Abstract
Frequent and severe droughts typically intensify wildfires provided that there is enough fuel in situ. The extent to which climate change may influence the fire regime and long time-scale hydrological processes may soften the effect of inter-annual climate change and, more specifically, whether soil-water retention capacity can alleviate the harsh conditions resulting from droughts and affect fire regimes, are still largely unexplored matters. The research presented in this paper is a development of a previous investigation and shows in what way, and to what extent, rainfall frequency, dry season length, and hydraulic response of different soil types drive forest fires toward different regimes while taking into consideration the typical seasonality of the Mediterranean climate. The soil-water holding capacity, which facilitates biomass growth in between fire events and hence favors fuel production, may worsen the fire regime as long dry summers become more frequent, such that the ecosystem’s resilience to climate shifts may eventually be undermined.
Highlights
The southern European countries of the Mediterranean belt are characterized by significant intra-annual and inter-annual seasonality
Since the model control volume is not an actual soil profile, but rather an equivalent uniform soil, in this study we take advantage of the recent findings made by Nasta and Romano [43], who set up a functional evaluation and an analytical procedure to identify the effective value of soil moisture at field capacity in the case of an actual layered soil profile
According to the SPI classification of drought conditions, a period is severely dry for SPI values ranging from −1.5 to −1.99, whereas it is extremely dry when SPI values are lower than −2.00
Summary
The southern European countries of the Mediterranean belt are characterized by significant intra-annual and inter-annual seasonality. The fire paradox of self-sustaining Mediterranean fire-prone forests is often associated with the display of a chaotic-type fire regime that is characterized by a highly variable return period and, especially at high vegetation growth rates, by complex non-linear dynamics within the space of relevant model parameter values [22] Far from this chaotic-type regime, different dynamics can be envisioned under persistent climate change scenarios [23], or substantial land-use changes [24]. By applying a conceptual eco-hydrological fire model to the case study of the southern Italian region of Campania, we address the question of whether observed climate change could drive the forest ecosystem far from its characteristic, self-sustaining fire regime and to what extent soil-mediated water cycling may oppose such shifts in the ensuing decades. The results demonstrate that the soil water holding capacity, facilitating biomass growth in between fire events, and favoring fuel production, may intensify the fire regime when long dry summers become more frequent
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