Invasive Species Compendium

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Abstract

An introduced pine shapes gastropod assemblages in the Central European broadleaved forest.

Abstract

The aim of this study was to determine the impact of the introduction of Pinus sylvestris on the mesofauna of the forest floor in the Central European oak-hornbeam forest, using gastropods as a model group. Data on terrestrial gastropods and environmental variables were collected in 2012-2014 from 25 study plots (14 without pine and 11 with pine) at 14 localities scattered across Wielkopolska province in mid-western Poland. Forty-two species (34 of snails and 8 of slugs) were recorded, with significantly lower numbers of individuals and species in plots with pine. The negative effect of the presence of pine trees was most evident at the level of gastropod abundance. The species composition of gastropod assemblage was also significantly different between plots with and without pine. The symptoms of the assemblage's reduction, impoverishment and trivialization thus suggested a long-term effect of the introduced pine on natural mesofauna. However, gastropod assemblage was shaped not by one dominating factor, but by a multifactorial combination of interacting variables, particularly related to herbaceous vegetation and to the tree- and shrub layer. Herb layer cover, moisture (reflected in the herbs), fertility (reflected in the herbs), and locally also the amount of calcium in the soil and insolation were found to be significant for the structure of gastropod assemblages. More environmental variables were significant at the sample level (i.e. within forest) than at the plot level (i.e. between forests), which is likely to be due to greater variation in the conditions within a rich forest as opposed to lower variation between forests. This highlighted the importance of using a two-scale approach to understand the conditions affecting gastropod assemblage structure in a habitat that is seemingly homogenous on the macro scale, but diversified and mosaic in the micro scale. The negative effects of pine introduction and the positive significance of the multifactorial combination of habitat factors at the macro- and micro level appear as important guidelines for favourable biodiversity management in the Central European oak-hornbeam forest and in other broadleaved forests.