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 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   

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   

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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Characterization of the July 2007 Swaziland fire disaster using satellite remote sensing and GIS     

Wisdom M. Dlamini   《Applied geography (Sevenoaks, England)》2009,29(3):299-307

Data from the NASA'S MODIS (Aqua and Terra) and EUMETSAT'S MSG-SEVIRI satellite sensors is analysed to characterise the geographic and temporal (including diurnal) evolution of the July 2007 fire disaster in the Kingdom of Swaziland using a geographic information system (GIS). Significant fire activity was observed during a three-day period beginning on the 27th July 2007. A total of 1358 and 4365 active fire hotpots were detected by MODIS and MSG-SEVIRI, respectively, mainly concentrated in the Highveld (70.91% for MODIS, 89.89% for MSG) and Middleveld (11.27% for MODIS, 5.23% for MSG) with MSG/MODIS active fire count ratio ranging from a high of 3.69 in the Highveld to a low of 0.06 in the Lubombo Plateau. The results indicate complex differences in spatial fire distribution, behaviour and risk within the country and the effect of sensor differences. A pronounced fire diurnal cycle with a broad afternoon peak centred on 14:00 local time is observed, in general agreement with observations from the region. Despite their limitations, the study demonstrates the importance and usefulness of remotely sensed data and GIS technology for fire disaster and risk assessment for a developing country, where fire monitoring resources are scarce.  相似文献   

火烧迹地信息遥感快速提取方法研究     

高中灵  汪小钦  周小成 《国土资源遥感》2005,(4):38-41,i0002

利用福建省福州地区ETM图像，在分析火烧迹地光谱特征的基础上，研究了火烧迹地信息遥感快速提取方法。文中设置了4种提取方案，即监督分类法、NDVI参与的监督分类法、NDVI差值法及谱间关系法，最后，对提取结果进行了精度评价。  相似文献   

Postglacial vegetation, fire, and climate history of the Siskiyou Mountains, Oregon, USA   总被引：1，自引：0，他引：1  

Christy E. Briles  Cathy Whitlock 《Quaternary Research》2005,64(1):44-56

The forests of the Siskiyou Mountains are among the most diverse in North America, yet the long-term relationship among climate, diversity, and natural disturbance is not well known. Pollen, plant macrofossils, and high-resolution charcoal data from Bolan Lake, Oregon, were analyzed to reconstruct a 17,000-yr-long environmental history of high-elevation forests in the region. In the late-glacial period, the presence of a subalpine parkland of Artemisia, Poaceae, Pinus, and Tsuga with infrequent fires suggests cool dry conditions. After 14,500 cal yr B.P., a closed forest of Abies, Pseudotsuga, Tsuga, and Alnus rubra with more frequent fires developed which indicates more mesic conditions than before. An open woodland of Pinus, Quercus, and Cupressaceae, with higher fire activity than before, characterized the early Holocene and implies warmer and drier conditions than at present. In the late Holocene, Abies and Picea were more prevalent in the forest, suggesting a return to cool wet conditions, although fire-episode frequency remained relatively high. The modern forest of Abies and Pseudotsuga and the present-day fire regime developed ca. 2100 cal yr B.P. and indicates that conditions had become slightly drier than before. Sub-millennial-scale fluctuations in vegetation and fire activity suggest climatic variations during the Younger Dryas interval and within the early Holocene period. The timing of vegetation changes in the Bolan Lake record is similar to that of other sites in the Pacific Northwest and Klamath region, and indicates that local vegetation communities were responding to regional-scale climate changes. The record implies that climate-driven millennial- to centennial-scale vegetation and fire change should be considered when explaining the high floristic diversity observed at present in the Siskiyou Mountains.  相似文献   

Comparison of Techniques for Visualising Fire Behaviour   总被引：1，自引：0，他引：1  

Julian Black  Colin Arrowsmith  Michael Black  William Cartwright 《Transactions in GIS》2007,11(4):621-635

During every Australian summer fires are common in the south‐eastern region of the continent. The combined forces of climate, topography and vegetation make Victoria in particular, one of the most fire prone regions on earth ( DSE 2003 ). Throughout its history, Victoria has seen a number of devastating bushfires, including Black Friday 1939, Ash Wednesday 1983, and more recently in the northeast of the State in 2003. The loss of life combined with the damage caused to land and property results in a heavy cost to the community. In Victoria, two of the organizations involved in fire management are the Victorian Department of Sustainability and Environment (DSE) and the Country Fire Authority (CFA). Both use fire ‘meters’ to determine potential fire behaviour given certain conditions. Values for temperature, wind speed, fuel load and vegetation type are input and a numerical estimate of fire danger given. There are a number of different meters used for different locations and environmental types. The most common meter used in Victoria is the McArthur Meter ( CSIR0 2001b ). The output data from this meter is numerical, and provides no spatial representation of fire danger. This paper looks at a variety of techniques used to visualise the numerical output from the McArthur Forest Fire Danger Meter. The article outlines the different models used by fire managers to simulate a fire situation, to assess future scenarios and for decision making involving fire management. Particular emphasis is placed on the McArthur Forest Fire Danger Meter as this is commonly used by fire departments in Australia. The article then focuses on geographical visualisation and a number of techniques employed to convey spatial information are discussed. The article then goes on to describe the fire simulation prototypes created for a study, a visualisation proof‐of‐concept product for organizations involved in managing bushfires in Australia. Finally, results from the evaluation of the prototype are presented.  相似文献   

Remotely sensed characterization of forest fuel types by using satellite ASTER data     

《International Journal of Applied Earth Observation and Geoinformation》2007,9(3):225-234

The characterization of fuel types is very important for computing spatial fire hazard and risk and simulating fire growth and intensity across a landscape. However, due to the complex nature of fuel characteristic a fuel map is considered one of the most difficult thematic layers to build up. The advent of sensors with increased spatial resolution may improve the accuracy and reduce the cost of fuels mapping. The objective of this research is to evaluate the accuracy and utility of imagery from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery. In order to ascertain how well ASTER data can provide an exhaustive classification of fuel properties a sample area characterized by mixed vegetation covers was analysed. The selected sample areas has an extension at around 60 km² and is located inside the Sila plateau in the Calabria Region (South of Italy). Fieldwork fuel type recognitions, performed before, after and during the acquisition of remote sensing ASTER data, were used as ground-truth dataset to assess the results obtained for the considered test area. The method comprised the following three steps: (I) adaptation of Prometheus fuel types for obtaining a standardization system useful for remotely sensed classification of fuel types and properties in the considered Mediterranean ecosystems; (II) model construction for the spectral characterization and mapping of fuel types based on a maximum likelihood (ML) classification algorithm; (III) accuracy assessment for the performance evaluation based on the comparison of ASTER-based results with ground-truth. Results from our analysis showed that the use ASTER data provided a valuable characterization and mapping of fuel types being that the achieved classification accuracy was higher than 90%.  相似文献   

Terrestrial and Submerged Aquatic Vegetation Mapping in Fire Island National Seashore Using High Spatial Resolution Remote Sensing Data     

Yeqiao Wang  Michael Traber  Bryan Milstead  Sara Stevens 《Marine Geodesy》2013,36(1-2):77-95

The vegetation communities and spatial patterns on the Fire Island National Seashore are dynamic as the result of interactions with driving forces such as sand deposition, storm-driven over wash, salt spray, surface water, as well as with human disturbances. We used high spatial resolution QuickBird-2 satellite remote sensing data to map both terrestrial and submerged aquatic vegetation communities of the National Seashore. We adopted a stratified classification and unsupervised classification approach for mapping terrestrial vegetation types. Our classification scheme included detailed terrestrial vegetation types identified by previous vegetation mapping efforts of the National Park Service and three generalized categories of high-density seagrass, low-density seagrass coverages, and unvegetated bottom to map the submerged aquatic vegetation habitats. We used underwater videography, GPS-guided field reference photography, and bathymetric data to support remote sensing image classification and information extraction. This study achieved approximately 82% and 75% overall classification accuracy for the terrestrial and submnerged aquatic vegetations, respectively, and provided an updated vegetation inventory and change analysis for the Northeast Coastal and Barrier Network of the National Park Service.  相似文献