Seedling establishment of the invasive tree Acer pseudoplatanus (sycamore)

摘要

Acer pseudoplatanus L. (sycamore) is a fast-growing tree that is invasive in many parts of the world, including New Zealand and Australia. The aim of this field experiment was to investigate the seedling establishment requirements of sycamore, in order to better predict where invasion is likely to occur. Sycamore seeds were sown into four different light environments in secondary native forest, ranging from full sun to deep shade, and also into a closed-canopy sycamore forest. The percentage of seedgermination was calculated nine months after sowing, and seedling survival was calculated 16 months later. The average percent seed germination was similar across all light environments. However, seedling survival was highly variable: 60-70% in the fullsun and edge plots, 25% in the native understory plots, and 0% in the sycamore and deep shade plots. These results indicate that sycamore seedlings establish most successfully under high light conditions. They do not establish well in deep shade or in closed canopy sycamore forest, which means they are unlikely to form an extensive seedling/sapling bank. Accordingly, in the absence of disturbance, sycamore could eventually be replaced by native succession in some areas of New Zealand.