Vegetation fires are intrinsic ecosystem disturbances of the Earth system. Global burned area products have been delivered from several space-borne instruments, and have recently provided pixel-level information underpinning fire spread processes. Here we present FRY, a global database of fire patches with morphology-based functional traits reconstructed from pixel-based burned areas derived from the MODIS and MERIS imagery using a flood-fill algorithm. Each fire patch is characterized by the geo-location of its center, area, perimeter, the features of the ellipse fitted over its pixel’s spatial distribution, and different indices of patch complexity. We obtained a consistent spatial distribution of global fire patch functional traits between the MCD64A1 Collection 6 and the MERIS fire_cci v4.1 datasets during their overlap period (2005-2011), confirming the robustness of the applied algorithm and the consistency between both products. This database is relevant to a broad spectrum of fire-related applications such as local to global functional pyrodiversity, fire emissions quantification, and the benchmarking of fire modules embedded in dynamic global vegetation models.

Vegetation fires are an important process in the Earth system. Fire intensity locally impacts fuel consumption, damage to the vegetation, chemical composition of fire emissions and also how fires spread across landscapes. It has been observed that fire occurrence, defined as the frequency of active fires detected by the MODIS sensor, is related to intensity with a hump-shaped empirical relation, meaning that occurrence reaches a maximum at intermediate fire intensity. Raw burned area products obtained from remote sensing can not discriminate between ignition and propagation processes. To go beyond burned area and to test if fire size is driven by fire intensity at a global scale as expected from empirical fire spread models, we used the newly delivered global FRY database, which provides fire patch functional traits based on satellite observation, including fire patch size, and the fire radiative power measures from the MCD14ML dataset. This paper describes the varying relationships between fire size and fire radiative power across biomes at a global scale. We show that in most fire regions of the world defined by the GFED database, the linear relationship between fire radiative power and fire patch size saturates for a threshold of intermediate-intensity fires. The value of this threshold differs from one region to another and depends on vegetation type. In the most fire-prone savanna regions, once this threshold is reached, fire size decreases for the most intense fires, which mostly happen in the late fire season. According to the percolation theory, we suggest that the decrease in fire size for more intense late season fires is a consequence of the increasing fragmentation of fuel continuity throughout the fire season and suggest that landscape-scale feedbacks should be developed in global fire modules.

The concept of fire regime refers to a variety of fire characteristics occurring at a given place and period of time. Understanding fire regimes is relevant to fire ecology and fire management because it provides a better understanding of effects of fire as well as the potential effects of different future scenarios. Recent changes in the traditional fire regimes linked to climate and socioeconomic transformations in European Mediterranean areas have influenced fire regimes and their effects on both ecosystems and people. This paper presents a methodology for characterising fire regimes based on historical fire statistics. The analysis includes three dimensions: density, seasonality and interannual variability. The raw records were pre-processed to eliminate errors, and a principal component analysis was performed to identify the primary factors involved in the variation. A cluster analysis was then used to define the fire regimes. Approximately 38% of the spatial cells examined were found to have significant fire activity, but in spite that fires are important in these areas, fire activity showed a high interannual variability. Four fire regimes in the Spanish peninsular territory were described in terms of the density and seasonality of fire activity.

The term wildfire regime refers to the wildfires characteristics in a given region during a given period of time. Here we examine one aspect of the wildfire regime, burned area frequency-area statistics of wildfires, for different regions of Spain, as defined by climate zones, for the period 1988-2007. We use the EGIF (General Statistics of Wildfires) database from the MARM (Ministry of Environment and Rural and Marine) using the Reports of Wildfires of the Autonomous Communities. An initial exploration of data showed some inconsistency in reporting sizes of fire both spatially and temporally, with in general underreporting of fire sizes below about 1ha. For the five climatic regions examined, frequency-area statistics showed robust inverse power-laws, with exponents ranging from 1.54 to 1.99. We found that in Spain, lower values tended to correlate with Mediterranean climate regions, and higher values with Oceanic climate region. The use of frequency-area statistics characteristics has allowed us to examining the spatial and temporal variability of the power-law exponents. The characteristics of these values might further inform the complex environmental and human factors that have changed both spatially and temporally in Spain