Abstract
AbstractUnderstanding fine-scale fire patchiness has significant implications for ecological processes and biodiversity conservation. It can affect local extinction of and recolonisation by relatively immobile fauna and poorly seed-dispersed flora in fire-affected areas. This study assesses fine-scale fire patchiness and severity, and associated implications for biodiversity, in north Australian tropical savanna systems. We used line transects to sample burning patterns of ground layer vegetation in different seasons and vegetation structure types, within the perimeter of 35 fires that occurred between 2009 and 2011. We evaluated two main fire characteristics: patchiness (patch density and mean patch length) and severity (inferred from char and scorch heights, and char and ash proportions). The mean burned area of ground vegetation was 83 % in the early dry season (EDS: May to July) and 93 % in the late dry season (LDS: August to November). LDS fires were less patchy (smaller and fewer unburned patches), and had higher fire severity (higher mean char and scorch heights, and twice the proportion of ash) than EDS fires. Fire patchiness varied among vegetation types, declining under more open canopy structure. The relationship between burned area and fire severity depended on season, being strongly correlated in the EDS and uncorrelated in the LDS. Simulations performed to understand the implications of patchiness on the population dynamics of fire-interval sensitive plant species showed that small amounts of patchiness substantially enhance survival. Our results indicate that the ecological impacts of high frequency fires on fire-sensitive regional biodiversity elements are likely to be lower than has been predicted from remotely sensed studies that are based on assumptions of homogeneous burning.
Highlights
North Australian tropical savannas cover 1.9 M km2 and are among the most fire-prone ecosystems in the world
Relative proportions of char and ash were dependent on season: mean percentage ash was twice as high in the late dry season (LDS) (12 %) than in the EDS (6 %), and mean percentage char was lower in the LDS (59 %) compared to the EDS (65 %)
The results suggest that percentage burned, percentage char, percentage ash, and unburned patch density differed by season; percentage char, percentage ash, unburned patch density, and patch length differed by vegetation type; and significant interaction effects between season and vegetation type were observed for percentage char, percentage ash, and unburned patch length
Summary
North Australian tropical savannas cover 1.9 M km and are among the most fire-prone ecosystems in the world. The distribution of unburned patches within a burned area can be deterministic, attributed to a landscape condition (e.g., heterogeneity of fuel type, topography, drainage lines), fire behaviour, or weather; or it may be stochastic, regarded as being caused by chance, if their place of occurrence in successive fires is unpredictable (Gill et al 2003) These unburned patches provide refuge for relatively immobile animals and fire-sensitive plants, becoming an important source for the propagation of seeds, especially when an area is burned so frequently that local extinction of obligate-seeder plant species can occur (Bradstock et al 1998, Edwards et al 2001, Burrows and Wardell-Johnson 2003, Panzer 2003). Fire patchiness has implications for watershed hydrology and soil stability, and may be applied strategically to reduce the risk of hazardous wildfires (Bradstock et al 1998)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
