Quarrying is a form of mining distinguished by the fact that the product is for building or architectural purposes, rather than being destined for further processing (Lahiri-Dutt, 2004). Limestone is part of the rocks the more extracted, as this rock is also used as a source of aggregates and in the manufacturing of lime, whose global output in 2008 reached 290 million tonnes (USGS, 2009). In Benin, the limestone is mainly used for the cement production. Extraction activities can have both negative and positive effects on the various environmental components of the quarries areas. Indeed, although limestone quarries provide refuges for some endemic species (Clements et al., 2006), extraction activities lead to a complete loss of topsoil, compaction of the remaining soil, nutrient depletion and high pH that makes natural establishment of vegetation very unlikely (Cohen-Fernández, 2012). Therefore, revegetation requires the addition of amendments for soil improvement. Our study aims to assess the floristic characteristics of the Fongba limestone quarry in Benin for implementing strategies to restore the degraded sites. Plant communities and soil physico-chemical parameters in pits will be compared to the surrounding plants communities and soil, considered as the reference (Aïtondji et al., 2015a). An adapted restoration strategy will be developed through an experimental culture of useful species on amended sites.

Results: Ecological characteristics of vegetation (Ecosociological subdivisions )

Ecosociologically, ruderal and segetal species were the most abundant (56.9%) in the post quarry vegetation, while the reference was characterized by the forest (28.1%), savanna and post cultural species (40.6%).

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23juin

Results: Ecological characteristics of vegetation (Chorological subdivisions)

Results revealed that the native species were more abundant (34.8%) in the reference than the post quarry vegetation (12.7%), the latter being characterized by an abundant of the wide-spatial occurence species (57.7%).

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23juin

Results: Ecological characteristics of vegetation (life forms)

Life forms spectrum analysis shows a large distribution of Therophytes (50.7%) in the post quarry vegetation, while Phanerophytes were the most abundant (72.5%) in the reference.

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23juin

Results: Discrimination of the plant communities

On the basis of a detrended Correspondence Analysis (DCA) in PCORD version 5, a matrix of 111 species x 8 relevés resulted in two plant communities (figure 5 & 6). The DCA clearly separated the pit relevés from the reference. This result shows that plant communities of the post quarry vegetation are different from those of the reference.

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23juin

Results: Threatened plant species in Fongba quarry area (2)

Zanthoxylum zanthoxyloides (Lam.) Zepernick & Timler (Fagara; Rutaceae) is a Benin Red List species considered Vulnerable (Neuenschwander et al., 2011). It is a medicinal plant (Akoegninou et al., 2006).

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23juin

Results: Threatened plant species in Fongba quarry area (1)

Floristic relevés revealed the occurence of Milicia excelsa (Welw.) C.C.Berg (Iroko; Moraceae)), a Benin Red List species. Milicia excelsa is considered Endangered (Neuenschwander et al., 2011). It is a great value lumber found inside Fongba quarry area, near the excavated site. It is therefore very important to restore the excavated areas as the quarrying activities continue. So that, this species will found a favorable habitat for its survival in Fongba.

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23juin

Growth of the nursery seedlings: Stage 2

Two weeks seedlings of Lonchocarpus sericeus (Poir.) Kunth.

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23juin

Growth of the nursery seedlings: Stage 2

Two weeks seedlings of Albizia zygia (DC.) J.F.Macbr.

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23juin

Growth of the nursery seedlings: Stage 1

Cotyledon leaf stage of Lonchocarpus sericeus (Poir.) Kunth.

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22juin

Growth of the nursery seedlings: Stage 1

Cotyledon leaf stage of Albizia zygia (DC.) J.F.Macbr.

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22juin

Nursery watering

After seeding, the polyethylene bags were watered twice a day.

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22juin

Native plant nursery

For the soil restoration, we used native species because many exotic species become invasive and disrupt even agricultural activities in the surrounding area. This strategy of restoring reduces costs and promotes a better return of species in the area. The planting of these nursery plants in the backfilled pit will accelerate the reconstitution of soil fertility. Thus, the lands could be returned to the owners, for their original fonction. Two plant species were used: Albizia zygia (DC.) J.F....

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22juin

Identification of scientific names of the species

The scientific names of all plant samples were identified with assistance of an expert in plant systematics.

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22juin

Samples conditioning

For a long-term conservation of plant samples, they were be kept dry in newspapers using adhesive tape.

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22juin

Phytosociological relevés

Phytosociological relevés carried out using the Braun-Blanquet scale, in post quarry vegetation and fallows in order to characterize the post quarry vegetation. (Des relevés phytosociologiques ont été réalisés en utilisant les coefficients de Braun-Blanquet, afin de caractériser la végétation post carrière).

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22juin

Land use, land cover (closed quarry area)

The closed quarry area is one of the land cover, land use created by the quarrying activities. (La zone de carrière fermée est une des formes d'occupation et d'utilisation des terres issue des activités d'extraction).

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21juin

Land use, land cover (fallow)

Fallow is one of the land cover, land use of the study area. (La jachère est une des formes d'occupation et d'utilisation des terres de la zone d'étude).

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21juin

Land use, land cover (teak plantation)

Teak plantation is one of the land cover, land use of the study area. (La teckeraie est une des formes d'occupation et d'utilisation des terres de la zone d'étude).

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21juin

Land use, land cover (palm grove)

Palm grove is one of the land cover, land use of the study area. (La palmeraie est une des formes d'occupation et d'utilisation des terres de la zone d'étude).

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21juin

Study area

An aerial exploration of the quarry area using a Pro MAVIC drone helped us to identify the different types of vegetation in the limestone quarry area of Fongba. A mosaic of the drone photos was done using Pix 4d. The most undisturbed vegetation was the fallows considered in this study as the reference of the removed vegetation. The Fongba limestone quarry vegetation is characterized by palm groves, teak plantations and fallows. The other land use are created by the quarrying activities. (Une...

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13juin

Native species and substrates used for the site restoration (espèces et substrats utilisés pour la r

Two native species of Leguminosae (Albizia zygia (DC.) J.F.Macbr. and Lonchocarpus sericeus (Poir.) Kunth) and three soil amendments (compost; wood shavings; topsoil from surrounding) were used for the site restoration. (Deux espèces endogènes de la famille des Leguminosae (Albizia zygia (DC.) J.F.Macbr. and Lonchocarpus sericeus (Poir.) Kunth) et trois traitements (compost; copeaux de bois; terre arable des environs) ont été utilisés pour restaurer le sol.

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13juin

Methods (Méthodes)

This study is characterized by three key methodological steps (figure 3): 1. The study area characterization: we used a MAVIC Pro drone to explore the limestone quarry area of Fongba. This activity helped us to describe the quarry area and to identify the floristic ecosystem which can be considered as the reference of the removed vegetation. 2. Floristic analysis: some phytosociological relevés carried out in the quarry pits and in the reference. All species were identified. Data were analyzed...

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08mai

The expected results (les résultats attendus)

As shown in figure 2, at the end of this research work: - the floristic list of the spontaneous vegetation of the quarry and his surrounding will be established and analyzed; - restoration species identified among the local vegetation; - a strategy for recovering pits developed; - plant performance evaluated; - a report will be available in september 2018. (Comme le montre la figure 2, les résultats attendus à la fin de ce travail sont: - la liste floristique de la végétation spontanée de la...

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19mar

The research problem [La problématique de la recherche]

In Benin Republic, the limestone is mainly used for the cement production. The extraction of this subsoil resource leads to a complete loss of topsoil, compaction of the remaining soil, nutrient depletion and high pH that makes natural establishment of vegetation very unlikely (Cohen-Fernández, 2012). Therefore, revegetation requires the addition of amendments for soil improvement. Our study largely corroborates with this view. It aims to assess the floristic characteristics of the Fongba...

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19mar