Spread intensity and invasiveness of sycamore maple (Acer pseudoplatanus L.) in Lithuanian forests

Abstract

The primary objectives of this study were to estimate seedling abundance, spread intensity, and invasiveness of sycamore maple (Acer pseudoplatanus L.) in Lithuanian forests. The species was introduced to Lithuania in 1802, and since then has subsequently become gradually invasive. Seedling understory abundance, colonization and dispersal were investigated in six forest blocks covering the principal sycamore distribution areas in southwestern Lithuania. Seedlings height and densities in the undestory were evaluated, and seedlings assigned to four height groups. Species invasiveness was estimated applying the Pest Plant Prioritization Process (PPPP), based on the Analytic Hierarchy Process (AHP) method. Results showed the average spread distance from the parent tree was 257 m, with a mean seedling number per hectare of 2064. Sycamore maple invasive score was 0.6426 (range: 0-1), the current relative to potential distribution rating was 0.57, and the social, environmental, and eco¬nomic impact score was 0.1682. Such values were used to assess the Pest Plant Score for sycamore maple, obtaining a value (0.3537) lower than expectations (0.5). Results indicated that the species exhibits invasive properties and a rapid spread in the study area. Some implications of the above results in view of the upcoming climate change and the use of sycamore maple in Lithuanian forest plantations are discussed.