Post-fire regeneration of the Holm oak in Mediterranean pine reforestations

Abstract

Leverkus, A.B., Castro, J., Rey Benayas, J.M. 2014. Post-fire regeneration of the Holm oak in Mediterranean pine reforestations. Ecosistemas 23(2): 48-54. Doi.: 10.7818/ECOS.2014.23-2.07

The extraction of the burnt wood is a common practice after wildfire, yet its effects on the recolonisation by Quercus species are poorly known. We established an 18-ha plot in a burnt pine reforestation in Sierra Nevada (S Spain), with three experimental wood-management treatments: Salvage Logging (felling the trees, chopping off the main branches, piling the logs, and masticating the remaining branches), Partial Cut (felling 90 % of the trees without further actions), and Control (no actions taken). Some clusters of pines survived within the limits of the plot and were left standing (totalling 1.5 ha), and adjacent to the plot were some unburnt, acorn-producing Holm oaks (Quercus ilex subsp. ballota) from which biotic dispersal occurred. We monitored emergence, survival, and size of oak seedlings in the plot for seven years. We found 801 oaks the first year, corresponding either to post-fire resprouts or to acorns dispersed right after the fire and before treatment implementation. After post-fire treatment implementation, 447 seedlings emerged throughout the plot, likely due to dispersal by European jays (Garrulus glandarius): 62.9 % under live pines and 37.1 % in the rest of the plot. Emergence was greatest in Control during the first years. The treatment factor lost importance in later years, as acorn dispersal became more directed towards the live pines. Seedlings under pines had greater survival but lower growth, likely due to competition for nutrients, light, and water. We conclude that small patches of pines that survive a fire, as well as dead standing trees during the first years, can attract acorn dispersers and that, in case of the surviving pines, a second disturbance will be needed to free the recruited oaks from competition. Management practices that favour these structures can aid the natural recovery of the ecosystem.