JWSS - Journal of Water and Soil Science

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Plant communities of the Kolah-Ghazi National Park have been studied. The park with a wide diversity of fauna and flora species is located 36 Km south of Isfahan. 214 plant species were collected for the purposes of this study. Plant communities of the park are of an aridland vegetation type. Minimal areas of the plant communities were determined using nested plots technique. After studying the Species/Area curves, a l00-square-meter quadrat was employed to collect the cover and density data for each species. The cover data were analysed to determine plant communities using the ordination method.

Crown cover of the vegetation was found to be poor and varied from zero to a maximum of five percent in the park. The following species form the major plant communities in the park: Artemisia sieberi, Anabasis aphylla, Acantholimon spp., Cousinia piptocephala, Ebenus stellata, Pteropyrum aucheri & Scariola orientalis. The combination of these species with others forms plant communities and subcommunities. The overlapping of habitats makes mosaics which cause the formation of ecotones, thus increasing the diversity of the subcommunities in the park. Mesophytic plant communities are narrowly scattered along streams. Most of the plant communities are controlled by the adaphic factor while the biological factor has only a limited control. A Ficus spp. specimen was also collected from the mountainous region in the park which could be a new species or variety and requires further study.

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In order to determine the reciprocal relationship between the important characteristics of soil and the growth of Haloxylon ammodendron (C.A. Mey) plant in segsi plain of Isfahan., ordination method was used. The study was performed through the stratified random sampling and the regions were separated according to the plant age and physical physiognomy, then 10 samples of Haloxylon ammodendron (C.A. Mey) of the same age were selected in each region. Meanwhile, factors such as height, canopy cover area, canopy cover perimeter, canopy cover diameter, and basal area were considered. Also, 30 profiles from viewpoint of growth situations in 10 different regions were dug. Soil characteristics such as : pH, Ec, total soluble Ca²⁺ and Mg²⁺, Cl^-, CO3^--, HCO3^-, SP%, CaCO3%, CaSO4%, organic matter%, total nitrogen percentage, phosphorous, Na⁺, K⁺, SAR, and hardpan depth were measured. Data was analyzed using ordination method. According to the results, samples of the same age showed significant differences in plant features. Other results showed that physical characteristics such as depth of hardpan from soil surface, SP%, and chemical characteristics such as salinity, alkalinity and total nitrogen had the highest effect on qualities of this kind of plant. In other words, the results mentioned above showed the important role of Haloxylon ammodendron (C.A. Mey) in sharp increase of salinity and alkanity in it's stratum.

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Ordination is the part of statistical ecology which has developed and integrated in recent years. Finding environmental factors which important in ecological structure determination of plant species is the final purpose of ordination. Ordination method was used for finding the effect of important variables on Bromus tomentellus species quantitative and qualitative changes in Esfahan's Fereidan region. For this purpose, fifteen sites were studied. Density, Cover percentage and Soil factors containing EC, pH, % caco₃ , % gravel and stone, % clay, % silt, % sand, Na⁺, Ca²⁺, K⁺, Mg²⁺, Cl^-, SAR, C/N and % OC. In A (0-30 cm) and B (30-60 cm) horizons over a line transaction in each site, were measured. The matrix of environmental and species characteristics were prepared. The relationship between environmental and species characteristics were determined using of PC-ORD and CANOCO software's and Redundancy Detrended Analysis (RDA) method. The results show that there are meaningful correlation between Density and Cover percentage with soil factors. The results implicate that C/N factor in A horizon and SAR in B horizon have the most effect on Bromus tomentellus density and cover percentage. EC, pH and …. Factors don't have much effect on Bromus tomentellus species characteristics.

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Vegetation is the most important factor in sustainable and dynamic equilibrium of natural ecosystems. Considering the relation between environmental factors and vegetation is an essential step in order to identify the effective factors in the habitats. The purpose of this study was to evaluate the relations between vegetation and soil characteristics in rangelands of Ferydounshahr (Sardab-Sibak watershed). The flora and vegetation types were studied using Physionomic-floristic method in the field and eight vegetation types were identified. Vegetation was sampled by Systematic–randomized method in 1× 2 m plots. The canopy cover and species composition percentage were estimated in each plot. After digging a soil profile in vegetation types, the physical and chemical factors were measured. The influences of edaphic factors on vegetation were analyzed using RDA ordination technique. Results showed that based on soil characteristics the eight vegetation types can be classified in to three main range habitats including, Ferula ovina, Astragalus adscendens and Astragalus brachycalyx. The most important factors which cause the separation in these three habitat ranges were clay percentage, organic matter, soil depth, CaCO3, pavement and barren soil.