Relationships between seasonal patterns of live fuel moisture and meteorological drought indices for Mediterranean shrubland species

Abstract

Measurements of seasonal patterns of live fuel moisture content and ignitability (in terms of time to ignition) of four Mediterranean shrub species were performed in North Western Sardinia (Italy). Relationships between the two variables were evaluated. Relationships between live fuel moisture content and environmental conditions (i.e. rainfall, air temperature and soil moisture) were analysed. Two groups of species were identified in relation to the different response of live fuel moisture content to seasonal meteorological conditions. Seasonal patterns of live fuel moisture content were also compared with five meteorological drought indices: Duff Moisture Code and Drought Code of the Canadian Forest Fire Weather Index System, Keetch–Byram Drought Index, Canopy Drought Stress Index and Cumulative Water Balance Index. In addition, the capability of the meteorological drought indices to describe moisture variation for each species was evaluated. Although the Drought Code was formulated to describe changes in the moisture content of dead fuel, it was shown to have a good potential for modelling live fuel moisture variation of a group of shrubland species that are sensitive to meteorological conditions, with a clear and large decrease of moisture content during the drought season.

Regional Equivalent Water Thickness Modeling from Remote Sensing across a Tree Cover/LAI Gradient in Mediterranean Forests of Northern Tunisia

“…Our peculiar pattern of LAI-dependent (EWTCAN, VI) relationship points out the heterogeneous plant functioning in Mediterranean-type ecosystems. We measured contrasted species' desiccation rates, including litter, in accordance with previous studies on Mediterranean vegetation [51][52][53]. These contrasted species-specific fuel moistures could partly explain the non-linearities of the (EWTCAN, VI) relationship as a response of LAI-dependent differential functional diversity.…”

Soil Moisture Affects Growing-Season Wildfire Size in the Southern Great Plains

“…Pellizzaro et al (2007) provided evidence for the importance of soil moisture when they reported that soil moisture was more highly correlated with LFM than weather variables or drought indices in some plant species. Likewise, Qi et al (2012) found that in situ soil moisture measurements were more strongly correlated with LFM than were remote sensing measurements.…”

“…We hypothesize that soil moisture is an important driver of wildfires during the growing season (May-October in Oklahoma) when it strongly influences LFM (Pellizzaro et al, 2007), and that soil moisture is less important during the dormant season when vegetation has senesced or is dormant. Soil moisture is often at its maximum during the dormant season because of low evaporative demand, yet at the same time fuel moisture is low because vegetation is primarily dehydrated plant material from the previous growing season (Wittich, 2011).…”

“…However, direct measurements of LFM for the purposes of wildfire danger assessment are not widely available because fuel moisture sampling is labor inten-sive. Instead, LFM, and consequently wildfire danger, are estimated from weather data (Bradshaw et al, 1983;Forestry Canada Fire Danger Group, 1992;Viegas et al, 2001;Castro et al, 2003;Carlson et al, 2007;Dennison et al, 2008;Matthews, 2014), related to drought indices (Dimitrakopoulos and Bemmerzouk, 2003;Pellizzaro et al, 2007), or estimated using satellite remote sensing techniques (Chuvieco et al, 2002;Caccamo et al, 2012;Jurdao et al, 2012).…”

Short communication: On the effect of live fuel moisture content on fire-spread rate

“…Although the M l evolution in Fig. 1 is not necessarily representative of a general shrubland, several yearround Mediterranean M l assessments for a great number of shrub species (Piñol et al, 1998;Pellizzaro et al, 2007;Yebra et al, 2008;Yebra & Chuvieco, 2009), report a similar seasonal pattern, with a M l decrease between spring and summer, followed by an increase until winter. Because dry soils are frequently concurrent with meteorological conditions that yield low M d values as well, the relationship between M l and soil moisture content found by Qi et al (2012) for a shrubland in Northern Utah (USA), also lends support to our hypothesis of correlated M d and M w damping effects.…”