Effects of high initial densities on early growth of mountain ash seedlings.  P. J. van der Meer.  July 2000.  10pp. (unpubl.)

SUMMARY

The effects of high initial seedling densities on early growth of mountain ash seedlings were investigated. Seedlings were planted at 14, 20, 28, and 40 cm spacings, both under controlled conditions (Noojee) and in the field (Bennets Creek) in October 1997.

After 7 months, at Noojee, the wider-spaced seedlings were taller than the closer-spaced seedlings, with seedling heights varying between 223 cm (40 cm spacing) and 189 cm (14 cm spacing). Diameter growth and above-ground biomass production showed the same trend, with seedlings at wider spacings doing better than those at closer spacings. However, seedlings at closer spacings produced more stem biomass per ha than seedlings at wider spacings; this will continue until full site occupancy is reached - then production is likely to reduce as density dependent mortality begins. Also, branchiness was reduced under higher seedling densities. Effects on seedling growth after 7 months at Bennets Creek were less clear but showed the same trend. Results are compared to an experiment with potted seedlings (i.e. without root competition) which was done in the previous year.

It is concluded that high seedling densities will initially be beneficial for individual seedling growth through a sheltering effect. However, with increasing age and expansion of the plants, (root) competition will become more important, leading to slower plant growth and, eventually, higher mortality rates. The findings could possibly be applied in revised spot sowing techniques.