Fire and late‐Holocene expansion of Quercus ilex and Pinus pinaster on Corsica

Abstract

Abstract. The natural origin of old Quercus ilex (holm oak) forests on the west coast of Corsica is a matter of dispute. This paper discusses the use of pedoanthracology, especially adapted to approach topics in palaeoecology requiring a high spatial precision. It also shows the importance of fire in vegetation change during the Holocene. Pedoanthracology relies on botanical identification and AMS 14C dating of micro‐charcoal found in soil. Three test pits were dug in a forest currently protected within the ‘Man and Biosphere’ program. These pits yielded large quantities of charcoal. There is evidence that Pinus nigra ssp. laricio (laricio pine) and understorey heather species (Ericaceae) played an important role in the vegetation at the beginning of the Subatlantic (ca. 2500 BP). The importance of Pinus pinaster (maritime pine), Quercus ilex and a few mesophilic species increased between 2000 and 1000 BP. Charcoal fragments found in the soil show the role of fire in the vegetation changes recorded. The late expansion of P. pinaster results from a high fire frequency. The hypothesis proposed in the paper suggests that fires destroyed the remaining toxic humus that had accumulated during the millennia which preceded the arrival of Q. ilex to our study sites. The late development of holm oak forest is a combination of the migration of the species and the increase of fire frequency since 2500 BP, most probably resulting from slash‐and‐burn agriculture.

Comparison of postfire mortality in endemic Corsican black pine (Pinus nigra ssp. laricio) and its direct competitor (Pinus pinaster)

“…The postfire regeneration of laricio pine is unknown, but other P. nigra generally lack regeneration, especially when compared to maritime pine (Pausas et al 2008). These results are consistent with Carcaillet et al (1997), who explain that the extension of maritime pine and the decrease in laricio pine were caused by an increase in fire frequency during the Holocene.…”

“…After the last ice age, laricio pine was the first to undergo extension (2500 BP), followed by maritime pine (between 2000 and 1000 BP). Charcoal fragments suggest that fire and slash-and-burn agriculture favor the expansion of maritime pine (Carcaillet et al 1997), and its postfire regeneration is far denser than that seen with P. nigra (Pausas et al 2008). Maritime pine currently covers 18% of Corsican forest, compared with 31% for laricio pine (French National Forestry Inventory-FNI).…”

Negative responses of highland pines to anthropogenic activities in inland Spain: a palaeoecological perspective

“…yr B.P. During this succession, P. nigra would have become locally extinct and would have been replaced by other Mediterranean tree taxa (Carcaillet et al 1997). The palynological data from Lac de Creno (and some other sites in Corsica) correspond well to this pattern, although considerable oscillations exist during the mid-Holocene.…”

The Holocene at Lac de Creno, Corsica, France: a key site for the whole island

“…Previous historical studies have clearly shown that everywhere in Corsica Q. ilex could establish itself only after the optimum of E. arborea climax formations, human action being accountable for the opening of the latter (Reille, 1984(Reille, , 1992aReille & Burr, 1997 ;Carcaillet et al, 1997).…”