Restoration criteria on dolomite quarries on "Sierra de Mijas" mountain range
There are many dolomitic outcrops at Rondean sector (into the biogeographical Betic Province). Most of them, involve floral richness and vegetal endemic species due to its calcareous origin. These diverse organisms build peculiar plant communities. They can survive in extreme conditions as drought and high levels of Mg2+ cation. Many studies pronounce that these communities are unique, so they have to be conserved, and some of these plant communities are in the Habitats Directive 92/43 EC.
38% of the dolomitic outcrops can be affected by mining processes. Those particularly affected are dolomitic outcrops located in the mountains range of “Sierra Blanca” and “Sierra de Mijas”. Nowadays, there are 21 quarries in these mountains and they occupy more than 409 Ha. We have studied 11 dolomite quarries and surroundings on “Sierra de Mijas”. There is one vegetation serie on these areas (Rhamno oleoidis-Querco rotundifoliae sigmetum. Dolomitic section), knowing the plant communities we could draw with a Geographical Information System (GIS) the polygons where they are. And using the modified Botanic Value Index equation (Nieto et al., 1999) we could calculate the botanical value of these polygons. After that, we could establish a classification of the study area from the point of view of conservation interest, and we could set up new restoration criteria on these lands.
We have found that approximately the 53 % of the studied area has a high botanic value. There are many endemic taxa in the studied area and 4 species exclusive of the “Sierra de Mijas” mountain range. 90 % of the present communities are included in the Habitats Directive 92/43 CE, and three of the communities are exclusive of the studied area. This is the reason why these quarries have to be restored with a sustainable criteria.
Current restoration plans try to reforest with the climax vegetation (Quercus rotundifolia) or different species of pines (used in several previous reforestations). However, to restore a quarry these plans should include, in addition, other factors such as soil depth, structure of vegetal communities, botanic value, etc. And the Reforest Models of Valle (2004) propose sustainable restoration that could be usefull in the dolomite quarries of “Sierra de Mijas” mountain range.
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