Ontogenetic variation in the relative influence of light and belowground resources on European beech seedling growth
Christian Ammer (1, 2), Bernd Stimm (3) and Reinhard Mosandl (3)
1. Department of Silviculture and Forest Ecology, Georg-August-Universität Göttingen, Büsgenweg 1, D-37077 Göttingen, Germany / 2. Corresponding author () / 3. Chair of Silviculture, Technische Universität München, Am Hochanger 13, D-85354 Freising, Germany / Received June 27, 2007; accepted September 18, 2007; published online March 3, 2008
Summary
We used height growth data from a 7-year field experiment with European beech (Fagus sylvatica L.) seedlings to test the hypothesis that the effects of above- and belowground resources on height growth depend on seedling
size and age. Photosynthetically active radiation (PAR) was determined by hemispheric photography, and estimates of fine root
biomass of the overstory trees were used as an inverse proportional surrogate for belowground resource availability. For recently
germinated seedlings growing under the canopy of Picea abies (L.) Karst., belowground resource availability affected height growth more than light. During subsequent stages of seedling
development, apart from initial seedling size, PAR increasingly determined seedling growth. Besides initial size, seedling
age determined the effects of above- and belowground resources on seedling height growth. In seedlings identical in initial
size but differing in age, the increase in height growth with increasing PAR was greater in older seedlings than in younger
seedlings. The ranking of seedling height by year showed that small differences in size at the end of the first growing season
resulted in continuously increasing differences during the following years. Mortality data indicated that the chances of a
seedling surviving intraspecific competition was strongly determined by its dominance ranking within the first 5 years after
establishment.
