Is the Reproduction Capacity of Pinus brutia Stands 20 Years after Wildfire Efficient to Secure Forest Restoration in the Case of a Fire Re-Occurrence?

Abstract

A critical issue in effective post-fire regeneration and re-establishment of a burnt forest is the stage concerning the burned stands. When stands are mature and produce seeds, the regeneration can theoretically be achieved, while in the case of immature stands, they may not be able to produce enough quantities of germinable seeds that can secure stand re-establishment. It is estimated that a period of 15–16 years after fire is needed for enough seed production to achieve natural forest re-establishment. This study aimed at the estimation of the real reproduction capacity of Pinus brutia stands 20 years after a wildfire, in an area of northern Greece. The study focused on stand structure, cone production and their morphological characteristics, the morphological characteristics of the produced seed as well as quality of produced seeds. Results analyses showed that despite the young age of the stands, they are quite productive, producing a high number of cones per ha, with a high percentage of trees bearing cones, but with a low number of cones per tree (11.0 cones). An average number of 58.0 fully developed seeds per cone were found, which corresponds to a total number of 620,136 seeds per ha. Considering that the average rate of seed germination is 25.6% (at laboratory conditions), and the theoretical possibility for establishing viable seedling under ambient conditions, these data give an estimation of 1587.5 of one-year old seedlings to recruit the burnt area, in the case of a fire event, if all other parameters remain favorable. These data confirmed the hypothesis that a period of 15–16 years interval between two fires is enough for a burnt serotinous pine forest to reach in such a reproductive stage, able to secure its renewal if a fire occurs. This should be greatly considered in forest fire protection and management plans, which should aim to effectively protect young post-fire forests at least to the age of 15–16 years.

A Sustainable Strategy for Reforestation and Restoration of Burnt Natural Areas in Mediterranean Regions: A Case Study from Greece

“…These factors include subsequent intensive post-fire human interventions (e.g., land-use change, grazing, and trampling); unsuitable site conditions (e.g., erosion, total loss of topsoil, or steep slopes preventing the establishment of seedlings); the reproductive inability of the plant species in burnt forest ecosystems (e.g., an insufficient number of seeds that can germinate) as a result of fire recurrence within a short time period, for example, within 15 years of the last fire event in the same area. The choice of a 15-year period depends on the forest species, but, as a rule, this applies in many cases of forest ecosystems at a global level [39]. As for ecosystems in the second category, their post-fire restoration is a particularly important issue, and this is almost always achieved only through reforestation [18][19][20].…”

Spatiotemporal modeling of vegetation dynamics in a changing environment: combining earth observation and machine learning

“…however, black pine lacks fire-adaptation mechanisms (Rodrigo et al, 2004); it can tolerate low intensity surface fires, but crown fires are usually either stand replacing or lead to the development of non-forest ecosystems (i.e. grasslands or shrublands) (Ganatsas, 2010;Lucas-Borja et al, 2021). This behavior is consistent with the negative trends observed for the species in Catalonia, which, according to the disturbance type map we used from Senf and Seidl (2021b), is also one of the two hot spots mostly affected by wildfires in Mediterranean Europe.…”