Effects of silviculture treatments on vegetation after fire in Pinus halepensis Mill. woodlands (SE Spain)

Abstract

-In August 1994, two great fires occurred in SE Spain burning 44 000 ha of mature Pinus halepensis Mill. forests. Experimental silviculture treatments were carried out on five-year-old P. halepensis seedlings from natural regeneration: thinning to a final density of 1 600 trees/ha, total scrubbing, thinning plus scrubbing, thinning plus pruning to half the total height, scrubbing plus pruning and thinning, scrubbing plus pruning. Treatments were carried out in 45 permanent plots located in two localities with different ombroclimates: semiarid and dry. Two years after treatments were carried out, floristic richness, diversity, life form rates and vegetation cover were measured or estimated for each plot. Results showed a high capability of post-fire colonizing vegetation to rapidly recover the ecological values recorded before carrying out silviculture treatments. Floristic richness and cover values did not vary significantly. Significant differences in the vegetation life form rate were detected after thinning and scrubbing. Therophyte cover showed a significant increase two years after these treatments. great fire / forest management / Mediterranean ecosystem / pine seedlings Résumé -Effets des traitements sylvicoles sur la végétation après un feu dans des forêts de Pinus halepensis Mill. (sud-est de l'Espagne).En août 1994, deux grands feux se sont produits dans le sud-est de l'Espagne et ont brûlé 44 000 ha de forêt de Pinus halepensis Mill. adultes. Après le feu, il y a eu une régénération intense de la forêt qui a formé des bosquets touffus de plantules. On a alors procédé à des études sur la régénération naturelle du pin en appliquant différents traitements sylvicoles expérimentaux sur ces bosquets : dépressage jusqu'à une densité finale de 1 600 arbres/ha ; débroussaillement total ; dépressage plus débroussaillement ; dépressage plus élagage jusqu'à la moitié de la hauteur totale ; débroussaillement plus élagage et débroussaillement plus dépressage plus élagage. Les traitements se sont effectués sur 45 parcelles permanentes situées dans deux endroits différents ayant des ombroclimats différents : semi-aride et sec. Deux ans après avoir subi les traitements, on a mesuré la richesse de la flore, la diversité, le ratio de formes de vie et la couverture de la végétation sur chaque parcelle. Les résultats ont montré une grande capacité de la végétation colonisatrice postérieure à l'incendie pour récupérer les valeurs écologiques enregistrées avant l'application des traitements sylvicoles. La richesse de la flore et la couverture de la végétation n'ont pas changé significativement. Néanmoins, on a détecté quelques différences dans les ratios de formes de vie après éclaircie et débroussaillement : la couverture de thérophytes a augmenté significativement. On peut conclure que le dépressage peut être considéré comme un traitement approprié pour des masses très denses de forêt de pins de régénération après un incendie. grands feux de forêt / gestion forestière / écosystèmes méditerranéens / plantules de pin

Tree density and site quality influence on Pinus halepensis Mill. reproductive characteristics after large fires

“…Background studies demonstrated the same conclusions [21,44] in other Mediterranean areas. Thus, site quality seems to play an important role in seed production, which is linked to tree density, and in turn influences seed number [13].…”

“…If a new fire occurred before the tree reached the reproductive phase, post-fire natural regeneration might be deficient [10,43] which produces important environmental impacts as risk of soil loss, loss of biodiversity, loss of carbon sink, etc. This information could be very useful for foresters when making management decisions, for example in applying silvicultural treatments in the early stages of regrowth [13].…”

Effect of wildfires and post-fire forest treatments on rabbit abundance

“…For instance, it is known that P. bituminosa, which is very common during the first years after fires (Martínez-Sánchez and Herranz 1999; De las Heras et al 2004) and R. peregrina (both positively correlated with the abundance of rabbits), are commonly favoured by other herbivores due to their high nutritive value (Chapuis et al 1995;Bartolomé et al 1998;Sternberg et al 2000;Ventura et al 2000;Sternberg et al 2006).…”

“…Observed rabbit colonisation and the increase in rabbit abundance in burnt areas could be related to the appearance of open habitats with a significant surface area occupied by bare ground and a high diversity of low herbaceous, mostly gramineous and leguminous vegetation (Martínez-Sánchez and Herranz 1999; De las Heras et al 2004), which coincides with known habitat preferences for rabbits (Fa et al 1999;Beja et al 2007;Ferreira and Alves 2009). Our study shows an increase in rabbit abundance for at least 5 years after the fire indicating that in the mid-term, forest fires have a relatively positive effect on rabbit abundance.…”

Reproduction de pinèdes de Pinus halepensis Mill. six ans après incendies et traitements sylvicoles

“…Thinning can be performed with a clearing saw (portable swinging arm scythe) since the more expensive use of the chain-saw is still not needed. Although effects of silvicultural treatments on pine growth [13] and on the accompanying vegetation [6] two years after treatments have been studied, effects of silvicultural treatments on the first stage of cone and seed production are currently not well known. In this sense [13] points out that silvicultural treatments including thinning improved the probability of cone production by a factor of 2.07 in relation to the control 22 months after treatment.…”