Subalpine forests that historically burned every 100–300 yr are expected to burn more frequently as climate warms, perhaps before trees reach reproductive maturity or produce a serotinous seedbank. Tree regeneration after short‐interval (<30‐yr) high‐severity fire will increasingly rely on seed dispersal from unburned trees, but how dispersal varies with age and structure of surrounding forest is poorly understood. We studied wind dispersal of three conifers (
Fire is an integral part of Earth’s system that links regional and global biogeochemical cycles, human activities, and ecosystems. Global estimates for biomass burning indicate that Africa is responsible for ~70% of global burned area and ~50% of fire-related carbon emissions. Previous studies have documented an overall decline in burned area in the African continent, but changes in fire patterns, such as the frequency and size of different fire categories, have not been assessed. In this study, long-term fire trends were investigated using the latest burned area data from the MODerate resolution Imaging Spectroradiometer (MODIS) and the Global Fire Emission Database (GFED4s) over Central Africa (10°E–40°E, 15°N–15°S). A 3D (latitude, longitude, time) connected-component labeling algorithm was applied to identify individual fires and their sizes. The results show a decline in burned area by 2.7–3.2 Mha yr−1(~1.3% yr−1) for the period 2003–2017, particularly in northern Central Africa. This decline was attributed to significant decreases in both fire frequency and size, particularly for large fires (>100 ha) which contribute to ~90% of the total burned area. Burned area declined in tropical savannas and grasslands but increased at the edges of the Congolese rainforest. A random forest regression model was applied to quantify the influences of climatic conditions, fuel availability, and agricultural activity on burned area changes. Overall, suppressed fuel, increased dry season length, and decreased rainfall contributed to significant declines in burned area in savannas and grasslands. At the edges of the southern Congolese rainforest, suppressed rainfall and warmer temperature were responsible for the increased burned area.
more » « less- NSF-PAR ID:
- 10191486
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Environmental Research Letters
- Volume:
- 15
- Issue:
- 9
- ISSN:
- 1748-9326
- Page Range / eLocation ID:
- Article No. 0940b8
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Picea engelmannii ,Abies lasiocarpa , andPinus contorta var.latifolia , which can be serotinous and nonserotinous) after a stand‐replacing fire that burned young (≤30 yr) and older (>100 yr)P. contorta forest in Grand Teton National Park (Wyoming, USA). We asked how propagule pressure varied with time since last fire, how seed delivery into burned forest varied with age and structure of live forest edges, what variables explained seed delivery into burned forest, and how spatial patterns of delivery across the burned area could vary with alternate patterns of surrounding live forest age. Seeds were collected in traps along 100‐m transects (n = 18) extending from live forest edges of varying age (18, 30, and >100 yr) into areas of recent (2‐yr) high‐severity fire, and along transects in live forests to measure propagule pressure. Propagule pressure was low in 18‐yr‐old stands (~8 seeds/m2) and similarly greater in 30‐ and 100‐yr‐old stands (~32 seeds/m2). Mean dispersal distance was lowest from 18‐yr‐old edges and greatest from >100‐yr‐old edges. Seed delivery into burned forest declined with increasing distance and increased with height of trees at live forest edges, and was consistently higher forP. contorta than for other conifers. Empirical dispersal kernels revealed that seed delivery from 18‐yr‐old edges was very low (≤2.4 seeds/m2) and concentrated within 10 m of the live edge, whereas seed delivery from >100‐yr‐old edges was >4.9 seeds/m2out to 80 m. When extrapolated throughout the burned landscape, estimated seed delivery was low (<49,400 seeds/ha) in >70% of areas that burned in short‐interval fire (<30 yr). As fire frequency increases, immaturity risk will be compounded in short‐interval fires because seed dispersal from surrounding young trees is limited. -
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Abstract. We present the Fire Inventory from National Center for Atmospheric Research (NCAR) version 2.5 (FINNv2.5), a fire emissions inventory that provides publicly available emissions of trace gases and aerosols for various applications, including use in global and regional atmospheric chemistry modeling. FINNv2.5 includes numerous updates to the FINN version 1 framework to better represent burned area, vegetation burned, and chemicals emitted. Major changes include the use of active fire detections from the Visible Infrared Imaging Radiometer Suite (VIIRS) at 375 m spatial resolution, which allows smaller fires to be included in the emissions processing. The calculation of burned area has been updated such that a more rigorous approach is used to aggregate fire detections, which better accounts for larger fires and enables using multiple satellite products simultaneously for emissions estimates. Fuel characterization and emissions factors have also been updated in FINNv2.5. Daily fire emissions for many trace gases and aerosols are determined for 2002–2019 (Moderate Resolution Imaging Spectroradiometer (MODIS)-only fire detections) and 2012–2019 (MODIS + VIIRS fire detections). The non-methane organic gas emissions are allocated to the species of several commonly used chemical mechanisms. We compare FINNv2.5 emissions against other widely used fire emissions inventories. The performance of FINNv2.5 emissions as inputs to a chemical transport model is assessed with satellite observations. Uncertainties in the emissions estimates remain, particularly in Africa and South America during August–October and in southeast and equatorial Asia in March and April. Recommendations for future evaluation and use are given.
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Summary Pyrogenic savannas with a tree–grassland ‘matrix’ experience frequent fires (i.e. every 1–3 yr). Aboveground responses to frequent fires have been well studied, but responses of fungal litter decomposers, which directly affect fuels, remain poorly known. We hypothesized that each fire reorganizes belowground communities and slows litter decomposition, thereby influencing savanna fuel dynamics.
In a pine savanna, we established patches near and away from pines that were either burned or unburned in that year. Within patches, we assessed fungal communities and microbial decomposition of newly deposited litter. Soil variables and plant communities were also assessed as proximate drivers of fungal communities.
Fungal communities, but not soil variables or vegetation, differed substantially between burned and unburned patches. Saprotrophic fungi dominated in unburned patches but decreased in richness and relative abundance after fire. Differences in fungal communities with fire were greater in litter than in soils, but unaffected by pine proximity. Litter decomposed more slowly in burned than in unburned patches.
Fires drive shifts between fire‐adapted and sensitive fungal taxa in pine savannas. Slower fuel decomposition in accordance with saprotroph declines should enhance fuel accumulation and could impact future fire characteristics. Thus, fire reorganization of fungal communities may enhance persistence of these fire‐adapted ecosystems.
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Abstract Aim We provide the first European‐scale geospatial training set relating the charcoal signal in surface lake sediments to fire parameters (number, intensity and area) recorded by satellite moderate resolution imaging spectroradiometer (MODIS) sensors. Our calibration is intended for quantitative reconstructions of key fire‐regime parameters by using sediment sequences of microscopic (MIC from pollen slides, particles 10–500 µm) and macroscopic charcoal (MAC from sieves, particles > 100 µm).
Location North–south and east–west transects across Europe, covering the mediterranean, temperate, alpine, boreal and steppe biomes.
Time period Lake sediments and MODIS active fire and burned area products were collected for the years 2012–2015.
Methods Cylinder sediment traps were installed in lakes to annually collect charcoal particles in sediments. We quantitatively assessed the relationships between MIC and MAC influx (particles/cm2/year) and the MODIS‐derived products to identify source areas of charcoal and the extent to which lake‐sediment charcoal is linked to fire parameters across the continent.
Results Source area of sedimentary charcoal was estimated to a 40‐km radius around sites for both MIC and MAC particles. Fires occurred in grasslands and in forests, with grass morphotypes of MAC accurately reflecting the burned fuel‐type. Despite the lack of local fires around the sites, MAC influx levels reached those reported for local fires. Both MIC and MAC showed strong and highly significant relationships with the MODIS‐derived fire parameters, as well as with climatic variation along a latitudinal temperature gradient.
Main conclusions MIC and MAC are suited to quantitatively reconstructing fire number and fire intensity on a regional scale. However, burned area may only be estimated using MAC. Local fires may be identified by using several lines of evidence, e.g. analysis of large particles (> 600 µm), magnetic susceptibility and sedimentological data. Our results offer new insights and applications to quantitatively reconstruct fires and to interpret available sedimentary charcoal records.
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That fire facilitated the late Miocene C4grassland expansion is widely suspected but poorly documented. Fire potentially tied global climate to this profound biosphere transition by serving as a regional-to-local driver of vegetation change. In modern environments, seasonal extremes in moisture amplify the occurrence of fire, disturbing forest ecosystems to create niche space for flammable grasses, which in turn provide fuel for frequent fires. On the Indian subcontinent, C4expansion was accompanied by increased seasonal extremes in rainfall (evidenced by δ18Ocarbonate), which set the stage for fuel accumulation and fire-linked clearance during wet-to-dry seasonal transitions. Here, we test the role of fire directly by examining the abundance and distribution patterns of fire-derived polycyclic aromatic hydrocarbons (PAHs) and terrestrial vegetation signatures in
n -alkane carbon isotopes from paleosol samples of the Siwalik Group (Pakistan). Two million years before the C4grassland transition, fire-derived PAH concentrations increased as conifer vegetation declined, as indicated by a decrease in retene. This early increase in molecular fire signatures suggests a transition to more fire-prone vegetation such as a C3grassland and/or dry deciduous woodland. Between 8.0 and 6.0 million years ago, fire, precipitation seasonality, and C4-grass dominance increased simultaneously (within resolution) as marked by sharp increases in fire-derived PAHs, δ18Ocarbonate, and13C enrichment inn -alkanes diagnostic of C4grasses. The strong association of evidence for fire occurrence, vegetation change, and landscape opening indicates that a dynamic fire–grassland feedback system was both a necessary precondition and a driver for grassland ecology during the first emergence of C4grasslands.
