Productivity and persistence of prairie grass (Bromus willdenowii Kunth) 2. Effects of natural reseeding

Abstract

A field trial with different populations of prairie grass (Bromus willdenowii Kunth) plants in 1-year-old simulated swards enabled changes in plant and tiller populations, and natural reseeding, to be studied. At establishment, half of the plants in this trial were infected with the head smut fungus (Ustilago bullata Berk.), but the disease had disappeared within 2 years as all infected plants died. Where plant populations were low, surviving plants compensated by producing more and heavier tillers than where populations were higher. There was an overall decline in plant population, mostly during the period from mid summer to mid autumn. Numbers of seedlings resulting from natural reseeding were greatest (1600 seedlings/m²) in swards with the highest populations of mature plants, and lowest (650/m²) in plots with few mature plants. Most seedlings emerged in autumn and early winter, with early emergence giving the greatest seedling survival. Seedling growth was slow so that 1 year after emergence, seedlings were still increasing in size. Seedling survival after 1 year was low (1%), but contribution to total plant and tiller populations from seedlings were 28 and 11% respectively. These results indicate that natural reseeding, plant compensation, and survival of original plants all play important roles in the persistence of prairie grass swards.

Keywords:

• prairie grass
• Bromus willdenowii
• ‘Grasslands Matua’
• natural reseeding
• plant population
• tiller population