An evaluation of the gradsect biological survey method

Publication Type:Journal Article
Year of Publication:1998
Authors:K. J. Wessels, Van Jaarsveld, A. S., Grimbeek, J. D., Van der Linde, M. J.
Journal:Biodiversity and Conservation
Date Published:Aug
Accession Number:ISI:000078129800007
Keywords:ecological data analysis

Biological surveys are necessary to gather species distribution data for the identification of priority conservation areas. The rationale of the gradsect method is that sampling (transects) oriented along the steepest environmental gradient should detect the maximum number of species in an area. The efficiency of the gradsect survey method was evaluated by comparing it to random, systematic and habitat-specific survey methods, during faunal held surveys (target groups: birds and dung beetles). Three gradsects were positioned within the study area to follow the major physiographical characteristics, incorporate all environmental strata (land facets) and yet be as logistically convenient as possible. The efficiency of survey methods was expressed as the number of species recorded per sampling unit effort and illustrated using bootstrap estimations to plot species accumulation curves. The gradsect method proved to be as efficient as the habitat-specific survey method and consistently more efficient than the systematic and random surveys for both taxa sampled. The present study therefore illustrates that the gradsect survey method provides a cost- effective and swift representative sample of regional fauna. Moreover, the results indicate that land-form sequences, specifically 'land facets', are useful surrogates when sampling environmental diversity where distinct environmental gradients such as altitude and rainfall are absent.

URL:<Go to ISI>://000078129800007
Alternate Journal:Biodivers. Conserv.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith