Holocene fire occurrence and alluvial responses at the leading edge of pinyon–juniper migration in the Northern Great Basin,USA     

Kerrie N. Weppner  Jennifer L. Pierce  Julio L. Betancourt 《Quaternary Research》2013

Fire and vegetation records at the City of Rocks National Reserve (CIRO), south-central Idaho, display the interaction of changing climate, fire and vegetation along the migrating front of single-leaf pinyon (Pinus monophylla) and Utah juniper (Juniperus osteosperma). Radiocarbon dating of alluvial charcoal reconstructed local fire occurrence and geomorphic response, and fossil woodrat (Neotoma) middens revealed pinyon and juniper arrivals. Fire peaks occurred ~ 10,700–9500, 7200–6700, 2400–2000, 850–700, and 550–400 cal yr BP, whereas ~ 9500–7200, 6700–4700 and ~ 1500–1000 cal yr BP are fire-free. Wetter climates and denser vegetation fueled episodic fires and debris flows during the early and late Holocene, whereas drier climates and reduced vegetation caused frequent sheetflooding during the mid-Holocene. Increased fires during the wetter and more variable late Holocene suggest variable climate and adequate fuels augment fires at CIRO. Utah juniper and single-leaf pinyon colonized CIRO by 3800 and 2800 cal yr BP, respectively, though pinyon did not expand broadly until ~ 700 cal yr BP. Increased fire-related deposition coincided with regional droughts and pinyon infilling ~ 850–700 and 550–400 cal yr BP. Early and late Holocene vegetation change probably played a major role in accelerated fire activity, which may be sustained into the future due to pinyon–juniper densification and cheatgrass invasion.  相似文献   

Multiscale mapping of burn area and severity using multisensor satellite data and spatial autocorrelation analysis     

《International Journal of Applied Earth Observation and Geoinformation》2013

Traditional methods of recording fire burned areas and fire severity involve expensive and time-consuming field surveys. Available remote sensing technologies may allow us to develop standardized burn-severity maps for evaluating fire effects and addressing post fire management activities. This paper focuses on multiscale characterization of fire severity using multisensor satellite data. To this aim, both MODIS (Moderate Resolution Imaging Spectroradiometer) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) data have been processed using geo-statistic analyses to capture pattern features of burned areas.Even if in last decades different authors tried to integrate geo-statistics and remote sensing image processing, methods used since now are only variograms, semivariograms and kriging. In this paper, we propose an approach based on the use of spatial indicators of global and local autocorrelation. Spatial autocorrelation statistics, such as Moran's I and Getis–Ord Local Gi index, were used to measure and analyze dependency degree among spectral features of burned areas. This approach enables the characterization of pattern features of a burned area and improves the estimation of fire severity.  相似文献   

Seedbank responses to spring and fall prescribed fire in mountain big sagebrush ecosystems of differing ecological condition at Lava Beds National Monument,California     

《Journal of Arid Environments》2013

Land use change in the American West has altered sagebrush dominated ecosystems, facilitating exotic grass invasion, increased woody species, altered fire regimes, and native species losses. Restoring fire regimes may be integral to the restoration of sagebrush ecosystems. However, little is known about how the timing of prescribed fire differentially impacts the soil seedbank. Further, sites of different ecological condition may variably respond to fire. To address these uncertainties, we quantified germination of invasive cheatgrass and plant functional groups (native dicots, exotic dicots, native bunchgrasses, and native shrubs) following spring and fall prescribed burns in three mountain big sagebrush communities at Lava Beds National Monument, California. At cheatgrass and native-dominated sites, there were fewer cheatgrass seedlings (91% and 86%, respectively) immediately following spring fire than in unburned controls, but this reduction did not persist one year later. Fall burns did not significantly impact cheatgrass or exotic dicot germination. At a native dominated site, native dicots increased one year following spring (1620%) and fall burns (67%), suggesting adaptation to a natural fire regime. This research shows that the prefire condition of an ecosystem greatly influences the postfire germination response, and that fire-adapted ecosystems can benefit from the natural disturbance regime.  相似文献   

Reconstructing a cultural fire regime in the Pennsylvania Anthracite Region     

Thomas Saladyga 《自然地理学》2013,34(5):404-422

Abstract

Fire history reconstructions provide fire managers with valuable information regarding historical fire regime dynamics. Yet, in the Central Hardwood Forest Region (CHF), there is an absence of dendroecological studies where frequent wildfires have persisted into the twenty-first century. This study presents the first documented tree-ring reconstruction of fire history in the Pennsylvania anthracite coal-producing region. An approximately 150-year fire chronology was developed from fire-scarred pitch pine (Pinus rigida) and sassafras (Sassafras albidum) collected on Spring Mountain in Schuylkill County. Principal component analysis and k-means cluster analysis were used to identify four fire regime clusters based on interacting fire and non-fire parameters. Results indicate that fires occurred under a variety of moisture conditions and that a mid-twentieth century increase in fire activity on Spring Mountain was associated with the collapse of the regional anthracite industry and possibly amplified by the 1960s drought. Fires continue to burn on Spring Mountain in the twenty-first century, contrary to the dominant pattern of fire exclusion across the CHF. Future research needs are highlighted regarding historical fire regime dynamics and cultural ties to landscape burning in the Pennsylvania Anthracite Region.  相似文献   

Mapping flood pressure points: assessing vulnerability of the UK Fire Service to flooding     

Dorian Speakman 《Natural Hazards》2008,44(1):111-127

A vulnerability index for the Fire Service in the UK has been designed to identify vulnerable locations during episodes of severe floods. Taking recent case studies with the UK Fire Service, the patterns of vulnerability, in terms of demand on time and resources, can be explained by investigating the environmental causes and their interaction with the adaptive capacity of the response agencies.

Dorian SpeakmanEmail:

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Changing fire regimes in the temperate rainforest region of southern Chile over the last 16,000 yr     

Ana M. Abarzúa  Patricio I. Moreno 《Quaternary Research》2008,69(1):62-71

A high-resolution macroscopic charcoal record from Lago Melli (42°46′S, 73°33′W) documents the occurrence of forest fires in the lowlands of Isla Grande de Chiloé, southern Chile, over the last 16,000 yr. Our data suggest that fire activity in this region was largely modulated by the position/intensity of the southern westerlies at multi-millennial time scales. Fire activity was infrequent or absent between 16,000-11,000 and 8500-7000 cal yr BP and was maximal between ∼ 11,000-8500 and 3000-0 cal yr BP. A mosaic of Valdivian/North Patagonian rainforest species started at ∼ 6000 cal yr BP, along with a moderate increase in fire activity which intensified subsequently at 3000 cal yr BP. The modern transition between these forest communities and the occurrence of fires are largely controlled by summer moisture stress and variability, suggesting the onset of high-frequency variability in summer precipitation regimes starting at ∼ 5500 cal yr BP. Because negative anomalies in summer precipitation in this region are teleconnected with modern El Niño events, we propose that the onset of El Niño-like variability at ∼ 5700-6200 cal yr BP led to a reshuffling of rainforest communities in the lowlands of Isla Grande de Chiloé and an increase in fire activity.  相似文献   

8000 yr of black carbon accumulation in a colluvial soil from NW Spain   总被引：1，自引：0，他引：1  

Joeri Kaal  Antonio Martínez-Cortizas  Felipe Criado Boado 《Quaternary Research》2008,69(1):56-61

Analytical pyrolysis-GC/MS and solid-state ¹³C NMR (nuclear magnetic resonance) were applied to the NaOH-extractable organic matter fraction of a colluvial soil from Galicia (NW Spain) that represents more than 8500 yr of accumulation. While molecular indicators of vegetation change were looked for, it seemed likely that any such signal was disturbed by the intense fire regime of the area. This conclusion was drawn from (1) the presence of three charcoal layers, (2) the high proportion of aryl C in NMR spectra (non-quantitative) and (3) the prevalence of benzenes and polycyclic aromatic hydrocarbons (PAHs) in the chromatograms (38 ± 6% of total identified peak area), also in charcoal-poor samples. If this conclusion is accurate, the area has been subjected to burning episodes for at least 8000 yr. Additionally, the results indicate that biomass burning residues (black carbon; BC) may become NaOH extractable after long periods of degradation in mineral soil. These results add to our knowledge of the long-term fate of BC in soil, which is a potential agent in the global C cycle.  相似文献   

Drought, vegetation change, and human history on Rapa Nui (Isla de Pascua, Easter Island)     

Daniel Mann  James Edwards  Warren Beck  Michele Mass  John Loret 《Quaternary Research》2008,69(1):16-28

Stratigraphic records from lake sediment cores and slope deposits on Rapa Nui document prehistoric human impacts and natural environmental changes. A hiatus in sedimentation in Rano Raraku suggests that this lake basin dried out sometime after 4090-4410 cal yr BP and refilled only decades to centuries before AD 1180-1290. Widespread ecosystem changes caused by forest clearance by Polynesian farmers began shortly after the end of this drought. Terrestrial sections show a chronology of burning and soil erosion similar to the lake cores. Although changing sediment types and shifts in the pollen rain suggest that droughts occurred earlier in the Holocene, as yet there is no evidence for droughts occurring after AD 1180-1290. The timing of the agricultural colonization of Rapa Nui now seems well established at ca. AD 1200 and it was accompanied by rapid deforestation that was probably exacerbated by the island's small size, its droughty climate, and the rarity of primeval fires. Detailed records of a large interval of Rapa Nui's ecological history remain elusive due to the drought hiatus in the Rano Raraku sediment record. We find no evidence for a “rat outbreak impact” on Rapa Nui's vegetation preceding anthropogenic forest clearance.  相似文献   

Late Holocene high resolution palaeoclimatic reconstruction inferred from Sebkha Mhabeul, southeast Tunisia   总被引：1，自引：0，他引：1  

L. Marquer  S. Pomel  E. Schulz  E. Van Campo 《Quaternary Research》2008,70(2):240-250

Relations between climate change and landscape evolution during the last two millennia in southeastern coastal Tunisia have been documented using high-resolution reconstruction of flood history and fire activity in the Sebkha Mhabeul core. The age model, based on tephrochronology, indicates that the core extends from Roman to modern times and encompasses the well-defined climatic periods of the last two millennia. This record provides a first palaeoecological/palaeoclimatic high resolution reconstruction in North Africa using a cross-disciplinary approach with both physical (grey-scale intensity, quartz particles) and biological (charcoal and pollen) indicators. The flood history shows four wet/dry cycles (ca. AD 550-950, 950-1300, 1300-1570 and 1570-1870) of different duration. Major hydrological instabilities are concentrated during the Medieval Climate Anomalies and the early Little Ice Age, between AD 1000 and 1550. Direct correlation between climate and fire cannot be established suggesting that the fire history of the Sebkha environment is mainly influenced by human activity. This study demonstrates the great value of sebkhas as palaeoenvironmental archives.  相似文献   

Late Holocene fire impact and post-fire regeneration from the Bereket basin, Taurus Mountains, southwest Turkey     

David Kaniewski  Etienne Paulissen  Marc Waelkens 《Quaternary Research》2008,70(2):228-239

The 800 cm long sequence from the Bereket provides the first detailed fire history in the western Taurus Mountains for the last three millennia. The main disturbances occurred during the Bey?ehir Occupation Phase (BO Phase), a period of intensive polyculture and dated at Bereket from ca. 2230 to 1550 cal yr BP. Four phases of local and extra-local fire periods have been recorded at 2320-2240, 1985-1970, 1865-1820 cal yr BP and post-AD 1950. The fire history established for the BO Phase is complex, with fire periods alternating with periods without local fires, as is the case for the late BO Phase from 1820 until 1550 cal yr BP. It is suggested that the past agricultural practices including fires cause a higher soil erodibility than agricultural practices without fires. A climatic shift towards aridity during Roman times may have triggered the observed change in fire regime but local processes, mainly human disturbances, appear to be the proximal cause of all recorded changes. In the Bereket surroundings, fires led to a simplification of the vegetation structure, favouring soil erosion, pastures and intensive cultivation.  相似文献