Directional succession and species-specific patterns observed in repeat study of vascular plants at three glacier foreland chronosequences in the Canadian High Arctic

Abstract

This paper presents the first repeat study of glacier foreland chronosequences conducted in the Canadian High Arctic. Vascular plant species at three forelands on Ellesmere Island, Nunavut first surveyed in 1995 were resurveyed 21 years later to (1) test the original hypothesis that succession on these forelands was directional, and (2) investigate the use of the chronosequence method in High Arctic succession studies. Forelands were surveyed using percent cover estimates or presence/absence counts. Indicator species analysis and rates of change were used to quantify shifts. Total plant cover and species richness increased on younger terrain. Rates of peak cover and first appearance advance varied greatly between species and forelands, but were generally faster for graminoid and forb species than shrub species. We observed a pattern of directional succession at all three forelands, supporting the original hypothesis. However, species-specific patterns and rates of change acted to create assemblages that differed between 1995 and 2016, different successional trajectories were observed between the three forelands, and the first occurrence of most species was further from the glacier margin in 2016 compared to 1995. These results demonstrate the importance of repeat studies over time and replication over space to confirm observations in chronosequence studies.