This study seeks to investigate the dynamics of dead plant carbon over fifty years of old-field f... more This study seeks to investigate the dynamics of dead plant carbon over fifty years of old-field forest development at the Calhoun Long Term Soil-Ecosystem Experiment (LTSE) in South Carolina, USA. Emphasis is on the transition phase of the forest, which is less well studied than the establishment and early thinning phase or the steady state phase.
Page 1. A Critical Comparison and Virtual Field Test of Forest Management Carbon Offset Protoco... more Page 1. A Critical Comparison and Virtual Field Test of Forest Management Carbon Offset Protocols October 2008 Christopher S. Galik1 Daniel deB. Richter2 Megan L. Mobley2 Lydia P. Olander3 Brian C. Murray3 1Climate ...
A number of scientists have named our age the Anthropocene because humanity is globally affecting... more A number of scientists have named our age the Anthropocene because humanity is globally affecting Earth systems, including the soil. Global soil change raises important questions about the future of soil, the environment, and human society. Although many soil scientists strive to understand human forcings as integral to soil genesis, there remains an explicit need for a science of anthropedology to detail how humanity is a fully fledged soil-forming factor and to understand how soil change affects human well being. The development and maturation of anthropedology is critical to achieving land-use sustainability and needs to be nurtured by all soil disciplines, with inputs from allied sciences and the humanities,. The Soil Science Society of America (SSSA) has recently approved a cross-divisional Working Group on Soil Change, which aims to advance the basic and applied science of anthropedology, to facilitate networks of scientists, long-term soil field studies, and regional databases and modeling, and to engage in new modes of communications about human–soil relations. We challenge all interested parties, especially young scientists and students, to contribute to these activities and help grow soil science in the Anthropocene.
To understand the role biota play in resilience or vulnerability to environmental change, we inve... more To understand the role biota play in resilience or vulnerability to environmental change, we investigated soil, plant, and microbial responses to a widespread environmental change, increased nitrogen (N). Our aim was to test the plant–soil threshold hypothesis: that changed biotic structure influences resilience to accumulated changes in N. For six years, we removed one of two codominant species, Geum rossii and Deschampsia caespitosa, in moist-meadow alpine tundra in Colorado, USA. We also manipulated nutrient availability by adding carbon (C) or N, separately and in combination with the species removals.
Consistent with our hypothesis, Geum was associated with soil feedbacks that slowed rates of N cycling and Deschampsia with feedbacks that increased rates of N cycling. After a four-year initial resilience period, Geum dramatically declined (by almost 70%) due to increasing N availability. In contrast, Deschampsia abundance did not respond to changes in N supply; it only responded to the removal of Geum. Forbs and graminoids responded more positively to Deschampsia removal than to Geum removal, indicating stronger competitive effects by Deschampsia. The changed biotic interactions appear to have community-level consequences: after six years of Geum (but not Deschampsia) removal, evenness of the community declined by over 35%.
Increased N affected the soil–microbial feedbacks, particularly in association with Geum. Microbial biomass N declined at higher N, as did the activities of two C-acquiring and one N-acquiring extracellular microbial enzymes. In the presence of Geum, N fertilization slowed the activity of phenol oxidase, a tannin-degrading enzyme, suggesting that microbes shift from degrading Geum-derived compounds. In the absence of Geum, acid phosphatase activity increased, suggesting increased phosphorus limitation in association with Deschampsia.
With continued N deposition forecast for this system, these results suggest that initial resilience of Geum to increased N will be overwhelmed through elimination of microbial feedbacks. Once Geum declines, the loss will indirectly facilitate Deschampsia via competitive release. Because Deschampsia exerts strong competitive effects on subordinate species, increased Deschampsia abundance may be accompanied by a community-wide drop in diversity. We conclude that plant–soil feedbacks through the microbial community can influence vulnerability to exogenous changes in N and contribute to threshold dynamics.
Geologists tell us that we live in the Anthropocene, the period marked by humanity's global trans... more Geologists tell us that we live in the Anthropocene, the period marked by humanity's global transformation of the environment (1). More than half of Earth's terrestrial surface is now plowed, pastured, fertilized, irrigated, drained, fumigated, bulldozed, compacted, eroded, reconstructed, manured, mined, logged, or converted to new uses. These activities have long-lasting effects on life-sustaining processes of the near-surface environment, recently termed Earth's “critical zone” (2). The full range of Anthropocene changes in Earth's critical zone is not well quantified, especially belowground (see the figure) (3–6), where observed changes justify a major expansion in monitoring to better ensure the sustainability of crop and soil productivity, and the functioning of the global atmosphere and hydrosphere (3).
Tuesday, August 4, 2009 - 8:20 AM COS 19-2: Transformations of pine forest-derived dissolved orga... more Tuesday, August 4, 2009 - 8:20 AM COS 19-2: Transformations of pine forest-derived dissolved organic matter in a temperate zone soil. Megan L. Mobley 1 , Daniel deB Richter 1 , Song S Qian 1 , Ryan L. Fimmen 2 , and Paul ...
Of the greenhouse gas (GHG) mitigation options available from U.S. forests and agricultural lands... more Of the greenhouse gas (GHG) mitigation options available from U.S. forests and agricultural lands, forest management presents amongst the lowest cost and highest volume opportunities. A number of carbon (C) accounting schemes or protocols have recently emerged to track the mitigation achieved by individual forest management projects. Using 50-year C cycling data from the Calhoun Experimental Forest in South Carolina, USA, C storage is estimated for a hypothetical forest management C offset project operating under seven of these protocols. After 100 years of project implementation, net C sequestration among the seven protocols varies by nearly a full order of magnitude. This variation stems from differences in how individual C pools, baseline, leakage, certainty, and buffers are addressed under each protocol. This in turn translates to a wide variation in the C price required to match the net present value of the non-project, business-as-usual alternative. Collectively, these findings suggest that protocol-specific restrictions or requirements are likely to discount the amount of C that can be claimed in “real world” projects, potentially leading to higher project costs than estimated in previous aggregate national analyses.
Tuesday, August 3, 2010 - 2:50 PM Accumulation and decay of coarse woody detritus over 50 years o... more Tuesday, August 3, 2010 - 2:50 PM Accumulation and decay of coarse woody detritus over 50 years of pine forest development. Megan L. Mobley, Daniel deB. Richter, and Paul R. Heine. Duke University. Background/Question/Methods ...
This study seeks to investigate the dynamics of dead plant carbon over fifty years of old-field f... more This study seeks to investigate the dynamics of dead plant carbon over fifty years of old-field forest development at the Calhoun Long Term Soil-Ecosystem Experiment (LTSE) in South Carolina, USA. Emphasis is on the transition phase of the forest, which is less well studied than the establishment and early thinning phase or the steady state phase.
Page 1. A Critical Comparison and Virtual Field Test of Forest Management Carbon Offset Protoco... more Page 1. A Critical Comparison and Virtual Field Test of Forest Management Carbon Offset Protocols October 2008 Christopher S. Galik1 Daniel deB. Richter2 Megan L. Mobley2 Lydia P. Olander3 Brian C. Murray3 1Climate ...
A number of scientists have named our age the Anthropocene because humanity is globally affecting... more A number of scientists have named our age the Anthropocene because humanity is globally affecting Earth systems, including the soil. Global soil change raises important questions about the future of soil, the environment, and human society. Although many soil scientists strive to understand human forcings as integral to soil genesis, there remains an explicit need for a science of anthropedology to detail how humanity is a fully fledged soil-forming factor and to understand how soil change affects human well being. The development and maturation of anthropedology is critical to achieving land-use sustainability and needs to be nurtured by all soil disciplines, with inputs from allied sciences and the humanities,. The Soil Science Society of America (SSSA) has recently approved a cross-divisional Working Group on Soil Change, which aims to advance the basic and applied science of anthropedology, to facilitate networks of scientists, long-term soil field studies, and regional databases and modeling, and to engage in new modes of communications about human–soil relations. We challenge all interested parties, especially young scientists and students, to contribute to these activities and help grow soil science in the Anthropocene.
To understand the role biota play in resilience or vulnerability to environmental change, we inve... more To understand the role biota play in resilience or vulnerability to environmental change, we investigated soil, plant, and microbial responses to a widespread environmental change, increased nitrogen (N). Our aim was to test the plant–soil threshold hypothesis: that changed biotic structure influences resilience to accumulated changes in N. For six years, we removed one of two codominant species, Geum rossii and Deschampsia caespitosa, in moist-meadow alpine tundra in Colorado, USA. We also manipulated nutrient availability by adding carbon (C) or N, separately and in combination with the species removals.
Consistent with our hypothesis, Geum was associated with soil feedbacks that slowed rates of N cycling and Deschampsia with feedbacks that increased rates of N cycling. After a four-year initial resilience period, Geum dramatically declined (by almost 70%) due to increasing N availability. In contrast, Deschampsia abundance did not respond to changes in N supply; it only responded to the removal of Geum. Forbs and graminoids responded more positively to Deschampsia removal than to Geum removal, indicating stronger competitive effects by Deschampsia. The changed biotic interactions appear to have community-level consequences: after six years of Geum (but not Deschampsia) removal, evenness of the community declined by over 35%.
Increased N affected the soil–microbial feedbacks, particularly in association with Geum. Microbial biomass N declined at higher N, as did the activities of two C-acquiring and one N-acquiring extracellular microbial enzymes. In the presence of Geum, N fertilization slowed the activity of phenol oxidase, a tannin-degrading enzyme, suggesting that microbes shift from degrading Geum-derived compounds. In the absence of Geum, acid phosphatase activity increased, suggesting increased phosphorus limitation in association with Deschampsia.
With continued N deposition forecast for this system, these results suggest that initial resilience of Geum to increased N will be overwhelmed through elimination of microbial feedbacks. Once Geum declines, the loss will indirectly facilitate Deschampsia via competitive release. Because Deschampsia exerts strong competitive effects on subordinate species, increased Deschampsia abundance may be accompanied by a community-wide drop in diversity. We conclude that plant–soil feedbacks through the microbial community can influence vulnerability to exogenous changes in N and contribute to threshold dynamics.
Geologists tell us that we live in the Anthropocene, the period marked by humanity's global trans... more Geologists tell us that we live in the Anthropocene, the period marked by humanity's global transformation of the environment (1). More than half of Earth's terrestrial surface is now plowed, pastured, fertilized, irrigated, drained, fumigated, bulldozed, compacted, eroded, reconstructed, manured, mined, logged, or converted to new uses. These activities have long-lasting effects on life-sustaining processes of the near-surface environment, recently termed Earth's “critical zone” (2). The full range of Anthropocene changes in Earth's critical zone is not well quantified, especially belowground (see the figure) (3–6), where observed changes justify a major expansion in monitoring to better ensure the sustainability of crop and soil productivity, and the functioning of the global atmosphere and hydrosphere (3).
Tuesday, August 4, 2009 - 8:20 AM COS 19-2: Transformations of pine forest-derived dissolved orga... more Tuesday, August 4, 2009 - 8:20 AM COS 19-2: Transformations of pine forest-derived dissolved organic matter in a temperate zone soil. Megan L. Mobley 1 , Daniel deB Richter 1 , Song S Qian 1 , Ryan L. Fimmen 2 , and Paul ...
Of the greenhouse gas (GHG) mitigation options available from U.S. forests and agricultural lands... more Of the greenhouse gas (GHG) mitigation options available from U.S. forests and agricultural lands, forest management presents amongst the lowest cost and highest volume opportunities. A number of carbon (C) accounting schemes or protocols have recently emerged to track the mitigation achieved by individual forest management projects. Using 50-year C cycling data from the Calhoun Experimental Forest in South Carolina, USA, C storage is estimated for a hypothetical forest management C offset project operating under seven of these protocols. After 100 years of project implementation, net C sequestration among the seven protocols varies by nearly a full order of magnitude. This variation stems from differences in how individual C pools, baseline, leakage, certainty, and buffers are addressed under each protocol. This in turn translates to a wide variation in the C price required to match the net present value of the non-project, business-as-usual alternative. Collectively, these findings suggest that protocol-specific restrictions or requirements are likely to discount the amount of C that can be claimed in “real world” projects, potentially leading to higher project costs than estimated in previous aggregate national analyses.
Tuesday, August 3, 2010 - 2:50 PM Accumulation and decay of coarse woody detritus over 50 years o... more Tuesday, August 3, 2010 - 2:50 PM Accumulation and decay of coarse woody detritus over 50 years of pine forest development. Megan L. Mobley, Daniel deB. Richter, and Paul R. Heine. Duke University. Background/Question/Methods ...
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Consistent with our hypothesis, Geum was associated with soil feedbacks that slowed rates of N cycling and Deschampsia with feedbacks that increased rates of N cycling. After a four-year initial resilience period, Geum dramatically declined (by almost 70%) due to increasing N availability. In contrast, Deschampsia abundance did not respond to changes in N supply; it only responded to the removal of Geum. Forbs and graminoids responded more positively to Deschampsia removal than to Geum removal, indicating stronger competitive effects by Deschampsia. The changed biotic interactions appear to have community-level consequences: after six years of Geum (but not Deschampsia) removal, evenness of the community declined by over 35%.
Increased N affected the soil–microbial feedbacks, particularly in association with Geum. Microbial biomass N declined at higher N, as did the activities of two C-acquiring and one N-acquiring extracellular microbial enzymes. In the presence of Geum, N fertilization slowed the activity of phenol oxidase, a tannin-degrading enzyme, suggesting that microbes shift from degrading Geum-derived compounds. In the absence of Geum, acid phosphatase activity increased, suggesting increased phosphorus limitation in association with Deschampsia.
With continued N deposition forecast for this system, these results suggest that initial resilience of Geum to increased N will be overwhelmed through elimination of microbial feedbacks. Once Geum declines, the loss will indirectly facilitate Deschampsia via competitive release. Because Deschampsia exerts strong competitive effects on subordinate species, increased Deschampsia abundance may be accompanied by a community-wide drop in diversity. We conclude that plant–soil feedbacks through the microbial community can influence vulnerability to exogenous changes in N and contribute to threshold dynamics.
Consistent with our hypothesis, Geum was associated with soil feedbacks that slowed rates of N cycling and Deschampsia with feedbacks that increased rates of N cycling. After a four-year initial resilience period, Geum dramatically declined (by almost 70%) due to increasing N availability. In contrast, Deschampsia abundance did not respond to changes in N supply; it only responded to the removal of Geum. Forbs and graminoids responded more positively to Deschampsia removal than to Geum removal, indicating stronger competitive effects by Deschampsia. The changed biotic interactions appear to have community-level consequences: after six years of Geum (but not Deschampsia) removal, evenness of the community declined by over 35%.
Increased N affected the soil–microbial feedbacks, particularly in association with Geum. Microbial biomass N declined at higher N, as did the activities of two C-acquiring and one N-acquiring extracellular microbial enzymes. In the presence of Geum, N fertilization slowed the activity of phenol oxidase, a tannin-degrading enzyme, suggesting that microbes shift from degrading Geum-derived compounds. In the absence of Geum, acid phosphatase activity increased, suggesting increased phosphorus limitation in association with Deschampsia.
With continued N deposition forecast for this system, these results suggest that initial resilience of Geum to increased N will be overwhelmed through elimination of microbial feedbacks. Once Geum declines, the loss will indirectly facilitate Deschampsia via competitive release. Because Deschampsia exerts strong competitive effects on subordinate species, increased Deschampsia abundance may be accompanied by a community-wide drop in diversity. We conclude that plant–soil feedbacks through the microbial community can influence vulnerability to exogenous changes in N and contribute to threshold dynamics.