A survey of habitats on agricultural land in Estonia II. Detailed interpretation of the habitats' landscape ecology and how this relates to alien plant species

The main objectives of the paper are to provide a description of the ecological character of Estonian agricultural landscapes and also their contribution to biodiversity resources. Agricultural landscapes are vulnerable to alterations in environmental factors and management that lead to changes in the balance of plant species and, therefore, to modifications in the structure and character of vegetation. The results show that the distribution and expansion of alien plant species contributes significantly to changes in the composition native plant species in Estonia. Such species are spreading rapidly in Estonia and elsewhere in Europe, leading to major changes in local vegetation and damage worth billions of Euros to the European economy every year (European Commission, 2020). Field visits to representative sites were made to record vegetation data from agricultural landscapes from 2015 to 2017. 35 dispersed random 1-km squares were selected according to the extent of the eight classes of the Environmental Classification of Estonia. 250 sample plots were thus recorded from the 1-km squares, using predetermined rules for their location. 453 vascular plant species (27% of all Estonian species) were recorded in 11 habitats (neglected patches, abandoned patches, clear cuts, forests, tall herbs, patches of alien plant species, mixed grasslands, water margins, lines of scrub/trees, field edges, roadsides). These results indicate the efficiency of small stratified samples and are relevant at a broader scale in Europe for monitoring and surveillance of habitats. Mixed grasslands were later excluded from the analyses as there were insufficient samples. 19 alien plant species were recorded in 141 plots, whereas the cover of alien species was over 25% of the plot in 38 plots. Mature forests had the fewest aliens and roadsides the most, emphasizing the importance of dispersal by vehicles. The most common high cover species were Bunias orientalis, Galega orientalis, Sambucus racemosa, and Melilotus albus. The dispersal of the most common aliens shows the role of management, as these species had the highest cover in linear features especially in roadsides and field edges. The first part of the paper provides tables of the mean figures for the ten habitats of Ellenberg values and the frequency of competitors, stress-tolerators and ruderal species (CSR), which are indicative of the quality and characteristics of the habitats. The second part of the paper provides detailed interpretations of each of the ten habitats based on statistical analyses, combined with the experience of the second author to describe the ecological significance of the habitats. The habitats vary from tall herbs, which are of minimal ecological importance, to water margins and roadsides, which are important for seed dispersal, as well as a resource of biodiversity. Each of the habitats is set in the context of the Estonian landscape, and their contribution to biodiversity is described. (c) 2021 The Author(s). Published by Elsevier B.V. CC_BY_NC_ND_4.0

Automated summary

This study aims to describe the ecological character of Estonian agricultural landscapes and their contribution to biodiversity resources. The results show that the spread of alien plant species significantly affects the composition of native plant species in Estonia, leading to major changes in local vegetation and causing billions of Euros worth of damage to the European economy annually.