scholarly journals Fog and live fuel moisture in coastal California shrublands

2017 ◽  
Author(s):  
Nathan Emery ◽  
Carla M. D'Antonio ◽  
Christopher J. Still
Keyword(s):  
Water Uptake ◽  
Critical Time ◽  
Fire Risk ◽  
Moisture Loss ◽  
Summer Drought ◽  
Fuel Moisture ◽  
Fog Water ◽  
Fog Deposition ◽  
Sage Scrub ◽  
Live Fuel Moisture

Across most Mediterranean-type climate regions, seasonal drought desiccates plants, facilitating ignition and the spread of wildfires. Along the California coast, summertime fog has the potential to ameliorate drought conditions and thus reduce plant flammability during a critical time of elevated fire risk. This study investigated the uptake of dry season fog and how it affects live fuel moisture in six dominant shrub species from chaparral and sage scrub plant associations. Fog water uptake was evaluated using stable isotopes of hydrogen and oxygen at several field sites in Santa Barbara County, California. Clear evidence of fog water uptake was identified only in Baccharis pilularis, from the sage scrub association. To determine the effects of fog on live fuel moisture, meteorological variables and indices including fog deposition were combined into principal components and the scores regressed against the live fuel moisture loss rate during the summer drought. Fog deposition slowed rates of live fuel moisture loss for all three sage scrub species tested, but it did not affect the chaparral species. Fog is a more regular occurrence in the sage scrub association and thus it is likely that fog ameliorates drought for species that experience consistent fog during the summer months. In coastal California, summer fog can be essential to plant water relations and reduce live fuel moisture loss rates during the summer drought. Understanding these effects is important in the context of changing climate in southern California and Mediterranean-type climate regions around the world.

Ignition and fire behaviour of Juniperus virginiana in response to live fuel moisture and fire temperature in the southern Great Plains

2014 ◽  
Vol 23 (6) ◽  
pp. 839 ◽  
Author(s):  
John R. Weir ◽  
J. Derek Scasta
Keyword(s):  
Great Plains ◽  
Fire Risk ◽  
Critical Threshold ◽  
Juniperus Virginiana ◽  
Fuel Moisture ◽  
Fire Temperature ◽  
Expected Time ◽  
Fuel Loads ◽  
Critical Knowledge ◽  
Live Fuel Moisture

Fire is the most effective tool for managing Juniperus virginiana encroachment and associated fire risk, but its application has been limited. In a laboratory experiment we assessed a critical knowledge gap: how fire temperature and live fuel moisture (LFM) influences ignitability, sustainability, combustibility and consumability of J. virginiana. Percentage occurrence of ignition rose as fire temperature increased. The time to ignition increased while the occurrence of ignition decreased with increasing LFM. LFM and fire temperature each had a significant effect on all measured dependent variables (P≤0.05) as was their interaction, except in the case of sustainability. As expected, time to flaming was shortest and flame lengths were the highest under the hottest fire and lowest LFM scenarios. Flame heights increased quadratically as LFM decreased with a critical threshold at 60% LFM. Land managers can select burning prescriptions based on the interaction between fire temperature and LFM to either increase J. virginiana ignition or reduce hazards. In this study, the low and moderate fire temperatures were similar to those of prescribed fires at low and high fuel loads and the high temperature level mimics conditions found in extreme wildfires. Thus, higher fuel loads and hotter fires are required to maximise efficacy of fires targeting J. virginiana control.

Soil Moisture and Live Fuel Moisture Content as key remote sensing variables to unlock improved wildfire predictions

2021 ◽  
Author(s):  
Florian Briquemont ◽  
Akli Benali
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Fire Risk ◽  
Simulation Models ◽  
Fire Spread ◽  
Fuel Moisture ◽  
Live Fuel Moisture ◽  
Risk Maps ◽  
Fuel Moisture Content ◽  
The Impact

<p>Large wildfires are amongst the most destructive natural disasters in southern Europe, posing a serious threat to both human lives and the environment.</p><p>Although wildfire simulations and fire risk maps are already very a useful tool to assist fire managers in their decisions, the complexity of fire spread and ignition mechanisms can greatly hinder their accuracy. An important step in improving the reliability of wildfire prediction systems is to implement additional drivers of fire spread and fire risk in simulation models.</p><p>Despite their recognized importance as factors influencing fuel flammability and fire spread, soil moisture and live fuel moisture content are rarely implemented in the simulation of large wildfires due to the lack of sufficient and accurate data. Fortunately, new satellite products are giving the opportunity to assess these parameters on large areas with high temporal and spatial resolution.</p><p>The purpose of this study is twofold. First, we aimed to evaluate the capabilities of satellite data to estimate soil moisture and live fuel moisture content in different landcovers.  Secondly, we focused on the potential of these estimates for assessing fire risk and fire spread patterns of large wildfires in Portugal. Ultimately, the goal of this study is to implement these estimated variables in fire spread simulations and fire risk maps.<br><br>We compared datasets retrieved from Sentinel 1, SMAP (Soil Moisture Active Passive radiometer) and MODIS (Moderate Resolution Imaging Spectrometer) missions. Several estimators of LFMC based on spectral indices were tested and their patterns were compared with field data. Based on these estimators, we assessed the impact of LFMC and soil moisture on the extent and occurrence of large wildfires. Finally, we built a database of detailed historical wildfire progressions, which we used to evaluate the influence of soil moisture and LFMC on the velocity and direction of the fire spread.</p>

scholarly journals Fire weather effects on flammability of indigenous and invasive alien plants in coastal fynbos and thicket shrublands (Cape Floristic Region)

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10161
Author(s):  
Samukelisiwe T. Msweli ◽  
Alastair J. Potts ◽  
Herve Fritz ◽  
Tineke Kraaij
Keyword(s):  
Fire Risk ◽  
Weather Conditions ◽  
Cape Floristic Region ◽  
Alien Plants ◽  
Fuel Load ◽  
Fire Weather ◽  
Fuel Moisture ◽  
Invasive Alien Plants ◽  
Live Fuel Moisture ◽  
Plant Shoots

Background Globally, and in the Cape Floristic Region of South Africa, extreme fires have become more common in recent years. Such fires pose societal and ecological threats and have inter alia been attributed to climate change and modification of fuels due to alien plant invasions. Understanding the flammability of different types of indigenous and invasive alien vegetation is essential to develop fire risk prevention and mitigation strategies. We assessed the flammability of 30 species of indigenous and invasive alien plants commonly occurring in coastal fynbos and thicket shrublands in relation to varying fire weather conditions. Methods Fresh plant shoots were sampled and burnt experimentally across diverse fire weather conditions to measure flammability in relation to fire weather conditions, live fuel moisture, fuel load and vegetation grouping (fynbos, thicket and invasive alien plants). Flammability measures considered were: burn intensity, completeness of burn, time-to-ignition, and the likelihood of spontaneous ignition. We also investigated whether the drying of plant shoots (simulating drought conditions) differentially affected the flammability of vegetation groups. Results Fire weather conditions enhanced all measures of flammability, whereas live fuel moisture reduced burn intensity and completeness of burn. Live fuel moisture was not significantly correlated with fire weather, suggesting that the mechanism through which fire weather enhances flammability is not live fuel moisture. It furthermore implies that the importance of live fuel moisture for flammability of evergreen shrublands rests on inter-specific and inter-vegetation type differences in fuel moisture, rather than short-term intra-specific fluctuation in live fuel moisture in response to weather conditions. Fuel load significantly increased burn intensity, while reducing ignitability. Although fire weather, live fuel moisture, and fuel load had significant effects on flammability measures, vegetation and species differences accounted for most of the variation. Flammability was generally highest in invasive alien plants, intermediate in fynbos, and lowest in thicket. Fynbos ignited rapidly and burnt completely, whereas thicket was slow to ignite and burnt incompletely. Invasive alien plants were slow to ignite, but burnt with the highest intensity, potentially due to volatile organic composition. The drying of samples resulted in increases in all measures of flammability that were comparable among vegetation groups. Flammability, and by implication fire risk, should thus not increase disproportionately in one vegetation group compared to another under drought conditions—unless the production of dead fuels is disproportionate among vegetation groups. Thus, we suggest that the dead:live fuel ratio is a potentially useful indicator of flammability of evergreen shrublands and that proxies for this ratio need to be investigated for incorporation into fire danger indices.

scholarly journals Atmospheric inorganic nitrogen input via dry, wet, and sea fog deposition to the subarctic western North Pacific Ocean

2013 ◽  
Vol 13 (1) ◽  
pp. 411-428 ◽  
Author(s):  
J. Jung ◽  
H. Furutani ◽  
M. Uematsu ◽  
S. Kim ◽  
S. Yoon
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
Western North Pacific ◽  
Inorganic Nitrogen ◽  
North Pacific Ocean ◽  
Inorganic N ◽  
Fog Water ◽  
Western North Pacific Ocean ◽  
Sea Fog ◽  
Fog Deposition

Abstract. Aerosol, rainwater, and sea fog water samples were collected during the cruise conducted over the subarctic western North Pacific Ocean in the summer of 2008, in order to estimate dry, wet, and sea fog deposition fluxes of atmospheric inorganic nitrogen (N). During sea fog events, mean number densities of particles with diameters larger than 0.5 μm decreased by 12–78%, suggesting that particles with diameters larger than 0.5 μm could act preferentially as condensation nuclei (CN) for sea fog droplets. Mean concentrations of nitrate (NO3−), methanesulfonic acid (MSA), and non sea-salt sulfate (nss-SO42−) in sea fog water were higher than those in rainwater, whereas those of ammonium (NH4+) in both sea fog water and rainwater were similar. These results reveal that sea fog scavenged NO3− and biogenic sulfur species more efficiently than rain. Mean dry, wet, and sea fog deposition fluxes for atmospheric total inorganic N (TIN; i.e. NH4+ + NO3−) over the subarctic western North Pacific Ocean were estimated to be 4.9 μmol m−2 d−1, 33 μmol m−2 d−1, and 7.8 μmol m−2 d−1, respectively. While NO3− was the dominant inorganic N species in dry and sea fog deposition, inorganic N supplied to surface waters by wet deposition was predominantly by NH4+. The contribution of dry, wet, and sea fog deposition to total deposition flux for TIN (46 μmol m−2 d−1) were 11%, 72%, and 17%, respectively, suggesting that ignoring sea fog deposition would lead to underestimate of the total influx of atmospheric inorganic N into the subarctic western North Pacific Ocean, especially in summer periods.

Improved fuel moisture prediction in non-native tropical Megathyrsus maximus grasslands using Moderate-Resolution Imaging Spectroradiometer (MODIS)-derived vegetation indices

2017 ◽  
Vol 26 (5) ◽  
pp. 384
Author(s):  
L. M. Ellsworth ◽  
A. P. Dale ◽  
C. M. Litton ◽  
T. Miura
Keyword(s):  
Vegetation Index ◽  
Vegetation Indices ◽  
Fuel Moisture ◽  
Fire Behaviour ◽  
Native Grass ◽  
Tropical Ecosystems ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Live Fuel Moisture ◽  
Moderate Resolution Imaging Spectroradiometer

The synergistic impacts of non-native grass invasion and frequent human-derived wildfires threaten endangered species, native ecosystems and developed land throughout the tropics. Fire behaviour models assist in fire prevention and management, but current models do not accurately predict fire in tropical ecosystems. Specifically, current models poorly predict fuel moisture, a key driver of fire behaviour. To address this limitation, we developed empirical models to predict fuel moisture in non-native tropical grasslands dominated by Megathyrsus maximus in Hawaii from Terra Moderate-Resolution Imaging Spectroradiometer (MODIS)-based vegetation indices. Best-performing MODIS-based predictive models for live fuel moisture included the two-band Enhanced Vegetation Index (EVI2) and Normalized Difference Vegetation Index (NDVI). Live fuel moisture models had modest (R2=0.46) predictive relationships, and outperformed the commonly used National Fire Danger Rating System (R2=0.37) and the Keetch–Byram Drought Index (R2=0.06). Dead fuel moisture was also best predicted by a model including EVI2 and NDVI, but predictive capacity was low (R2=0.19). Site-specific models improved model fit for live fuel moisture (R2=0.61), but limited extrapolation. Better predictions of fuel moisture will improve fire management in tropical ecosystems dominated by this widespread and problematic non-native grass.

scholarly journals Monitoring Live Fuel Moisture Using Soil Moisture and Remote Sensing Proxies

Fire Ecology ◽  
2012 ◽  
Vol 8 (3) ◽  
pp. 71-87 ◽  
Author(s):  
Yi Qi ◽  
Philip E. Dennison ◽  
Jessica Spencer ◽  
David Riaño
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Fuel Moisture ◽  
Live Fuel Moisture

scholarly journals SAR-enhanced mapping of live fuel moisture content

2020 ◽  
Vol 245 ◽  
pp. 111797 ◽  
Author(s):  
Krishna Rao ◽  
A. Park Williams ◽  
Jacqueline Fortin Flefil ◽  
Alexandra G. Konings
Keyword(s):  
Moisture Content ◽  
Fuel Moisture ◽  
Live Fuel Moisture ◽  
Fuel Moisture Content
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