Riparian Habitats as Tropical Forest Refugia

Meave, Jorge A.; Kellman, Martin; MacDougall, Andrew; Rosales, Joaquín Muñoz-Cobo

doi:10.2307/2997492

Cited by 78 publications

(53 citation statements)

References 21 publications

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“…Gallery forests, of course, also served as refugia for some tropical forest biotas in open regions during dry climatic phases (Meave et al, 1991;1994). Their significance as centers of differentiation and speciation, however, remains open.…”

Section: Refuge Hypothesismentioning

confidence: 99%

Hypotheses to explain the origin of species in Amazonia

Haffer¹

2008

Braz. J. Biol.

196

176

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The main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological history are based on different factors, as follow: (1) Changes in the distribution of land and sea or in the landscape due to tectonic movements or sea level fluctuations (Paleogeography hypothesis), (2) the barrier effect of Amazonian rivers (River hypothesis), (3) a combination of the barrier effect of broad rivers and vegetational changes in northern and southern Amazonia (River-refuge hypothesis), (4) the isolation of humid rainforest blocks near areas of surface relief in the periphery of Amazonia separated by dry forests, savannas and other intermediate vegetation types during dry climatic periods of the Tertiary and Quaternary (Refuge hypothesis), (5) changes in canopy-density due to climatic reversals (Canopy-density hypothesis) (6) the isolation and speciation of animal populations in small montane habitat pockets around Amazonia due to climatic fluctuations without major vegetational changes (Museum hypothesis), (7) competitive species interactions and local species isolations in peripheral regions of Amazonia due to invasion and counterinvasion during cold/warm periods of the Pleistocene (Disturbance-vicariance hypothesis) and (8) parapatric speciation across steep environmental gradients without separation of the respective populations (Gradient hypothesis). Several of these hypotheses probably are relevant to a different degree for the speciation processes in different faunal groups or during different geological periods. The basic paleogeography model refers mainly to faunal differentiation during the Tertiary and in combination with the Refuge hypothesis. Milankovitch ‡ cycles leading to global main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological history are based on different factors, as follow: (1) Changes in the distribution of land and sea or in the landscape due to tectonic movements or sea level fluctuations (Paleogeography hypothesis), (2) the barrier effect of Amazonian rivers (River hypothesis), (3) a combination of the barrier effect of broad rivers and vegetational changes in northern and southern Amazonia (River-refuge hypothesis), (4) the isolation of humid rainforest blocks near areas of surface relief in the periphery of Amazonia separated by dry forests, savannas and other intermediate vegetation types during dry climatic periods of the Tertiary and Quaternary (Refuge hypothesis), (5) changes in canopy-density due to climatic reversals (Canopy-density hypothesis) (6) the isolation and speciation of animal populations in small montane habitat pockets around Amazonia due to climatic fluctuations without major vegetational changes (Museum hypothesis), (7) competitive species interactions and local species isolations in peripheral regions of Amazonia due to invasion and counterinvasion during cold/warm p...

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Section: Refuge Hypothesismentioning

confidence: 99%

Hypotheses to explain the origin of species in Amazonia

Haffer¹

2008

Braz. J. Biol.

196

176

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“…There is little similarity with the dominant savanna physiognomies of the Cerrado biome (Felfili & SilvaJúnior, 1992). Meave et al (1991) regarded them as present day refugia for moist forest species within the savanna dominium. According to Felfili (1997), gallery forests are vulnerable to the influence of external factors such as recurrent fires coming from the neighbouring cerrado formations.…”

Section: Introductionmentioning

confidence: 99%

Environmental determinants for natural regeneration of gallery forest at the Cerrado/Amazonia boundaries in Brazil

et al. 2010

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Natural regeneration and structure and their relationship to environmental variables were studied in three sections of a gallery forest, in Eastern Mato Grosso, Brazil (14º43′S and 52º21′W). The assumption was that natural regeneration is constrained by environmental determinants at all stages of development of the tree community. The objective was to analyse the forest structure and to verify the relationship between species distribution and abundance at different stages of regeneration and environmental variables. In each section, 47 contiguous (10x10m) permanent plots were established to sample trees (gbh≥15cm), following a systematic design. Seedlings (0.01 to 1m height), saplings (1.01 to 2m) and poles (from 2.01m height to gbh<15cm) were sampled in sub-plots of 1x1m, 2x2m and 5x5m, respectively. In each plot, soil properties, gaps projection, bamboos, rocky cover, declivity and depth of ground watertable were determined. The relationships between the environmental variables with trees and seedling communities were assessed by canonical correspondence analysis. In spite of the sections being near to each other, they presented large differences in floristics, structure and site conditions. The forest soil presented a low cation exchange capacity and a high level of Al saturation. The occurrence of bamboos and gaps and the depth of ground watertable limited the occurrence of poles and trees. The high degree of structural heterogeneity for each regeneration category was related primarily to a humidity gradient; but soil fertility (Ca+Mg) was also a determinant of seedling and sapling communities.KEYWORDS: Brazil; diversity; riparian forest; soils; tropics. Determinantes ambientais para regeneração natural de mata de galeria na transição Cerrado/Amazônia no Brasil RESUMOFoi estudada a regeneração natural e a estrutura de três seções de uma floresta de galeria no leste de Mato Grosso, Brasil (14º43′S e 52º21′W). O objetivo foi analisar a estrutura da floresta e verificar a relação entre a distribuição e abundância das espécies nos diferentes estágios de regeneração e entre as variáveis ambientais. Em cada seção de floresta foram estabelecidas, sistematicamente, 47 parcelas (10x10m) contíguas e permanentes para amostrar as árvores (CAP≥15cm). As plântulas jovens (0,01 a 1m de altura), as plântulas maiores (1,01 a 2m) e as arvoretas (de 2,01m de altura a CAP≥15cm) foram amostradas em sub-parcelas de 1x1m, 2x2m e 5x5m, respectivamente. Para cada parcela foram determinadas as propriedades do solo, projeção das clareiras, cobertura de bambus, rochosidade, declividade e profundidade do lençol freático. A relação das variáveis ambientais com as árvores e comunidades de plântulas e arvoretas foi determinada a partir de uma análise de correspondência canônica. Apesar das seções de floresta serem próximas entre si, apresentaram diferenças importantes em relação à composição florística, estrutura e variáveis ambientais. Os solos apresentaram reduzida capacidade de troca catiônica e elevados níveis de saturação de a...

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“…However, there is some evidence that riparian ecosystems may be more resilient than other systems because of their inherently heterogeneous environmental conditions, which include alternating periods of wet and dry conditions. Understanding the fate of tropical riparian forests in increasingly fragmented landscapes is important because these forests are highly valued for providing critical ecosystem services, including refugia for plant and animal species in aquatic, semiaquatic, and terrestrial areas, and protecting stream resources by maintaining stream temperature and reducing erosion of sediments and nutrients (Meave et al 1991, Naiman et al 2005, Malhi et al 2008.…”

Section: Introductionmentioning

confidence: 99%

Structure and composition of altered riparian forests in an agricultural Amazonian landscape

Nagy

Porder

Neill

et al. 2015

Ecological Applications

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Abstract. Deforestation and fragmentation influence the microclimate, vegetation structure, and composition of remaining patches of tropical forest. In the southern Amazon, at the frontier of cropland expansion, forests are converted and fragmented in a pattern that leaves standing riparian forests whose dimensions are mandated by the Brazilian National Forest Code. These altered riparian forests share many characteristics of well-studied upland forest fragments, but differ because they remain connected to larger areas of forest downstream, and because they may experience wetter soil conditions because reduction of forest cover in the surrounding watershed raises groundwater levels and increases stream runoff. We compared forest regeneration, structure, composition, and diversity in four areas of intact riparian forest and four areas each of narrow, medium, and wide altered riparian forests that have been surrounded by agriculture since the early 1980s. We found that seedling abundance was reduced by as much as 64% and sapling abundance was reduced by as much as 67% in altered compared to intact riparian forests. The most pronounced differences between altered and intact forest occurred near forest edges and within the narrowest sections of altered riparian forests. Woody plant species composition differed and diversity was reduced in altered forests compared to intact riparian forests. However, despite being fragmented for several decades, large woody plant biomass and carbon storage, the number of live or dead large woody plants, mortality rates, and the size distribution of woody plants did not differ significantly between altered and intact riparian forests. Thus, even in these relatively narrow forests with high edge : area ratios, we saw no evidence of the increases in mortality and declines in biomass that have been found in other tropical forest fragment studies. However, because of the changes in both species community and reduced regeneration, it is unclear how long this relative lack of change will be sustained. Additionally, Brazil recently passed a law in their National Forest Code allowing narrower riparian buffers than those studied here in restored areas, which could affect their long-term sustainability.

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Riparian Habitats as Tropical Forest Refugia

Cited by 78 publications

References 21 publications

Hypotheses to explain the origin of species in Amazonia

Hypotheses to explain the origin of species in Amazonia

Environmental determinants for natural regeneration of gallery forest at the Cerrado/Amazonia boundaries in Brazil

Structure and composition of altered riparian forests in an agricultural Amazonian landscape

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