Date of Award

2004

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Dr. Ali Ali M. EI-Keblawy

Second Advisor

Dr. Taoufiq Saleh ksiksi

Third Advisor

Dr. Annette PatzeIt

Abstract

The effects of the invasive exotic Prosopis juliflora shrubs on the natural plant communities were assessed in three regions (Sharja, Ras Al-Khima and Fujira) of the UAE. The effect of the P. juliflora shrubs on the associated annual and perennial plants was studied in a number of quadrats distributed under, at the margin and outside the crown of a shrub. The results indicate that the effect of P. juliflora on the associated species depends significantly on the density and size of their individuals. Large individuals and greater densities have significantly adverse effect on the associated species. All of the studied community attributes were significantly lower in the quadrats under the P. juliflora crown, compared to those outside it. The analysis of size structure of the different regions showed that most of the populations are rapidly growing. It is interesting to note that P. juliflora individuals improved most of the examined soil characters and grew in highly saline habitats indicating the potentiality of this species to be used in the afforestation of the salty habitats and its reclamation.

The effects of maternal habitat, time of seed maturation and seed storage, and their interaction were assessed on light and temperature requirements during seed incubation on final germination percentage and germination rate of P. juliflora. Seeds were collected at different times (autumn, winter and spring) during the growing seasons from three maternal habitats (Sharja, Fujira, and Khor Facan). Seeds were germinated immediately after collection and after eight months of storage. The results showed significant effects for maternal habitat, time of seed collection, seed storage and both light and temperature of seed incubation and their interaction on both germination percentage and rate. Fresh seeds of autumn and winter germinated greater at high temperature (40 °C), but stored seeds of the same seasons did not differ significantly in their germination in the three incubation temperatures. Seed storage reduced the light and temperature requirement for seed germination especially for seed matured during autumn and winter.

The effect of salinity, temperature, light and their interactions on final germination percentage and germination rate evaluated were evaluated for seed collected from Fujira and stored for 18 months in paper bags at room temperatures. Non-saline treated seeds germinated well in a wide range of temperatures and in both light and dark. Seed germination decreased with the increase in both NaCl concentration and temperature. The optimal germination was at 25°C and both 15°C and 25°C attained significantly greater germination than 40°C. The inhibitory effect of high salinity on final germination was greater at 40°C than at 15°C and 25°C. The germination was completed inhibited in 400 mM at 40°C and in 600 mM NaCl at 25°C.

The effect of different types and concentrations of dormancy regulating chemicals (DRCs) on innate and induced dormancy of P. juliflora was evaluated. Lower concentration of gibberellic acid (0.3 mM) and kinetin (0.05 mM) was more effective in enhancing germination percentage and speed in higher concentration of NaCl, but the reverse was true for thiourea. None of the DRCs succeeded to alleviate the innate dormancy of P. juliflora. Germination reduction in 500 mM NaCl was not alleviated by any of the DRCs, but inhibition induced in 600 mM NaCl was partially alleviated by the different chemicals. Gibberellic acid has significantly greater effect than kinetin in alleviating the germination inhibition. For restoration of saline soil by using P. juliflora, the results suggest using DRCs, especially gibberellic acids and thiourea, for the treatment of the seeds prior to scattering in the saline soils, to overcome the problem of their germination.

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