Differences in species composition of the bryophyte layer of some Belgian and Dutch pinewoods with and without the invading hepatic Lophocolea semiteres (Lehm.) Mitt.

Abstract

Detrended Correspondence Analysis (DCA) and logit regression were used to search for differences in species co-occurrence in the bryophyte layer of pinewoods. Plots where the invasive Lophocolea semiteres was already present have been compared to similar plots where it was not yet present.

The first axis of the DCA ordination of 1 m² subplots shows for both data-sets a similar floristic gradient with Plagiothecium curvifolium as a dominant at one side and Hypnum jutlandicum, Dicranum scoparium and Pleurozium schreberi as dominants at the other. More opportunistic mosses (e.g. Campylopus spp., Orthodontium lineare), Lophocolea heterophylla and L. bidentata occur in the central part of this gradient. When present, L. semite res occupies a dominant position in the central part of this gradient, whereas L. heterophylla is nearly absent and L. bidentata is strongly reduced. A DCA ordination was applied to the complete data set, but with the Lophocolea spp. made passive. Logit regression of the presence-absence data on the first axis of this ordination shows complete overlap of the response curves of L. semite res and L. heterophylla, but not for L. semiteres and L. bidentata.

The results suggest strongly that, after arrival, L. semiteres will become the dominant Lophocolea in these pine forests, nearly excluding L. heterophylla, whereas L. bidentata will persist in lower quantities than previously.