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Sun M, Glenn CK, El Hajj O, Kumar KV, Anosike A, Penland R, Callaham MA, Loudermilk EL, O'Brien JJ, Saleh R, Smith GD. Aqueous Photolysis of Water-Soluble Brown Carbon from Simulated Prescribed and Wildfire Biomass Burning. ACS ES&T AIR 2024; 1:989-999. [PMID: 39295745 PMCID: PMC11406525 DOI: 10.1021/acsestair.4c00016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 06/20/2024] [Accepted: 06/21/2024] [Indexed: 09/21/2024]
Abstract
This work, as part of the Georgia Wildland fire Simulation Experiment (G-WISE) campaign, explores the aqueous photolysis of water-soluble brown carbon (W-BrC) in biomass burning aerosols from the combustion of fuel beds collected from three distinct ecoregions in Georgia: Piedmont, Coastal Plain, and Blue Ridge. Burns were conducted under conditions representative of wildfires, which are common unplanned occurrences in Southeastern forests (low fuel moisture content), and prescribed fires, which are commonly used in forest management (higher fuel moisture content). Upon exposure to radiation from UV lamps equivalent to approximately 5 h in the atmosphere, the absorption spectra of all six samples exhibited up to 40% photobleaching in the UV range (280-400 nm) and as much as 30% photo-enhancement in the visible range (400-500 nm). Together, these two effects reduced the absorption Ångström exponent (AAE), a measure of the wavelength dependence of the spectrum, from 6.0-7.9 before photolysis to 5.0-5.7 after. Electrospray ionization ultrahigh-resolution mass spectrometry analysis shows the potential formation of oligomeric chromophores due to aqueous photolysis. This work provides insight into the impacts that aqueous photolysis has on W-BrC in biomass burning aerosols and its dependence on fuel bed composition and moisture content.
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Affiliation(s)
- Mingrui Sun
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Chase K Glenn
- School of Environmental, Civil, Agricultural and Mechanical Engineering, University of Georgia, Athens, Georgia 30602, United States
| | - Omar El Hajj
- School of Environmental, Civil, Agricultural and Mechanical Engineering, University of Georgia, Athens, Georgia 30602, United States
| | - Kruthika V Kumar
- School of Environmental, Civil, Agricultural and Mechanical Engineering, University of Georgia, Athens, Georgia 30602, United States
| | - Anita Anosike
- School of Environmental, Civil, Agricultural and Mechanical Engineering, University of Georgia, Athens, Georgia 30602, United States
| | - Robert Penland
- School of Environmental, Civil, Agricultural and Mechanical Engineering, University of Georgia, Athens, Georgia 30602, United States
| | - Mac A Callaham
- U.S. Department of Agriculture Forest Service, Southern Research Station, Athens Prescribed Fire Science Laboratory, Athens, Georgia 30602, United States
| | - E Louise Loudermilk
- U.S. Department of Agriculture Forest Service, Southern Research Station, Athens Prescribed Fire Science Laboratory, Athens, Georgia 30602, United States
| | - Joseph J O'Brien
- U.S. Department of Agriculture Forest Service, Southern Research Station, Athens Prescribed Fire Science Laboratory, Athens, Georgia 30602, United States
| | - Rawad Saleh
- School of Environmental, Civil, Agricultural and Mechanical Engineering, University of Georgia, Athens, Georgia 30602, United States
| | - Geoffrey D Smith
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
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Hutchinson TF, Adams BT, Dickinson MB, Heckel M, Royo AA, Thomas-Van Gundy MA. Sustaining eastern oak forests: Synergistic effects of fire and topography on vegetation and fuels. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2024; 34:e2948. [PMID: 38351586 DOI: 10.1002/eap.2948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 08/25/2023] [Accepted: 10/03/2023] [Indexed: 04/04/2024]
Abstract
Across much of the eastern United States, oak forests are undergoing mesophication as shade-tolerant competitors become more abundant and suppress oak regeneration. Given the historical role of anthropogenic surface fires in promoting oak dominance, prescribed fire has become important in efforts to reverse mesophication and sustain oaks. In 2000 we established the Ohio Hills Fire and Fire Surrogate (FFS) study to examine whether repeated prescribed fire (Fire), mechanical partial harvest (Mech), and their combined application (Mech + Fire) reduced the dominance of subcanopy mesophytic competitors, increased the abundance of large oak-hickory advance regeneration, created a more diverse and productive ground-layer flora, and produced fuel beds more conducive to prescribed fire, reducing the risk of high-severity wildfire. Here we report on the ~20-year effects of treatments on vegetation and fuels and examine the support for interactive effects across a topographic-moisture and energy gradient. In general, we found that Fire and Mech + Fire treatments tended to reverse mesophication while the Mech-only treatment did not. The moderate and occasionally high-intensity fires resulted in effects that were ultimately very similar between the two fire treatments but were modulated by topography with increasing fire severity on drier sites. In particular, we found support for an interaction effect between treatment and topography on forest structure and tree regeneration responses. Fire generally reduced mesophytic tree density in the midstory and sapling strata across all site conditions, while leading to substantial gains in the abundance of large oak-hickory advance regeneration on dry and intermediate landscape positions. Fire also promoted ground-layer diversity and created compositionally distinct communities across all site conditions, primarily through the increased richness of native perennial herbs. However, the fire had limited effects on fine surface fuel loading and increased the loading of large woody fuels, potentially increasing the risk of high-severity wildfire during drought conditions. We conclude that two decades of repeated fires, with and without mechanical density reduction, significantly shifted the trajectory of mesophication across most of the landscape, particularly on dry and intermediate sites, highlighting the capacity of a periodic fire regime to sustain eastern oak forests and promote plant diversity but modulated by topography.
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Affiliation(s)
| | - Bryce T Adams
- Northern Research Station, US Forest Service, Delaware, Ohio, USA
| | | | - Maryjane Heckel
- Six Rivers National Forest US Forest Service, Eureka, California, USA
| | - Alejandro A Royo
- Northern Research Station, US Forest Service, Irvine, Pennsylvania, USA
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McDanold JS, Malik N. Spatially extended radiant heat fire model. Phys Rev E 2023; 107:034133. [PMID: 37072983 DOI: 10.1103/physreve.107.034133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 02/03/2023] [Indexed: 04/20/2023]
Abstract
Recent wildfire prevalence and destruction have led to new initiatives in the search for better land management techniques and prescriptions for controlled burns. With limited data on low-intensity prescribed burns, finding models that can represent fire behavior is of great importance to learning how to control fires with more accuracy while also maintaining the purpose for the burn, be it reducing fuels or managing the ecosystem. Here we use a data set of infrared temperatures collected in the New Jersey Pine Barrens from 2017 through 2020 to develop a model for very fine-scale fire behavior (≈0.05 m^{2}). The model uses distributions from the data set to define five stages in fire behavior in a cellular automata framework. For each cell, the transition between each stage is probabilistically driven based on the radiant temperature values of the cell and its immediate neighbors in a coupled map lattice. With five distinct initial conditions, we performed 100 simulations and used the parameters derived from the data set to develop metrics for model verification. To validate the model, we also expanded it to include variables not in the data set that are important for fire behavior, e.g., fuel moisture levels and spotting ignitions. The model matches several metrics compared to the observational data set and exhibits behavioral characteristics expected from low-intensity wildfire behavior including a long and varied burn time for each cell after initial ignition, and lingering embers in the burn zone.
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Affiliation(s)
- Jenna S McDanold
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA and School of Mathematical Sciences, Rochester Institute of Technology, Rochester, New York 14623, USA
| | - Nishant Malik
- School of Mathematical Sciences, Rochester Institute of Technology, Rochester, New York 14623, USA
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Ottinger SL, Miniat CF, Wurzburger N. Nitrogen and light regulate symbiotic nitrogen fixation by a temperate forest tree. Oecologia 2023; 201:565-574. [PMID: 36637524 DOI: 10.1007/s00442-023-05313-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 01/03/2023] [Indexed: 01/14/2023]
Abstract
Symbiotic nitrogen fixation (SNF) is a critical mechanism of ecosystem recovery, and in forests of the eastern United States, the most common tree species that supports SNF is black locust (Robinia pseudoacacia L.). Despite its prevalence, black locust's fixation strategy-whether it maintains fixation at a constant rate (obligate fixation) or reduces its fixation rate (facultative fixation)-is unknown. Here, we examined how nitrogen and light control SNF by black locust, by growing seedlings under two nitrogen levels and across four levels of light. Seedlings were harvested after 12 weeks to determine biomass changes, nodule activity, and photosynthetic rates. Black locust seedlings increased biomass growth with increasing light, but only in the absence of nitrogen addition, while seedling root:shoot (biomass) modestly declined with increasing light regardless of nitrogen level. We found that black locust behaved like a facultative fixer, and regulated fixation by excising or maintaining nodules, and by controlling nodule biomass and activity. Specifically, nitrogen addition reduced seedling investment in nodule biomass (g g-1) by 63%, and reduced seedling allocation to nitrogen fixation (µmol C2H4 g-1 h-1) by 66%. In contrast, light affected nitrogen fixation through two indirect pathways. First, light increased plant growth, and hence nitrogen demands, which caused an increase in nitrogen fixation proportional to biomass. Second, light increasd photosynthetic activity, which was positively associated with nodule activity, but only in the absence of nitrogen addition. Our findings for how black locust regulates SNF can improve predictions of ecosystem SNF under the changing environmental conditions.
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Affiliation(s)
| | - Chelcy Ford Miniat
- USDA Forest Service, Rocky Mountain Research Station, Albuquerque, NM, USA
| | - Nina Wurzburger
- Odum School of Ecology, University of Georgia, Athens, GA, USA.
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Robbins ZJ, Loudermilk EL, Reilly MJ, O'Brien JJ, Jones K, Gerstle CT, Scheller RM. Delayed fire mortality has long‐term ecological effects across the Southern Appalachian landscape. Ecosphere 2022. [DOI: 10.1002/ecs2.4153] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Zachary J. Robbins
- Forestry and Environmental Resources Department North Carolina State University Raleigh North Carolina USA
| | - E. Louise Loudermilk
- Southern Research Station, Center for Forest Disturbance Science Athens Prescribed Fire Laboratory, U.S. Forest Service Athens Georgia USA
| | - Matthew J. Reilly
- Pacific Northwest Research Station Western Wildland Environmental Threat Assessment, U.S. Forest Service Corvallis Oregon USA
| | - Joseph J. O'Brien
- Southern Research Station, Center for Forest Disturbance Science Athens Prescribed Fire Laboratory, U.S. Forest Service Athens Georgia USA
| | - Kate Jones
- Center for Geospatial Analytics North Carolina State University Raleigh North Carolina USA
| | - Christopher T. Gerstle
- Forestry and Environmental Resources Department North Carolina State University Raleigh North Carolina USA
| | - Robert M. Scheller
- Forestry and Environmental Resources Department North Carolina State University Raleigh North Carolina USA
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6
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Pausas JG, Bond WJ. On the Scale of the Terrestrial Recycling Pathways. Trends Ecol Evol 2020; 36:11-12. [PMID: 33190950 DOI: 10.1016/j.tree.2020.10.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 10/21/2020] [Indexed: 10/23/2022]
Affiliation(s)
- Juli G Pausas
- Centro de Investigaciones sobre Desertificación (CIDE-CSIC), Valencia, Spain.
| | - William J Bond
- Department of Biological Sciences, University of Cape Town, Cape Town, South Africa; South African Environmental Observation Network, National Research Foundation, Claremont, South Africa
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