An ecological study of the subalpine shrub Senecio bennettii (Compositae) at Arthur's pass South Island, New Zealand

Abstract

Stands of Senecio bennettii at Pegleg Flat, Arthur's Pass National Park, were the subject of an ecological study. S. bennettii is the dominant shrub in various scrub and low forest associations in the area. Mean annual shoot extension growth of S. bennettii ranges from 11 to 72 mm and is correlated with the leaf area production of the respective shoots. There is a marked variation in the number of annually produced lateral shoots, which support the terminal inflorescences, and this has an important bearing on the subsequent flowering intensity. Mean annual leaf area production of apical shoots ranged from 50–80 cm² in shrubland stands to 100–120 cm² in specimens in the shrub layer of subalpine low forest. The annual variation in leaf area production of apical shoots is a result of different temperature regimes experienced during the period of leaf primordia initiation in the previous growing season; leaf area production of lateral shoots is correlated with mean temperatures during the current growing season. Litterfall occurs throughout the year but is much more pronounced from January to July. Partial or no flowering occurred in 1981/82, 1982/83, 1983/84 and was followed by a heavy flowering season in 1984/85.

Keywords:

• Senecio bennettii
• subalpine scrub
• composite scrub
• growth rates
• leaf area production
• periodic flowering
• seed production
• seed germination