Title: Characteristics and Distribution of Halophytes at a Jordanian Saltpan
Abstract: Vegetation structure was examined in a radial transect of 800 m length at the saltpan of Azraq ad Duruz (Jordan). It covered three of the traditionally described halophytic zones, and traversed twelve smaller geomorphological and vegetational zonations. Due to this fine scale of observation, the transect exhibited no continuous salinity and water gradient. Species zonational distribution showed preferences with respect to salinity and moisture in the zones. Chorotype and life form of some, but not all species could be correlated with flooding line, moisture, texture or salinity of soil. Salinity tolerance types as leafsucculents (L), crinohalophytes (X) and pseudo-halophytes (P) also cooccured as mixtures in most zonations. Due to low species numbers and high grazing pressure, quantitative evaluation of these criteria was not used to characterize the zonations and was held to mask edaphic, man-made and plant-induced habitat niches. The spatial subdivision of the zonations by NAA-associations improved the detection of niche boundaries. NAA (Normal Association Analysis) of the perennials gave a vegetation map which was nearly identical with the dominance releve and superior to the physiognomic-ecological map. All species devised by NAA to lead an association had a dominating cover/abundance within the NAA-group. The pattern of associations within a zonation was reflected by the pattern of habitat conditions of the leading species. For the leading species, out of the many traits (listed in a schema) that may be of interest for species/site correlations, type of mineral balance was investigated. As with the halophytic traits L, X and P, ion balances did not correlate with vegetation zones, but with microsites of associations: species with very high (> 15) leaf Na+/K+-ratios occured on phytogenic sandhills; this trait was associated with high salt tolerance, leaf succulence, laterally extended roots and low flooding tolerance. Halophilous species with leaf Na+/K+ -ratios of 2-7 occured in various site conditions and possessed salt glands. Species with leaf Na+/K+ -ratios < 0 grew on easily penetrable soil with access to brackish water, posessed deep roots and only a moderate salt tolerance. At the associational scale of observation, other habitat/plant correlations were observed, and the importance of plant/habitat effects of salinizing or moundforming halophytes is stressed. The strongest animal/plant impact, maninduced overgrazing, was a strain of high comparative importance and masked the effect of many other adaptations in this rare type of community.
Publication Year: 1990
Publication Date: 1990-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 5
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