Are bryophyte communities different?

Abstract

It has been suggested that bryophyte communities differ from those of higher plants, in that species coexistence is not limited by inter-specific competition. To test this hypothesis, bryophyte ‘lawns’ were-sampled at six locations in southern New Zealand. At each site, 625 quadrats, each ca 1 X 1cm, were arranged on a contiguous grid.

Variance in quadrat richness was significantly less than expected on a random basis at four sites, with the same trend in a fifth, i.e. quadrat richness was relatively constant. Since a patch model was used to reduce the effects of micro-environmental variation and spatial autocorrelation, this suggests that competition was restricting coexistence. The degree of restriction was similar to that found previously in grass lawn communities.

Species association was calculated on a patch basis, examining only small spatial-scale deviations from expectations. At four- sites this gave only negative associations. At the other two sites there were both positive and negative associations, but the pattern of associations gave no indication of Root/Pianka-type guilds.

Examination of the variance in guild proportions, using taxonomic (moss vs liverwort) and morphological (prostrate vs erect) guilds, gave- no indication of significant guild structure for any site (i.e. in the overall analyses for each site, index RV_gp was very close to the null-model expectation of 1.0).

Searches using the Wilson- Roxburgh method failed to reveal any significant intrinsic guild classification. That is, there was no indication of groups of species within a community that tended to be mutually exclusive because of similarity in resource use. Thus, lack of guild proportionality using a priori guilds was not due to the use of an inappropriate guild classification, but to lack of a guild structure in the communities.

It is concluded that there is community structure among bryophytes, in that species exclude each other to the same degree as higher-plants do in their communities. However, there is no evidence of structuring of these bryophyte communities into guilds; it seems that bryophyte species all form one guild.