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

Abstract

-In Spain, many Pinus halepensis Mill. forests have been seriously affected by significant forest fires in the past decade, in 1994 alone, more than 100 000 ha were burned in Eastern Spain. In order to study the reproductive characteristics of P. halepensis after forest fires, six locations were selected in four areas affected by serious fires in the summer of 1994, and the following different precipitation zones were studied: dry-subhumid, dry and semi-arid. Ten years after the fires, data relevant to the production of pine cones: serotinous (grey), mature (brown), immature (green) and opened cones, was collected from areas with natural post-fire regeneration. Various cone and seed characteristics, such as pine cone seed number and weight, and germination percentage, were measured. The results showed greater production of cones and strobili in high-density sites. The biggest cone sizes (volume) and seed number per cone were related to site quality (dry-subhumid precipitation zone). Also, viability and germination percentages were higher with better site quality, with significant differences in values for serotinous and non-serotinous cones. Despite these differences, the canopy seed bank was large enough to ensure regeneration in this area for this age stand.Pinus halepensis / serotiny / canopy seed bank / natural regeneration Résumé -Influence de la densité du peuplement et de la fertilité de la station sur la dynamique de reproduction de Pinus halepensis Mill., dix ans après d'importants incendies. En Espagne, dans les dix dernières années, de nombreuses forêts de Pin d'Alep ont été gravement touchées par d'importants feux de forêt. Rien qu'en 1994, plus de 100 000 ha ont brûlé dans l'est de l'Espagne. Dans le cadre d'une étude de la dynamique de la reproduction du Pin d'Alep après incendie, six sites, situés dans des zones de feux de forêt survenus lors de l'été 1994, ont été observés. Ces sites présentent des niveaux de précipitations différents : sec à sub-humide, sec et semi-aride. Dix ans après incendie, des données concernant la production de cônes de pin : sérotineux (gris), mûrs (marrons), immatures (vert) et cônes ouverts, ont été collectées dans des zones de régénération naturelle. Diverses caractéristiques des cônes et des graines ont été relevées : nombre et poids des cônes et des graines, taux de germination. Les résultats révèlent une production importante de cônes et de strobiles dans les sites à forte densité de pin. Le volume des cônes et le nombre de graines par cône étaient liés à la fertilité de la station (zone sèche à sub-humide). Les taux de viabilité et de germination étaient aussi plus importants dans les zones présentant le plus de précipitations et des écarts significatifs ont été observés entre les valeurs de cônes sérotineux et non sérotineux. Malgré ces différences, les banques de graines dans les peuplements étaient suffisamment importantes pour assurer la régénération du pin dans cette zone.Pinus halepensis / sérotine / banque de graines de la canopée / régénération na...

Aleppo pine regeneration after fire along an aridity gradient

“…Early flowering and cone production is promoted by low pine tree density [8,11,14], as per our results. Low pine tree density induces a lower intraspecific competition, so a higher amount of water, light and nutrients are available for the individuals.…”

“…The H-Dbase relationship for Aleppo pine has been described in Moya et al [11]. These factors were also related to the De Martonne Aridity index (Im Three GLM were developed to obtain relationships between Reproductive trees (RT), Serotiny (S) and cone production (CP) and between the factors studied.…”

“…Differences in cone production, pine tree growth and foliar nutrient content [9,10,15] have been described for different fire events in various locations. In coetaneous regenerated stands (burned in the same year) in different locations along the eastern Iberian peninsula, growth, cone production, time to reach reproductive phase and serotiny have been related to site quality and tree density [11,13] but aridity indices were not included.…”

Remote sensing support for post fire forest management

“…in forest burnt stands requires the functional and structural assessment of the landscape mosaic and of the size and behaviour of the considered wildfires. In this framework, monitoring may have several aims to support post-fire management: to locate and estimate the extent of the burnt areas (burnt scar peri meter mapping: e.g., Eva & Lambin 1998, Smith et al 2002, Holden et al 2005; to as sess the damages suffered by the forest stands (e.g., McHugh & Kolb 2003); to check the ability of the ecosystem to natur ally recover after the fire (e.g., Henry & Hope 1998, Diaz-Delgado et al 2003, Moya et al 2007; to support the planning of re clamation interventions; to assess the dy namics (pattern and speed) of the natural re covery (e.g., Turner et al 1997, Davis et al 2005; to check the outcome of any eventual restoration intervention (e.g., Raftoyannis & Spanos, 2005).…”

Relative Contributions of Forest Vegetation, Land Cover, Topography and Climate in Explaining Fire Regime Patterns (1974–2005) in Peninsular Spain

“…Some of the largest fires registered in Spain have occurred on the Mediterranean coast and many of these were caused by lightning, as happened in 1994, [7]. These fires mainly affected P. halepensis reforestations or areas invaded by the species where cultivation has been abandoned (e.g., [31,32]). In this area (type 7) the pattern obtained shows that a higher proportion of wooded forest (according to the CLC-1) was correlated with longer rotation periods.…”