Abstract:

Competition and environmental stress are crucial factors for structuring plant population in natural habitats. Cyperus arenarius, a sedge of coastal sand dunes habitat, is a suitable species for coastal restoration and dune stabilization, but how salinity and plant density interact in affecting its growth is still unknown. Here, growth, survival, and physiological responses of C. arenarius to salinity (sea-salt) and plant density were investigated. A set of growth experiments in which combinations of 4 salinity levels (0, 2, 4, and 6 S m-1 sea-salt) and 3 planting densities (2, 5, 8 plants pot-1) were tested under controlled greenhouse conditions. Plant biomass and height were optimal in 2 S m-1 sea-salt while biomass decreased considerably at 6 S m-1. The inhibitory effect of high salinity was more severe in shoot dry mass relative to that of root dry mass, which resulted in increasing root/shoot dry mass ratio. Tissue succulence declined while the accumulation of Na and Cl increased with the increment of salinity, especially in root. Plant nutrient (K+, Ca2+, and Mg2+) contents decreased under salinity. Plant height was more sensitive with increasing plant density than biomass. High plant density (8 plants pot-1) lowered tissue biomass and water content in non-saline conditions to the similar levels observed under the 6 S m-1 seasalt salinity. Moreover, the combined effect of high salinity and increasing plant density had highly negative effects on plant growth attributes and water relations than their individual effect.

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