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.
Highlights
Forest fires are a common phenomenon worldwide, and their frequency is expected to increase due to climate change [1,2]
Considering that the average rate of seed germination is 25.6%, 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
They usually occur in forest ecosystems which are adapted to fires [3], such as the Mediterranean pines Pinus halepensis Miller and Pinus brutia Ten
Summary
Forest fires are a common phenomenon worldwide, and their frequency is expected to increase due to climate change [1,2]. If the stands are mature and produce seeds, the regeneration can be achieved (for the species adapted to wildfires such as P. brutia), while in the case of immature stands, they most likely are not able to produce enough quantities of germinated seeds that can secure stand re-establishment. This immaturity risk period depends on the amount of seeds stored in the canopy seed bank and the quantity of viable seeds available after a fire event. Post-fire regeneration of these species is exclusively related to the quality and quantity of the canopy seed bank, since soil seed banks have a transient character [7,8]
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