Vegetational patterns within coastal salines in southern Yemen

Abstract

AbstractFor the first time, the species diversity and zonation of coastal dunes and littoral salt marshes of the extensive coastal belt of southern Arabia is analyzed by means of two transects (Aden/Madinat as‐Shab; al‐Mukalla/Feleq). The vegetation analysis results five (Aeluropus lagopoides‐, Halopeplis perfoliata‐, Halopyrum mucronatum‐, Sevada schimperi‐association, and one rest group – Aden transect) respectively seven (Anabasis ehrenbergii‐, Arthrocnemum macrostachyum‐, Cyperus conglomeratus‐, Stipagrostis paradisea‐, Urochondra setulosa‐Arthrocnemum macrostachyum‐, Urochondra setulosa‐association, and one rest group – Feleq transect) homogenous ecological groups, which form clearly defined belts following a strong edaphical gradient. While the associations in the vicinity of Aden are in good accordance with those, reported from the coasts of the Red Sea and the Arabian Gulf, three new associations, partly rich in endemics are reported from the southern coast of Hadramout (Feleq transect). Due to the plantgeographical relationships of the taxa (Eritreo‐Arabian chorotype), they are strongly related to the coasts of NE Africa. In addition, Coelachyrum piercei is reported as new to the flora of Yemen, closing herewith a gap in the distribution pattern of this Omano‐Makranian taxon.All taxa were examined with respect to their photosynthetic pathway type (Kranz syndrome, δ13C‐values) to clarify, if there is a correlation between the distribution of C3‐/C4‐plants and the ecological requirements of the halophytes. It turned out, that hygrohalophytes and oligohaline, xerix associations are dominated by C3‐plants, whereas C4‐plants are typical of xerohalophytic associations and those, showing an intermediate position with respect to soil salinity and available water.