Begun in 2016, the botanical explorations are walks that invite to make together the inventory of the flora of ForestA, vast space around the great letters of Marseille. The botanical explorations are a proposal of the collective Safi and Espigaou within the framework of ForestA, a project carried by Yes we camp in collaboration with Hotel du Nord.
The small forest that has resisted the Foresta has been of interest to us for a long time…
A FORESTA, AN AMAZING FOREST
Climbing a little in the Hill, under the Pink House, a forest of pubescent Oaks hides among the pines of Aleppo. They are perhaps fifty years old or more, they are relatively rare trees in Marseille, because the pubescent oak usually develops on rich, deep and fresh soils, which is not really the case of this former quarry of clay that is ForestA.
So how did these trees get there? What are they telling us? What flora do they host? Is the forest evolving, stable or declining? This is the subject of this exploration on February 9, 2019, the first of the year.
A RELIC OF THE OLD CASTLE ESTATE
ForestA has been modelled by the activities that have crossed him: State forest, clay quarry of the Tuileries, area of embankment of Grand Littoral… Despite all these transformations, the oak forest is visible on all the archival images of GeoPortal since the ciqnant years. A persistence may be due to his situation.
Little accessible and difficult to see from the road, it is located at the level of a huge Boulder and stretches along a steep slope. It thus collects rainwater and may benefit from the groundwater of ForestA. This is certainly what has favoured the installation of these Oaks which, although Mediterranean, like freshness.
A TREE ADAPTED TO WARM AND COLD
Quercus pubescens means oak with short and soft hairs, in reference to the inner face of leaves and young twigs. These hairs trap the dew and maintain a humid environment. Its range is quite extensive. Moving north, it can be subjected to negative temperatures that would freeze the water of its cells, also this oak also has a strategy to adapt to the cold: in autumn, its leaves dry on the tree, and will fall to the ground only to regrowth of the following, they say they are marcescing.
However, losing its leaves is not a common strategy in the Mediterranean. Think of the pine, the olive tree, the green oak, its neighbors here, who keep their leaves all winter. As winter temperatures are not very intense, they do not freeze. For these trees, it is therefore preferable to keep their leaves protected with hairs or a layer of wax, rather than to incur an energy expenditure in the spring to make new ones.
A WELCOMING AND SOCIAL FOREST
The carpet of leaves at our feet is home to many insects and fungi mycelia. They participate in transforming this litter into rich and fertile humus. A handful of land taken from the road is without a call on the work done by these organisms. taken from the slopes, the Earth is red ochre when the one at the foot of the Oaks is dark brown.
Acorns, pubescent oak fruits, attract and feed many animals including the oak Jays, which by their hoarding behavior contribute very actively to the spread of acorns.
In our forest, the pubescent Oaks are associated with Green Oaks. When they are together, these two trees indicate the meso-Mediterranean climatic stage (neither too hot nor too cold) which welcomes, thanks to the disappearance of the leaves of the pubescent oak which lets penetrate the light in the undergrowth, a procession of plants associated characteristics.
When plants generate favourable reception conditions for other plants (availability of light, soil structure…), it is referred to as vegetal sociability.
MEDITERRANEAN UNDERGROWTH PLANTS
Viorne-Tin Viburnum Tinus, nerprun alaternus Rhamnus alaternus, narrow-leaved corded Phillyrea angustifolia, European salsaparilla smilax ASPERA and Aleppo Pine Pinus halepensis… Plants that we found in the forest inventory (see map site) which have joined more thermophilic plants, which love the heat.
We observed in the heart of the forest, young Oaks mixed with older trees, their number from the Center to the periphery. When the oak loories, the Aleppo Pine appears.
These two trees are easily cohabiting, because their demographic strategies are very different and complete: the oak has a slow growth, it blooms around 20 years and a life of 500 years and more. The pine, has a fast growth and lives about 100 years. In the vicinity of the forest, a burned-out area reveals a car carcass and skeletons of calcined trees. One question then arises to us, the pine Halep, very flammable, can it endanger the forest?
A FERN WITH SCALES
Naturalised IRIS, from the Immortelle of Italy… populate the rock. And even a very beautiful fern, the ceterach compendial (Asplenium ceterach), whose underside is covered with silver scales that participate in a thorough adaptation to drought. In dry weather its leaves curl to present only the scales that are barrier to evapotranspiration.
We also discovered a small cave at the top of the site, a nice surprise for the little explorers botanists…