Changes in Structure and Function of Ammophila during Primary Succession

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Abstract
Quantitative changes in the aging process of Ammophila [A. baltica, A. arenaria and A. arenaria .times. Calamagrostis epigeios] were studied on dunes at Sandhammaren, Sweden. The decline of the marram grass vegetation during a 10 yr period was mainly quantified as a decrease in the yearly formation of above ground biomass from approximately 400 g/m2 to approximately 125 g/m2, a decrease of the maximum green leaf area from approximately 0.75 m2/m2 to approximately 0.25 m2/m2 and a decrease of the yearly formation of below ground organs from approximately 200 g/m2 to zero. A method for measuring the above ground production was used, which compensates for wind transport of litter during the growth period. The life span of the above ground biomass increased by time, which indicates that the decline in the vegetation and in net production does not correspond to a decline in gross production, but a changing balance between assimilating and non-assimilating tissue towards a state, in which annual respiration equals annual assimilation, and no further net increase of biomass takes place. A model for the accumulation of organic matter by time was tested for different courses of the decrease in litter formation.