Sand accretion and salinity as constraints on the establishment of Leymus arenarius for land reclamation in Iceland

Abstract

Seed harvested from wild populations of Leymus arenarius is sown extensively in Iceland to stabilize sandy barrens, on the coast and inland. Sand accretion can reach 50 cm over 3 months in summer near the outwash of glacial rivers on the south coast of Iceland and thus may be an important factor influencing survival and growth of L. arenarius. Newly germinated seedlings had great potential for elongation in darkness (etiolation). The length of the longest etiolated leaf increased significantly with seed mass. The etiolation response proved to be a good predictor of their ability to emerge from burial with sand. The mean length of etiolated shoots was approx. 16 cm and 40% of seedlings emerged when germinating seeds were buried with 15 cm of sand, whereas none emerged from burial under 20 cm of sand. A moderately high and sustained rate of sand deposition (2-4 cm week-1), applied to 10-week old seedlings in a glasshouse experiment, significantly increased leaf length and the allocation of biomass to shoots, such that overall biomass was slightly but not significantly increased. The growth responses of seedlings of one coastal population and two inland populations of Leymus arenarius were compared when challenged with salinities ranging from 0 to 600 mM NaCl in sand culture. The numbers of tillers produced by the coastal population was stimulated by salinity in the range 200-400 mM NaCl, unlike their inland counterparts. The total dry mass of the coastal population was less adversely affected by high salinity than that of the two inland populations, mainly because root biomass was reduced less; total leaf area was also slightly less reduced in the coastal population. The reclamation of sand barrens in Iceland with high accretion rates would benefit from sowing seeds from larger-seeded populations, at a depth of 5-10 cm; at coastal reclamation sites, it would be preferable to use seed from the more salt-tolerant coastal populations.