United States were cleared for agriculture, abandoned, harvested for wood, and burned were reconstructed from historical data for the period 1700-1990 and used in a terrestrial carbon model to calculate annual changes in the amount of carbon stored in terrestrial ecosystems, including wood products. Changes in land use released 27 +/- 6 petagrams of carbon to the atmosphere before 1945 and accumulated 2 +/- 2 petagrams of carbon after 1945, largely as a result of fire suppression and forest growth on abandoned farmlands. During the 1980s, the net flux of carbon attributable to land management offset 10 to 30 percent of U.S. fossil fuel emissions.
1,035 citations
"Fire suppression and ecosystem carb..." refers background or methods in this paper
...Houghton et al. (1999) estimated various sources of C storage in the United States....
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...Because fire suppression might lead to a period of C accumulation (Houghton et al. 1999), current fire suppression in the United States (Fig....
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...This work was supported by National Science Foundation Grant 9411972 and by the Andrew Mellon Foundation....
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...2680 Key words: carbon storage; fire suppression; missing carbon; oak savanna....
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