In the following a short and not complete overview on selected non-granitoid rock outcrops is given which show ecological similarities with typical inselbergs.
In certain parts of the tropics massive table mountains consisting of old sedimentary sandstones occur. Most spectacular are the “tepuis” which form huge isolated mountains on the Guyana shield. Characterized by very steep vertical sides they may tower over 1500m above the surrounding landscape. They comprise a unique flora which is adapted to extremely low amounts of nutrients. Similar in appearance are the table mountains of the West African Fouta Djallon highland.
Little information is available about plant communities associated with iron-rich outcrops, such as African, Australian and Indian ferricretes and cangas in Brazil. They are formed by processes of weathering/lateritization, but have different physico-chemical characteristics, because they originated from different lithologies. The vegetation of ironstone outcrops, besides sharing physiological, morphological and reproductive adaptations typical lato sensu to rock outcrops, also exhibits adaptations to living on a substrate rich in heavy metals, and possibly contains metallophytes or at least metal-tolerant species. These plant communities are associated with large mineral reserves, and in many areas the intensity of opencast mining is steeply increasing, which is a huge threat to these ecosystems. Since these outcrops are disappearing, the chance of improving our knowledge of plant tolerance to metals and desiccation becomes scarce.
Plant communities on exposed, bare limestone rocks occur in both temperate (e.g. on the Balkan Peninsula) and tropical regions. Spectacular examples from the tropics are the cone and tower karsts fmationsrom Cuba (known as “mogotes”) and Southeast Asia (e.g. in Malaysia). They frequently support an extraordinarily flora which is rich in endemics.
Brazilian “campos rupestres"
The Brazilian “campos rupestres” sensu lato include montane, grassy-shrubby, fire-prone vegetation mosaics with rocky outcrops of quartzite, sandstone or ironstone (i.e., banded iron formation such as itabirites and cuirasses known as canga) along with sandy, stony and waterlogged grasslands. It occurs in eastern and central Brazil but a few disjunct areas are also found in the country’s interior, as well as in Bolivia. Campo rupestre is rich in plant species (5000 – nearly 15 % of Brazil’s flora occupying just 0.8 % of the land area) and endemics (up to 80 % in some taxa). Patches of transitional vegetation such as cerrado, gallery forests, and relictual hilltop forests also occur within the campo rupestre landscape. Campo rupestre sensu stricto can be defined as grassland mosaic and associated vegetation on the rocky outcrops. Major current threats to campo rupestre are opencast mining, annual anthropogenic burning to support cattle breeding, wood extraction, invasive species, overharvesting of ornamental species and uncontrolled urbanization.