Eric Rigolot

Landscape – wildfire interactions in southern Europe: Implications for landscape management

Every year approximately half a million hectares of land are burned by wildfires in southern Europe, causing large ecological and socio-economic impacts. Climate and land use changes in the last decades have increased fire risk and danger. In this paper we review the available scientific knowledge on the relationships between landscape and wildfires in the Mediterranean region, with a focus on its application for defining landscape management guidelines and policies that could be adopted in order to promote landscapes with lower fire hazard. The main findings are that (1) socio-economic drivers have favoured land cover changes contributing to increasing fire hazard in the last decades, (2) large wildfires are becoming more frequent, (3) increased fire frequency is promoting homogeneous landscapes covered by fire-prone shrublands; (4) landscape planning to reduce fuel loads may be successful only if fire weather conditions are not extreme. The challenges to address these problems and the policy and landscape management responses that should be adopted are discussed, along with major knowledge gaps.

Predicting postfire mortality of Pinus halepensis Mill. and Pinus pinea L.

The probability of mortality of Pinus halepensis and P. pinea trees after 6 separate wildfires (which took place from 1989 to 1991 in South Eastern France) was modelled with logistic regression analysis using data on tree size and fire-damage descriptors from 998 trees in 13 stands. For both species, probability of mortality increased with increasing percentage of crown scorched and estimated depth of bark charring, and with decreasing tree DBH. The best fitted and field convenient model was selected for each species. Fire-caused mortality of P. halepensis is a function of these three variables and for P. pinea is a function of the first two variables only. Analysis of receiver operating characteristic (ROC) curves indicated that the selected models perform well for both species with 85 and 95 percent concordance between predicted probabilities and observed outcomes for P. halepensis and P. pinea respectively. Models may be used for guiding salvage fire-damaged P. halepensis or P. pinea stands. This paper reports on cases of different management scenarios by selecting different decision criteria when using the proposed models. Comparative analysis of fire resistance and survival of the two Mediterranean pine species shows that P. halepensis is more fire sensitive than P. pinea.

Estimating Leaf Bulk Density Distribution in a Tree Canopy Using Terrestrial LiDAR and a Straightforward Calibration Procedure

Leaf biomass distribution is a key factor for modeling energy and carbon fluxes in forest canopies and for assessing fire behavior. We propose a new method to estimate 3D leaf bulk density distribution, based on a calibration of indices derived from T-LiDAR. We applied the method to four contrasted plots in a mature Quercus pubescens forest. Leaf bulk densities were measured inside 0.7 m-diameter spheres, referred to as Calibration Volumes. Indices were derived from LiDAR point clouds and calibrated over the Calibration Volume bulk densities. Several indices were proposed and tested to account for noise resulting from mixed pixels and other theoretical considerations. The best index and its calibration parameter were then used to estimate leaf bulk densities at the grid nodes of each plot. These LiDAR-derived bulk density distributions were used to estimate bulk density vertical profiles and loads and above four meters compared well with those assessed by the classical inventory-based approach. Below four meters, the LiDAR-based approach overestimated bulk densities since no distinction was made between wood and leaf returns. The results of our method are promising since they demonstrate the possibility to assess bulk density on small plots at a reasonable operational cost.

Live fuel moisture content (LFMC) time series for multiple sites and species in the French Mediterranean area since 1996

Live fuel moisture content (LFMC), the ratio of water mass to dry mass of living shoots, is a primary driver of wildfire activity (Chandler et al. 1983; Dennison andMoritz 2009; Nolan et al. 2016) and fuel flammability (Marino et al. 2012; Rossa et al. 2016; Fares et al. 2017 Ruffault et al. 2018). LFMC is an input variable in several fire behavior models (Sullivan 2009; Alexander and Cruz 2013) and is often implicitly accounted for in fire hazard indices in Mediterranean areas (e.g. Viegas et al. 1999; Ruffault and Mouillot 2017). Despite the importance of LFMC for a wide range of wildfire research studies, its estimation at stand to landscape scales is still highly uncertain, because LFMC results from complex interactions between the antecedent and concurrent weather and several biological mechanisms that influence water content (i.e. plant water relations) and dry matter accumulation (i.e. carbon allocation at the leaf level) (Turner 1981; Jolly et al. 2014). There is therefore a need for robust and longterm LFMC datasets to improve our understanding of LFMC variations and refine our predictions. In 1996, the French organization in charge of protection of the Mediterranean forest (DPFM) initiated the systematic measurement of LFMC to improve its operational fire danger rating system during the fire season. Weekly measurements have been performed in various sites and shrub species over the fire-prone French Mediterranean. This operational network, called the “Reseau Hydrique” (what could be translated as “hydric network”) has been operated by the National Forest Service (Office National des Forêts (ONF)) since then. To date, the “Reseau Hydrique” produced a dataset that includes 584 “Sites × Years”, on 24 species, with 7 to 20 measurement dates per year. In addition, rainfall amounts during the fire season have been recorded since 2009 on some sites. The raw dataset is currently available on demand via the Reseau Hydrique website but, in its current form, cannot be easily used for scientific purposes for several reasons: (i) the database is not referenced (i.e. does not have a DOI); (ii) information is in French only; (iii) the labels and names of sampling sites and species names are not always consistent; (iv) outliers, duplications and inconsistencies in LFMC data have not been corrected; (v) measurement uncertainties (confidence levels) are not provided.

Modeling thinning effects on fire behavior with STANDFIRE

Key messageWe describe a modeling system that enables detailed, 3D fire simulations in forest fuels. Using data from three sites, we analyze thinning fuel treatments on fire behavior and fire effects and compare outputs with a more commonly used model.ContextThinning is considered useful in altering fire behavior, reducing fire severity, and restoring resilient ecosystems. Yet, few tools currently exist that enable detailed analysis of such efforts.AimsThe study aims to describe and demonstrate a new modeling system. A second goal is to put its capabilities in context of previous work through comparisons with established models.MethodsThe modeling system, built in Python and Java, uses data from a widely used forest model to develop spatially explicit fuel inputs to two 3D physics-based fire models. Using forest data from three sites in Montana, USA, we explore effects of thinning on fire behavior and fire effects and compare model outputs.ResultsThe study demonstrates new capabilities in assessing fire behavior and fire effects changes from thinning. While both models showed some increases in fire behavior relating to higher winds within the stand following thinning, results were quite different in terms of tree mortality. These different outcomes illustrate the need for continuing refinement of decision support tools for forest management.ConclusionThis system enables researchers and managers to use measured forest fuel data in dynamic, 3D fire simulations, improving capabilities for quantitative assessment of fuel treatments, and facilitating further refinement in physics-based fire modeling.

Correction to: “Modeling thinning effects on fire behavior with STANDFIRE”

The original article shows unit errors in Table 2: The torching index (TI) and crowning index (CI).

A simple model for shrub-strata-fuel dynamics in Quercus coccifera L. communities

Key messageWe model the dynamics of fuel characteristics in shrub strata dominated byQuercus cocciferaL. with data gathered in available literature. The model expresses the variability of this important fire-prone fuel type thanks to yield classes, and it can be used to investigate management scenarios. The approach could easily be applied to other shrub communities.ContextCharacterizing fuel is a basic requirement for fire hazard assessment. Quercus coccifera L. is present in several Mediterranean fire-prone communities, and its fuel characteristics have been studied over various Mediterranean countries, but no general model describes its dynamics.AimsHerein, we present such a general model, initially developed for operational purposes at the French Forest Service.MethodsWe review available literature and fit statistical relationships to predict the dynamics of fuel height and biomass, by size categories of fine fuel elements.ResultsThe model estimates fuel characteristics from shrub-strata age, overstorey cover, and yield class with a reasonable degree of accuracy considering the heterogeneity of the datasets. It shows that bulk density is highly sensitive to overstorey, and in a lesser extent to strata age, which could lead to significant bias when assessing fuel properties from general allometries. The model is integrated in the FuelManager software, which is devoted to fuel modeling for physics-based-fire-behavior models.ConclusionThis simple approach enables to provide a fuel model for the Quercus coccifera L. shrub strata in the Mediterranean basin. It is more general than the existing relationships available for local data. This approach could be generalized to other fire-prone communities.

Correction: Pimont, F. et al. Estimating Leaf Bulk Density Distribution in a Tree Canopy Using Terrestrial LiDAR and a Straightforward Calibration Procedure. Remote Sens. 2015, 7(6), 7995-8018

After publication of the research paper [1] an error during the data analysis process was recognized. [...]

Conservation, ecology, restoration, and management of Mediterranean pines and their ecosystems: challenges under global change

Initiated in 1999 in Mt. Carmel in Israel, the cycle of MEDPINE conferences has already traveled to Chania in Greece (Arianoutsou and Thanos 2004) and Bari in Italy (Leone and Lovreglio 2007). The fourth edition of the conference was organized in June 2011 by the research group on Ecology of Mediterranean Forests from INRA Avignon, France, and was entitled “Conservation, Ecology, Restoration and Management of Mediterranean Pines and their Ecosystems: Challenges under global change.” The main emphasis of the conference was placed on the euMediterranean pine species Pinus halepensis, Pinus brutia, Pinus pinea, Pinus sylvestris, Pinus pinaster, and Pinus canariensis, but contributions relating to other pines of the Mediterranean mountains (Pinus nigra, Pinus mugo, Pinus uncinata, and Pinus heldreichii) or from other regions under the Mediterranean bioclimate were also presented. All together, the Mediterranean pines represent a group of species of key importance not only because of their contribution to planted and natural woodlands in the Mediterranean basin (13 million ha), but also because of their high ecological and economical values (Sheffer 2012). The main objective of the conference was to bring together researchers of all disciplines studying Mediterranean pines in order to bring forward available knowledge, identify research gaps, and make recommendations for sustainable management. The climate change context was an added complexity for all the attendees, and a special session was dedicated to this issue. More than 150 participants from 14 countries attended the MEDPINE 4 conference in Avignon, substantially more than the previous editions. The conference program was built to stimulate a multidisciplinary dialog and to strengthen the research community working on a common object, Mediterranean pines. Fifty-two oral communications and more than 100 posters were presented in sessions dealing with ecology, genetics and breeding, pine and insect interactions, stand dynamics and forest management, ecophysiology, fire sciences, and climate change. An exhaustive synthesis of the main results of the conference was published for French readers in Forêt Méditerranéenne (Rigolot et al. 2012). This thematic issue of Annals of Forest Science comprises nine original papers including three review papers, selected to present a sample of the most significant scientific results. The first three papers address Mediterranean pine dynamics. Pines are mostly pioneer species colonizing disturbed sites or expanding from existing stands or past plantations (Sheffer 2012). Pine expansion in the Mediterranean region is favored by harsh local conditions, high disturbance pressures, and important land use changes. Accordingly, many studies were carried out to disentangle the effects of land use, environmental conditions, and climate on pine expansion (e.g., Boulant et al. 2009). Piermattei et al. (2012) discuss the relative importance of climate compared to land use changes, such as decreased grazing, on the spatiotemporal expansion dynamics of P. nigra at tree line in the Central Apennines. Coutts et al. (2012) address the reproductive ecology of an exotic population of P. nigra Arn. ssp. laricio in New Zealand which behaves as an invasive species in this part of the world. They conclude on the key role of two opposite features impacting the dynamics of these invasive pines: right-skewed fecundity distributions may slow pine rate of spread, while preferential release of seeds Handling Editor: Erwin Dreyer