Plant Ecology in ‘Campos Rupestres’ of the Chapada Diamantina, Bahia

Abel Augusto Conceição

The Chapada Dimanatina

In central Bahia, the Chapada Diamantina presents several kinds of ecosystems, resulting in a very species-rich area. Remarkable variations of substrate, relief and climate determine distinct kinds of vegetation, such as forests, caatingas (Introduction and Chapter 6), cerrados (savanna-like vegetation) and campos rupestres. Species composition and structure in each vegetation type also vary and are visually perceptible under extreme situations, such as between an open field and a dense bush-like vegetation, or between a seasonally semideciduous forest (plateau forest) and a moist montane forest (cloud forest). In campos rupestres, however, physiognomic variations are unclear, usually presenting subtle changes concerning their floristic composition and vegetation structure.


The Campos Rupestres and the Importance of Scale

The campos rupestres are the predominant vegetation in higher portions of the Espinhaço Range, in the States of Minas Gerais and Bahia. They are present in large extensions, on rocky quartzite-sandstone substrate and sandy soils, which looks like a uniform landscape when seen from distance. Comprising large fields and portions of rocks with small vegetation islands, they are mainly composed by herbs and shrubs, with trees usually restricted to places with deeper soil and where the drying effect of weather is smaller.

There is no exact concept for the vegetation of campos rupestres. Generally, definitions use floristic, physiognomic and geographic aspects, such as reported by Luetzelburg for the Serra das Almas, Itobira and Três Morros, which are mountains of the Chapada Diamantina. He described gradual changes in landscape according to the rising altitude, characterizing the flora on the peak of Serra das Almas as “scarce vegetation composed by Vellozias, Ericaceas, Compositas, Vochysiaceas and shrubs with hard leaves”; and that on the peak of Itobira as “composed by shrubs of Melastomataceas, sparse Eriocaulaceas, low Ericaceas and wooly leaved Compositas”. Phytogeographical and ecological studies have shown that the campos rupestres are marked by a floristic unity with dominant families, such as Asteraceae, Bromeliaceae, Cyperaceae, Eriocaulaceae, Leguminosae, Melastomataceae, Orchidaceae, Poaceae and Velloziaceae , and a high number of endemic species.

Despite this generalized floristic unity, the campos rupestres present high spatial heterogeneity under a closer view. They include different habitats side by side, sometimes separated only by few centimeters, producing a high diversity in small areas . Despite this heterogeneity, distinct places present environmental conditions determining similar physiognomy, which makes scale decisive for analysis and interpretation of biological patterns of campos rupestres.



Habitats

There are large extensions of exposed rocks on the top of the mountains, characterizing the outcrop habitat, which is occupied by typical species, usually from the families Amaryllidaceae, Bromeliaceae, Clusiaceae, Cyperaceae, Orchidaceae and Velloziaceae . These plants are able to survive under restrict water supply, severe variations of daily temperature, high sunlight incidence, strong winds and on shallow soils. In these rocky habitats, some of the most striking features of plants from the campos rupestres are found, such as: effective root systems that hold the plants to the rocks (orchids and bromeliads), even under the action of strong winds; reduced aerial growth with most species up to 1 m tall; small and densely crowded leaves (species of Lychnophora - Asteraceae, and Cuphea - Lythraceae), reducing the surface exposed to sunlight and evaporation; vegetative desiccation tolerance (species of Vellozia and Barbacenia – Velloziaceae, and Trilepis lhotzkiana - Cyperaceae), which enable them to occupy places with extremely low supply of water; CAM ( crassulacean acid metabolism) photosynthetic mechanism (orchids, bromeliads, cacti and species of Clusia - Clusiaceae or Guttiferae), allowing accumulation of CO2 in the thick leaves at night and so reducing the loss of water for gas exchanges during the light time; subterranean systems that allow plants to survive after fire or intense drought (species of Hippeastrum - Amaryllidaceae, and Mandevilla - Apocynaceae); and rosettes that stock water among the leaves (typically in bromeliads).

Around areas of exposed rocks there is the ‘entremeio’ habitat, which is characterized by more continuous vegetation dominated by species of Cyperaceae and Poaceae on sandy soil, besides other families, such as Asteraceae, Leguminosae, Melastomataceae and Verbenaceae.

Clefts and rock fragments of different sizes support differentiated habitats. They are occupied by species with higher nutritional needs and less tolerant to sun and wind, such as ferns (Pteridophyta) and dicots from the families Aquifoliaceae, Asteraceae, Begoniaceae, Euphorbiaceae, Gesneriaceae, Labiatae, Melastomataceae, Myrtaceae, Piperaceae, Verbenaceae , among others.

In the low plains between the rocky outcrops on the top of the mountains, there is a kind of vegetation occupying large fields. It is locally known as ‘gerais’ andis composed by many species of Cyperaceae, Eriocaulaceae, Poaceae, Xyridaceae and Gentianaceae. These gerais have deep soils periodically damp, providing good conditions for small invertebrates, some of which are sources of food for carnivorous bladderworts (species of Utricularia - Lentibulariaceae).

Although dominant families in particular habitats are usually the same in most mountains of the Chapada Diamantina, many species are distinct and exclusive to individual mountains. This is a remarkable aspect of the campos rupestres, and probably the most plausible cause for such a high richness. Most species present very low frequency, and some are restricted to only special habitats, suggesting how vulnerable this vegetation can be. Due to interactions among physical, chemical and biological factors, changes in one or more of these elements may damage the dynamic that maintain the natural biological diversity, reducing or extinguishing populations of species not yet described or of species whose economical potential is yet unknown.


Vegetation Dynamics

Phenology and syndromes of pollination and dispersal

A two-year survey of 58 islands of vegetation on rocky outcrops at the top of mountains (monthly observations ) has shown greater importance of biotic vectors to pollination (mainly bee and bird pollination) than those of dispersal (mainly wind and self dispersal). Analysis of the phenology at community level suggests that plants pollinated by biotic agents present continuous flowering through the year (always in flower with no or few brief interruptions), whereas those pollinated by the wind present one cycle of flowers per year (annual). In the case of dispersal, fruit related to abiotic agents were continuous, whereas those dispersed by animals were annual. Temporal patterns reveal that pollination depends mainly on animals and rain, whereas abiotic dispersal is mostly independent, occurring even during dry seasons. Blooming and fruiting seasons of different species provide continuous resources to the fauna, and the amount of rain does affect the production of flowers and fruits; so that rainy seasons are more favorable to the reproduction of plants pollinated and dispersed by animals.


Succession

Spatial patterns detected in campos rupestres of the Chapada Diamantina and the phenological survey of vegetation islands on rocks can be used as base for inferences on spatial changes through time, and a successional model was elaborated for vegetation on the rocks . Organisms better adapted to extreme environments colonize exposed rocks and are gradually replaced by those less tolerant to extreme conditions. The tendency is to reduce the level of isolation among vegetation islands until new disturbances, such as severe drought, fire, flood, or even death by aging or diseases, cause decrease of vegetation.


Lack of Knowledge

Most studies on the campos rupestres are floristic surveys, such as those carried out on the Pico das Almas , Catolés , Morro do Pai Inácio and Serra dos Brejões (‘Chapadinha’). The large number of species per site and variation of floristic composition among them suggest that several mountains yet unexplored represent potential sources of new taxa. However, a larger gap than the one posed by the floristic knowlegde is that concerning the structural and dynamic aspects of the campos rupestres.

The campos rupestres form a peculiar environment with many species endemic to the Chapada Diamantina. They are distributed in a wide variety of environments spread through a mountains range. Each environment has its own characteristics and together they form a mosaic composition along mountain peaks isolated at different levels. They can be analyzed just like an archipelago, where the interactions of ecological processes are multifactorial and particular to each region. Knowing their spatial and temporal patterns is essential to determine the conservation importance of the campos rupestres besides enable us to test a series of hypotheses in this ‘natural laboratory’.

The main disturbances in the campos rupestres are fires and intense drought. Therefore, continuous studies on vegetation are crucial. This must include continuous monitory of composition and structure as well as the abiotic factors that may affect the understanding of biological patterns of these communities, such as temperature, humidity, wind and light.

The expression ‘campos rupestres’ (literally rocky fields) refers to a kind of vegetation associated with mountains in tropical areas of Brazil, usually at altitudes above 900 m, overlying quartzites or sandstone, with elevated rainfall and cloudiness, among rock outcrops, damp sands and high altitude bogs (Harley, R.M. & A.M. Giulietti. 2004. Wild Flowers of the Chapada Diamantina. Ed. Rima, São Carlos ).

Luetzelburg, P. 1922. Estudo Botânico do Nordeste. Inspetoria federal de obras contra as secas 57: 1-108.

Many of these families are known by common representatives such as the daisies (Asteraceae), bromeliads (Bromeliaceae), sedges (Cyperaceae), everlasting flowers (Eriocaulaceae), legumes (Leguminosae), orchids (Orchidaceae) and grasses (Poaceae)

Conceição, A.A. & A.M. Giulietti. 2002. Composição florística e aspectos estruturais de campo rupestre em dois platôs do Morro do Pai Inácio, Chapada Diamantina, Bahia, Brasil. Hoehnea 29: 37-48.

Conceição, A.A. 2003. Ecologia da Vegetação em Afloramentos Rochosos na Chapada Diamantina, Bahia, Brasil. Tese de Doutorado, Universidade de São Paulo, São Paulo.

Conceição, A.A. & J.R. Pirani. 2005. Delimitação de habitats em campos rupestres na Chapada Diamantina, Bahia: substratos, composição florística e aspectos estruturais. Boletim de Botânica da Universidade de São Paulo 23: 85-111.

NE – Some familiar examples are amaryllis (Amaryllidaceae), mangosteen (Clusiaceae). For examples of the other families, see NE 2.

Examples of some of the cited families are holly plants (Aquifoliaceae), begonias (Begoniaceae), spurge family (Euphorbiaceae), African violets (Gesneriaceae), mint family (Labiatae), myrtle family (Myrtaceae), black pepper (Piperaceae) and verbena family (Verbenaceae).

Stannard, B.L. (ed.). 1995. Flora of the Pico das Almas Chapada Diamantina, Bahia, Brazil. Royal Botanic Gardens, Kew.

Zappi, D.C. et al. 2003. Lista das plantas vasculares de Catolés, Chapada Diamantina, Bahia, Brasil. Boletim de Botânica da Universidade de São Paulo 21: 345-398.

Guedes, M.L. & M.D.R. Orge. 1998. Check-list das Espécies Vasculares de Morro do Pai Inácio (Palmeiras) e Serra da Chapadinha (Lençóis), Chapada Diamantina, Bahia, Brasil. Universidade Federal da Bahia, Salvador.