Phytosociological data give biased estimates of species richness

CHYTRÝ, Milan. Phytosociological data give biased estimates of species richness. Journal of Vegetation Science. Uppsala: Opulus Press, 2001, vol. 12, No 3, p. 439-444. ISSN 110-9233.

Basic information

• Original name: Phytosociological data give biased estimates of species richness
• Authors: CHYTRÝ, Milan (203 Czech Republic).
• Edition: Journal of Vegetation Science, Uppsala, Opulus Press, 2001, 110-9233.

Other information

• Original language: English
• Type of outcome: Article in a journal
• Field of Study: 10600 1.6 Biological sciences
• Country of publisher: Sweden
• Confidentiality degree: is not subject to a state or trade secret
• WWW: URL
• RIV identification code: RIV/00216224:14310/01:00004667
• Organization unit: Faculty of Science
• UT WoS: 000171440600015

Abstract

Large phytosociological datasets of three types of grassland and three types of forest vegetation from the Czech Republic were analysed with a focus on plot size used in phytosociological sampling and on the species-area relationship. The datasets included altogether 12,975 relevés, sampled by different authors in different parts of the country between 1922-1999. It was shown that in the grassland datasets, the relevés sampled before the 1960s tended to have a larger plot size than the relevés made later. No temporal variation in plot sizes used was detected in forest relevés. Species-area curves fitted to the data showed unnatural shapes, with levelling-off or even decrease in plot sizes higher than average. This distortion is explained by the subjective, preferential method of field sampling used in phytosociology. When making relevés in species-poor vegetation, many researchers probably tend to use larger plots in order to obtain species-richer relevés. They seem to do that because a higher number of species gives a higher probability of more diagnostic species being found in the relevé; in the Braun-Blanquet classification system such a relevé can be more easily classified. This behaviour of phytosociologists has at least two consequences: (1) phytosociological databases under-represent species-poor vegetation types or are artificially biased towards higher species richness; (2) the suitability of phytosociological data for species richness estimation is severely limited.

Links

• GA206/99/1523, research and development project: Name: Parametrizace fytocenologického systému pomocí velkých souborů dat

Investor: Czech Science Foundation, Parameterization of the phytosociological classification using large datasets

• MSM 143100010, plan (intention): Name: Časoprostorová dynamika biodiverzity v ekosystémech střední Evropy.

Investor: Ministry of Education, Youth and Sports of the CR, Spatiotemporal biodiversity dynamics in ecosystems of Central Europe