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Magnani M, Díaz-Sierra R, Sweeney L, Provenzale A, Baudena M. Fire Responses Shape Plant Communities in a Minimal Model for Fire Ecosystems across the World. Am Nat 2023; 202:E83-E103. [PMID: 37606944 DOI: 10.1086/725391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
AbstractAcross plant communities worldwide, fire regimes reflect a combination of climatic factors and plant characteristics. To shed new light on the complex relationships between plant characteristics and fire regimes, we developed a new conceptual mechanistic model that includes plant competition, stochastic fires, and fire-vegetation feedback. Considering a single standing plant functional type, we observed that highly flammable and slowly colonizing plants can persist only when they have a strong fire response, while fast colonizing and less flammable plants can display a larger range of fire responses. At the community level, the fire response of the strongest competitor determines the existence of alternative ecological states (i.e., different plant communities) under the same environmental conditions. Specifically, when the strongest competitor had a very strong fire response, such as in Mediterranean forests, only one ecological state could be achieved. Conversely, when the strongest competitor was poorly fire adapted, alternative ecological states emerged-for example, between tropical humid savannas and forests or between different types of boreal forests. These findings underline the importance of including the plant fire response when modeling fire ecosystems, for example, to predict the vegetation response to invasive species or to climate change.
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Dos Santos Ferreira BH, da Rosa Oliveira M, Mariano Fernandes RA, Fujizawa Nacagava VA, Arguelho BA, Ribeiro DB, Pott A, Damasceno Junior GA, Garcia LC. Flowering and fruiting show phenological complementarity in both trees and non-trees in mosaic-burnt floodable savanna. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 337:117665. [PMID: 36940604 DOI: 10.1016/j.jenvman.2023.117665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2022] [Revised: 02/16/2023] [Accepted: 03/02/2023] [Indexed: 06/18/2023]
Abstract
The homogenization of fire regimes in a landscape may imply a temporal reduction in the availability of resources, such as flowers and fruits, which affect the fauna, as well as ecosystem services. We hypothesized that maintaining mosaic burning regimes, and thereby pyrodiversity, can diversify phenological patterns, ensuring year-round availability of flowers and fruits. Here we monitored open grassy tropical savanna phenology under different historical fire frequencies and fire seasons in a highly heterogeneous landscape in an Indigenous Territory in Brazil. We evaluated phenological patterns of tree and non-tree plants through monthly surveys over three years. These two life forms responded differently to climate and photoperiod variables and to fire. Different fire regimes led to a continuous availability of flowers and fruits, due to the complementarity between tree and non-tree phenologies. Late-season fires are supposed to be more devastating, but we did not detect a significant reduction in flower and fruit production, especially under moderate fire frequency. However, late burning in patches under high frequency resulted in a low availability of ripe fruits in trees. The fruiting of non-tree plants in patches under low fire frequency and early burning ensure ripe fruit, when there are practically no trees fruiting in the entire landscape. We conclude that maintaining a seasonal fire mosaic should be prioritized over historical fire regimes, which lead to homogenization. Fire management is best conducted between the end of the rainy season and the beginning of the dry season, when the risk of burning fertile plants is lower.
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Affiliation(s)
- Bruno Henrique Dos Santos Ferreira
- Programa de Pós-graduação em Ecologia e Conservação, Instituto de Biociências, Fundação Universidade Federal de Mato Grosso do Sul, Brazil; Laboratório Ecologia da Intervenção, Instituto de Biociências, Fundação Universidade Federal de Mato Grosso do Sul, Brazil.
| | | | | | - Vivian Ayumi Fujizawa Nacagava
- Programa de Pós-graduação em Ecologia e Conservação, Instituto de Biociências, Fundação Universidade Federal de Mato Grosso do Sul, Brazil
| | - Bruno Arrua Arguelho
- Programa de Pós-graduação em Ecologia e Conservação, Instituto de Biociências, Fundação Universidade Federal de Mato Grosso do Sul, Brazil
| | - Danilo Bandini Ribeiro
- Programa de Pós-graduação em Ecologia e Conservação, Instituto de Biociências, Fundação Universidade Federal de Mato Grosso do Sul, Brazil
| | - Arnildo Pott
- Laboratório de Ecologia Vegetal, Instituto de Biociências, Fundação Universidade Federal de Mato Grosso do Sul, Brazil
| | | | - Letícia Couto Garcia
- Laboratório Ecologia da Intervenção, Instituto de Biociências, Fundação Universidade Federal de Mato Grosso do Sul, Brazil
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Thomsen AM, Ooi MKJ. Shifting season of fire and its interaction with fire severity: Impacts on reproductive effort in resprouting plants. Ecol Evol 2022; 12:e8717. [PMID: 35342578 PMCID: PMC8931712 DOI: 10.1002/ece3.8717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 01/24/2022] [Accepted: 01/28/2022] [Indexed: 01/18/2023] Open
Abstract
Fire regimes shape plant communities but are shifting with changing climate. More frequent fires of increasing intensity are burning across a broader range of seasons. Despite this, impacts that changes in fire season have on plant populations, or how they interact with other fire regime elements, are still relatively understudied. We asked (a) how does the season of fire affect plant vigor, including vegetative growth and flowering after a fire event, and (b) do different functional resprouting groups respond differently to the effects of season of fire? We sampled a total of 887 plants across 36 sites using a space‐for‐time design to assess resprouting vigor and reproductive output for five plant species. Sites represented either a spring or autumn burn, aged one to three years old. Season of fire had the clearest impacts on flowering in Lambertia formosa with a 152% increase in the number of plants flowering and a 45% increase in number of flowers per plant after autumn compared with spring fires. There were also season × severity interactions for total flowers produced for Leptospermum polygalifolium and L. trinervium with both species producing greater flowering in autumn, but only after lower severity fires. Severity of fire was a more important driver in vegetative growth than fire season. Season of fire impacts have previously been seen as synonymous with the effects of fire severity; however, we found that fire season and severity can have clear and independent, as well as interacting, impacts on post‐fire vegetative growth and reproductive response of resprouting species. Overall, we observed that there were positive effects of autumn fires on reproductive traits, while vegetative growth was positively related to fire severity and pre‐fire plant size.
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Affiliation(s)
- Alexandria M. Thomsen
- School of Biological, Earth and Environmental Sciences Centre for Ecosystem Science University of New South Wales Sydney New South Wales Australia
| | - Mark K. J. Ooi
- School of Biological, Earth and Environmental Sciences Centre for Ecosystem Science University of New South Wales Sydney New South Wales Australia
- NSW Bushfire Risk Management Research Hub Sydney New South Wales Australia
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Tangney R, Merritt DJ, Miller BP. Environmental Factors Driving Seed Hydration Status of Soil Seed Banks and the Implications for Post-fire Recruitment. FRONTIERS IN PLANT SCIENCE 2022; 12:795003. [PMID: 35069650 PMCID: PMC8767118 DOI: 10.3389/fpls.2021.795003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 12/02/2021] [Indexed: 05/31/2023]
Abstract
Changes in fire regimes due to climate change and fire management practices are affecting the timing, length, and distribution of vegetation fires throughout the year. Plant species responses and tolerances to fire differ from season to season and are influenced by species-specific phenological processes. The ability of seeds to tolerate extreme temperatures associated with fire is one of these processes, with survival linked to seed moisture content at the time of exposure. As fire is more often occurring outside historic dry fire seasons, the probability of fire occurring when seeds are hydrated may also be increasing. In this study, we set out to understand the seasonal dynamics of seed hydration for seeds of Banksia woodland species, and how certain seed traits interact with environmental conditions to influence survival of high temperatures associated with fire. We measured the moisture content of seeds buried to 2 cm in the soil seed bank for four common native species and one invasive species on a weekly basis throughout 2017, along with soil moisture content and environmental correlates. We determined water sorption isotherms at 20°C for seeds of each species and used these functions to model weekly variation in seed water activity and predict when seeds are most sensitive to soil heating. Using Generalised additive models (GAMs), we were able to describe approximately 67% of the weekly variance in seed water activity and explored differences in seed hydration dynamics between species. Seed water activity was sufficiently high (i.e., ≥ 0.85 a w) so as to have created an increased risk of mortality if a fire had occurred during an almost continuous period between May and November in the study period (i.e., 2017). There were brief windows when seeds may have been in a dry state during early winter and late spring, and also when they may have been in a wet state during summer and late autumn. These data, and the associated analyses, provide an opportunity to develop approaches to minimize seed mortality during fire and maximize the seed bank response.
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Affiliation(s)
- Ryan Tangney
- Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia
- Kings Park Science, Biodiversity and Conservation Science, Department of Biodiversity, Conservation and Attractions, Kings Park, WA, Australia
- UWA School of Agriculture and Environment, The University of Western Australia, Perth, WA, Australia
| | - David J. Merritt
- Kings Park Science, Biodiversity and Conservation Science, Department of Biodiversity, Conservation and Attractions, Kings Park, WA, Australia
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia
| | - Ben P. Miller
- Kings Park Science, Biodiversity and Conservation Science, Department of Biodiversity, Conservation and Attractions, Kings Park, WA, Australia
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia
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Miller RG, Fontaine JB, Merritt DJ, Miller BP, Enright NJ. Experimental seed sowing reveals seedling recruitment vulnerability to unseasonal fire. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2021; 31:e02411. [PMID: 34255387 DOI: 10.1002/eap.2411] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 02/25/2021] [Accepted: 03/22/2021] [Indexed: 06/13/2023]
Abstract
Unseasonal fire occurrence is increasing globally, driven by climate change and other human activity. Changed timing of fire can inhibit postfire seedling recruitment through interactions with plant phenology (the timing of key processes, e.g., flower initiation, seed production, dispersal, germination), and therefore threaten the persistence of many plant species. Although empirical evidence from winter-rainfall ecosystems shows that optimal seedling recruitment is expected following summer and autumn (dry season) fires, we sought experimental evidence isolating the mechanisms of poor recruitment following unseasonal (wet season) fire. We implemented a seed-sowing experiment using nine species native to fire-prone, Mediterranean-climate woodlands in southwestern Australia to emulate the timing of postfire recruitment and test key mechanisms of fire seasonality effects. For seeds sown during months when fire is unseasonal (i.e., August-September: end of the wet winter season), seedling recruitment was reduced by up to 99% relative to seeds sown during seasonal fire months (i.e., May-June: end of the dry summer season) because of varying seed persistence, seedling emergence, and seedling survival. We found that up to 70 times more seedlings emerged when seeds were sown during seasonal fire months compared to when seeds were sown during unseasonal fire months. The few seedlings that emerged from unseasonal sowings all died with the onset of the dry season. Of the seeds that failed to germinate from unseasonal sowings, only 2% survived exposure on the soil surface over the ensuing hot and dry summer. Our experimental results demonstrate the potential for unseasonal fire to inhibit seedling recruitment via impacts on pregermination seed persistence and seedling establishment. As ongoing climate change lengthens fire seasons (i.e., unseasonal wildfires become more common) and managed fires are implemented further outside historically typical fire seasons, postfire seedling recruitment may become more vulnerable to failure, causing shifts in plant community composition towards those with fewer species solely dependent on seeds for regeneration.
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Affiliation(s)
- Russell G Miller
- Environmental and Conservation Sciences, Murdoch University, Murdoch, Perth, 6150, Western Australia, Australia
- Biodiversity and Conservation Science, Department of Biodiversity, Conservation and Attractions, 1 Kattidj Close, Kings Park, Perth, 6005, Western Australia, Australia
| | - Joseph B Fontaine
- Environmental and Conservation Sciences, Murdoch University, Murdoch, Perth, 6150, Western Australia, Australia
| | - David J Merritt
- Biodiversity and Conservation Science, Department of Biodiversity, Conservation and Attractions, 1 Kattidj Close, Kings Park, Perth, 6005, Western Australia, Australia
- School of Biological Sciences, University of Western Australia, Crawley, Perth, 6009, Western Australia, Australia
| | - Ben P Miller
- Biodiversity and Conservation Science, Department of Biodiversity, Conservation and Attractions, 1 Kattidj Close, Kings Park, Perth, 6005, Western Australia, Australia
- School of Biological Sciences, University of Western Australia, Crawley, Perth, 6009, Western Australia, Australia
| | - Neal J Enright
- Environmental and Conservation Sciences, Murdoch University, Murdoch, Perth, 6150, Western Australia, Australia
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Seed Dormancy Interacts with Fire Seasonality Mechanisms. Trends Ecol Evol 2020; 35:1057-1059. [DOI: 10.1016/j.tree.2020.09.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 09/30/2020] [Indexed: 11/21/2022]
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