Natural Re-Seeding and Trifolium repens Demography in Grazed Hill Pastures. II. Seedling Appearance and Survival

Abstract

(1) The appearance and survival of Trifolium repens seedlings from naturally deposited seed were monitored for 3 years under different sheep grazing managements and phosphate fertilizer inputs, and in four slope/aspect zones, in summer moist New Zealand hill country. (2) A mean of 5 5 seedlings m-2 per year appeared, representing 4 2% of the seeds deposited each summer. (3) Only 44% of seedlings survived to form established, stolon-bearing plants, representing a mean recruitment rate of one seedling per 5 5 m2 per year. Survival was highest on steep north-west sites (10%), and nil on flat south-west sites, reflecting likely competitive stresses from surrounding vegetation. (4) Such low recruitment rates clearly indicate seedling regeneration plays only a minor role in T. repens persistence in this environment. Vegetative stolon densities of 3000-4000 m-2 and high rates of stolon initiation and death confirm that the species behaves essentially as a true perennial. (5) A useful ecological role for low seedling recruitment rates in maintaining genetic diversity within the T. repens population must be recognized, however, especially in highly variable environments.