CONTROLS ON SEED PRODUCTION AND SEED GERMINABILITY IN ERIOPHORUM-VAGINATUM

Controls on seed production in Eriophorum vaginatum were studied at tw o Low Arctic sites, Latnjajaure in Sweden and Toolik Lake in Alaska. A t Latnjajaure, seed production was monitored for 3 years (1993-1995) i n control plants and in plants that were experimentally warmed using I TEX open-topped chambers (OTCs). At Toolik Lake, experimental treatmen ts included a factorial greenhouse x NP fertilizer experiment and arti ficial shading: data collection occurred in 1995, after eight seasons of treatment. Temperature differences between sites, years, and treatm ents all had significant effects on components of Eriophorum seed prod uction. Pre-floration and post-floration times were decreased in warme r treatments and years. Ovule number per inflorescence was greater in warm years and at the warmer site, Toolik Lake. Although seed set was reduced in the OTCs at Latnjajaure, probably due to low pollination ra tes, in the larger greenhouses at Toolik Lake seed set was increased. The most consistent responses to temperature were in seed weight, wher e treatment effects were greatest at lower temperatures, such that, fo r example, at Latnjajaure the increases in seed weight in the OTCs wer e greatest in the coldest year. Fertilizer treatment had no significan t effect on seed number or weight at Toolik Lake, and in the fertilize r + greenhouse treatment there were no inflorescences because Eriophor um had been nearly eliminated from the treated plots. In the shade tre atment at Toolik Lake, inflorescences were fertilized but only a singl e mature seed was collected. Overall, the results indicate that seed p roduction by E. vaginatum is strongly responsive to environmental vari ation and that only a small increase in mean summer temperatures would result in a much larger and more stable seed production.