Action of eradication of invasive species on the temporary pond of Chiuvina (Corsica, Agriate)
20 July 2018
Sorba L.1, Pietri C.1, Piazza C.2, Garrido M.1, Leccia S.3, Spinosi P.2, Favier C.2
1 Office de l’Environnement de la Corse, Service "Espèces et Milieux Naturels"
2 Office de l’Environnement de la Corse, "Conservatoire Botanique National de Corse"
3 Office de l’Environnement de la Corse, Service "Espaces Protégés"
Several departments of the Office of the Environment of Corsica (OEC) have joined forces this summer to eradicate two invasive species (Dittrichia viscosa, native species of the island, and Paspalum distichum, exogenous species) in a temporary pool of Agriate (Figure 1): Chiuvina (municipality of Santu Pietru di Tenda).
For a few years these two taxa have colonized a large part of the pond of Chiuvina and compete with the characteristic species of these environments and in particular Elatine brochonii (photos 1 to 3), small annual plant and amphibian, protected on the French territory.
Corsica is the only island locality of this species. Three stations are currently known: Chiuvina, Purcilella and Padulellu; all are endangered (heavy use, filling, presence of invasive species).
As part of the CARE-MEDIFLORA project and the action program for the conservation of Corsican temporary ponds, which has been run for several years by the OEC, an eradication operation for D. viscosa and P. distichum has therefore been decided, to allow the development of characteristic species of "temporary Mediterranean pools" (priority habitat of the Habitat Directive). This action should be beneficial for E. brochonii, but also for: Isoetes velata, I. histrix, Pilularia minuta, Littorella uniflora, Pulicaria vulgaris, Ranunculus ophioglossifolius, R. revelierei, protected and / or rare species present on the Chiuvina pond.
The operation began on June 14, 2018 and ended on July 18, 2018. Prior to the uprooting of invasive species, an inventory was conducted and a monitoring protocol was implemented:
- transect and vegetation surveys,
- mapping of D. viscosa, P. distichum and E. brochonii areas,
- establishment of fixed points for the realization of a photographic follow-up on the long term.
The pulling of D. viscosa has proved difficult, whether or not the pond is in water (photos 4 and 5). The very compact soil and the size of the individuals (up to 40 cm in diameter) required the use of tools (shovels, 4-tooth digging fork, claws). More than 600 feet of D. viscosa were uprooted (about 230 m2) while they were not yet in bloom to prevent seed spread (photos 6 and 7). Because of the remoteness of the site from any road, the heaps were not evacuated, but put in windrows, for drying, on rocky slabs present nearby.
Concerning the invasive alien species, P. distichum, the pulling out was very tedious and could not be realized in totality. Also, priority areas have been identified in the field (Figure 1): contact area E. brochonii / P. distichum especially and only these have been treated. Ten hours of work were needed to eradicate 120 m2 of P. distichum from the 390 m2 mapped. The grubbing was done manually, taking care not to leave any piece of rhizome in the ground. The species was then packaged in two 50-liter bags and exported for destruction.
The monitoring will be carried out every 6 months by the agents of the OEC and the agents of the municipality of Santu Pietru di Tenda which will ensure the sustainability of the action over the long term. It will consist of:
update the transect,
- map and record the phenology of each foot of D. viscosa,
- map areas with E. brochonii and P. distichum,
- and make a photographic follow-up from previously selected fixed points.
During each monitoring and after having realized the inventory of the pond, a complementary uprooting of D. viscosa and P. distichum will be realized. Long-term monitoring will also assess the life of the D. viscosa seed bank in the soil.
Figure 1: Localisation of temporary pond of Chiuvina
Photos 1-3: Elatine brochonii
Photos 4-5: Dittrichia viscosa uprooting
Photos 6-7: General view of the east side of the pond before and after the uprooting of Dittrichia viscosa