Abstract
Concern regarding global change has increased the need to understand the relationship between fire regime characteristics and the environment. Pyrogeographical theory suggests that fire regimes are constrained by climate, vegetation and fire ignition processes, but it is not obvious how fire regime characteristics are related to those factors. We used a three-matrix approach with a multivariate statistical methodology that combined an ordination method and fourth-corner analysis for hypothesis testing to investigate the relationship between fire regime characteristics and environmental gradients across Spain. Our results suggest that fire regime characteristics (i.e., density and seasonality of fire activity) are constrained primarily by direct gradients based on climate, population, and resource gradients based on forest potential productivity. Our results can be used to establish a predictive model for how fire regimes emerge in order to support fire management, particularly as global environmental changes impact fire regime characteristics.
Highlights
Fire regimes play an important role in many terrestrial ecosystems [1,2,3], and changes in fire regime characteristics affect the structure and composition of vegetation, which in turn might affect different ecosystem characteristics, such as biodiversity [1,2]
Based on pyrogeographical theory [13,17,18,19] and considering fires as a ‘herbivore’ according to some authors [2,33], we expected that fire regime characteristics would change along three types of environmental gradients (Table 2): (i) direct gradients based on climate and humans because both affect fuel flammability and fire ignition processes; (ii) resource gradients based on forest potential productivity and land cover because fuel is consumed by fires; and (iii) indirect gradients based on livestock grazing and land cover changes from afforestation, forest degradation and the abandonment of traditional activities, which indirectly affect ignition, structure and the amount of fuel [34]
Our results indicate that environmental gradients constrain fire regime characteristics across Spain
Summary
Fire regimes play an important role in many terrestrial ecosystems [1,2,3], and changes in fire regime characteristics affect the structure and composition of vegetation, which in turn might affect different ecosystem characteristics, such as biodiversity [1,2]. Pyrogeographical theory suggests that fire regimes are structured by spatial gradients of climate, vegetation and ignitions, which constrain fuel flammability, fuel loading and ignition sources [13,17,18,19]. Such relationships are complex because of their feedback and interactions, and some of them remains unclear [17,20,21]. Meyn et al [22] proposed a pyrogeographical model based on the premise that fire activity varies across fuel loading and fuel moisture gradients This theory was later supported by Batllori et al [23], who studied Mediterranean ecosystems. This paper presents the main structure of fire regime characteristics, density and seasonality of fire activity, and environmental gradients in Spain as well as the statistical significance of the associations
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