Pub Date : 2023-12-12DOI: 10.1186/s42408-023-00232-0
José Manuel Fernández-Guisuraga, Leonor Calvo
Fire-vegetation feedbacks can modulate the global change effects conducive to extreme fire behavior and high fire severity of subsequent wildfires in reburn areas by altering the composition, flammability traits, and spatial arrangement of fuels. Repeated, high-severity wildfires at short return intervals may trigger long-term vegetation state transitions. However, empirical evidence about these feedbacks is absent in fire-prone ecosystems of the western Mediterranean Basin, where the response of fire activity has been enhanced by contemporary socioeconomic and land-use changes. Here, we evaluated whether fire severity differs between initial burns and subsequent wildfires in reburn areas (fire-free periods = 10–15 years) of maritime pine and Aleppo pine forests, holm oak woodlands, and shrublands in the western Mediterranean Basin, and whether there is a relationship between the severity of such interactive wildfire disturbances. We also tested how the type of ecosystem and changes in vegetation structure after the initial wildfires influence these relationships. We leveraged Landsat-based fire severity estimates for initial and last wildfires using the Relativized Burn Ratio (RBR) and Light Detection and Ranging (LiDAR) data acquired before the last wildfire. Fire severity of the last wildfire was significantly higher than that of the initial wildfire for each dominant ecosystem type in reburn areas. These differences were very pronounced in maritime pine forests and shrublands. For consistency, the same patterns were evidenced for the fire severity in reburn and first-entry areas of the last wildfire for each dominant ecosystem type. Fire severity of the last wildfire in forests and woodlands (particularly maritime pine-dominated) raised with increasing severity of the previous wildfire to a greater extent than in shrublands. Pre-fire fuel density in the lower vegetation strata (up to 4 m high in maritime and Aleppo pine forests, as well as in shrublands, and up to 2 m high in holm oak forests) was significantly higher in reburn than in first-entry areas of the last wildfire. Our results suggest that land managers should promote more fire-resistant landscapes to high fire severity by minimizing fuel build-up and thus fire hazard through pre-fire fuel reduction treatments such as prescribed burning.
{"title":"Fuel build-up promotes an increase in fire severity of reburned areas in fire-prone ecosystems of the western Mediterranean Basin","authors":"José Manuel Fernández-Guisuraga, Leonor Calvo","doi":"10.1186/s42408-023-00232-0","DOIUrl":"https://doi.org/10.1186/s42408-023-00232-0","url":null,"abstract":"Fire-vegetation feedbacks can modulate the global change effects conducive to extreme fire behavior and high fire severity of subsequent wildfires in reburn areas by altering the composition, flammability traits, and spatial arrangement of fuels. Repeated, high-severity wildfires at short return intervals may trigger long-term vegetation state transitions. However, empirical evidence about these feedbacks is absent in fire-prone ecosystems of the western Mediterranean Basin, where the response of fire activity has been enhanced by contemporary socioeconomic and land-use changes. Here, we evaluated whether fire severity differs between initial burns and subsequent wildfires in reburn areas (fire-free periods = 10–15 years) of maritime pine and Aleppo pine forests, holm oak woodlands, and shrublands in the western Mediterranean Basin, and whether there is a relationship between the severity of such interactive wildfire disturbances. We also tested how the type of ecosystem and changes in vegetation structure after the initial wildfires influence these relationships. We leveraged Landsat-based fire severity estimates for initial and last wildfires using the Relativized Burn Ratio (RBR) and Light Detection and Ranging (LiDAR) data acquired before the last wildfire. Fire severity of the last wildfire was significantly higher than that of the initial wildfire for each dominant ecosystem type in reburn areas. These differences were very pronounced in maritime pine forests and shrublands. For consistency, the same patterns were evidenced for the fire severity in reburn and first-entry areas of the last wildfire for each dominant ecosystem type. Fire severity of the last wildfire in forests and woodlands (particularly maritime pine-dominated) raised with increasing severity of the previous wildfire to a greater extent than in shrublands. Pre-fire fuel density in the lower vegetation strata (up to 4 m high in maritime and Aleppo pine forests, as well as in shrublands, and up to 2 m high in holm oak forests) was significantly higher in reburn than in first-entry areas of the last wildfire. Our results suggest that land managers should promote more fire-resistant landscapes to high fire severity by minimizing fuel build-up and thus fire hazard through pre-fire fuel reduction treatments such as prescribed burning.","PeriodicalId":12273,"journal":{"name":"Fire Ecology","volume":"2 1","pages":""},"PeriodicalIF":5.1,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138573009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-23DOI: 10.1186/s42408-023-00225-z
Kendall M. L. Becker, James A. Lutz
Snags, standing dead trees, are becoming more abundant in forests as tree mortality rates continue to increase due to fire, drought, and bark beetles. Snags provide habitat for birds and small mammals, and when they fall to the ground, the resulting logs provide additional wildlife habitat and affect nutrient cycling, fuel loads, and fire behavior. Predicting how long snags will remain standing after fire is essential for managing habitat, understanding chemical cycling in forests, and modeling forest succession and fuels. Few studies, however, have quantified how fire changes snag fall dynamics. We compared post-fire fall rates of snags that existed pre-fire (n = 2013) and snags created during or after the fire (n = 8222), using 3 years of pre-fire and 5 years of post-fire data from an annually monitored, 25.6-ha spatially explicit plot in an old-growth Abies concolor–Pinus lambertiana forest in the Sierra Nevada, CA, USA. The plot burned at low to moderate severity in the Rim Fire of 2013. We used random forest models to (1) identify predictors of post-fire snag fall for pre-existing and new snags and (2) assess the influence of spatial neighborhood and local fire severity on snag fall after fire. Fall rates of pre-existing snags increased 3 years after fire. Five years after fire, pre-existing snags were twice as likely to fall as new snags. Pre-existing snags were most likely to persist 5 years after fire if they were > 50 cm in diameter, > 20 m tall, and charred on the bole to heights above 3.7 m. New snags were also more likely to persist 5 years after fire if they were > 20 m tall. Spatial neighborhood (e.g., tree density) and local fire severity (e.g., fire-caused crown injury) within 15 m of each snag barely improved predictions of snag fall after fire. Land managers should expect fall rates of pre-existing snags to exceed fall rates of new snags within 5 years after fire, an important habitat consideration because pre-existing snags represent a wider range of size and decay classes.
{"title":"Predicting snag fall in an old-growth forest after fire","authors":"Kendall M. L. Becker, James A. Lutz","doi":"10.1186/s42408-023-00225-z","DOIUrl":"https://doi.org/10.1186/s42408-023-00225-z","url":null,"abstract":"Snags, standing dead trees, are becoming more abundant in forests as tree mortality rates continue to increase due to fire, drought, and bark beetles. Snags provide habitat for birds and small mammals, and when they fall to the ground, the resulting logs provide additional wildlife habitat and affect nutrient cycling, fuel loads, and fire behavior. Predicting how long snags will remain standing after fire is essential for managing habitat, understanding chemical cycling in forests, and modeling forest succession and fuels. Few studies, however, have quantified how fire changes snag fall dynamics. We compared post-fire fall rates of snags that existed pre-fire (n = 2013) and snags created during or after the fire (n = 8222), using 3 years of pre-fire and 5 years of post-fire data from an annually monitored, 25.6-ha spatially explicit plot in an old-growth Abies concolor–Pinus lambertiana forest in the Sierra Nevada, CA, USA. The plot burned at low to moderate severity in the Rim Fire of 2013. We used random forest models to (1) identify predictors of post-fire snag fall for pre-existing and new snags and (2) assess the influence of spatial neighborhood and local fire severity on snag fall after fire. Fall rates of pre-existing snags increased 3 years after fire. Five years after fire, pre-existing snags were twice as likely to fall as new snags. Pre-existing snags were most likely to persist 5 years after fire if they were > 50 cm in diameter, > 20 m tall, and charred on the bole to heights above 3.7 m. New snags were also more likely to persist 5 years after fire if they were > 20 m tall. Spatial neighborhood (e.g., tree density) and local fire severity (e.g., fire-caused crown injury) within 15 m of each snag barely improved predictions of snag fall after fire. Land managers should expect fall rates of pre-existing snags to exceed fall rates of new snags within 5 years after fire, an important habitat consideration because pre-existing snags represent a wider range of size and decay classes.","PeriodicalId":12273,"journal":{"name":"Fire Ecology","volume":"286 1","pages":""},"PeriodicalIF":5.1,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138536350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-21DOI: 10.1186/s42408-023-00230-2
Jeanne C. Chambers, Jessi L. Brown, Matthew C. Reeves, Eva K. Strand, Lisa M. Ellsworth, Claire M. Tortorelli, Alexandra K. Urza, Karen C. Short
Sagebrush shrublands in the Great Basin, USA, are experiencing widespread increases in wildfire size and area burned resulting in new policies and funding to implement fuel treatments. However, we lack the spatial data needed to optimize the types and locations of fuel treatments across large landscapes and mitigate fire risk. To address this, we developed treatment response groups (TRGs)—sagebrush and pinyon-juniper vegetation associations that differ in resilience to fire and resistance to annual grass invasion (R&R) and thus responses to fuel treatments. We developed spatial layers of the dominant sagebrush associations by overlaying LANDFIRE Existing Vegetation Type, Biophysical Setting, and Mapping Zone, extracting vegetation plot data from the LANDFIRE 2016 LF Reference Database for each combination, and identifying associated sagebrush, grass, shrub, and tree species. We derived spatial layers of pinyon-juniper (PJ) cover and expansion phase within the sagebrush associations from the Rangeland Analysis Platform and identified persistent PJ woodlands from the LANDFIRE Biophysical Setting. TRGs were created by overlaying dominant sagebrush associations, with and without PJ expansion, and new indicators of resilience and resistance. We assigned appropriate woody fuel treatments to the TRGs based on prior research on treatment responses. The potential area to receive woody fuel treatments was constrained to 52,940 km2 (18.4%) of the dominant sagebrush associations (272,501 km2) largely because of extensive areas of low R&R (68.9%), which respond poorly and were not assigned treatments. Prescribed fire was assigned to big sagebrush associations with moderate or higher resilience and moderately low or higher resistance (14.2%) due to higher productivity, fuels, and recovery potential. Mechanical treatments were assigned to big sagebrush associations with moderately low resilience and to low, black, and mixed low sagebrush associations with moderately low or higher R&R (4.2%) due to lower productivity, fuels, and recovery potential. Persistent PJ woodlands represent high value resources and were not assigned treatments (9%). Mapped TRGs can help identify the dominant sagebrush associations and determine appropriate fuel treatments at intermediate scales and provide the basis for quantitative wildfire risk assessments and outcome-based scenario planning to prioritize fuel treatment investments at large landscape scales.
{"title":"Fuel treatment response groups for fire-prone sagebrush landscapes","authors":"Jeanne C. Chambers, Jessi L. Brown, Matthew C. Reeves, Eva K. Strand, Lisa M. Ellsworth, Claire M. Tortorelli, Alexandra K. Urza, Karen C. Short","doi":"10.1186/s42408-023-00230-2","DOIUrl":"https://doi.org/10.1186/s42408-023-00230-2","url":null,"abstract":"Sagebrush shrublands in the Great Basin, USA, are experiencing widespread increases in wildfire size and area burned resulting in new policies and funding to implement fuel treatments. However, we lack the spatial data needed to optimize the types and locations of fuel treatments across large landscapes and mitigate fire risk. To address this, we developed treatment response groups (TRGs)—sagebrush and pinyon-juniper vegetation associations that differ in resilience to fire and resistance to annual grass invasion (R&R) and thus responses to fuel treatments. We developed spatial layers of the dominant sagebrush associations by overlaying LANDFIRE Existing Vegetation Type, Biophysical Setting, and Mapping Zone, extracting vegetation plot data from the LANDFIRE 2016 LF Reference Database for each combination, and identifying associated sagebrush, grass, shrub, and tree species. We derived spatial layers of pinyon-juniper (PJ) cover and expansion phase within the sagebrush associations from the Rangeland Analysis Platform and identified persistent PJ woodlands from the LANDFIRE Biophysical Setting. TRGs were created by overlaying dominant sagebrush associations, with and without PJ expansion, and new indicators of resilience and resistance. We assigned appropriate woody fuel treatments to the TRGs based on prior research on treatment responses. The potential area to receive woody fuel treatments was constrained to 52,940 km2 (18.4%) of the dominant sagebrush associations (272,501 km2) largely because of extensive areas of low R&R (68.9%), which respond poorly and were not assigned treatments. Prescribed fire was assigned to big sagebrush associations with moderate or higher resilience and moderately low or higher resistance (14.2%) due to higher productivity, fuels, and recovery potential. Mechanical treatments were assigned to big sagebrush associations with moderately low resilience and to low, black, and mixed low sagebrush associations with moderately low or higher R&R (4.2%) due to lower productivity, fuels, and recovery potential. Persistent PJ woodlands represent high value resources and were not assigned treatments (9%). Mapped TRGs can help identify the dominant sagebrush associations and determine appropriate fuel treatments at intermediate scales and provide the basis for quantitative wildfire risk assessments and outcome-based scenario planning to prioritize fuel treatment investments at large landscape scales.","PeriodicalId":12273,"journal":{"name":"Fire Ecology","volume":"23 1","pages":""},"PeriodicalIF":5.1,"publicationDate":"2023-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138536349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Background With the increase in forest fire emissions, an increasing amount of nitrogen is released from combustibles and taken up by plant leaves in the form of PM 2.5 smoke deposition. Concurrently, the stress from PM 2.5 also disrupts the physiological processes of plants. This study aims to reveal the migration paths of N in combustibles in smoke and plants during forest fires and the stress response of plant leaves to smoke particle deposition. This study conducted a simulated smoke deposition treatment on Schima superba and Cunninghamia lanceolata , analyzing the changes in plant 15 N content and stress-related products. Results The main findings include the following: (1) Nitrogen in combustibles can be transported to plant leaves via PM 2.5 smoke during combustion and can be allocated and assimilated in various parts of the plant after being absorbed by the leaves. (2) The stress response of Schima superba to PM 2.5 is less pronounced than that of Cunninghamia lanceolata . (3) Under PM 2.5 stress, the correlation between nitrogen accumulation in the leaves of Schima superba and Cunninghamia lanceolata and their respective stress responses differs. Conclusions In forest fires involving different tree species, there are variations in the migration pathways of nitrogen and the stress effects of PM 2.5 on leaves, with a significant correlation observed between leaf nitrogen accumulation and stress response. Graphical Abstract
{"title":"Nitrogen allocation in PM2.5 smoke-exposed plants: implications for ecosystem nitrogen cycling and stress response","authors":"Haichuan Lin, Yuanfan Ma, Pingxin Zhao, Ziyan Huang, Xiaoyu Zhan, Mulualem Tigabu, Futao Guo","doi":"10.1186/s42408-023-00229-9","DOIUrl":"https://doi.org/10.1186/s42408-023-00229-9","url":null,"abstract":"Abstract Background With the increase in forest fire emissions, an increasing amount of nitrogen is released from combustibles and taken up by plant leaves in the form of PM 2.5 smoke deposition. Concurrently, the stress from PM 2.5 also disrupts the physiological processes of plants. This study aims to reveal the migration paths of N in combustibles in smoke and plants during forest fires and the stress response of plant leaves to smoke particle deposition. This study conducted a simulated smoke deposition treatment on Schima superba and Cunninghamia lanceolata , analyzing the changes in plant 15 N content and stress-related products. Results The main findings include the following: (1) Nitrogen in combustibles can be transported to plant leaves via PM 2.5 smoke during combustion and can be allocated and assimilated in various parts of the plant after being absorbed by the leaves. (2) The stress response of Schima superba to PM 2.5 is less pronounced than that of Cunninghamia lanceolata . (3) Under PM 2.5 stress, the correlation between nitrogen accumulation in the leaves of Schima superba and Cunninghamia lanceolata and their respective stress responses differs. Conclusions In forest fires involving different tree species, there are variations in the migration pathways of nitrogen and the stress effects of PM 2.5 on leaves, with a significant correlation observed between leaf nitrogen accumulation and stress response. Graphical Abstract","PeriodicalId":12273,"journal":{"name":"Fire Ecology","volume":"90 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134957223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-07DOI: 10.1186/s42408-023-00228-w
Miguel Ángel Blanco-Rodríguez, Aitor Ameztegui, Pere Gelabert, Marcos Rodrigues, Lluís Coll
Abstract Background Climate change is altering the fire regime and compromising the post-fire recovery of vegetation worldwide. To understand the factors influencing post-fire vegetation cover restoration, we calculated the recovery of vegetation in 200,000 hectares of western Mediterranean forest burned by 268 wildfires over a 27-year period (1988–2015). We used time series of the Tasseled Cap Transformation Brightness (TCTB) spectral transformation over Landsat imagery to calculate vegetation recovery. Then, we quantified the importance of the main drivers of post-fire vegetation recovery (climate, fire severity, and topography) along an aridity gradient (semi-arid, sub-humid, and humid) using Random Forest models. Results In most models (99.7%), drought duration was the most important factor, negatively affecting post-fire recovery especially in the extremes of the aridity gradient. Fire severity was the second most important factor for vegetation cover recovery, with its effect varying along the aridity gradient: there was a positive relationship between fire severity and recovery in sub-humid and humid areas, while semi-arid areas showed the opposite pattern. Topographic variables were the least important driver and had a marginal effect on post-fire recovery. Additionally, semi-arid areas exhibited a low mean recovery rate, indicating limitations in the short-term recovery after a fire. Conclusions Our study highlights the key role that drought duration plays in the recovery of vegetation after wildfires in the Mediterranean basin and, particularly, in forests located in climatically extreme areas. The results suggest that the predicted increase in drought duration coupled with a higher frequency and intensity of large fires may modify the structure and composition of Mediterranean forest ecosystems. Our analysis provides relevant information to evaluate and design adaptive management strategies in post-fire recovery hotspots of Mediterranean forest ecosystems.
{"title":"Short-term recovery of post-fire vegetation is primarily limited by drought in Mediterranean forest ecosystems","authors":"Miguel Ángel Blanco-Rodríguez, Aitor Ameztegui, Pere Gelabert, Marcos Rodrigues, Lluís Coll","doi":"10.1186/s42408-023-00228-w","DOIUrl":"https://doi.org/10.1186/s42408-023-00228-w","url":null,"abstract":"Abstract Background Climate change is altering the fire regime and compromising the post-fire recovery of vegetation worldwide. To understand the factors influencing post-fire vegetation cover restoration, we calculated the recovery of vegetation in 200,000 hectares of western Mediterranean forest burned by 268 wildfires over a 27-year period (1988–2015). We used time series of the Tasseled Cap Transformation Brightness (TCTB) spectral transformation over Landsat imagery to calculate vegetation recovery. Then, we quantified the importance of the main drivers of post-fire vegetation recovery (climate, fire severity, and topography) along an aridity gradient (semi-arid, sub-humid, and humid) using Random Forest models. Results In most models (99.7%), drought duration was the most important factor, negatively affecting post-fire recovery especially in the extremes of the aridity gradient. Fire severity was the second most important factor for vegetation cover recovery, with its effect varying along the aridity gradient: there was a positive relationship between fire severity and recovery in sub-humid and humid areas, while semi-arid areas showed the opposite pattern. Topographic variables were the least important driver and had a marginal effect on post-fire recovery. Additionally, semi-arid areas exhibited a low mean recovery rate, indicating limitations in the short-term recovery after a fire. Conclusions Our study highlights the key role that drought duration plays in the recovery of vegetation after wildfires in the Mediterranean basin and, particularly, in forests located in climatically extreme areas. The results suggest that the predicted increase in drought duration coupled with a higher frequency and intensity of large fires may modify the structure and composition of Mediterranean forest ecosystems. Our analysis provides relevant information to evaluate and design adaptive management strategies in post-fire recovery hotspots of Mediterranean forest ecosystems.","PeriodicalId":12273,"journal":{"name":"Fire Ecology","volume":"12 10","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135480432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-02DOI: 10.1186/s42408-023-00217-z
Tom Le Breton, Laura Schweickle, Craig Dunne, Mitchell Lyons, Mark Ooi
Abstract Background Climate change is driving global fire regimes toward greater extremes, potentially threatening plant species that are adapted to historic fire regimes. Successful conservation of threatened plant species depends upon improving our understanding of how they respond to these changing fire regimes in fire prone regions. The 2019–2020 Australian megafires burnt at very high to extreme severity across an unprecedented extent and overlaid a complex history of prescribed burns and wildfires, providing an ideal foundation to study the consequences of multiple fire regime elements. We examined the recruitment response of Pomaderris bodalla , one of many threatened obligate-seeding shrub species growing in wet sclerophyll (mesic) forest in south-east Australia. We surveyed seedling recruitment at sites across a gradient of fire severity and frequency. Our aims were to (i) confirm in vitro results that suggest a positive relationship with fire severity; (ii) determine the species response to fire frequency and (iii) identify the nature of the effect of fire severity and fire frequency in combination. Results We found that recruitment had a positive response to fire severity, peaking at high severity sites as soil temperatures reached optimal levels for dormancy-break but declining, while still remaining positive, at moderate and extreme severity sites. The pattern of response matched in vitro studies, which had established that physically dormant P. bodalla seeds had minimal dormancy broken at low fire-related temperatures, peak dormancy broken at high fire-related temperatures and heat-induced mortality at extreme temperatures. Fire frequency had an overall negative effect on recruitment, with fewer recruits at more frequently burnt sites and this effect appeared to be additive with fire severity. Conclusion Our findings indicate that increased fire frequency poses an ongoing threat to P. bodalla and similar obligate-seeding shrub species. The hump-shaped relationship with fire severity suggests that future large-scale extreme fires will cause seed mortality-induced reduction in recruitment, with the potential to exacerbate the negative effects of high fire frequency. Informed management of threatened species requires detailed knowledge of species responses to multiple fire regime elements, and novel fire response traits like seed dormancy can provide beneficial insights for robust conservation strategies.
{"title":"Fire frequency and severity mediate recruitment response of a threatened shrub following severe megafire","authors":"Tom Le Breton, Laura Schweickle, Craig Dunne, Mitchell Lyons, Mark Ooi","doi":"10.1186/s42408-023-00217-z","DOIUrl":"https://doi.org/10.1186/s42408-023-00217-z","url":null,"abstract":"Abstract Background Climate change is driving global fire regimes toward greater extremes, potentially threatening plant species that are adapted to historic fire regimes. Successful conservation of threatened plant species depends upon improving our understanding of how they respond to these changing fire regimes in fire prone regions. The 2019–2020 Australian megafires burnt at very high to extreme severity across an unprecedented extent and overlaid a complex history of prescribed burns and wildfires, providing an ideal foundation to study the consequences of multiple fire regime elements. We examined the recruitment response of Pomaderris bodalla , one of many threatened obligate-seeding shrub species growing in wet sclerophyll (mesic) forest in south-east Australia. We surveyed seedling recruitment at sites across a gradient of fire severity and frequency. Our aims were to (i) confirm in vitro results that suggest a positive relationship with fire severity; (ii) determine the species response to fire frequency and (iii) identify the nature of the effect of fire severity and fire frequency in combination. Results We found that recruitment had a positive response to fire severity, peaking at high severity sites as soil temperatures reached optimal levels for dormancy-break but declining, while still remaining positive, at moderate and extreme severity sites. The pattern of response matched in vitro studies, which had established that physically dormant P. bodalla seeds had minimal dormancy broken at low fire-related temperatures, peak dormancy broken at high fire-related temperatures and heat-induced mortality at extreme temperatures. Fire frequency had an overall negative effect on recruitment, with fewer recruits at more frequently burnt sites and this effect appeared to be additive with fire severity. Conclusion Our findings indicate that increased fire frequency poses an ongoing threat to P. bodalla and similar obligate-seeding shrub species. The hump-shaped relationship with fire severity suggests that future large-scale extreme fires will cause seed mortality-induced reduction in recruitment, with the potential to exacerbate the negative effects of high fire frequency. Informed management of threatened species requires detailed knowledge of species responses to multiple fire regime elements, and novel fire response traits like seed dormancy can provide beneficial insights for robust conservation strategies.","PeriodicalId":12273,"journal":{"name":"Fire Ecology","volume":"21 8","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135934565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-31DOI: 10.1186/s42408-023-00227-x
David A. Davim, Carlos G. Rossa, José M. C. Pereira, Nuno Guiomar, Paulo M. Fernandes
Abstract Background The study of wildfire interactions (i.e., spread limitation and reburns) is gaining traction as a means of describing the self-limiting process of fire spread in the landscape and has important management implications but has scarcely been attempted in Europe. We examined to what extent previously burned areas restricted the development of individual large wildfires (> 500 ha) in mainland Portugal. Results For the 1984–2021 period, we (1) modeled the proportion of large wildfire perimeters coinciding with transitions to shorter time since fire (TSF), i.e., locations where fire spread ceased upon encountering assumedly less flammable fuels, and (2) characterized the prevalence of different TSF in the composition of the area burned by large wildfires in relation to available TSF. Only 4% of the large wildfires did not comprise edges intersecting past wildfires. Low TSF (especially up to 8 years) resulted in large-wildfire perimeter limitation at TSF transitions. This effect was further enhanced by high historical burn probability and proximity to roadways and watercourses. Perimeter limitation did also increase under high (but not very high or extreme) fire danger, benefiting from maximum seasonal firefighting preparedness. TSF prevalence in the composition of large-wildfire area was extremely variable and thus an overall weak pattern emerged, with minimum and maximum prevalence respectively at TSF < 2 years and TSF ≥ 6 years. Conclusions Large wildfire limitation in Portugal is hampered by fast fuel build-up after fire, indicating a short-lived fire-hazard reduction effect under the prevailing Mediterranean humid climate of the study region. Nonetheless, such effect should be considered when planning fuel-reduction treatments and can be used opportunistically during large-wildfire suppression operations.
{"title":"The effectiveness of past wildfire at limiting reburning is short-lived in a Mediterranean humid climate","authors":"David A. Davim, Carlos G. Rossa, José M. C. Pereira, Nuno Guiomar, Paulo M. Fernandes","doi":"10.1186/s42408-023-00227-x","DOIUrl":"https://doi.org/10.1186/s42408-023-00227-x","url":null,"abstract":"Abstract Background The study of wildfire interactions (i.e., spread limitation and reburns) is gaining traction as a means of describing the self-limiting process of fire spread in the landscape and has important management implications but has scarcely been attempted in Europe. We examined to what extent previously burned areas restricted the development of individual large wildfires (> 500 ha) in mainland Portugal. Results For the 1984–2021 period, we (1) modeled the proportion of large wildfire perimeters coinciding with transitions to shorter time since fire (TSF), i.e., locations where fire spread ceased upon encountering assumedly less flammable fuels, and (2) characterized the prevalence of different TSF in the composition of the area burned by large wildfires in relation to available TSF. Only 4% of the large wildfires did not comprise edges intersecting past wildfires. Low TSF (especially up to 8 years) resulted in large-wildfire perimeter limitation at TSF transitions. This effect was further enhanced by high historical burn probability and proximity to roadways and watercourses. Perimeter limitation did also increase under high (but not very high or extreme) fire danger, benefiting from maximum seasonal firefighting preparedness. TSF prevalence in the composition of large-wildfire area was extremely variable and thus an overall weak pattern emerged, with minimum and maximum prevalence respectively at TSF < 2 years and TSF ≥ 6 years. Conclusions Large wildfire limitation in Portugal is hampered by fast fuel build-up after fire, indicating a short-lived fire-hazard reduction effect under the prevailing Mediterranean humid climate of the study region. Nonetheless, such effect should be considered when planning fuel-reduction treatments and can be used opportunistically during large-wildfire suppression operations.","PeriodicalId":12273,"journal":{"name":"Fire Ecology","volume":"38 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135809210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-27DOI: 10.1186/s42408-023-00224-0
Rodrigo Balaguer-Romano, Rubén Díaz-Sierra, Miquel De Cáceres, Jordi Voltas, Matthias M. Boer, Víctor Resco de Dios
Abstract Background Current assessments of the effects of climate change on future wildfire risk are based on either empirical approaches or fire weather indices. No study has yet used process-based models over national scales to understand how and where will increases in climate aridity affect the likelihood of fire activity through changes in the moisture content of live (LFMC) and of dead (DFMC) fuels. Here, we used process-based models to forecast changes in LFMC and DFMC under the 21st century climatic conditions projected from moderate and high greenhouse gas emission scenarios (RCP4.5 and RCP8.5). Predictions were performed across broad productivity gradients in peninsular Spain to understand how productivity mediates the effects of climate change on fuel moisture dynamics. Results LFMC and DFMC were predicted to decline under the climatic conditions projected for the coming decades. Increases in the annual frequency of days with fuel moisture content below wildfire occurrence thresholds were predicted to extend fire season lengths by 20 days under RCP4.5 and by 50 days under RCP8.5. The effects of climate change on LFMC and DFMC varied linearly and negatively with productivity (stronger fuel moisture decreases in least productive environments). Although we observed a significant mitigation effect from rising CO 2 (via increases in water-use efficiency), it was not enough to offset LFMC declining trends induced by increased temperature and aridity. Conclusions We predicted that the warmer and more arid climatic conditions projected for the 21st century will lead to generalized declines in fuel moisture, lengthening fire seasons, and increasing wildfire danger. The use of process-based models to forecast LFMC dynamics allowed the consideration of plant species capabilities to buffer climate change impacts. Significant increases in the fire season length predicted in the most productive environments, currently with large fire return intervals, would pose an increase of fire danger in major Spanish carbon sinks. Finally, the CO 2 mitigation effect would not be enough to offset climate change-driven declines in seasonal LFMC levels.
{"title":"Modeling fuel moisture dynamics under climate change in Spain’s forests","authors":"Rodrigo Balaguer-Romano, Rubén Díaz-Sierra, Miquel De Cáceres, Jordi Voltas, Matthias M. Boer, Víctor Resco de Dios","doi":"10.1186/s42408-023-00224-0","DOIUrl":"https://doi.org/10.1186/s42408-023-00224-0","url":null,"abstract":"Abstract Background Current assessments of the effects of climate change on future wildfire risk are based on either empirical approaches or fire weather indices. No study has yet used process-based models over national scales to understand how and where will increases in climate aridity affect the likelihood of fire activity through changes in the moisture content of live (LFMC) and of dead (DFMC) fuels. Here, we used process-based models to forecast changes in LFMC and DFMC under the 21st century climatic conditions projected from moderate and high greenhouse gas emission scenarios (RCP4.5 and RCP8.5). Predictions were performed across broad productivity gradients in peninsular Spain to understand how productivity mediates the effects of climate change on fuel moisture dynamics. Results LFMC and DFMC were predicted to decline under the climatic conditions projected for the coming decades. Increases in the annual frequency of days with fuel moisture content below wildfire occurrence thresholds were predicted to extend fire season lengths by 20 days under RCP4.5 and by 50 days under RCP8.5. The effects of climate change on LFMC and DFMC varied linearly and negatively with productivity (stronger fuel moisture decreases in least productive environments). Although we observed a significant mitigation effect from rising CO 2 (via increases in water-use efficiency), it was not enough to offset LFMC declining trends induced by increased temperature and aridity. Conclusions We predicted that the warmer and more arid climatic conditions projected for the 21st century will lead to generalized declines in fuel moisture, lengthening fire seasons, and increasing wildfire danger. The use of process-based models to forecast LFMC dynamics allowed the consideration of plant species capabilities to buffer climate change impacts. Significant increases in the fire season length predicted in the most productive environments, currently with large fire return intervals, would pose an increase of fire danger in major Spanish carbon sinks. Finally, the CO 2 mitigation effect would not be enough to offset climate change-driven declines in seasonal LFMC levels.","PeriodicalId":12273,"journal":{"name":"Fire Ecology","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136234371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-26DOI: 10.1186/s42408-023-00223-1
Matthew J. Reilly, Aaron Zuspan, Zhiqiang Yang
Abstract Background Despite recent advances in understanding the drivers of tree-level delayed mortality, we lack a method for mapping delayed mortality at landscape and regional scales. Consequently, the extent, magnitude, and effects of delayed mortality on post-fire landscape patterns of burn severity are unknown. We introduce a remote sensing approach for mapping delayed mortality based on post-fire decline in the normalized burn ratio (NBR). NBR decline is defined as the change in NBR between the first post-fire measurement and the minimum NBR value up to 5 years post-fire for each pixel. We validate the method with high-resolution aerial photography from six wildfires in California, Oregon, and Washington, USA, and then compare the extent, magnitude, and effects of delayed mortality on landscape patterns of burn severity among fires and forest types. Results NBR decline was significantly correlated with post-fire canopy mortality ( r 2 = 0.50) and predicted the presence of delayed mortality with 83% accuracy based on a threshold of 105 NBR decline. Plots with NBR decline greater than 105 were 23 times more likely to experience delayed mortality than those below the threshold ( p < 0.001). Delayed mortality occurred across 6–38% of fire perimeters not affected by stand-replacing fire, generally affecting more areas in cold (22–41%) and wet (30%) forest types than in dry (1.7–19%) types. The total area initially mapped as unburned/very low-severity declined an average of 38.1% and generally persisted in smaller, more fragmented patches when considering delayed mortality. The total area initially mapped as high-severity increased an average of 16.2% and shifted towards larger, more contiguous patches. Conclusions Differences between 1- and 5-year post-fire burn severity maps depict dynamic post-fire mosaics resulting from delayed mortality, with variability among fires reflecting a range of potential drivers. We demonstrate that tree-level delayed mortality scales up to alter higher-level landscape patterns of burn severity with important implications for forest resilience and a range of fire-driven ecological outcomes. Our method can complement existing tree-level studies on drivers of delayed mortality, refine mapping of fire refugia, inform estimates of habitat and carbon losses, and provide a more comprehensive assessment of landscape and regional scale fire effects and trends.
{"title":"Characterizing post-fire delayed tree mortality with remote sensing: sizing up the elephant in the room","authors":"Matthew J. Reilly, Aaron Zuspan, Zhiqiang Yang","doi":"10.1186/s42408-023-00223-1","DOIUrl":"https://doi.org/10.1186/s42408-023-00223-1","url":null,"abstract":"Abstract Background Despite recent advances in understanding the drivers of tree-level delayed mortality, we lack a method for mapping delayed mortality at landscape and regional scales. Consequently, the extent, magnitude, and effects of delayed mortality on post-fire landscape patterns of burn severity are unknown. We introduce a remote sensing approach for mapping delayed mortality based on post-fire decline in the normalized burn ratio (NBR). NBR decline is defined as the change in NBR between the first post-fire measurement and the minimum NBR value up to 5 years post-fire for each pixel. We validate the method with high-resolution aerial photography from six wildfires in California, Oregon, and Washington, USA, and then compare the extent, magnitude, and effects of delayed mortality on landscape patterns of burn severity among fires and forest types. Results NBR decline was significantly correlated with post-fire canopy mortality ( r 2 = 0.50) and predicted the presence of delayed mortality with 83% accuracy based on a threshold of 105 NBR decline. Plots with NBR decline greater than 105 were 23 times more likely to experience delayed mortality than those below the threshold ( p < 0.001). Delayed mortality occurred across 6–38% of fire perimeters not affected by stand-replacing fire, generally affecting more areas in cold (22–41%) and wet (30%) forest types than in dry (1.7–19%) types. The total area initially mapped as unburned/very low-severity declined an average of 38.1% and generally persisted in smaller, more fragmented patches when considering delayed mortality. The total area initially mapped as high-severity increased an average of 16.2% and shifted towards larger, more contiguous patches. Conclusions Differences between 1- and 5-year post-fire burn severity maps depict dynamic post-fire mosaics resulting from delayed mortality, with variability among fires reflecting a range of potential drivers. We demonstrate that tree-level delayed mortality scales up to alter higher-level landscape patterns of burn severity with important implications for forest resilience and a range of fire-driven ecological outcomes. Our method can complement existing tree-level studies on drivers of delayed mortality, refine mapping of fire refugia, inform estimates of habitat and carbon losses, and provide a more comprehensive assessment of landscape and regional scale fire effects and trends.","PeriodicalId":12273,"journal":{"name":"Fire Ecology","volume":"14 3-4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134908941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-23DOI: 10.1186/s42408-023-00215-1
Abigail R. Croker, Jeremy Woods, Yiannis Kountouris
Abstract Background Late dry-season wildfires in sub-Saharan Africa’s savanna-protected areas are intensifying, increasing carbon emissions, and threatening ecosystem functioning. Addressing these challenges requires active local community engagement and support for wildfire policy. Savanna burning emissions abatement schemes first implemented in Northern Australia have been proposed as a community-based fire management strategy for East and Southern Africa’s protected areas to deliver win–win-win climate, social, and biodiversity benefits. Here, we review and critically examine the literature exploring the design and application of savanna burning emissions abatement schemes in this region, characterizing their contextual and implementation challenges. Results We show that the application of Northern Australian savanna burning methodologies in East and Southern Africa tends to adopt centrally determined objectives and market-based approaches that prioritize carbon revenue generation at the national level. The exclusive prescription of early-dry season burns in African mesic savannas prone to woody thickening can compromise savanna burning objectives to mitigate late-dry season wildfires and their greenhouse gas emissions in the long-term, as well as present multiple biodiversity trade-offs in the absence of formal metrics monitoring species’ responses to changes in fire regime. These features restrict indigenous participation and leadership in fire management, creating uncertainties over the opportunities for local income generation through carbon trading. Findings suggest that future savanna burning applications will need to address asymmetries between formal institutions and local land governance systems, explicitly acknowledging colonial legacies in institutional arrangements across protected areas and hierarchies in agrarian politics that threaten processes of equitable decentralization in natural resource management. Conclusion We argue that the effective transfer of the Northern Australian fire management model is limited by a lack of long-term ecological and emissions data and political and institutional barriers, and is hindered by the region’s recent colonial history, population growth, and consequences of rapid climatic change. To provide a community-based strategy, savanna burning schemes need to establish context-specific legal frameworks and implement Free, Prior, and Informed Consent to safeguard the roles and responsibilities of indigenous and local people and their distribution of carbon benefits.
{"title":"Changing fire regimes in East and Southern Africa’s savanna-protected areas: opportunities and challenges for indigenous-led savanna burning emissions abatement schemes","authors":"Abigail R. Croker, Jeremy Woods, Yiannis Kountouris","doi":"10.1186/s42408-023-00215-1","DOIUrl":"https://doi.org/10.1186/s42408-023-00215-1","url":null,"abstract":"Abstract Background Late dry-season wildfires in sub-Saharan Africa’s savanna-protected areas are intensifying, increasing carbon emissions, and threatening ecosystem functioning. Addressing these challenges requires active local community engagement and support for wildfire policy. Savanna burning emissions abatement schemes first implemented in Northern Australia have been proposed as a community-based fire management strategy for East and Southern Africa’s protected areas to deliver win–win-win climate, social, and biodiversity benefits. Here, we review and critically examine the literature exploring the design and application of savanna burning emissions abatement schemes in this region, characterizing their contextual and implementation challenges. Results We show that the application of Northern Australian savanna burning methodologies in East and Southern Africa tends to adopt centrally determined objectives and market-based approaches that prioritize carbon revenue generation at the national level. The exclusive prescription of early-dry season burns in African mesic savannas prone to woody thickening can compromise savanna burning objectives to mitigate late-dry season wildfires and their greenhouse gas emissions in the long-term, as well as present multiple biodiversity trade-offs in the absence of formal metrics monitoring species’ responses to changes in fire regime. These features restrict indigenous participation and leadership in fire management, creating uncertainties over the opportunities for local income generation through carbon trading. Findings suggest that future savanna burning applications will need to address asymmetries between formal institutions and local land governance systems, explicitly acknowledging colonial legacies in institutional arrangements across protected areas and hierarchies in agrarian politics that threaten processes of equitable decentralization in natural resource management. Conclusion We argue that the effective transfer of the Northern Australian fire management model is limited by a lack of long-term ecological and emissions data and political and institutional barriers, and is hindered by the region’s recent colonial history, population growth, and consequences of rapid climatic change. To provide a community-based strategy, savanna burning schemes need to establish context-specific legal frameworks and implement Free, Prior, and Informed Consent to safeguard the roles and responsibilities of indigenous and local people and their distribution of carbon benefits.","PeriodicalId":12273,"journal":{"name":"Fire Ecology","volume":"33 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135413210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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