الفهرس 
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Abstract
The present study aimed at investigating the monthly accumulation potential of P. dioscoridis for macronutrients (N, P, K and Ca) and heavy metals (Cu, Pb, Cd, Zn and Cr) in its biomass from soils and the impact of this accumulation on the morphology, density, and biomass of the study species under the effect of habitat heterogeneity in Tanta district, the middle Nile Delta, Egypt. It aimed also at determining of the soil quality exposed to heavy metal contamination in the different urban habitats and evaluation of the environmental impact of these habitats by using certain pollution indices. In addition, it constructed a holistic urban N, P, K and Ca budget model representing the cycle of these macronutrients in the different studied habitats. It investigated the most important environmental factors affecting the distribution of P. dioscoridis and its associated species in the eight districts of El-Gharbia Governorate, the middle Nile Delta, Egypt. Regarding the sampling in Tanta district, three urban habitats, wastelands, road sides and residential habitats, had been selected representing different degree of disturbance. Each habitat had been represented by three sites. In each site, three permanent quadrats (each of 10 × 10 m) were sampled monthly from March 2015 to February 2016. For studying the environmental factors affecting the distribution of the study species, seventy three stands were selected, in the eight districts of El-Gharbia Governorate, to represent the current distribution of P. dioscoridis populations during the year of (2016-2017) through regular seasonal visits to the study area. In each stand, the floristic elements had been surveyed and the associated perennial and annual species were recorded seasonally indicating the first and second dominant species. Voucher specimens were kept in Tanta University Herbarium (TANE).
The present study indicated that the variation in the soil physico-chemical properties such as pH, chlorides, sulphates and electrical conductivity varied significantly with habitats, month and intercept between them, except that of sand and clay. In addition, the analysis of soil inorganic nutrients and heavy metals indicated significant variation in all macronutrients and heavy metals except Ca and Zn. It was found that inorganic nutrients concentrations (mg 100g-1) in the soil were in the order: Ca > N > K > P, soil heavy metals concentrations were in the order : Pb > Cu > Zn > Cr > Cd in the three habitats. The pollution indices (single and integrated) had been used in this study in order to evaluate the soil quality and define if accumulation of heavy metals in urban soils was caused by natural processes or was the result of human activities. These indices indicated serious anthropogenic contribution to the contamination load for Pb and Cd in the road sides and residential habitats, and moderate contamination level for Cu in all habitats. Moreover, Zn and Cr, in all studied habitats, indicated uncontaminated or low contaminated soil samples by these metals. In addition, wasteland habitats exhibited moderate overall ecological risk, while road sides and residential habitats were subjected to overall considerable ecological risk. The present study indicated that the variation in the activities of the different phenological stages of P. dioscoridis varied significantly with the habitats and months. Furthermore, the flowering of P. dioscoridis was active during the whole year, except winter months (December-February) with a peak in the road sides and residential areas during July, and minimum in residential areas of in November. Likewise, fruiting was recorded all over the year, except in January and February. The fruiting phase had the maximum activity at the road sides and residential areas during September and at the wastelands during August. The withering phenophase of P. dioscoridis was observed during the whole year, and had the maximum activity at the three studied habitats during November, and its minimum in wastelands. The monthly variation in the growth parameters of P. dioscoridis varied significantly with habitats, months and the interaction between them. P. dioscoridis populations exhibited the lowest values of growth parameters (height, diameter, size index and volume) along the three different habitat in March, while the highest was in August and September. Moreover, the dimensions of P. dioscoridis indicated that the individuals from wastelands had the highest values of investigated growth parameters. In contrary, the residential habitats exhibited the lowest values of all examined growth parameters. On the other hand, the total mean density of individuals of P. dioscoridis decreased from March to a minimum in November. Moreover, residential habitat had the highest annual mean density, while the wasteland had the lowest. There was a negative relationship between the density and size variables of P. dioscoridis population. Among the regression models tested for biomass of different shrub compartment, simple linear regression based on plant size index as an independent variable was found to be the best fitted equation for the determination of the biomass of stem, flower, leaf and standing dead parts, while the shrub diameter alone was a good predictor for the coarse root biomass of P. dioscoridis. In addition, stems contributed to the highest annual dry weight, while flowers had the lowest value in all studied habitats. The highest above-and below ground biomasses were recorded in August, while the lowest were recorded in March in the three studied habitats. In addition, wastelands had the highest annual mean of the total biomass of P. dioscoridis. In contrary, the residential areas had the lowest annual mean of the total biomass.