How life regains its rights one year after the Massif des Maures fire

In this photo we see the regeneration in the crown of a tree heather (Tree Erica) burned in the fire of august 2021 of the Plaine des Maures National Nature Reserve in Var.

Fires are “global herbivores”: they destroy the generally unburied parts of plants, such as foliage and branches, even the trunk of trees, but also sometimes the tops of roots or stumps.

Many plants are quite tolerant to “classic” mediterranean fires, small magnitudes. They have adapted to it physiologically (mobilization of secondary buds, water storage) and/or morphologically. Cork oaks and certain conifers, for example, have special barks that are thick and shaped to protect the living parts.

Fires acting as “environmental management tools”

Other plants have buds placed at the base of the plants to regenerate as soon as the vegetative part is gone.

Finally, many species rely on regeneration from seed rather than vegetative regeneration. Seed dispersal from the cones of conifers (such as cones) can be favored by heat, causing them to burst and spread. Germination is also favored in the upper part of the soil, especially in the post-fire availability of nutrients.

Thus, with the vegetation it has adapted, possessing capacities to regenerate after some of the catastrophic events what constitutes fires. For millennia, these fires have also served as environmental management tools: they sculpt landscapes, from logging to “cleaning” forests. An “openness” of the environment often sought by planners, for pastoral practices… as well as for fire preventionexactly.

A terrible fire for the biodiversity of the Plaine des Maures nature reserve
A terrible fire for the biodiversity of the Plaine des Maures nature reserve – Romain Garrouste / MNHN (via The Conversation)

The crown, a particular form of regeneration in the Massif des Maures

This species of fire bonsai crowns bear witness to past fires and the ability of these plants to regenerate from the stump, from semi-buried buds that awaken after the fire, sometimes very quickly, depending on the season. and the moisture present in the soil.

The interior of the stump is usually burned and then excavated by xylophagous organisms (fungi, insects). The growth of these plants is thus made by these successive concentric crowns that become witnesses of past fires, often forming a bead or “lignotuber”. Years after the fires, we can thus find hidden stumps of oversized bushes that seem modest, much older than the diameter and height of their stems would suggest.

heathers (Erica sp.), wiring (Phyllirea spp.) but also strawberry trees (united strawberry tree) form those characteristic bright green crowns that mark the scorched landscape and attract wildlife, including the first insects Y birds.

The consequences of the Massif des Maures megafire are still being studied. Regeneration has started but it does not allow to prejudge the direct and indirect impacts on wildlife notably. It will take several years to take stock of this, in addition to the effects of the fire, those of the summer and winter droughts, due to global warming.

This review was written by Romain Garrousteresearcher at the Institute of Systematics, Evolution, Biodiversity of the National Museum of Natural History.
The original article was published on the site of The conversation.

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