Interrelationships between Different Generations of Interconnected Tillers of Carex bigelowii

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Abstract
(1) The interrelationships between tiller generations of Carex bigelowii Torr. ex Schwein. were investigated at two subarctic sites by labelling young tiller modules with 14C and detecting its translocation, and by severing modules at increasing distances from the youngest tiller generation. Tiller survival, regeneration and physiological continuity were all measured. All of the investigations were on systems produced by vegetative proliferation and subsequent fragmentation: recruitment from seedlings was not observed. (2) 14C-assimilates were translocated through the rhizome system, from the one to two years old assimilating tillers into the roots and rhizomes of nine to eleven years old tillers with only below-ground organs remaining. This shows that the roots and rhizomes of the numerous interconnected old non-assimilating tillers were alive and that their roots were probably still functioning. (3) The severing-experiment showed that the few assimilating young tiller generations were to some extent dependent on the old below-ground, non-assimilating tiller generations for their survival, growth and reproduction. Water and nutrients are probably the forms of subsidy. (4) The minimum size of a successful physiologically functional unit was around five interconnected tiller generations. The maximum size could not be determined. (5) Apical dominance effects were detected within the rhizome system. The rhizomes keep a reserve of dormant buds. When the connection between tiller generations was severed, buds on the old rhizomes, which had been dormant for several years, developed into new tillers. These tillers were characterized by having only short rhizomes and they produced green leaves in the first season of growth. (6) The integrated system of old and young tiller generations, together with a spatial network of modules controlled by apical dominance, provide Carex bigelowii with mechanisms for locating and exploiting favorable patches in a nutrient poor, but patchy environment.