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Pilon NAL, Cava MGB, Hoffmann WA, Abreu RCR, Rossatto DR, Durigan G. Effects and response of the Cerrado ground-layer to frost along the canopy cover gradient. Oecologia 2022; 200:199-207. [PMID: 36127474 DOI: 10.1007/s00442-022-05259-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 09/07/2022] [Indexed: 11/29/2022]
Abstract
Frost effects on savanna plant communities have been considered as analogous to those from fire, both changing community structure and filtering species composition. However, while frost impacts have been well-studied for the woody component of savannas, it is still poorly explored for the ground-layer community. Here, we investigated effects of frost in the Cerrado along a gradient of tree cover, focusing on ground-layer plant species, near the southern limit of the Cerrado in Brazil. We aimed to elucidate if the pattern already described for the tree layer also extends to the ground layer in terms of mimicking the effects of fire on vegetation structure and composition. We assessed how damage severity differs across species and across the tree-cover gradient, and we examined the recovery process after frost in terms of richness and community structure along the canopy cover gradient. Frost caused immediate and widespread dieback of the perennial ground-layer, with greatest impact on community structure where tree cover was lowest. However, frost did not reduce the number of species, indicating community resilience to this natural disturbance. Although frost mimicked the effects of fire in some ways, in other ways it differed substantially from fire. Unlike fire, frost increases litter cover and decreases the proportion of bare soil, likely hindering crucial processes for recovery of plant populations, such as seed dispersal, seed germination and plant resprouting. This finding calls attention to the risk of misguided conclusions when the ground layer is neglected in ecological studies of tropical savannas and grasslands.
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Affiliation(s)
- Natashi A Lima Pilon
- Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Caixa Postal 6109, Campinas, São Paulo, 13083-865, Brazil.
| | - Mário G B Cava
- Lab of Vegetation Ecology, Instituto de Biociências, Universidade Estadual Paulista, Rio Claro, São Paulo, Brazil
| | - William A Hoffmann
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, USA
| | - Rodolfo C R Abreu
- Departamento de Ciências Ambientais, Universidade Federal Rural do Rio de Janeiro, Seropédica, Rio de Janeiro, 23897-000, Brazil
| | - Davi R Rossatto
- Campus de Jaboticabal Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, Brazil
| | - Giselda Durigan
- Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Caixa Postal 6109, Campinas, São Paulo, 13083-865, Brazil.,Laboratório de Ecologia e Hidrologia Florestal, Floresta Estadual de Assis, Instituto de Pesquisas Ambientais de São Paulo (IPA-SP), Assis, São Paulo, 19802-970, Brazil
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Abreu RCR, Durigan G, Melo ACG, Pilon NAL, Hoffmann WA. Facilitation by isolated trees triggers woody encroachment and a biome shift at the savanna–forest transition. J Appl Ecol 2021. [DOI: 10.1111/1365-2664.13994] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rodolfo C. R. Abreu
- Department of Plant and Microbial Biology North Carolina State University (NCSU) Raleigh NC USA
| | - Giselda Durigan
- Laboratório de Ecologia e Hidrologia Florestal Floresta Estadual de Assis Instituto Florestal São Paulo Brazil
- Instituto de Biologia Universidade Estadual de Campinas (UNICAMP) São Paulo Brazil
| | - Antônio C. G. Melo
- Laboratório de Ecologia e Hidrologia Florestal Floresta Estadual de Assis Instituto Florestal São Paulo Brazil
| | - Natashi A. L. Pilon
- Instituto de Biologia Universidade Estadual de Campinas (UNICAMP) São Paulo Brazil
| | - William A. Hoffmann
- Department of Plant and Microbial Biology North Carolina State University (NCSU) Raleigh NC USA
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Flake SW, Abreu RCR, Durigan G, Hoffmann WA. Savannas are not old fields: Functional trajectories of forest expansion in a fire‐suppressed Brazilian savanna are driven by habitat generalists. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13818] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Samuel W. Flake
- Department of Plant and Microbial Biology NC State University Raleigh NC USA
| | - Rodolfo C. R. Abreu
- Department of Plant and Microbial Biology NC State University Raleigh NC USA
- Departamento de Ciências Ambientais Universidade Federal Rural do Rio de Janeiro Seropédica Brazil
| | | | - William A. Hoffmann
- Department of Plant and Microbial Biology NC State University Raleigh NC USA
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Newberry BM, Power CR, Abreu RCR, Durigan G, Rossatto DR, Hoffmann WA. Flammability thresholds or flammability gradients? Determinants of fire across savanna-forest transitions. New Phytol 2020; 228:910-921. [PMID: 33410161 DOI: 10.1111/nph.16742] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 06/01/2020] [Indexed: 06/12/2023]
Abstract
Vegetation-fire feedbacks are important for determining the distribution of forest and savanna. To understand how vegetation structure controls these feedbacks, we quantified flammability across gradients of tree density from grassland to forest in the Brazilian Cerrado. We experimentally burned 102 plots, for which we measured vegetation structure, fuels, microclimate, ignition success and fire behavior. Tree density had strong negative effects on ignition success, rate of spread, fire-line intensity and flame height. Declining grass biomass was the principal cause of this decline in flammability as tree density increased, but increasing fuel moisture contributed. Although the response of flammability to tree cover often is portrayed as an abrupt, largely invariant threshold, we found the response to be gradual, with considerable variability driven largely by temporal changes in atmospheric humidity. Even when accounting for humidity, flammability at intermediate tree densities cannot be predicted reliably. Fire spread in savanna-forest mosaics is not as deterministic as often assumed, but may appear so where vegetation boundaries are already sharp. Where transitions are diffuse, fire spread is difficult to predict, but should become increasingly predictable over multiple fire cycles, as boundaries are progressively sharpened until flammability appears to respond in a threshold-like manner.
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Affiliation(s)
- Brooklynn M Newberry
- Department of Plant and Microbial Biology, North Carolina State University, Campus Box 7612, Raleigh, NC, 27695, USA
| | - Collin R Power
- Department of Fisheries, Wildlife, and Conservation Biology, North Carolina State University, Raleigh, NC, 27695, USA
| | - Rodolfo C R Abreu
- Department of Plant and Microbial Biology, North Carolina State University, Campus Box 7612, Raleigh, NC, 27695, USA
- Departamento de Ciências Ambientais, Universidade Federal Rural do Rio de Janeiro, Seropédica, RJ, CEP 23897-000, Brazil
| | - Giselda Durigan
- Laboratório de Ecologia e Hidrologia Florestal, Floresta Estadual de Assis, Instituto Florestal, Assis, SP, 19802-970, Brazil
| | - Davi R Rossatto
- Departamento de Biologia, Universidade Estadual Paulista (UNESP), Campus de Jaboticabal, Jaboticabal, SP, 14884-900, Brazil
| | - William A Hoffmann
- Department of Plant and Microbial Biology, North Carolina State University, Campus Box 7612, Raleigh, NC, 27695, USA
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Abreu RCR, Hoffmann WA, Vasconcelos HL, Pilon NA, Rossatto DR, Durigan G. The biodiversity cost of carbon sequestration in tropical savanna. Sci Adv 2017; 3:e1701284. [PMID: 28875172 PMCID: PMC5576881 DOI: 10.1126/sciadv.1701284] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 08/06/2017] [Indexed: 05/04/2023]
Abstract
Tropical savannas have been increasingly viewed as an opportunity for carbon sequestration through fire suppression and afforestation, but insufficient attention has been given to the consequences for biodiversity. To evaluate the biodiversity costs of increasing carbon sequestration, we quantified changes in ecosystem carbon stocks and the associated changes in communities of plants and ants resulting from fire suppression in savannas of the Brazilian Cerrado, a global biodiversity hotspot. Fire suppression resulted in increased carbon stocks of 1.2 Mg ha-1 year-1 since 1986 but was associated with acute species loss. In sites fully encroached by forest, plant species richness declined by 27%, and ant richness declined by 35%. Richness of savanna specialists, the species most at risk of local extinction due to forest encroachment, declined by 67% for plants and 86% for ants. This loss highlights the important role of fire in maintaining biodiversity in tropical savannas, a role that is not reflected in current policies of fire suppression throughout the Brazilian Cerrado. In tropical grasslands and savannas throughout the tropics, carbon mitigation programs that promote forest cover cannot be assumed to provide net benefits for conservation.
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Affiliation(s)
- Rodolfo C. R. Abreu
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695–7612, USA
| | - William A. Hoffmann
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695–7612, USA
| | - Heraldo L. Vasconcelos
- Instituto de Biologia, Universidade Federal de Uberlândia (UFU), Av. Pará 1720, Uberlândia, Minas Gerais 38405-320, Brazil
| | - Natashi A. Pilon
- Laboratório de Ecologia e Hidrologia Florestal, Floresta Estadual de Assis, Instituto Florestal, Assis, São Paulo 19802-970, Brazil
- Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Caixa Postal 6109, Campinas, São Paulo 13083-865, Brazil
| | - Davi R. Rossatto
- Departamento de Biologia, Universidade Estadual Paulista (UNESP), Campus de Jaboticabal, Jaboticabal, São Paulo 14884-900, Brazil
| | - Giselda Durigan
- Laboratório de Ecologia e Hidrologia Florestal, Floresta Estadual de Assis, Instituto Florestal, Assis, São Paulo 19802-970, Brazil
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