TY - JOUR

T1 - Experiments and observations on seed dispersal by running water in an alpine floodplain

AU - Bill, H. C.

AU - Poschlod, P.

AU - Reich, M.

AU - Plachter, H.

PY - 1999

Y1 - 1999

N2 - 1. In-stream dispersal and floating capacity of 18 pioneer plants (nine chamaephytes, eight hemicryptophytes and one shrub) from alluvial floodplains on the upper Isar (Bavaria, Germany) were studied using field and laboratory experiments between 1994 and 1996. 2. Drift collection of seeds with nets at the water surface proved unsuitable because of the great amount of invertebrates drifting along the river, though it allowed an estimation of the amount of drifting seeds. In August and September we found over 9,000 drifting seeds per meter stream width and day or over 120,000 seeds over the whole stream width in 24 h. Sediment-filled baskets proved to be better traps but were often destroyed during flooding periods. Although drift collection was of limited value for sampling seeds in a highly dynamic floodplain, water transport of viable seeds could be demonstrated for nine of the 18 species. 3. In laboratory experiments, in which seeds were placed into a beaker, stirred up to five days and then used for germination tests, seeds of 16 of the 18 species showed a moderate to good floating capacity. Only two species had seeds that could not float longer than a few minutes (Gypsophila repens and Silene vulgaris ssp. glareosa). 4. We hypothesised that dispersability decreases with increasing seed mass, but the assumption that heavy seeds are not dispersed over great distances is valid only for environments without the possibility of in-stream dispersal.

AB - 1. In-stream dispersal and floating capacity of 18 pioneer plants (nine chamaephytes, eight hemicryptophytes and one shrub) from alluvial floodplains on the upper Isar (Bavaria, Germany) were studied using field and laboratory experiments between 1994 and 1996. 2. Drift collection of seeds with nets at the water surface proved unsuitable because of the great amount of invertebrates drifting along the river, though it allowed an estimation of the amount of drifting seeds. In August and September we found over 9,000 drifting seeds per meter stream width and day or over 120,000 seeds over the whole stream width in 24 h. Sediment-filled baskets proved to be better traps but were often destroyed during flooding periods. Although drift collection was of limited value for sampling seeds in a highly dynamic floodplain, water transport of viable seeds could be demonstrated for nine of the 18 species. 3. In laboratory experiments, in which seeds were placed into a beaker, stirred up to five days and then used for germination tests, seeds of 16 of the 18 species showed a moderate to good floating capacity. Only two species had seeds that could not float longer than a few minutes (Gypsophila repens and Silene vulgaris ssp. glareosa). 4. We hypothesised that dispersability decreases with increasing seed mass, but the assumption that heavy seeds are not dispersed over great distances is valid only for environments without the possibility of in-stream dispersal.

KW - Alluvial floodplains

KW - Floating capacity, in-stream dispersal

KW - Pioneer plants

KW - River Isar

UR - http://www.scopus.com/inward/record.url?scp=0032784182&partnerID=8YFLogxK

U2 - 10.5169/seals-377823

DO - 10.5169/seals-377823

M3 - Article

AN - SCOPUS:0032784182

VL - 65

SP - 13

EP - 28

JO - Bulletin of the Geobotanical Institute ETH

JF - Bulletin of the Geobotanical Institute ETH

SN - 1420-6803

ER -