Primary plant succession at Franz Josef Glacier: Aspects of predictability and ecophysiology: A dissertation submitted in partial fulfilment of the requirement for the Degree of Bachelor of Horticultural Science (Honours) at Lincoln University

Abstract

8 distinct sites were selected from a previous study of plant succession and pedogenesis at Franz Josef Glacier by Stevens (1963; 1968). Plant species diversity and abundance were recorded on the 3 youngest sites, aged 45 to 85 years in the present study. Floristic composition was compared to composition recorded on the same sites 30 years previously. Sites in the present study were also compared to sites in the previous study, that were of equivalent age. Floristic composition did not appear to occur in a predictable manner, due to a dynamically changing understorey. Soil N levels were determined on all 8 successional sites. Total soil N increased over time, with initially rapid rates of accumulation declining with succession. The pattern of accumulation observed in the present study, was the same as that noted by Stevens (1963), confirming that N is increasing during early succession and pedogenesis. Total leaf N was determined for 3 species, Griselinia littoralis, Pseudopanax colensoi and Coprosma lucida, on each site. Leaf N (mg/g) was highly variable exhibiting no clear trends. Leaf N per unit leaf area (mg/cm² ) declined with increasing surface age and increasing specific leaf area (SLA). Leaf N did not correlate with soil N. This may be due to soil N availability levels declining, with increasing C/N ratios, associated with succession, or the inability of these species to utilise higher N. Chlorophyll levels and SLA were determined for the same 3 species, on the youngest and oldest sites of the successional sequence. An increase in SLA and total chlorophyll per weight (mg/g), and a decline in the chlorophyll a:b ratio suggest evidence of shade acclimation in these species.