Increased Fire Activity Research Articles

Rodent competition and fire alter patterns of mound and disk formation of western harvester ants.

Consumers exert top-down controls on dryland ecosystem function, but recent increases in fire activity may alter consumer communities in post-fire environments. Native consumers, including ants and rodents, likely have critical roles in defining post-fire plant community assembly and resilience to biological invasions. This study aimed to understand how western harvester ants (Pogonomyrmex occidentalis) that form mounds and large vegetation-free disks that significantly influence plant community structure in the Great Basin Desert respond to fire and rodent community abundance. We tested this by installing treatment plots that excluded or allowed rodents and were burned or unburned in a full factorial design. We measured ant disk and mound size and density in each experimental plot. Fire increased ant mound density by 126% compared to unburned plots. Rodent presence decreased mound density by 59%, mound diameter by 13%, and mound height by 166%. We also show an interaction where the adverse effects of rodents on ant disk density were greater in burned than in unburned plots. The results suggest that booms in rodent populations are likely to have suppressive effects on ant mound and disk formation in native shrublands but that harvester ants may be released from rodent competition with the emergence of invasive grass-fire cycles.

A Holocene fire history from Terra Nova National Park, Newfoundland, Canada: vegetation and climate change both influenced the fire regime

Fire is the largest natural disturbance factor in the boreal forest and plays a critical role in the composition, structure, and succession of stands and landscapes. The island of Newfoundland, located in eastern Canada, is subjected to a greater maritime influence, which may result in longer fire return intervals. The limited data on the fire regime does not account for interactions between fire, vegetation, and climate throughout the Holocene. We used sediment cores from Arnold’s Pond, Terra Nova National Park, which covered the last ~11,800 cal. yr BP, to investigate these interactions. We recognize 4 pollen zones and macroscopic charcoal analysis detected 45 local fire events. The 250-year mean fire return interval associated with the current vegetation is longer than a previous estimate for the park, but significantly shorter than other estimates for the island. Our mean fire return interval is within the range of fire estimates from Québec with similar vegetation. Our results suggest that the fire regime was primarily influenced by vegetation and climate. The transition to an open forest from a shrub tundra resulted in increased fire activity and fire frequency, which were likely driven by additional fuel on the landscape, but could have also been influenced by unknown climatic factors. We identified several examples of changes in the fire frequencies and/or charcoal accumulation that coincided with regional climate shifts, but we also identified a non-synchronous change. The non-synchronous shift to drier conditions resulted in a ~500-year time lag between peak Pinus strobus abundance and maximum fire frequency. Synchronous shifts in fire activity and/or fire frequency coincided with the 8200 event, Medieval Climate Anomaly and Little Ice Age. We also noted a decrease in fire frequency between 2600–1500 cal. yr BP that coincided with similar changes in the fire frequency from ~3000–1000 cal. yr BP in Québec. Our study highlights the complex interactions influencing the fire regime in our study area during the Holocene.

Climatic controls of fire activity in the red pine forests of eastern North America

Large-scale modes of climate variability influence forest fire activity and may modulate the future patterns of natural disturbances. We studied the effects of long-term changes in climate upon the fire regime in the red pine forests of eastern North America using (a) a network of sites with dendrochronological reconstructions of fire histories over 1700–1900 A.D., (b) reconstructed chronologies of climate indices (1700–1900), and (c) 20th century observational records of climate indices, local surface climate and fire (1950s-2021). We hypothesized that (H1) there are states of atmospheric circulation that are consistently associated with increased fire activity, (H2) these states mark periods of increased climatological fire hazard, and (H3) the observed decline in fire activity in the 20th century is associated with a long-term decline in the frequency of fire-prone states.At the annual scale, years with significantly higher fire activity in the reconstructed and modern fire records were consistently associated with the positive phases of the Pacific North American pattern (PNA), either independently or in combination with the positive phase of the El Niño-Southern Oscillation index (ENSO). During years with both ENSO and PNA in their positive state, the region experienced positive mid-tropospheric heights and temperature anomalies resulting in drought conditions. The fire-prone climate states identified in the reconstructed records became less frequent in 1850 but re-emerged in the 20th century. While our study did not demonstrate a direct influence of climate on the observed decrease in fire activity in the 20th century, it does reveal a clear climate signal embedded within the fire history reconstruction of the region over the past centuries. This study underscores the importance of considering large-scale climatic patterns in understanding historical fire regimes and highlights their role for future fire dynamics in the region and shaping ecological effects of future fires.

Carbon emissions from the 2023 Canadian wildfires

The 2023 Canadian forest fires have been extreme in scale and intensity with more than seven times the average annual area burned compared to the previous four decades1. Here, we quantify the carbon emissions from these fires from May to September 2023 on the basis of inverse modelling of satellite carbon monoxide observations. We find that the magnitude of the carbon emissions is 647 TgC (570–727 TgC), comparable to the annual fossil fuel emissions of large nations, with only India, China and the USA releasing more carbon per year2. We find that widespread hot–dry weather was a principal driver of fire spread, with 2023 being the warmest and driest year since at least 19803. Although temperatures were extreme relative to the historical record, climate projections indicate that these temperatures are likely to be typical during the 2050s, even under a moderate climate mitigation scenario (shared socioeconomic pathway, SSP 2–4.5)4. Such conditions are likely to drive increased fire activity and suppress carbon uptake by Canadian forests, adding to concerns about the long-term durability of these forests as a carbon sink5–8.

Nonlinear woody vegetation effects on Holocene fire activity across the world's highlands

The accelerated warming in the world's highlands has prompted significant ecological adjustments and an increase in the frequency of forest fires. Nevertheless, the correlation between woody biomass and increased fire activity in the past has received limited attention. A total of 138 charcoal and 145 pollen records were analyzed to investigate the relationship between fire and woody biomass (arboreal pollen, AP) in the world's highlands during the Holocene. The findings indicate biomass burning in the Rockies, Alps and Andes stepped increased in the early to middle Holocene but decreased in the late Holocene. The positive AP-fuel feedback was recorded in the early-middle Holocene, whereas the negative AP-fuel feedback emerged in the late Holocene, the latter were attributed to denser forests in the Rockies and intensified human activities in the Alps and Andes. Conversely, Holocene biomass burning in the Tianshan-Altai Mountains, Africa and Tibetan Plateaus exhibited overall decreasing trends with sudden decreases in the Tianshan-Altai Mountains and Tibetan Plateau and a notable increase in the African Plateau over the past millennium. The variability observed in fire regime changes in the past millennium is likely influenced by human activities. Results illustrate that fire responses to woody vegetation are nonlinear, such that the same direction of change in vegetation can elicit different fire responses depending on their components at a site. Our study offers crucial insights into the influence of woody biomass on fire dynamics in the world's highlands, providing important contextual information about how these montane systems may respond to future climate change and anthropogenic activity.

Examining the effects of climate change and human impacts on a high-resolution, late Holocene paleofire record from South Africa's winter rainfall zone

Fire is central to the Cape Floristic Region's highly biodiverse and disturbance-adapted Fynbos Biome. However, prehistoric fire regimes, their ecological consequences, and their relationships with large-scale climate drivers and human activities remain poorly understood. Here, we use a high-resolution sedimentary charcoal record from Verlorenvlei, a coastal lake situated on the west coast, to interrogate links between fire, climate, and pastoralism in the Fynbos Biome. Our record has a robust chronology supported by 24 radiocarbon dates and provides a continuous sedimentary sequence spanning the last 4200 years, documenting fire activity before and after the local arrival of pastoralists in the Verlorenvlei area ∼1500 cal years BP. Fire at Verlorenvlei over the last 4200 years is variable, with relatively low activity until ∼2000 cal years BP, after which variable but generally higher fire activity occurs until the highest period of fire activity from ∼1450 to 1800 CE (∼500–150 cal years BP). The increase in fire activity ∼2000 years ago corresponds with a shift in the diatom assemblage at Verlorenvlei from marine towards brackish and freshwater species, reflecting increased precipitation derived from a strengthening of the southern westerly winds. The peak in fire activity beginning ∼1450 CE (∼500 cal years BP), near the onset of the Little Ice Age, tracks a second diatom-inferred strengthening of the westerly winds. Other southern hemisphere and Antarctic records further corroborate this increased westerly influence after ∼2000 years. Linear regression modeling on the fire record indicates that moisture availability is the primary driver of fire at Verlorenvlei, with little evidence that human populations influenced fire. Our reconstruction suggests that fire activity at Verlorenvlei is limited by moisture availability and that wetter conditions facilitate increased vegetation (i.e., fuel) and intensified fire at this otherwise fuel-limited site. This work has implications for management and conservation decisions in response to future predictions of a warmer and drier climate along South Africa's west coast.

Are Northern Hemisphere boreal forest fires more sensitive to future aerosol mitigation than to greenhouse gas-driven warming?

Considerable interest exists in understanding how climate change affects wildfire activity. Here, we use the Community Earth System Model version 2 to show that future anthropogenic aerosol mitigation yields larger increases in fire activity in the Northern Hemisphere boreal forests, relative to a base simulation that lacks climate policy and has large increases in greenhouse gases. The enhanced fire response is related to a deeper layer of summertime soil drying, consistent with increased downwelling surface shortwave radiation and enhanced surface evapotranspiration. In contrast, soil column drying is muted under increasing greenhouse gases due to plant physiological responses to increased carbon dioxide and by enhanced melting of soil ice at a depth that increases soil liquid water. Although considerable uncertainty remains in the representation of fire processes in models, our results suggest that boreal forest fires may be more sensitive to future aerosol mitigation than to greenhouse gas-driven warming.

Two decades of fire activity over the PEEX domain: a look from space, with contribution from models and ground-based measurements

ABSTRACT It has been suggested that forest fires will become more frequent/intense with changing climate, which would increase aerosol/gas emissions into the atmosphere. A better understanding of the relations between meteorological conditions, fires, and fire emissions will help estimate the climate response via forest fires. In this study, we use ERA5 meteorological products, including temperature, precipitation, and soil moisture, to explain the frequency of forest fires and the amount of radiant energy released per time unit by burning vegetation (fire radiative power, FRP). We explore the relationships between satellite-retrieved fire products and aerosol properties (aerosol optical depth, AOD), carbon monoxide (CO), formaldehyde (HCHO), and nitrogen dioxide (NO2) concentrations over the PEEX domain, which covers different vegetation zones (e.g. croplands/grasslands, forest, arctic tundra) of Pan-Eurasia and China. We analyse the concentrations of black carbon and absorbing organic carbon using ground-based AErosol RObotic NETwork. The analysis covers the months of May to August from 2002 to 2022. We show positive temperature trends in the Northern zone (>65°N) in June and August (1.56°C and 0.64°C, respectively); all statistically significant trends for precipitation and soil moisture are negative. This can explain increased fire activity in Siberia over the recent years (2019–2022). Over the whole PEEX domain, FC and FRP trends remain insignificant or negative; a decrease in AOD may address those negative trends. We show that intra-summer variations exist for cropland/grassland fires, which occur most often in May and August, while Siberian forest fires occur more often in July and August. We show that CO concentration has been gradually decreasing in the last two decades in May and June. CO trends are negative in May, June, and over summer for all regions, in July in Europe, China, the Southern zone (<55°N), and the PEEX domain. HCHO trends are not significant in all regions. NO2 trends are positive in May and negative in June in all zones. We calculated total column enhancement ratios for satellite observations influenced by wildfires. A common feature has been recognized with measurements and ratios utilized in SILAM (System for Integrated Modelling of Atmospheric Composition): AOD(or PM):CO and AOD(or PM):HCHO ratios for grass are clearly lower than for shrubs, opposite for AOD:NO2. We showed that emission ratios are increasing towards South and are 2–3 times higher for high (>0.5) AOD. Using a 21-year satellite record of the AOD and CO, an 18-year record of NO2, and a 16-year record of HCHO, we created background products of those variables over the PEEX domain. In the regions with low anthropogenic activity and conditions where long-range transport is not happening, anomalies in AOD, CO, and HCHO over biomass-burning areas may be assigned directly to the wildfire emissions.

The time since land-use transition drives changes in fire activity in the Amazon-Cerrado region

AbstractDeforestation and climate change are expected to alter fire regimes along the Cerrado-Amazon transition, one of the world’s most active agricultural frontiers. Here we tested the hypothesis that the time since land-use transition (age of frontier) and agricultural intensification also drive changes in the region’s fire regimes by reducing fire probability in both drought and non-drought years. We modeled fire probability as a function of the time since land-use transitions based on MapBiomas Project datasets from 1986 to 2020. We find that, while burned area declined as pasturelands aged and croplands advanced, deforestation abruptly increased fire activity before (Amazon: 4 years; Cerrado: 3 years) and after (Amazon: 8 years; Cerrado: 7 years) land clearing for pasture, especially in the Amazon. Additionally, the combination of ignition risk, drought, and air-dryness increased the likelihood of large extents of burned areas associated with deforestation. Incorporating frontier age as a proxy for governance in fire modeling is crucial, given the ecological implications of changing fire regimes despite declining rates of fire probability. Most importantly, protecting against deforestation and preserving native vegetation are vital.

Enhanced future vegetation growth with elevated carbon dioxide concentrations could increase fire activity

Many regions of the planet have experienced an increase in fire activity in recent decades. Although such increases are consistent with warming and drying under continued climate change, the driving mechanisms remain uncertain. Here, we investigate the effects of increasing atmospheric carbon dioxide concentrations on future fire activity using seven Earth system models. Centered on the time of carbon dioxide doubling, the multi-model mean percent change in fire carbon emissions is 66.4 ± 38.8% (versus 1850 carbon dioxide concentrations, under fixed 1850 land-use conditions). A substantial increase is associated with enhanced vegetation growth due to carbon dioxide biogeochemical impacts at 60.1 ± 46.9%. In contrast, carbon dioxide radiative impacts, including warming and drying, yield a negligible response of fire carbon emissions at 1.7 ± 9.4%. Although model representation of fire processes remains uncertain, our results show the importance of vegetation dynamics to future increases in fire activity under increasing carbon dioxide, with potentially important policy implications.

Holocene environmental conditions in the Eastern Sayan foothills according to a comprehensive paleoecological study of the Sosnovka mire

This research is devoted to the study of the combined vegetation dynamics, hydroclimatic conditions and fires in the foothills of the Eastern Sayan northwestern macroslope in the Holocene. The paleoecological reconstruction results obtained on the basis of AMS-dating, pollen, macrofossils, charcoal and malacofaunal analysis of peat deposits of the Sosnovka mire (right bank of the Yenisei River), covering the last ≈11,000 calendar years are presented. It was established that the process of waterlogging began at ≈9700-8500 cal yr BP at the optimum heat and moisture, when the waterless valley were covered with a mixed siberian pine-spruce-fir forest, with the maximum participation of spruce and fir. According to the study of Sosnovka mire sediments the reaction of local and regional communities to the Holocene Thermal Maximum (7500-6000 years ago) was clearly manifested. The participation of spruce and fir in the trees layer stand decreased sharply. The increase in fire activity was noted, which contributed to the lightening of forests and greater development of the shrub layer. During this interval, the process of swamping actively began in the floodplains of rivers with a drainage area in the western part of the Eastern Sayan. Based on the results of charcoal analysis six stages of increased fire activity were identified: I – about 10,000-8,800 cal yr BP, II – 7500-7200, III – 5600-5000, IV – 3700-3000, V – 2100-1800, VI – 800 cal yr BP - until now.

Peat deposits for studying the Holocene fire regime in the example of Kansk forest-steppe mires

The results of Holocene fires history reconstruction in the Kansk forest-steppe Kranoyarsk Territory are presented using the example the Kuskun mire (Esaulovka river basin) and Rybnoye mire (Rybnaya river basin). The complex of paleoecological methods (analysis of macrofossils in peat and charcoal analysis) are using. The stages of increased fire activity were established at 4000-3000 and 1500-500 cal yr BP. These time intervals coincide with a decrease in moisture during the subboreal xerothermic maximum and a short dry period 1400-1300 cal. yr BP subsequently replaced by the Medieval Warm Period. When comparing the results obtained, a coincidence of long fire episodes with a change in local vegetation was revealed.

Cellular Mechanisms of Cognitive Enhancement: The InVivo Modulation of the Firing Activity and the Responsiveness of Rat Hippocampal Neurons by Memantine and Alpha7 Nicotinic Acetylcholine Receptor Ligands.

Promising new pharmacological strategies for the enhancement of cognition target either nicotinic acetylcholine receptors (nAChR) or N-methyl-D-aspartate receptors (NMDAR). There is also an increasing interest in low-dose combination therapies co-targeting the above neurotransmitter systems to reach greater efficacy over the monotreatments and to reduce possible side effects of high-dose monotreatments. In the present study, we assessed modulatory effects of the α7 nAChR-selective agonist PHA-543613 (PHA), a novel α7 nAChR positive allosteric modulator compound (CompoundX) and the NMDAR antagonist memantine on the invivo firing activity of CA1 pyramidal neurons in the rat hippocampus. Three different test conditions were applied: spontaneous firing activity, NMDA-evoked firing activity and ACh-evoked firing activity. Results showed that high but not low doses of memantine decreased NMDA-evoked firing activity, and low doses increased the spontaneous and ACh-evoked firing activity. Systemically applied PHA robustly potentiated ACh-evoked firing activity with having no effect on NMDA-evoked activity. In addition, CompoundX increased both NMDA- and ACh-evoked firing activity, having no effects on spontaneous firing of the neurons. A combination of low doses of memantine and PHA increased firing activity in all test conditions and similar effects were observed with memantine and CompoundX but without spontaneous firing activity increasing effects. Our present results demonstrate that α7 nAChR agents beneficially interact with Alzheimer's disease medication memantine. Moreover, positive allosteric modulators potentiate memantine effects on the right time and the right place without affecting spontaneous firing activity. All these data confirm previous behavioral evidence for the viability of combination therapies for cognitive enhancement.

Fire ecology in marine systems

Wildfire byproducts enter into the oceans via terrestrial and atmospheric routes. They pose a challenge to the sustainability of marine ecosystems, especially under the current increase in fire activity. Research is needed to unravel the dynamics between wildfires and marine life, and the oceans’ potential to mitigate wildfire emissions.

Effects of pre-gestational exposure to the stressors and perinatal bupropion administration on the firing activity of serotonergic neurons and anxiety-like behavior in rats

Exposure by women to stressors before pregnancy increases their risk of contracting prenatal depression, a condition which typically may require antidepressant treatment. And even though such perinatal antidepressant treatment is generally considered to be safe. For the mother, its effects on the development and functioning of the offspring`s brain remain unknown. In this study, we aimed to investigate the effects of pregestational chronic unpredictable stress (CUS) and perinatal bupropion on the anxiety behavior and firing activity of the dorsal raphe nucleus (DRN) serotonin (5-HT) neurons. Female rats underwent CUS for three weeks before mating. Bupropion was administered to them from gestation day ten until their offspring were weaned. Behavioral (elevated plus maze or EPM test) and neurophysiological (single-unit in vivo electrophysiology) assessments were performed on offspring who reached the age of 48–56 days. We found that maternal CUS and perinatal bupropion, as separate factors on their own, did not change offspring behavior. There was, however, an interaction between their effects on the number of entries to the open arms and time spent in the intersection: maternal CUS tended to decrease these values, and perinatal bupropion tended to diminish CUS effect. Maternal CUS increased the firing activity of 5-HT neurons in males, but not females. Perinatal bupropion did not alter the firing activity of 5-HT neurons but tended to potentiate the maternal CUS-induced increase in 5-HT neuronal firing activity. The CUS-induced increase in firing activity of 5-HT neurons might be a compensatory mechanism that diminishes the negative effects of maternal stress. Perinatal bupropion does not alter the offspring`s anxiety and firing activity of 5-HT, but it does intervene in the effects of maternal stress.

Soil fertility shapes fire activity across Mediterranean‐type climate regions

AbstractAimTo quantify the role of soil fertility in the spatial variability of fire activity and to identify the mechanisms that drive this variability.LocationThe five Mediterranean‐type climate regions of the world.Time Period2002–present.Major Taxa StudiedTerrestrial plants.MethodsWe compiled remotely sensed data on fire activity, climate, net primary productivity and chemical soil properties for bioclimatically homogeneous zones within the five Mediterranean‐type climate regions of the world. Putative direct and indirect effects of the environmental variables on fire activity were evaluated through structural equation modelling.ResultsFire activity increased with net primary productivity, as expected for ecosystems with fuel‐limited fire regimes. Soil acidity and the concentration of exchangeable aluminium also increased fire activity, supporting the idea that low fertility promotes plant characteristics that favour fire initiation and spread.Main ConclusionsOur research supports a positive relationship between wildfires and low soil fertility in Mediterranean‐type climate regions across the globe. Therefore, soil fertility should be incorporated into models predicting future fires in a warming world.

Patterns and drivers of early conifer regeneration following stand-replacing wildfire in Pacific Northwest (USA) temperate maritime forests

Tree regeneration is a critical mechanism of forest resilience to stand-replacing wildfire (i.e., where fire results in >90 % tree mortality), and post-fire regeneration is a concern worldwide as the climate becomes warmer. Although post-fire tree regeneration has been relatively well-studied in fire-prone forests across western North America, it is less understood in fire regimes characterized by large patches of stand-replacing fire at long intervals, such as the nominally infrequent, high-severity fire regimes of the western Cascades of Washington and northern Oregon, USA (northwestern Cascadia) where some of world’s highest-biomass forests reside. Recent wildfire activity (2015–2020) in northwestern Cascadia provides a unique opportunity to build understanding of the mechanisms underpinning forest resilience to fire, with implications for forest management and the myriad socio-ecological values associated with these landscapes. Here, we asked: how is post-fire conifer regeneration across northwestern Cascadia affected by pre-fire stand age, burn-patch size, and topo-climatic conditions? We established 39 1-ha long-term monitoring plots across four recent wildfires in northwestern Cascadia to measure post-fire conifer abundance and species composition. We used generalized linear models to test how rates of conifer regeneration (seedlings ha−1 yr−1 of all heights) and establishment (seedlings ha−1 yr−1 with heights >10 cm) respond to differences in pre-fire stand age/seral stage (young, mid-seral, late-seral), distance to the nearest live seed source, and post-fire topo-climate setting. In general, initial post-fire seedling densities suggest tree regeneration is abundant following stand-replacing fire in most areas across the region. For example, at 3–5 years post-fire, established seedlings were present in 100 % of plots, and regeneration and establishment levels exceeded state forest practices minimum density thresholds (470 seedlings ha−1) in 82.1 % and 64.1 % of plots, respectively. Post-fire conifer regeneration and tree species richness were greater when pre-fire stand age was older, and was more dominated by shade tolerant species than when pre-fire stand age was younger. Regeneration decreased with farther distances to the nearest live seed source, though seedlings were still moderately abundant at distances as far as 400 m from edges of high-severity patches. Conifer establishment was greater in areas characterized by cooler and wetter macrosite (e.g., greater post-fire precipitation) and microsite (e.g., greater bryophyte ground cover) conditions. By providing information on the drivers and conditions in which land managers can expect natural regeneration to occur or not, our findings are directly relevant to pre- and post-fire forest management objectives under future climate and increased fire activity in systems structured in part by infrequent and severe wildfires.

Fire‐regime variability and ecosystem resilience over four millennia in a Rocky Mountain subalpine watershed

Abstract Wildfires strongly influence forest ecosystem processes, including carbon and nutrient cycling, and vegetation dynamics. As fire activity increases under changing climate conditions, the ecological and biogeochemical resilience of many forest ecosystems remains unknown. To investigate the resilience of forest ecosystems to changing climate and wildfire activity over decades to millennia, we developed a 4800‐year high‐resolution lake‐sediment record from Silver Lake, Montana, USA (47.360° N, 115.566° W). Charcoal particles, pollen grains, element concentrations and stable isotopes of C and N serve as proxies of past changes in fire, vegetation and ecosystem processes such as nitrogen cycling and soil erosion, within a small subalpine forest watershed. A published lake‐level history from Silver Lake provides a local record of palaeohydrology. A trend towards increased effective moisture over the late Holocene coincided with a distinct shift in the pollen assemblage c. 1900 yr BP, resulting from increased subalpine conifer abundance. Fire activity, inferred from peaks in macroscopic charcoal, decreased significantly after 1900 yr BP, from one fire event every 126 yr (83–184 yr, 95% CI) from 4800 to 1900 yr BP, to one event every 223 yr (175–280 yr) from 1900 yr BP to present. Across the record, individual fire events were followed by two distinct decadal‐scale biogeochemical responses, reflecting differences in ecosystem impacts of fires on watershed processes. These distinct biogeochemical responses were interpreted as reflecting fire severity, highlighting (i) erosion, likely from large or high‐severity fires, and (ii) nutrient transfers and enhanced within‐lake productivity, likely from lower severity or patchier fires. Biogeochemical and vegetation proxies returned to pre‐fire values within decades regardless of the nature of fire effects. Synthesis. Palaeorecords of fire and ecosystem responses provide a novel view revealing past variability in fire effects, analogous to spatial variability in fire severity observed within contemporary wildfires. Overall, the palaeorecord highlights ecosystem resilience to fire across long‐term variability in climate and fire activity. Higher fire frequencies in past millennia relative to the 20th and 21st century suggest that northern Rocky Mountain subalpine ecosystems could remain resilient to future increases in fire activity, provided continued ecosystem recovery within decades.

Late Quaternary climatic inferences from southern Patagonia (∼53°S): A holistic palaeoecological approach to tracking the behaviour of the southern westerly winds

The glacial and vegetation patterns of Patagonia are strongly correlated to the behaviour of the Southern westerly winds (SWWs) with palaeoenvironmental evidence for the behaviour of the SWWs interpreted as past changes in southern hemisphere climate and ocean currents. To fully define shifts in the position and intensity of the SWWs palaeoenvironmental data sets must be generated from climate sensitive proxies with sites located in regions that are responsive to changes in effective moisture. Here we present a c. 15,700 yr-old record from a peat bog at Punta Arenas (53°09′S) which was analysed for pollen, pollen preservation, charcoal and organic content to reconstruct changes in the surrounding vegetation, fire history and mire surface wetness. The peat bog lies in a closed basin and so environmental changes likely reflect changes in effective moisture primarily driven by fluctuations in precipitation. During the Late glacial the landscape was virtually treeless and dominated by cold-tolerant steppe/tundra vegetation. This was followed by substantial vegetation changes as Nothofagus woodland expanded and the local site transitioned from a small lake to a fen and later a raised mire. The Early and Mid-Holocene (11,600–6000 cal a BP) was marked by a period of sustained drier conditions evidenced by reduced pollen preservation and increased fire activity. After c. 4600 cal a BP there was a shift to increased effective moisture superimposed with higher magnitude and higher frequency changes in precipitation. The palaeoenvironmental record presented here is used to better define the nature and timing of latitudinal shifts in the position of the SWWs. Careful interpretation of the Nothofagus pollen signal is required as during drier periods small increases in humidity can drive large woodland responses in the pollen record while during periods of higher humidity the woodland may appear to be unresponsive to climatic changes.

Long‐and short‐term vegetation change and inferred climate dynamics and anthropogenic activity in the central Cerrado during the Holocene

ABSTRACTA paleoecologic analysis of pollen, macrocharcoal and trace elements from a lacustrine sediment core located at Lake Feia, central Cerrado (Goiás State, Brazil), was used to evaluate the relationship between vegetation, fire and climate during the Holocene. The development of cerrado vegetation appears to have begun 6000 years ago, initially with the establishment of an open cerrado, followed from 4800 cal a bp by a change to a woody cerrado driven by an increase in summer insolation. The increases in precipitation levels in the central Cerrado during the last 5000 years are related to the increased influence of the Amazon in central Brazil, which has facilitated biomass burning and anthropogenic activities in the region of Lake Feia. Multi‐centennial‐scale changes in water level‐related and gallery forest pollen assemblages indicate three main dry episodes, at 3440–2760, 2700–1690 and 1330–1150 cal a bp, linked to regional shifts between northern and southern South American summer monsoon boundaries. The presence of low continuous fire activity does not appear to have affected vegetation recovery, whereas two intervals with increased fire activity, at ~3300 and ~1300 cal a bp, indicated a slower recovery.