GERMINATION AND SEEDLING EMERGENCE OF SCIRPUS-LACUSTRIS L AND SCIRPUS-MARITIMUS L WITH SPECIAL REFERENCE TO THE RESTORATION OF WETLANDS

Germination and seedling emergence of Scirpus lacustris L. ssp. lacust ris (S.l. lacustris), S. lacustris L. ssp. tabernaemontani (C.C. Gmeli n) Syme (S.l. tabernaemontani) and Scirpus maritimus L. were investiga ted in order to assess their ability to establish from seed in former tidal waters, where the original standing population has almost comple tely disappeared. Germination of 1-year-old seeds of all three taxa wa s improved by stratification (wet/cold storage) and in the case of S.l . lacustris and S. maritimus, by bleach-scarification (deeds pre-soake d in sodium hypochlorite). Germination of S.l. lacustris and S. mariti mus was equally improved by both pretreatments. When light was supplie d during daytime, the minimum stratification period required for maxim um germination was lower for S. maritimus (4 weeks) than for both S. l acustris subspecies (more than 6 weeks). In continuous darkness, seeds of the three taxa hardly germinated after a stratification period of less than 6 weeks, but after 80 weeks of stratification, germination i n light and darkness were almost equal. Fluctuating temperatures compa red with constant temperatures improved germination of S.l. tabernaemo ntani and S. maritimus, but not that of S.l. lacustris. The amplitude between day and night temperature (from 5 to 25 degrees C) did not aff ect germination. Germination of S. maritimus increased with increasing day temperature. Generally, at constant temperatures the germination of 66-month-old seeds was reduced compared with that of 14-month-old s eeds of all three taxa. At a fluctuating temperature of 30/5 degrees C , germination of old compared with young seeds of S.l. lacustris and S . maritimus was not reduced; it was halved, however, in S.l. tabernaem ontani. Underwater the three Scirpus taxa were able to emerge from the substrate after being buried at substrate depths of 0.5 and 2 cm. At a burial depth of 5 cm only a small portion of the S. maritimus seeds and none of the two S. lacustris subspecies emerged. The failure to ge rminate and emerge at 5 cm burial depth could not be ascribed to dimin ishing fluctuation of temperatures with increasing burial depth.