Assessing changes in global fire regimes

PAGES, Past Global Changes, is funded by the Swiss Academy of Sciences and the Chinese Academy of Sciences and supported in kind by the University of Bern, Switzerland. Financial support was provided by the U.S. National Science Foundation award numbers 1916565, EAR-2011439, and EAR-2012123. Additional support was provided by the Utah Department of Natural Resources Watershed Restoration Initiative. SSS was supported by Brigham Young University Graduate Studies. MS was supported by National Science Centre, Poland (grant no. 2018/31/B/ST10/02498 and 2021/41/B/ST10/00060). JCA was supported by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 101026211. PF contributed within the framework of the FCT-funded project no. UIDB/04033/2020. SGAF acknowledges support from Trond Mohn Stiftelse (TMS) and University of Bergen for the startup grant ‘TMS2022STG03’. JMP participation in this research was supported by the Forest Research Centre, a research unit funded by Fundação para a Ciência e a Tecnologia I.P. (FCT), Portugal (UIDB/00239/2020). A.-LD acknowledge PAGES, PICS CNRS 06484 project, CNRS-INSU, Région Nouvelle-Aquitaine, University of Bordeaux DRI and INQUA for workshop support.Background The global human footprint has fundamentally altered wildfire regimes, creating serious consequences for human health, biodiversity, and climate. However, it remains difficult to project how long-term interactions among land use, management, and climate change will affect fire behavior, representing a key knowledge gap for sustainable management. We used expert assessment to combine opinions about past and future fire regimes from 99 wildfire researchers. We asked for quantitative and qualitative assessments of the frequency, type, and implications of fire regime change from the beginning of the Holocene through the year 2300. Results Respondents indicated some direct human influence on wildfire since at least ~ 12,000 years BP, though natural climate variability remained the dominant driver of fire regime change until around 5,000 years BP, for most study regions. Responses suggested a ten-fold increase in the frequency of fire regime change during the last 250 years compared with the rest of the Holocene, corresponding first with the intensification and extensification of land use and later with anthropogenic climate change. Looking to the future, fire regimes were predicted to intensify, with increases in frequency, severity, and size in all biomes except grassland ecosystems. Fire regimes showed different climate sensitivities across biomes, but the likelihood of fire regime change increased with higher warming scenarios for all biomes. Biodiversity, carbon storage, and other ecosystem services were predicted to decrease for most biomes under higher emission scenarios. We present recommendations for adaptation and mitigation under emerging fire regimes, while recognizing that management options are constrained under higher emission scenarios. Conclusion The influence of humans on wildfire regimes has increased over the last two centuries. The perspective gained from past fires should be considered in land and fire management strategies, but novel fire behavior is likely given the unprecedented human disruption of plant communities, climate, and other factors. Future fire regimes are likely to degrade key ecosystem services, unless climate change is aggressively mitigated. Expert assessment complements empirical data and modeling, providing a broader perspective of fire science to inform decision making and future research priorities.Peer reviewe

Adding to the diversity of a latest Devonian gondwanan plant assemblage : a new anatomically preserved axis from Barraba, Australia

International audienceDocumenting a wide paleogeographic range of Famennian (latest Devonian) floras is essential to better understand the state of land plant diversity between the Kellwasser and the Hangenberg bio-events, two first-order global crises for the marine biota but whose impact on terrestrial organisms needs to be clarified.There are few well-documented plant assemblages of Famennian age in Gondwana. One of them occurs in the Mandowa Mudstone Formation at Barraba, in New South Wales (Australia). The plant remains recovered at Barraba are dated from the late to latest Famennian and are preserved both as adpressions and permineralizations. A recent assessment of the permineralized assemblage indicates that the spore-producing plants are dominant and include lycopsids, cladoxylopsids, and one iridopterid (Keraphyton).This presentation describes a second anatomically preserved iridopteridalean plant, represented by a 50 mm long and 7.7 mm wide fragment of axis with no branch or appendage bases attached along its length. Its tissues are entirely primary. The vascular system is actinostelic. In transverse section, it shows three fundamental ribs that divide twice slightly unequally. The protoxylem strands occur at the rib tips. Metaxylem tracheids are scalariform. The cortex is aerenchymatous in its innermost part.This new plant is the first iridopterid to show an adaptation to a wetland habitat. Together with Keraphyton, it confirms that a group of Iridopteridales characterized by a complex vascular system occurred beyond the Frasnian in Eastern Gondwana. This discovery is consistent with a limited impact of the Kellwasser bio-event on land plant diversity prior to the Devonian-Carboniferous boundary

Keraphyton gen. nov., a new Late Devonian fern-like plant from Australia

International audienceThe first plants related to the ferns are represented by several extinct groups that emerged during the Devonian. Among them, the iridopterids are closely allied to the sphenopsids, a group represented today by the genus Equisetum. They have been documented in Middle to early Late Devonian deposits of Laurussia and the Kazakhstan plate. Their Gondwanan record is poor, with occurrences limited to Venezuela and Morocco. Here we describe a new genus from a late Late Devonian locality of New South Wales. It is represented by a single anatomically preserved large stem characterized by a star-shaped vascular system with protoxylem strands located at rib tips, and by a lack of secondary tissues. Within the first fern-like plants, this stem shares the largest number of characters with iridopterid axes but differs by the pattern of its vascular system. Keraphyton mawsoniae gen. et sp. nov. adds a new record of early fern-like plants in eastern Gondwana. It provides new insights into the anatomical diversity within this key group of plants and supports the distinctiveness of the Australian flora in the latest Devonian

Adding to the diversity of a latest Devonian gondwanan plant assemblage : a new anatomically preserved axis from Barraba, Australia

International audienceDocumenting a wide paleogeographic range of Famennian (latest Devonian) floras is essential to better understand the state of land plant diversity between the Kellwasser and the Hangenberg bio-events, two first-order global crises for the marine biota but whose impact on terrestrial organisms needs to be clarified.There are few well-documented plant assemblages of Famennian age in Gondwana. One of them occurs in the Mandowa Mudstone Formation at Barraba, in New South Wales (Australia). The plant remains recovered at Barraba are dated from the late to latest Famennian and are preserved both as adpressions and permineralizations. A recent assessment of the permineralized assemblage indicates that the spore-producing plants are dominant and include lycopsids, cladoxylopsids, and one iridopterid (Keraphyton).This presentation describes a second anatomically preserved iridopteridalean plant, represented by a 50 mm long and 7.7 mm wide fragment of axis with no branch or appendage bases attached along its length. Its tissues are entirely primary. The vascular system is actinostelic. In transverse section, it shows three fundamental ribs that divide twice slightly unequally. The protoxylem strands occur at the rib tips. Metaxylem tracheids are scalariform. The cortex is aerenchymatous in its innermost part.This new plant is the first iridopterid to show an adaptation to a wetland habitat. Together with Keraphyton, it confirms that a group of Iridopteridales characterized by a complex vascular system occurred beyond the Frasnian in Eastern Gondwana. This discovery is consistent with a limited impact of the Kellwasser bio-event on land plant diversity prior to the Devonian-Carboniferous boundary

The Famennian flora of Barraba, New South Wales, Australia

International audienceStructurally preserved fossils reveal details of the internal organization that can be used to reconstruct the physiology of extinct plants and the evolution of significant functional traits. When looking at well-preserved fossil wood, one important feature that is relatively easy to spot is the presence of tyloses. Tyloses are protoplasmic swellings formed by a parenchyma cell into the lumen of an adjacent conducting cell. They have been reported in a diversity of vascular plants dating back to the Carboniferous. Plants may form tyloses in response to embolism to seal off air-filled conducting cells, but they may also help the plant to attenuate or prevent the spreading of pathogens through the vascular tissues. As a result, tyloses play important roles in the physiology and autecology of vascular plants, and investigating when and how these structures evolved based on the fossil record is critical to understand (1) the evolution of plant defense mechanisms, and (2) the establishment of hydraulic traits, especially strategies to render embolized conducting cells harmless.Here, we report on tyloses in Dameria hueberi, a progymnosperm or gymnosperm from the Tournaisian (lower Mississippian) of Australia. The secondary xylem of the specimens is composed of tracheids and low, uniseriate parenchymatous rays. Pitting consists of one, rarely two, rows of circular pits with a circular aperture. Two of the nine D. hueberi specimens provide evidence of tyloses, which typically occur in tracheids and fill the entire lumen of the cells. Small structures with a circular to irregular shape that also protrude into tracheids here and there are interpreted as early stages in tylosis formation. The trigger for the development of tyloses in D. hueberi remains unknown. There are no clear growth ring boundaries in the wood, suggesting relatively constant growth conditions. There is also no indication of increased fungal activity. Finally, the distribution of the tylose-filled tracheids does not seem to reflect heartwood formation. The discovery of D. hueberi is nevertheless important because this taxon predates the heretofore oldest fossil evidence of tylosis formation in vascular plants by several million years

Permineralized coniferophytes from the Autun Basin: specimens from two new localities of Renault zone 3

International audienceFour zones yielding silicified plant remains have been recognized in the Autun Basin by Renault (1893-1896). Zones 2, 3 and 4, characterized by Autunian plants, correspond to the successive formations of Igornay and Muse (lower Autunian), and Surmoulin-Millery (upper Autunian). Their paleobotanical content, together with that preserved as adpressions in the same formations, document paleofloral changes on the western side of the Tethys within a time interval extending from the latest Ghzelian (uppermost Pennsylvanian) to the early Sakmarian (lower Permian) (Broutin et al. 1999). The analyses realized so far indicate a progressive replacement of wetland plants by taxa better adapted to drier environments. The number of taxa referable to the Coniferophytes (i.e. belonging to the Cordaitales and Coniferales) increased during this time interval.In order to enlarge the record of permineralized plants from the Autun Basin and improve our understanding of their diversity patterns, prospections directed in 2011 by Jean-Luc Desage, and 2015 by Georges Gand, were conducted on the northwestern side of the village of Muse. Isolated fragments representing coniferophytic woods were collected in two new localities, one along the banks of the Arroux River, the second at Les Echars. Both localities fall in Renault’s zone 3. We present here the main characters of these specimens and compare them to Cordaixylon sp., Dadoxylon rollei and Scleromedulloxylon varollense, the three taxa of coniferophytic affinities found to date in zone 3 (Broutin et al. 1999). Many specimens show large spherical structures scattered in either rays or tracheids. They measure about 100 μm wide and show heavily silicified walls. The cells surrounding them are compressed, indicating that these structures developed inside living trees. Based on wood characters alone, the new discoveries confirm that the community of coniferophytic trees was well established in the Muse formation but suggest that it may not have been highly diversified

Dryad_DATA

climatic_past, climatic_present, continental areas data, nonclimatic_clay data. We also provided four README files for each data

A Late Devonian plant assemblage from New South Wales, Australia: Diversity and specificity

International audienceGondwanan floras of Late Devonian age are poorly known. In Australia, the rare studies that have been published on Late Devonian plants are old and need reinvestigation. This paper is an account of the plant macro- and micro-remains found in the Mandowa Mudstone at Barraba, New South Wales. According to the miospores, plants are late to latest Famennian in age. The record of anatomically preserved specimens is diversified, with nine taxa assigned to the Lycopsida, Cladoxylopsida, Iridopteridales and Archaeopteridales. One specimen is referrable to the spermatophytes. Several taxa are specific to Barraba, i.e., the lycopsid genera Cymastrobus and Lycaugea, the iridopteridalean genus Keraphyton, the cladoxylopsid species Polyxylon australe, and possibly a plant represented by a large Hierogramma branch showing exarch protoxylem strands. The adpression record is dominated by axes of the cosmopolitan lycopsid genus Leptophloeum. It also includes specimens interpreted as seed plants such as a possible ovule resembling Pseudosporogonites, and two types of foliage differing by their petiole width. One of this foliage consists of delicate fronds broadly comparable to those of Cosmosperma. The closest flora from Barraba is the late Famennian–earliest Tournaisian flora of the New Albany Shale in eastern USA, suggesting floral connexion and comparable environmental conditions between Northern Gondwana and Southern Laurussia

Data from: Climate‐driven shifts in the distribution of koala browse species from the Last Interglacial to the near future

The koala's (Phascolarctos cinereus) distribution is currently restricted to eastern and south‐eastern Australia. However, fossil records dating from 70 ± 4 ka (ka = 103 years) from south‐western Australia and the Nullarbor Plain are evidence of subpopulation extinctions in the southwest at least after the Last Interglacial (128‐116 ka). We hypothesize that koala sub‐population extinctions resulted from the eastward retraction of the koala's main browse species in response to unsuitable climatic conditions. We further posit a general reduction in the distribution of main koala‐browse trees in the near future in response climate change. We modelled 60 koala‐browse species and constructed a set of correlative species distribution models for five time periods: Last Interglacial (128‐116 ka), Last Glacial Maximum (~ 23‐19 ka), Mid‐Holocene (~ 7‐5 ka), present (interpolations of observed data, representative of 1960‐1990), and 2070. We based our projections on five hindcasts and one forecast of climatic variables extracted from WorldClim based on two general circulation models (considering the most pessimistic scenario of high greenhouse‐gas emissions) and topsoil clay fraction. We used 17 dates of koala fossil specimens identified as reliable from 70 (± 4) to 535 (± 49) ka, with the last appearance of koalas at 151 ka in the southwest. The main simulated koala‐browse species were at their greatest modelled extent of suitability during the Last Glacial Maximum, with the greatest loss of koala habitat occurring between the Mid‐Holocene and the present. We predict a similar habitat loss between the present and 2070. The spatial patterns of habitat change support our hypothesis that koala extinctions in the southwest, Nullarbor Plain, and central South Australia resulted from the eastward retraction of the dominant koala‐browse species in response to long‐term climate changes. Future climate patterns will likely increase the extinction risk of koalas in their remaining eastern ranges