A palaeoecological attempt to classify fire sensitivity of trees in the southern Alps.

Using pollen percentages and charcoal influx to reconstruct the Holocene vegetation and fire history, we differentiate six possible responses of plants to fire of medium and high frequency: fire-intolerant, fire-damaged, fire-sensitive, fire-indifferent, fire-enhanced and fire-adapted. The fire sensitivity of 17 pollen types, representing 20 woody species in the southern Alps, is validated by comparison with today’s ecological studies of plant chronosequences. A surprising coincidence of species reaction to fire of medium frequency is characteristic for completely different vegetation types, such as woodlands dominated by Abies alba (7000 years ago) and Castanea sativa (today). The temporal persistence of post-fire behaviour of plant taxa up to thousands of years suggests a generally valid species-related fire sensitivity that may be influenced only in part by changing external conditions. A non-analogous behaviour of woody taxa after fire is documented for high fire frequencies. Divergent behaviour patterns of plant taxa in response to medium and high fire frequencies (e.g., increases and decreases of Alnus glutinosa) also indicate that post-fire plant reactions may change with increasing fire frequency. [ABSTRACT FROM AUTHOR]