Estimating the species number and cover of a mangrove-root community: a comparison of methods

Abstract

Methods and designs have been validated for sampling coral reefs and reef-associated communities, but the accuracy and equivalence of results obtained from studies of mangrove-root communities can not be assured. Thus, it is convenient to establish the accuracy and reliability of sampling methods on a practical basis. Line interception, point interception, and quadrat sampling were used to estimate several basic features of the community associated with mangrove roots. Species-number estimates, cover estimates, sampling efforts, and some statistical properties of the three methods were compared.

A sampling design should be chosen if it yields estimates with the greatest accuracy at the lowest cost. Results showed that sampling of mangrove roots could start by using 4 × 4-cm quadrats with a mean sample size of 50 for detecting the number of species, and for establishing species cover it appears that the point-interception method with a sample size of 50 would be appropriate. The effort involved in such a sequence would be approximately 10 h for 20 roots. This combined strategy is clearly laborious and time-consuming in comparison with the use of just a 200-point interception, which would require only 3.25 h for the same number of roots. Although it would cost more than the above methods, a fast and accurate technique based upon existing computer hardware to estimate cover from photographic or video material would result in a census of the whole community. This might prove to be a reliable way to approach the problem.