مطالعه جوامع گياهي خاك هاي غني از فلزات سنگين در شمال غرب ايران

The phytosociological study of heavy metals-rich soils in NW. Iran

Heavy metals- rich areas have a characteristic flora. Some phytosociological studies were carried out in these areas in the world, but such investigations are rare in Iran. In the present research, vegetation of these areas were studied by phytosociological approach. Phytosociological studies data could provide information on potential mining sites as well as on floristic differences due to a given metal elements present in the soils. Plant associations of some heavy metals-rich soils in NW Iran, including Tikmedash, Choghanlu and Khorasanak (Mn-rich), Ghebchagh (Zn-rich), Ali Alamdar, Mazraeh and Hiagh (Cu-rich), Kalejar (Fe, S and Se -rich), Mahbub Abad and Gheshlagh of Khoy (Ni-rich) were studied on the base of Braun-Blanquet method. In vicinity of each studied mine, the area with the same climatic and topographical characteristics but without high concentration of metals in soils, were studied as control site. Forty two sample plots were located at each individual associations. Analysis of phytosociological data were carried, using AFC and CAH methods by Anaphyto software. In this study, seven plant associations were identified in both of heavy metal-rich soils and their control areas, as follows: Prangetum ulopteri, Astragaletum vegeti, Tannacetietum chilliophylli, Astragaletum hirticalycis, Astragaletum microcephali, Astragaletum caspici and Astragalo veri-Acantholimonetum blukelokii. The results showed that the plant associations distrubtion pattern was mainly related to climatic, soil saturated percentage, K concentration , sand%, Na concentration and altitude. Because, induction of same plant associations in mineral sites and their control sites, metal elements have not effected in induction of associations. These elements induce presence or absence some of these species in mineral sites. Among characteristic species of identified associations, there were also species which were grown exclusively on heavy metal- rich soils. These species were identified as indicators. Thus, Onobrychis buhseana, Leutea petiolaris, Astragalus cancelatus and Lamium amplexicaule were identified as Mn- indicators, Prangus uloptra, Rheum ribes and Scrophularia variegata as Ni-indicators, Astragalus recognitus and Gnaphalium supinum as Cu-indicators and Astragalus hohenackeri and Polygonum paronychioides as Zn-indicators from NW. Iran for the first time.