Alternative successional pathways in the Amazon Basin

Abstract

Summary1 Successional pathways were evaluated in two Amazonian secondary forest communities with different land-use histories. Sites which had been clearcut without subsequent use were dominated after 6-10 years by the pioneer genus Cecropia (Moraceae), whereas those used for pasture before abandonment were dominated by the pioneer genus Vismia (Clusiaceae). 2 There were 58 plant families and 300 species identified in Cecropia stands but only 43 families and 147 species were identified in Vismia stands. There were 77 species in common (Sorensen similarity = 0.34). 3 Differences in species number and composition of recruiting individuals between stand types were significant and were a function of the dominant pioneer genus, stem density, distance from primary forest, and land-use history. Regeneration under Vismia canopy was dominated by small Vismia individuals (25% of plants < 2 cm basal diameter), whereas regeneration under Cecropia canopy was more diverse and did not include a single young Cecropia . 4 The number of regenerating plants in both secondary stand types dropped off sharply with distance (5, 25, 50, and 100 m) from primary forest, suggesting that seed dispersal was limiting plant recruitment. Species richness also declined with distance and could be explained by the decline in plant density. Species richness in Cecropia stands increased linearly with plant density, but in Vismia stands the richness increase with density was a decelerating function. 5 For the central Amazon, secondary succession involves a more rapid return of primary forest species if deforestation is not followed by use as pasture before abandonment.

Isoprene and monoterpene fluxes measured above Amazonian rainforest and their dependence on light and temperature

“…As highly reactive monoterpenes have reactivities with oxidants many orders of magnitude higher than those of isoprene, a selective advantage under abiotic stress can be hypothesized -Amazon tree species that are capable of producing highly reactive monoterpenes may have an advantage in future surface warming scenarios as well as in the high light and temperature environments of degraded secondary rainforests as a result of increasing natural and human disturbances, potentially fueling increased monoterpene emissions to the atmosphere [Kanakidou et al, 2005]. For example, C. sciadophylla, is a fast-growing pioneer genus specializing in exposed open secondary habitats with high solar radiation [Mesquita et al, 2001;Bentos et al, 2008] abundant across the Amazon Basin [Ter Steege et al, 2013]. In this study with C. sciadophylla, nearly 88% of the total light-dependent monoterpenes emitted at maximum PAR were as the highly reactive cis-and trans-β-ocimene.…”

A regeneração florestal em áreas de floresta secundária na Reserva Florestal do Morro Grande, Cotia, SP

“…Em áreas antropicamente degradadas, um dos fatores mais importantes que limitam o recrutamento de plântulas é a baixa disponibilidade de sementes, afetada pela presença e distância de manchas de floresta, que funcionariam como fontes de sementes e de agentes dispersores (Kolb 1993, Duncan & Chapman 1999, Holl 1999, Cubiña & Aide 2001, Mesquita et al 2001. Como o banco de sementes tem sido considerado pouco representativo para a dinâmica da regeneração de florestas tropicais em habitats alterados (Loiselle et al 1996, Holl 1999, Grombone-Guaratini & Rodrigues 2002) devido à curta viabilidade das sementes da maioria das espécies arbóreas tropicais (Garwood 1983), a regeneração de florestas secundárias dependeria, inicialmente, da chuva de sementes de espécies florestaiso quanto é produzido e disperso na paisagem.…”

“…Apesar da reconhecida importância para a compreensão do processo de regeneração, estudos de comunidades de plântulas de espécies arbóreas tropicais são pouco comuns (Lieberman 1996, Benítez-Malvido 1998, Chazdon et al 1998, Metzger 1998, Scariot 1999, Sizer & Tanner 1999, Mesquita et al 2001, Benítez-Malvido & Martínez-Ramos 2003. Na Mata Atlântica, em particular, estudos que enfocam algum aspecto da estrutura e composição do estrato de regeneração florestal são ainda mais escassos (Rodrigues 1998, Grombone-Guaratini 1999, Durigan et al 2000, Grombone-Guaratini & Rodrigues 2002, Martini 2002, Toniato & Oliveira-Filho 2004, e as abordagens e metodologias são as mais diversas, dificultando comparações.…”

Biomass equations for forest regrowth in the eastern Amazon using randomized branch sampling

“…Forest regrowth occupying much of this land area are of significant ecological interest in their own right Buschbacher et al, 1988;Mesquita et al, 2001), and contribute to large-scale biogeochemical and atmospheric cycles (Fearnside & Guimarães, 1996;Houghton et al, 2000;Steininger, 2004).…”

“…Tropical forest regrowth contains complex mixtures of tree species Mesquita et al, 2001), and there is considerable variation in species composition of regrowth stands across this large region (Baar et al, 2004). However, few species-specific allometric equations have been published Saldarriaga et al, 1988;Nelson et al, 1999).…”