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Fire Scars (fire + scar)

Distribution by Scientific Domains

Life Sciences	57%

Selected Abstracts

Fire Scars on Amazonian Trees: Exploring the Cryptic Fire History of the Ilha de Maracá

BIOTROPICA, Issue 4 2010
Jos Barlow
ABSTRACT The presence of charcoal in the soils and fire scars on 8.2 percent of tree stems strongly suggest that one of the best studied Amazonian research localities (the Ilha de Maracá in Roraima, Brazil) has burned. The patterns and images of fire scars that we present here could help researchers explore the burn history of other tropical forests, which has important implications for interpreting their present-day ecology. [source]

Postfire response of North American boreal forest net primary productivity analyzed with satellite observations

GLOBAL CHANGE BIOLOGY, Issue 8 2003
Jeffrey A. Hicke
Abstract Fire is a major disturbance in the boreal forest, and has been shown to release significant amounts of carbon (C) to the atmosphere through combustion. However, less is known about the effects on ecosystems following fire, which include reduced productivity and changes in decomposition in the decade immediately following the disturbance. In this study, we assessed the impact of fire on net primary productivity (NPP) in the North American boreal forest using a 17-year record of satellite NDVI observations at 8- km spatial resolution together with a light-use efficiency model. We identified 61 fire scars in the satellite observations using digitized fire burn perimeters from a database of large fires. We studied the postfire response of NPP by analyzing the most impacted pixel within each burned area. NPP decreased in the year following the fire by 60,260 g C m,2 yr,1 (30,80%). By comparing pre- and postfire observations, we estimated a mean NPP recovery period for boreal forests of about 9 years, with substantial variability among fires. We incorporated this behavior into a carbon cycle model simulation to demonstrate these effects on net ecosystem production. The disturbance resulted in a release of C to the atmosphere during the first 8 years, followed by a small, but long-lived, sink lasting 150 years. Postfire net emissions were three times as large as from a model run without changing NPP. However, only small differences in the C cycle occurred between runs after 8 years due to the rapid recovery of NPP. We conclude by discussing the effects of fire on the long-term continental trends in satellite NDVI observed across boreal North America during the 1980s and 1990s. [source]

Influences of climate on fire regimes in montane forests of north-western Mexico

JOURNAL OF BIOGEOGRAPHY, Issue 8 2008
Carl N. Skinner
Abstract Aim, To identify the influence of interannual and interdecadal climate variation on the occurrence and extent of fires in montane conifer forests of north-western Mexico. Location, This study was conducted in Jeffrey pine (Pinus jeffreyi Grev. & Balf.)-dominated mixed-conifer forests in the central and northern plateau of the Sierra San Pedro Mártir, Baja California, Mexico. Methods, Fire occurrence was reconstructed for 12 dispersed sites for a 290-year period (1700,1990) from cross-dated fire-scarred samples extracted from live trees, snags and logs. Superposed epoch analysis was used to examine the relationships of tree-ring reconstructions of drought, the El Niño/Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) with fire occurrence and extent. Results, Years with no recorded fire scars were wetter than average. In contrast, years of widespread fires were dry and associated with phase changes of the PDO, usually from positive (warm) to negative (cold). The influence of the PDO was most evident during the La Niña phase of the ENSO. Widespread fires were also associated with warm/wet conditions 5 years before the fire. We hypothesize that the 5-year lag between warm/wet conditions and widespread fires may be associated with the time necessary to build up sufficient quantity and continuity of needle litter to support widespread fires. Two periods of unusually high fire activity (1770,1800 and 1920,1950) were each followed by several decades of unusually low fire activity. The switch in each case was associated with strong phase changes in both PDO and ENSO. Main conclusions, Climate strongly influences fire regimes in the mountains of north-western Mexico. Wet/warm years are associated with little fire activity. However, these years may contribute to subsequent fire years by encouraging the production of sufficient needle litter to support more widespread fires that occur in dry/cool years. [source]

Ecological effects of changes in fire regimes in Pinus ponderosa ecosystems in the Colorado Front Range

JOURNAL OF VEGETATION SCIENCE, Issue 6 2006
Rosemary L. Sherriff
Abstract Question: What is the relative importance of low- and high-severity fires in shaping forest structure across the range of Pinus ponderosa in northern Colorado? Location: Colorado Front Range, USA. Methods: To assess severities of historic fires, 24 sites were sampled across an elevation range of 1800 to 2800 m for fire scars, tree establishment dates, tree mortality, and changes in tree-ring growth. Results: Below 1950 m, the high number of fire scars, scarcity of large post-fire cohorts, and lack of synchronous tree mortality or growth releases, indicate that historic fires were of low severity. In contrast, above 2200 m, fire severity was greater but frequency of widespread fires was substantially less. At 18 sites above 1950 m, 34 to 80% of the live trees date from establishment associated with the last moderate- to high-severity fire. In these 18 sites, only 2 to 52% of the living trees pre-date these fires suggesting that fire severities prior to any effects of fire suppression were sufficient to kill many trees. Conclusions: These findings for the P. ponderosa zone above ca. 2200 m (i.e. most of the zone) contradict the widespread perception that fire exclusion, at least at the stand scale of tens to hundreds of hectares, has resulted in unnaturally high stand densities or in an atypical abundance of shade-tolerant species. At relatively mesic sites (e.g. higher elevation, north-facing), the historic fire regime consisted of a variable-severity regime, but forest structure was shaped primarily by severe fires rather than by surface fires. [source]

A long-term record of Quercus decline, logging and fires in a southern Swedish Fagus - Picea forest

JOURNAL OF VEGETATION SCIENCE, Issue 6 2002
Mats Niklasson
Tutin et al. (1964,1976) Abstract. We reconstructed forest development and disturbance events (fire and logging) during the last 1000 yr with tree-ring data, pollen and charcoal analysis from a semi-natural Fagus sylvatica-Picea abies forest (ca. 1 km2) in the hemiboreal zone. According to pollen analysis, Quercus robur together with Pinus sylvestris was abundant in the forest until the turn of the 18th/19th centuries when these species disappeared completely (Quercus) or nearly completely (Pinus) and were replaced by Fagus and Picea. The disappearance of Quercus was corroborated by the remarkable discovery of a single Quercus stump that had been cut in the 18th century and had become overgrown and preserved by a very old Picea. In total 11 fires were dated from 1555 to 1748 from fire scars in several Pinus stumps cut 100 - 200 yr ago. Since the last fire in 1748, no Quercus or Pinus have regenerated in the core of the reserve apart from single pines in neighbouring managed forest (80 yr ago). During the period of documented fires Fagus was protected from fires in a refuge made up of large boulders. Picea colonized the region at the time when the fires ceased 250 yr ago. We hypothesize that most of the fires were probably of human origin because of their patchiness and high frequency compared to the natural background levels of lightning ignitions in the region. On a 300-yr time scale, logging and fire suppression seem to strongly overshadow the effect of climate change on forest composition and dynamics. [source]

Two proxy records revealing the late Holocene fire history at a site on the central coast of New South Wales, Australia

AUSTRAL ECOLOGY, Issue 6 2006
SCOTT.
Abstract: The local fire history of a coastal swamp catchment in New South Wales was reconstructed using two proxy records of fire: sedimentary macroscopic charcoal and fire-scar analyses of Xanthorrhoea johnsonii. The charcoal analysis provided a record of fire activity spanning the last 2800 years, while the Xanthorrhoea record covered the last approx. 300 years. The ability of each method to accurately record fire events was verified by cross referencing against the recent (post 1968) historic fire record. Fire history was then extrapolated beyond the historic record, to reveal an unprecedented level of fire activity in the last 35 years, which coincides with increased human activity in the area. In the prehistoric period charcoal and fire scars are comparatively rare, which is most parsimoniously ascribed to little fire activity, but perhaps represents skilful fire manipulation, as is often attributed to Aboriginal people. The comparatively minor fluctuations in macroscopic charcoal during the prehistoric period were approximately coeval with previous evidence of late Holocene environmental change in south-eastern Australia, suggesting that fire frequency at the site responded to climatic variability. The longer temporal perspective of this palaeoenvironmental approach provides information for the contemporary management of fire in this conservation reserve. [source]