Plant–Plant and Plant–Topography Interactions on a Rock Outcrop at High Altitude in Southeastern Brazil¹

Abstract

Plant establishment and growth on rocky outcrops in the Itatiaia massif (2400 m a.s.l.), southeastern Brazil, are limited by lack of soil and by freezing temperatures in winter nights. Mat‐forming species of different sizes and shapes on bare rock provide substrate for other plants to establish. The habitat preference of two geophytes, Stevia camporum (Asteraceae) and Alstroemeria foliosa (Alstroemeriaceae), was compared with regard to their association with the type of mat species and distinct rock topographies. The habitat preference of the mat species in regard to topography was also assessed. We found 1706 ramets of S. camporum and 1317 of A. foliosa in 253 vegetation islands ranging in size from 0.005 to 18.097 m2. Mat species in these islands were Fernseea itatiaiae, Vriesea itatiaiae (both Bromeliaceae), Pleurostima gounelleana (Velloziaceae) and/or Campylopus pilifer (Dicranaceae) and other mosses. Mat species were segregated by topography. Geophytes were similarly distributed across types of topography but showed negative interspecific association. S. camporum occurred mostly on the moss‐dominated islands, whereas A. foliosa was more common in P. gounelleana islands. We found geophyte co‐occurrence in larger vegetation islands containing both P. gounelleana and mosses as mat species. Thus, the effect of topography on geophyte segregation was indirect, since topography affects mat species distribution, and the geophyte preference for distinct mat species as substrate resulted in their segregation.

Composição florística da vegetação altimontana do distrito de Monte Verde (Camanducaia, MG), Serra da Mantiqueira Meridional, Sudeste do Brasil

“…Asteraceae, Cyperaceae, Melastomataceae, Orchidaceae, Poaceae, Polygalaceae e Rubiaceae estão entre as famílias mais ricas nos afloramentos rochosos imersos em formações florestais no Sudeste brasileiro (Meirelles et al 1999;Safford & Martinelli 2000;Caiafa & Silva 2007;Ribeiro et al 2007). Cyperaceae geralmente não é citada como uma das famílias mais ricas em afloramentos rochosos no Sudeste, entretanto espécies dessa família são citadas como as principais espécies formadoras das ilhas de vegetação sobre afloramentos graníticos e sobre nifelina-sienito no Sudeste do Brasil (Caiafa & Silva 2007;Medina et al 2006 (Burkart 1979;Azevedo 1981;Landrum 1984;Mentz & Oliveira 2004).…”

Structural analysis of the vegetation on a highland granitic rock outcrop in Southeast Brazil

“…Ecological studies on plant communities on Brazilian rock outcrops are rare (Meirelles 1996, Porembski et al 1998, Safford & Martinelli 2000, particularly in altitudes higher than 1,000 m (e.g., Meirelles 1996, Meirelles et al 1999, Ribeiro 2002, Medina et al 2006. Most such studies focused on the vegetation structure on granitic outcrops, among other issues, and emphasized the lack of studies for comparison, the difficulties in sampling the vegetation and the need of adapting phytosociological methods to sample the rupicolous vegetation.…”

“…However, granitic outcrops of Southeast Brazil only seldomly contain such perennial pools (Safford & Martinelli 2000). Another microhabitat type, the monocotyledonous mats, is primarily formed by species tolerant to dehydration that are able to establish themselves and grow into dense tussocks directly on the bare rock (Barthlott et al 1993, Safford & Martinelli 2002, Medina et al 2006. Some species may grow roots into the substratum formed by the species that constitute these monocotyledonous mats (Porembski et al 1998).…”

Perspectives on biodiversity science in Brazil

“…Amazon rain forest (Fearnside, 2005), cerrado (Cavalcanti & Joly, 2002;Durigan et al, 2007) caatinga (Barbosa et al, 2005) and, perhaps most obviously, the Atlantic rain forest (Myers et al, 2000) -to name but a few -are all highly threatened biomes, with deep problems regarding biodiversity conservation and land use, still to be tackled both by scientists and decisionmakers. A similar paradox has been described by Melo et al (2006): while Brazilian limnology is experiencing unprecedented growth, there are growing problems related to water quantity and quality in the country. The second objective of this report is to discuss how the gap between scientists and decision-makers in Brazil can be overcome as regards biodiversity issues.…”

“…My research group has proposed that for most of the marginal habitats of the Atlantic rain forest (i.e., restingas, swamps, inselbergs, high altitude vegetation), structure and function of the vegetation rely on singular or a few keystone species (Scarano 2002(Scarano , 2006bDias et al, 2006;Medina et al, 2006;Dias & Scarano, 2007). Thus, local extinction of such species should prove to be particularly harmful for other species at the local level.…”