Comparing three classification strategies for use in ecology

Belbin, Lee; McDonald, C. K.

doi:10.2307/3235592

Cited by 139 publications

(96 citation statements)

References 31 publications

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“…Foi analisada a similaridade florística entre as fitofisionomias, por meio de classificação aglomerativa das parcelas pelo método de médias aritméticas (Unweighted Pair Groups Method using Arithmetic Averages -UPGMA), com o uso do coeficiente de similaridade de Jaccard (JAMES; MCCULLOCH, 1990;BELBIN;MCDONALD, 1993;BALDUINO et al, 2005), pela fórmula a seguir.…”

Section: Methodsunclassified

Diferenças florísticas e estruturais entre fitofisionomias do cerrado em Assis, SP, Brasil

Pinheiro

Durigan

2012

Rev. Árvore

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Eduardo da Silva Pinheiro 2 e Giselda Durigan 3 RESUMO -A classificação das fitofisionomias tem-se constituído em desafio entre os pesquisadores da vegetação de cerrado, seja por não haver critérios florísticos ou quantitativos claros para sua separação, seja pelas alterações que sofrem ao longo do tempo. O objetivo deste estudo foi caracterizar três tipos fitofisionômicos de cerrado na Estação Ecológica de Assis, bem como verificar se são florística e, ou, estruturalmente distintos, buscando-se as melhores variáveis para caracterizá-los. A área amostral compreendeu 30 parcelas permanentes de 20 x 50 m, sendo 10 parcelas para cada um dos tipos fisionômicos: cerrado típico, cerrado denso e cerradão, em que foram identificadas e medidas as árvores com diâmetro à altura do peito > 5 cm. As três fitofisionomias de cerradoestudadas mostraram-se estruturalmente distintas em classes de área basal, cobertura de copas e altura das maiores árvores. O melhor descritor para classificar as fitofisionomias, por ser facilmente mensurável e pouco variável com o critério de inclusão, é a área basal (m 2 ha -1 ). Floristicamente, as fitofisionomias savânicas (cerradotípico e cerrado denso) não se diferenciam, quer seja analisando apenas a presença e ausência das espécies, quer seja analisando a importância relativa das espécies na comunidade (fitossociologia). Em síntese, há três fitofisionomias distintas, mas a flora se diferencia apenas entre o cerradão e as fitofisionomias savânicas. A análise das espécies exclusivas de cada fitofisionomia quanto à tolerância à sombra, com base na literatura, indicou que a baixa disponibilidade de luz sob as copas no cerradão pode ter sido o fator condicionante da diferenciação entre esta e as demais fitofisionomias do cerrado lato sensu.Palavras-chave: Classificação fisionômica, Descritores estruturais, Savana, tipos fisionômicos e similaridade florística. FLORISTIC AND STRUCTURAL DIFFERENCES AMONG CERRADO PHYTOPHYSIOGNOMIES IN ASSIS, SP, BRAZIL ABSTRACT -Classification of physiognomies is a challenge for many cerrado vegetation researches either because there are no clear floristic and quantitative criteria for its classification and because the changes it had over come over the years. The objective of this study was to charactherize three phytophysiognomies types in the cerradovegetation (Brazilian savannah) in the Estação

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Section: Methodsunclassified

Diferenças florísticas e estruturais entre fitofisionomias do cerrado em Assis, SP, Brasil

Pinheiro

Durigan

2012

Rev. Árvore

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“…The objective of DCA in this research was to determine more precisely the relationship between the pollen in the surface sample data and the taxa within the surrounding vegetation. Although the program has a weakness in the analysis of two equally strong gradients (Van Groenewoud, 1992 ;Belbis & McDonald, 1993), it has proved to be successful for hypothesis generation (Birks & Gordon, 1985). For example, output from the ordination can be interpreted in terms of a causal factor; in our case this factor is how representative of the surrounding taxa is the pollen in surface sediments.…”

Section: Establishing a Modern Pollen-vegetation Relationshipmentioning

confidence: 99%

Pollen representivity of montane forest taxa in south‐west Uganda

Marchant

Taylor

2000

New Phytologist

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Results presented in this paper demonstrate the relationship between two data sets from Mubwindi Swamp, south-west Uganda. The first data set is from a survey of dryland montane forest within the immediate catchment and the second is in the form of pollen spectra recovered from surface samples of sediment. Numerical analysis grouped pollen types encountered into five categories, according to their level of representivity when compared with abundances of the same taxa in the sampled vegetation : under representative, moderately under representative, representative, moderately over representative, and over representative. The northern part of Mubwindi Swamp also yielded a 5-m-long sequence of organic-rich sediments (core MB6) from which sub-fossil pollen and radiocarbon data have been previously obtained. This provides an opportunity to apply calibration factors derived from modern pollen-vegetation relationships to sub-fossil pollen data that were obtained from the same site. These calibration factors effectively down-weighted the influence of over representative pollen types and permitted the discrimination of a phase of forest disturbance that had not previously been so clearly visible in subfossil pollen data.

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“…in both cases pseudospecies cut levels 0, 2, 5, 10 and 20 were used. One of the problems with TWiNSPAN classification is the assumption of a strong gradient that dominates the data structure and the failure to identify secondary gradients (van Groenewoud, 1992;Belbin & McDonald, 1993). However, for the present case we expected that each transect reflects the strong underlying aquatic-terrestrial gradient and that each group represents a portion of the local zonation pattern on the particular transitional zone.…”

Section: Study Sitementioning

confidence: 88%

Dinámica estacional de la vegetación litoral en el complejo lagunar inundable Zapatosa, Colombia

Schmidt-Mumm

Janauer

2014

RBT

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Floodplain lakes and associated wetlands in tropical dry climates are controlled by pronounced and severe seasonal hydrologic fluctuations. We examined the plant community response to a bimodal flooding pattern in the Zapatosa Floodplain Lake Complex (ZFLC), Northern Colombia. We measured floristic and quantitative change in four sampling periods emphasizing seasonal differences in plant abundance and life-form structure. Of 79 species identified in the lake complex, 52 were used to characterize eight community types via classification and ordination procedures. Results showed that community structure does not change significantly during the flooding/receding stages. But maximum drawdown phase significantly disrupts the aquatic community structure and the exposed shorelines become colonized by ruderal terrestrial plants. Early rainfalls at the beginning of the wet season are emphasized as an important feature of plant regeneration and community development. The general strategy of the ZFLC vegetation can be framed into the flood pulse concept of river-floodplain systems. Thus, plant communities are mainly responding to disturbances and destruction events imposed by extreme water level fluctuations. Rev. Biol. Trop. 62 (3): 1073-1097. Epub 2014 September 01.Key words: Cesar River, flood pulse, littoral, macrophytes, Magdalena River, shallow lakes, bimodal seasonality.Floodplains play an important role regarding the biogeochemistry and ecology of tropical river systems. Plant and animal life of this particular system are adapted to the seasonal variations in space and time caused by extreme water level fluctuations. This seasonality also represents an important factor in the speciation of several aquatic and wetland plants (Haynes & Holm-Nielsen, 1989). The dynamic character of these systems gives rise to complex primary and secondary production processes that are difficult to predict in detail, but nutrient input from rivers and streams are important in general, as a significant contribution can be expected following rainfall from the surrounding watershed. Nutrient cycling proceeds mainly through heterotrophic processes via bacteria, fungi, micro-zooplankton and shreddinginvertebrates (Melack & Fisher, 1990;Wantzen, Yule, Mathooko, & Pringle, 2008;Warfe et al., 2011). The interactions between rivers and their surrounding floodplain motivated Junk, Bayley, and Sparks (1989) to propose the 'flood pulse concept' as a main force controlling the biota of tropical floodplains. They considered the floodplain as the area periodically inundated by the waters of rivers, lakes, lagoons, and/or underground water, or by direct precipitation. The concept aims to explain the physical and chemical conditions that obligate the biota to respond through different phenological, morphological, anatomical and/or physiological adaptations to predictable hydrological cycles. Given its alternation between aquatic and terrestrial phases, the flooded area of the shoreline is defined as 'aquatic-terrestrial transitional zone' (AT...

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Comparing three classification strategies for use in ecology

Cited by 139 publications

References 31 publications

Diferenças florísticas e estruturais entre fitofisionomias do cerrado em Assis, SP, Brasil

Diferenças florísticas e estruturais entre fitofisionomias do cerrado em Assis, SP, Brasil

Pollen representivity of montane forest taxa in south‐west Uganda

Dinámica estacional de la vegetación litoral en el complejo lagunar inundable Zapatosa, Colombia

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