Plant-Plant and Plant-Topography Interactions on a Rock Outcrop at High Altitude in Southeastern Brazil

• Published in: Biotropica 2006-01, Vol.38 (1), p.27-34
• Main Authors: Medina, Branca Maria Opazo, Ribeiro, Kátia Torres, Scarano, Fabio Rubio
• Format: Article
• Language: English
• Subjects: Alstroemeria foliosa; Asteraceae; Brazil; Bromeliaceae; Campylopus pilifer; Dicranaceae; facilitation; geophytes; mat species; rocky outcrops; Stevia camporum; tropical alpine vegetation; Velloziaceae
• ISSN: 0006-3606; 1744-7429
• DOI: 10.1111/j.1744-7429.2006.00105.x

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 m super(2). 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.Original Abstract: O estabelecimento e crescimento de plantas nos afloramentos rochosos do macico do Itatiaia (2400 m s.n.m.) sao limitados por fatores como falta de solo e temperaturas congelantes nas noites de inverno. Plantas que formam tapetes sobre a rocha nua (especies-tapete), de diferentes tamanhos e formas, provem substrato para outras plantas se estabelecerem. A preferencia de habitat de duas geofitas, Stevia camporum (Asteraceae) and Alstroemeria foliosa (Alstroemeriaceae) foi comparada em relacao ao tipo de especie-tapete e as diferentes topografias. A preferencia de habitat das especies-tapete em relacao as classes de topografia tambem foi avaliada. No total foram encontrados 1706 ramos de S. camporum e 1317 de A. foliosa em 253 ilhas de vegetacao, variando em tamanho de 0.005 a 18.097 m super(2). As especies-tapete foram Fernseea itatiaiae, Vriesea itatiaiae (ambas Bromeliaceae), Pleurostima gounelleana (Velloziaceae) e-ou Campylopus