https://people.duke.edu/~ksv2/articles/21_Laurance_etal_2011_BDFFP_32y_review.pdf

The fate of Amazonian forest fragments: A 32-year investigation

Biodiversity conservation in human-modified Amazonian forest landscapes

We synthesize findings from the world’s largest and longest-running experimental study of habitat fragmentation, in central Amazonia. Over the past 36 years, 11 forest fragments ranging from 1 ha to 100 ha in size have experienced a wide array of ecological changes. Edge effects have been a dominant driver of fragment dynamics, strongly affecting forest microclimate, tree mortality, carbon storage and fauna. The matrix of vegetation surrounding fragments has changed markedly over time (evolving from large cattle pastures to mosaics of abandoned pasture and secondary regrowth forest), and this, in turn, has strongly influenced the dynamics of fragments and faunal communities. Both rare weather events and apparent global-change drivers have significantly influenced forest structure and dynamics across the entire study area, both in forest fragments and in nearby intact forest. Such large-scale drivers are likely to interact synergistically with habitat fragmentation.

An Amazonian rainforest and its fragments as a laboratory of global change

Adult odonate abundance and community assemblage measures as indicators of stream ecological integrity: A case study

Sensitive and cost-effective indicators of aquatic ecosystem condition in Amazon streams are necessary to assess the effects of anthropogenic disturbances on those systems in a viable and ecologically meaningful manner. We conducted the present study in the municipality of Paragominas, state of Para, northern Brazil, where we sampled adult dragonflies in 50 100-m-long wadeable stream sites in 2011. We collected 1769 specimens represented by 11 families, 41 genera and 97 species. The suborder Zygoptera contributed 961 individuals and Anisoptera 808. Among the 97 recorded species, nine were classified as useful indicators of ecological condition, with four species being associated with more degraded streams (three Anisoptera, one Zygoptera) and five with more preserved streams (all were Zygoptera). Anisoptera (dragonflies) tend to provide more useful indicators of more degraded environments because they have more efficient homeostatic mechanisms and are more mobile, enabling them to tolerate a wider range of environmental conditions. By contrast, Zygoptera (damselflies) tend to provide a more useful role as indicators of more preserved environments and high levels of environmental heterogeneity because of their smaller body sizes and home ranges and greater ecophysiological restrictions. We conclude from our assessment of this low-order Amazonian stream system that (i) the occurrence of specific odonate species is strongly associated with the configuration of riparian vegetation, (ii) agricultural activities appear to be the main factor determining changes in the composition of odonate assemblages and (iii) these insects can act as useful indicators of the ecological consequences of riparian habitat loss and disturbance. Because generalist species invade moderately degraded areas, those areas may have high species richness but host few species of Zygoptera. Therefore, preserving dense riparian vegetation is necessary to maintain aquatic ecological condition, and that condition can be rehabilitated by planting new trees. Both require enforcing existing environmental regulations, various types of incentives and educating local communities.

Neotropical dragonflies (Insecta: Odonata) as indicators of ecological condition of small streams in the eastern Amazon

The distribution and composition of aquatic insect communities in streams at a local scale are considered to be primarily determined by environmental factors and interactive relationships within the system. Here, we evaluated the effects of forest fragmentation and forest cover changes on habitat characteristics of streamlets (igarapes) in Amazonian forests and on the aquatic insect communities found there. We also developed a habitat integrity index (HII) based on Petersen’s protocol (1992) to evaluate physical integrity of these streamlets and to determine its efficiency to interpret the environmental impacts on this system. We studied 20 small streams at the Biological Dynamics of Forest Fragments Project (BDFFP INPA/SI) study areas, Central Amazonia, 80 km north of Manaus, Amazonas State, Brazil. The vegetation cover was estimated by using LANDSAT images and classified in the following categories: exposed soil, pastures, secondary forests (capoeiras), and primary forests. Stream habitat features were evaluated by using a HII based on visual assessment of local characteristics. Aquatic insects were sampled in four major stream substrates: litter deposited in pools or backwaters, litter retained in riffles, sand, and marginal banks. Stream habitat characteristics were significantly correlated to land use and riparian forest condition. Overall aquatic insect richness and Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness were significantly lower in pasture streams, and their taxonomic composition differed significantly from streams in forested areas. However, these metrics were not significantly correlated to the stream HII. Taxonomic composition of bank insect assemblages changed significantly between streams with low and high values of HII. There was no significant relationship between the proportion of primary forest cover and the faunal metrics. Only drastic changes in the vegetal cover seem to induce significant changes in the aquatic insect community. Matrix habitat heterogeneity, distance to forest fragments, the presence of areas of secondary forest, and the intrinsic capacity to disperse in many of the insect groups may have contributed to attenuate the effects of habitat disturbance on aquatic insect assemblages in streamlets.

Land use, habitat integrity, and aquatic insect assemblages in Central Amazonian streams

Igarapes de pequena ordem, nas reservas do Projeto Dinâmica Biologica de Fragmentos Florestais - INPA, a cerca de 80 km ao norte da cidade de Manaus, AM foram estudados quanto a composicao das comunidades de insetos aquaticos em diferentes substratos. Em cada um dos 20 trechos amostrados, foram coletadas amostras nos quatro substratos principais: folhico retido em areas de correnteza, folhico depositado no leito do igarape, areia e raizes/vegetacao nos barrancos marginais. Este estudo teve como objetivo avaliar a entomofauna aquatica e relaciona-la com substratos especificos dentro do igarape. O substrato com maior numero de generos foi folhico retido em areas de correnteza (106) enquanto areia apresentou o menor numero (55). As maiores similaridades ocorreram entre os substratos de folhico depositado em areas de remanso e barrancos marginais. As menores similaridades ocorreram entre folhico retido em areas de correnteza e areia. Alguns taxons coletados mostraram-se indicadores de um tipo de substrato, enquanto outros estiveram presentes em todos os substratos amostrados. Alguns taxons indicadores de folhas em correnteza foram encontrados em folhico depositado em areas de remanso em outros estudos na regiao Sudeste do pais. Isso indica que a velocidade da correnteza pode estar determinando a fauna que ocupa esse biotopo. Igarapes maiores, com maiores valores de vazao e ordem, apresentaram comunidades mais distintas nos diferentes substratos amostrados que os igarapes menores.

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Distribuição espacial de insetos aquáticos em igarapés de pequena ordem na Amazônia Central

Floating litter banks are an ephemeral habitat consisting of branches, twigs, flowers, seeds, and fruits that are trapped on the stream water surface by a variety of retention mechanisms. These heterogeneous materials form a deep layer of dead plant matter that is colonized by a variety of organisms, including fish that forage on the aquatic macroinvertebrates found in this unique habitat. In this study, we aimed to characterize which fish species occupy the floating litter banks and their trophic characteristics, as well as determine if fish assemblage composition and species richness can be predicted by the size of the floating litter banks. Fish sampling was conducted in five rivers located in the Amazon basin. Of the 31 floating litter banks sampled that contained fish, 455 individuals were recorded and were distributed within 40 species, 15 families and five orders. Siluriformes were the most representative order among the samples and contained the largest number of families and species. The fish fauna sampled was mainly composed of carnivorous species that are typically found in submerged litter banks of Amazonian streams. The fish assemblage composition in the kinon can be predicted by the volume of the floating litter banks using both presence/absence and abundance data, but not its species richness. In conclusion, kinon banks harbor a rich fish assemblage that utilizes this habitat for shelter and feeding, and may function as a refuge for the fishes during the peak of the flooding season.

/pdf/second-floor-please-the-fish-fauna-of-floating-litter-banks-px00igcr2t.pdf

Luana Fidelis

Papers

Land use, habitat integrity, and aquatic insect assemblages in Central Amazonian streams

Distribuição espacial de insetos aquáticos em igarapés de pequena ordem na Amazônia Central

Second floor, please: the fish fauna of floating litter banks in Amazonian streams and rivers