Relationships between vegetation zonation and edaphic factors in a salt-marsh community (Black Sea coast)

Abstract

The effects of pH, electrical conductivity (EC), soluble cations (Na +, K +, Ca 2+, Mg 2+), and soluble anions (HCO 3 -, Cl -, SO 4 2-) on vegetation zonation in a salt-marsh community (Black Sea coast) were investigated on two localities at Black Sea Coast differing as to the altitude, community composition and zonation. Three zones (25-80 m wide) - lower, middle and upper were distinguished in each locality along 150 m transect and according to the vegetation types which were analysed with Braun-Blanquet method. The dominant species were following: Juncus acutus L., Salicornia prostrata Pal l., Spergularia marina (L.) Gris, Hordeum geniculatum Al l., Plantago coronopus L. subsp. coronopus, Carex capitellata Boiss. and Bal, Artemisia santonicum L. and Juncus littoralis C. A. Mey. Soil samples were taken down to 50 cm. The results of soil analysis were evaluated by using Canonical Correspondence Analysis (CCA) from winter 1999 to autumn 2000. HCO 3 - concentration and inundation depth (2.22-21.44 cm) are the environmental variables that correlate the best with axis 1, whereas K + concentration and inundation depth (2.22-21.44 cm) correlate the best with axis 2 during the study period. During winter 1999, HCO 3 - concentration showed the highest correlation with the canonical axis 1 and associated zone was H. geniculatum. In spring, summer and autumn 2000, inundation depth (3.44-19.11 cm) was the most prominent factor correlated with the first and second axes, respectively, with associated zone of C. capitellata. EC, Na + and CI" concentrations were decreased during autumn in all vegetation zones except for C. capitellata and Artemisia santonicum zones in which Na + and Cl - concentrations and EC, respectively were increased during autumn. The C. capitellata (Cyperaceae) zone was located on the positive site of axis 1 during autumn 2000 and followed the gradient of inundation depth. S. prostrata, S. marina, H. geniculatum and P. coronopus subsp. coronopus seems to be adapted to the most saline soils, whereas C.capitellata indicates the wettest soils in the studied salt marsh. The Juncus littoralis zone followed the gradient of maximum salinity during autumn of the year 2000, but the zone was not related to the measured increase in soil salinity during winter, summer and spring. In both localities EC, Na + and Cl - concentrations were tended to decrease at upper zones. Inundation regime, K + concentration, and HCO 3 - concentration are key factors affecting vegetation zonation in studied salt marshes.