Charcoal and pollen analysis: Examples of Holocene fire dynamics in Mediterranean Iberian Peninsula

Abstract

The present study focuses on charcoal particles (a component of vegetal ashes, Bodí et al., 2014) counted during palynological analysis. The absolute frequencies of this microcharcoal have been correlated with pollen percentages of resprouts, mesic trees, Pinus or AP (arboreal pollen), in order to observe patterns in the spread of wildfires, dynamic changes in plant succession, and possible cyclicities in Holocene microclimatic changes. The sites selected for this work are located within the Mediterranean area of the Iberian Peninsula and in the Eivissa Balearic Islands, between 42°16′ N and 36°47′ N. Results show two brief changes in vegetation dynamics during the Holocene. The first coincides with the 8.2calkyr event and marks both the beginning of Holocene dynamic changes in plant succession and the Climatic Optimum. During this first phase, charcoal peaks coincide with minimum percentages of mesic taxa (low rainfall) and occur just before an increase of resprout taxa (taxa which grow after fires). The second change happens at the ~4.2calBPkyr event, when fires are most frequent and resprout taxa increase their values compared to mesic taxa and forest cover (AP). We have also observed some differences in vegetal dynamics studied at different latitudes, which appear to be punctuated by climate or insularity. In short, (i) actual succession of Mediterranean vegetation can be recognized in the past; (ii) resilience in vegetation is more common during the first half of the Holocene than in the recent Holocene: A trend to aridity, reduced biomass and anthropization has caused vegetation resilience to decline; (iii) synchronicity between fire peaks of different sequences studied is very rare; and (iv) coincidence of many peaks of charcoal with Bond events inclines us to think that fires are more conditioned by the climate than by anthropogenic impact.