Effects of management and environmental variables on species composition of orthopterans, carabids, and spiders in irrigated and non-irrigated meadows in the Queichtal, Germany.

<p>Significance was tested by permutational multivariate ANOVA (command ‘adonis’ in R package vegan). Significant results (P<0.05) are shown in bold.</p><p>Effects of management and environmental variables on species composition of orthopterans, carabids, and spiders in irrigated and non-irrigated meadows in the Queichtal, Germany.</p

Beta diversity (multivariate homogeneity of dispersions) of a) orthopterans, b) carabid and c) spider assemblages of irrigated and non-irrigated meadows.

<p>Distances (Sørensen similarity) are reduced to principal coordinates and distances to group centroids (irrigated or non-irrigated) are shown. Differences of mean distances between meadow types were tested by ANOVA.</p

Effects of Traditional Flood Irrigation on Invertebrates in Lowland Meadows

<div><p>Lowland meadow irrigation used to be widespread in Central Europe, but has largely been abandoned during the 20^th century. As a result of agri-environment schemes and nature conservation efforts, meadow irrigation is now being re-established in some European regions. In the absence of natural flood events, irrigation is expected to favour fauna typical of lowland wet meadows. We analysed the effects of traditional flood irrigation on diversity, densities and species composition of three invertebrate indicator taxa in lowland meadows in Germany. Unexpectedly, alpha diversity (species richness and Simpson diversity) and beta diversity (multivariate homogeneity of group dispersions) of orthopterans, carabids, and spiders were not significantly different between irrigated and non-irrigated meadows. However, spider densities were significantly higher in irrigated meadows. Furthermore, irrigation and elevated humidity affected species composition and shifted assemblages towards moisture-dependent species. The number of species of conservation concern, however, did not differ between irrigated and non-irrigated meadows. More variable and intensive (higher duration and/or frequency) flooding regimes might provide stronger conservation benefits, additional species and enhance habitat heterogeneity on a landscape scale.</p></div

Position of the study area ‘Queichtal’ in Germany (small figure) and of the 32 study sites.

<p>Position of the study area ‘Queichtal’ in Germany (small figure) and of the 32 study sites.</p

Relationship between species irrigation affinity (spearman rank correlation coefficient of species densities to irrigation) and moisture indicator value of a) orthopterans, b) carabids, and c) spiders.

<p>Relationship between species irrigation affinity (spearman rank correlation coefficient of species densities to irrigation) and moisture indicator value of a) orthopterans, b) carabids, and c) spiders.</p

Comparison of species richness (a–c), densities (d–f), and Simpson diversity (g–i) of orthopterans, carabids, and spiders between irrigated and non-irrigated meadows (mean and SE).

<p>Differences of species richness and densities were tested with Poisson GLM’s and of Simpson diversity (1−D) with non-parametric wilcoxon rang sum tests.</p

NMDS ordinations of a) orthopterans, b) carabid and c) spider species composition of irrigated and non-irrigated meadows.

<p>Only significant environmental variables are shown (permutational multivariate ANOVA, for statistics see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110854#pone-0110854-t001" target="_blank">Table 1</a>).</p