Modified TWINSPAN classification in which the hierarchy respects cluster heterogeneity

Roleček, Jan; Tichý, Lubomír; Zelený, David; Chytrý, Milan

doi:10.1111/j.1654-1103.2009.01062.x

Cited by 289 publications

(202 citation statements)

References 23 publications

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“…The minimum group size was set at 3 and the threshold levels of cover were set at 0%, 5% and 50%. Whittaker's beta diversity index (Whittaker 1972) was used for the analysis of heterogeneity of groups, as it provides balanced classifications, respecting group size and heterogeneity, but also because of its robustness (Roleček et al 2009). The phi coefficient of association was calculated after standardizing the size of the groups according to Tichý & Chytrý (2006) to compile the lists of diagnostic species for each relevé group derived from the TWINSPAN analysis.…”

Section: Resultsmentioning

confidence: 99%

“…For a floristic classification of the relevés stored in SWEA-Dataveg, a vegetation matrix including the original cover values was exported into the Juice software (Tichý 2002) to use the modified TWIN-SPAN algorithm (Roleček et al 2009). The minimum group size was set at 3 and the threshold levels of cover were set at 0%, 5% and 50%.…”

Section: Resultsmentioning

confidence: 99%

“…Resembling traditional subjective procedures, new statistical approaches have been developed to make phytosociological classifications more objective. These may involve the implementation of statistical fidelity measures (Bruelheide 2000, Chytrý et al 2002, Tichý & Chytrý 2006, Willner et al 2009), the improvement of the TWIN-SPAN algorithm (Roleček et al 2009), and the development of a specialised software like Juice (Tichý 2002), which executes all mentioned statistical analyses. Additionally Willner (2006) and Dengler et al (2008) offer conceptual reviews on the association concept and phytosociology, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Floristic classification of the vegetation in small wetlands of Kenya and Tanzania

Álvarez¹,

Becker²,

Böhme³

et al. 2012

Biodivers. Ecol.

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Small wetlands in East Africa are increasingly converted into sites for agricultural production. The resulting changes in land use and cropping systems will impact on the wetlands' vegetation. We characterized the plant communities in four wetlands of Kenya and Tanzania, each comprising four types of land use differentiated by the degree of anthropogenic disturbance (cropland, fallow, grazing land and unused). Since no syntaxonomical scheme was available as a reference, a first classification of vegetation units and the identification of diagnostic species is proposed. We collected 207 relevés in the representative wetlands in relation to the current land uses. The plant communities were determined using a modified TWINSPAN classification. For each vegetation unit, diagnostic species were selected according to their fidelity index (phi coefficient). Floristic relationships between vegetation units were surveyed by nMDS ordination analyses. We identified 15 plant communities and selected 147 diagnostic species. The communities were differentiated into (1) semi-natural wetland vegetation (associated with less disturbed environments), (2) grassland and fallow vegetation, and (3) weed communities (associated with eu-hemerobic, drained and cultivated cropland). While the semi-natural vegetation was distinctly matched with unused fields, the differential matching of the other plant communities with land use types was less clear. According to the floristic similarity, the weed communities associated with cropland tended to be aggregated in the nMDS configuration while the semi-natural vegetation was dispersed. The results of the ordination did not differ when involving all species or only the selected diagnostic ones. As the plant communities described are rankless syntaxa, the establishment of a comprehensive syntaxonomic classification for African wetlands will require further vegetation surveys as well as their comparison with published data.Keywords: flood plain; inland valley; land use; modified TWINSPAN; papyrus swamp. Nomenclature: African Plant Database (CJB & SANBI 2010).Abbreviations: nMDS = non-metric multidimensional scaling; SWEA = Small Wetlands in East Africa; TWINSPAN = Two-way indicator species analysis.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Floristic classification of the vegetation in small wetlands of Kenya and Tanzania

Álvarez¹,

Becker²,

Böhme³

et al. 2012

Biodivers. Ecol.

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“…The vegetation data was captured in TurboVeg (Hennekens & Schaminée 2001) and exported to Juice (Tichý 2002). In order to avoid observer bias, species which were likely to be confused during field surveys (e.g.…”

Section: Data Processingmentioning

confidence: 99%

Vegetation of the Okavango river valley in Kavango West, Namibia

Strohbach¹

2013

Biodivers. Ecol.

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Abstract:The vegetation of the Okavango River Valley has previously only been described in general terms along the gradient from base of the valley to the top of the sand plateau, without the clear definition of different vegetation types or distinct vegetation composition. Yet the valley bottom supports a large part of the population within the region, who are dependent on ecosystem services provided by the vegetation. A Braun-Blanquet type survey was conducted to describe the vegetation of the Okavango River Valley in the Kavango West Region of Namibia, with special emphasis on the floodplain vegetation. The survey followed the guidelines set out for the "Vegetation Survey of Namibia" project. The data was classified using the modified TWINSPAN procedure in Juice, resulting in four higher-order syntaxa and 11 vegetation associations. We described these associations informally according to diagnostic species, species richness and environmental variables. In the case of floodplain and wetland associations, information regarding the flooding regime (depth, duration and probability of flooding) is provided. Although the higher-order groupings within this association come out very clearly, only the wetlands could be related to similar higher-order syntaxa described for the oshana wetlands in the Cuvelai delta. The placement and validity of the other three higher-order syntaxa is unclear at this stage, and needs to be addressed in a synopsis of all existing vegetation descriptions for the greater Kalahari ecoregion. The various vegetation associations can very clearly be associated with distinct positions in the landscape. The degree of flooding at the one extreme, and the sandiness of the soil on the other extreme, defines the vegetation type and composition. The Acacia erioloba-Schinziophyton rautanenii association (7) has been cleared and ploughed to at least 90%, with only small patches of this vegetation remaining. Expansion of fields into the sands of the terrace embankment is worrisome, leading to fears of further soil degradation and ultimately desertification. Although signs of overgrazing are visible within the floodplains, this cannot be distinctly quantified as yet. Overgrazing in the wetlands will lead to the destruction of fish spawning and breeding habitats, damaging the other major food source of the people of the region.Keywords: Braun-Blanquet; desertification; floodplain vegetation; flooding regime; land degradation; land use; phytosociology; seasonal wetland vegetation. A vegetação do vale do Rio Okavango no Kavango West, NamíbiaResumo: A vegetação do vale do Rio Okavango foi apenas descrita previamente em termos gerais ao longo da encosta, da base do vale até o topo do platô de areia, sem uma definição clara dos diferentes tipos de vegetação ou sua composição distinta. No entanto, o fundo do vale auxilia uma grande parte da população da região, que é dependente dos serviços ecosistemicos fornecidos pela vegetação. Uma pesquisa do tipo "Braun-Blanquet" foi feita para descrever a vegetação do vale...

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“…All relevés were stored in a database using the JUICE program [78]. A TWlNSPAN analysis [79] was used to perform the preliminary classification of communities. As relevés data showed a clear unimodal response, allowing us to use a Detrended Correspondence Analysis (DCA) with the floristic data set (presenceabsence data, no downweighting of rare species) to check the floristic-sociological classification and to show the relationships between the groups.…”

Section: Data and Analysesmentioning

confidence: 99%

Vegetation of rock clefts and ledges in the Pamir Alai Mts, Tajikistan (Middle Asia)

Nowak

Nobis

et al. 2014

Open Life Sciences

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The paper presents the results of phytosociological research conducted on the vegetation of rock clefts and ledges in the Pamir-Alai Mountains (Tajikistan, Middle Asia). During the field studies, done in 2010–2012, 101 phytosociological relevés were taken. Plant species were recorded according to the Braun-Blanquet cover-abundance scale. Communities of calcareous rock clefts and ledges with small soil amounts from several ranges (Zeravshan Mts, Hissar Mts, Hazratishokh Mts, Darvaz Mts, Rushan Mts and Vanch Mts), inhabiting mainly the alpine and subnival zone, have been described. A synopsis of the rock communities of the Pamir-Alai is proposed. In the examined vegetation plots 77 vascular plant and 6 moss species were noted. The most frequent were: Achoriphragma pinnatifidum, Artemisia rutifolia, Asperula albiflora, Campanula incanescens, C. lehmanniana, Parietaria judaica, Pentanema albertoregelia, Poa relaxa and Stipa zeravshanica among vascular plants and Brachythecium albicans and Bryum caespiticum among mosses. Most of them are narrow endemics of Tajikistan or Middle Asia. The collected material presents most of the variability among the phytocoenoses of large crevices and rock ledges in limestone massifs in the alpine and subnival zones. As a result of field research and numerical analyses, 7 associations have been distinguished: Achoriphragmetum pinnatifidi, Asperulo albiflorae-Stipetum zeravshanicae, Inuletum glaucae, Paraquilegietum anemonoidis, Pentanemetum albertoregeliae, Rhinactinidietum popovii and Saussureaetum ovatae. The distinctiveness of habitat and species composition of Middle Asiatic rock communities makes it necessary to distinguish a new suballiance, Pentanemenion albertoregeliae, within the Asperulo albiflorae-Poion relaxae alliance. The main factors determining the species composition of classified associations seem to be the elevation above sea level and exposition. Alpine rock communities are one of the most unique and interesting plant formations in the moutainous areas of Pamir-Alai. Despite not being species-rich they often harbour many specialists adapted to harsh and extreme environments, especially in areas of Mediterranean-like climate.

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Modified TWINSPAN classification in which the hierarchy respects cluster heterogeneity

Cited by 289 publications

References 23 publications

Floristic classification of the vegetation in small wetlands of Kenya and Tanzania

Floristic classification of the vegetation in small wetlands of Kenya and Tanzania

Vegetation of the Okavango river valley in Kavango West, Namibia

Vegetation of rock clefts and ledges in the Pamir Alai Mts, Tajikistan (Middle Asia)

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