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Community‐level functional interactions with fire track long‐term structural development and fire adaptation

Brussel, Thomas, Minckley, Thomas A., Brewer, Simon C., Long, Colin J.
Journal of vegetation science 2018 v.29 no.3 pp. 450-458
biomass, fire frequency, fire history, fires, flammability, fossils, functional properties, lakes, paleoecology, plant communities, pollen, vegetation, Oregon
QUESTIONS: Functional interactions between fire and fire‐dependent plant communities have been considered to select for increased community flammability. We address this concept by resolving: (a) can fossil pollen records be used to examine past variations in functional attributes; (b) can community‐level, functional responses to fire be obtained by coupling fire history with pollen derived plant traits; and (c) has directional selection promoted attributes that increase community flammability? LOCATION: Breitenbush Lake, Oregon, USA. METHODS: We developed a framework based on ecological understanding of functional traits and pollen records to analyse variations in functional attribute expressions through time. Fire‐related functional attributes that indicate sensitivity to changes in fire activity were identified and associated with taxa from a pollen record. RESULTS: Nine of the 14 functional attributes were significantly related to fire frequency (number of fires 1,000 per year). When combined with fire history data, variation in the abundances of functional attributes suggest selection of plant community expressions that indicate community‐level responses to fire related to changes in structural development and changes in fire adaptation. Fire frequency variations may drive directional selection for fire‐adapted attributes, and against fire‐sensitive attributes. Our results indicate increased Holocene fire activity may have been linked to vegetation functional interactions with fire. CONCLUSIONS: Our method of combining paleoecological data with functional traits allowed reconstruction of community‐level changes in the expression of functional characteristics, providing evidence on structural development and changes in fire adaptation. Our results (a) highlight the capacity of paleoecological records to track plant community trait composition; (b) provide novel information on fire–vegetation relationships, independent of and complementary to conventional methods of disturbance‐based paleoecological interpretations; (c) suggest the Holocene fire trend may be linked to the type of biomass being burned through directional selection; and (d) suggest an application that may be applied to quantify community responses to various disturbances across broad temporal and spatial scales.