Article

El Omayed ' ROSELT' Observatory adopted a thematic procedure of evaluating and monitoring changes in natural resources. Data from previous studies was reworked to fit into the concerned themes. The trends of temporal change in the different va riables were evaluated using polynomi al curve fi tting confirmed by statisti cal analyses. The extracted trends indicate a steady increase in air temperature, re lative humidity and annual rain fa ll, while wind speed is declining. The standardi zed seasonal rainfa ll results in an autumn trend that approximates annual trend with amplitude of five years, while that during winter season is dec lining and that of spring is inclining above the long-term average starting mid nineti es. Concurrently, sodium, sulfate and chloride contents increased rapidly late in the nineti es joined with increasing the very fine sand fraction that refl ects the acti ve erosion and deposition processes associating recent human interference in the area. The temporal changes in the soil properties define the inland ridges as having the most stable conditions. The long-tenn records report 122 perenni als and 104 annuals of pl ant species residing in the observatory. Except for the inland plateau, there is a process of recharging the species di versity late in the nineties a l'ter experiencing a former sizable decline. Aiso detected is a change in the life-form spectrum towards larger woody component. Moreover and at the closing of the decade, the perenni al species exhibit less reproducti ve effort coupled with a decline in the annua I reproduction of both perennials and annuals. It is evident that 26 species can be considered in jeopardy in terms of decl ining density and spatia l occupation. With 54 % of these are ligneous, there is high risk imposed on the structure and function ofthe concerned ecosystems. Some ofthese species are transient with a trend of a five years cycle of species replacement. The values of alpha and beta di versity indices argue that the habitats most abet to pl ant diversity are inland ridges and inland pl ateau; hosting the highest species diversity and specifi city alld larger positive value of species turnover.The change in the di versity ofperennial species is allied to changes in rain fa ll, temperature and wind speed ofthe climatic, and salinity, bi carbonate, calcium, and sul fate of the edaphic vari ables. This applies also to the endangered species with especially air temperature and soil sulfates as the most detenninant dri ving factors. Further is the shitì ofthe rainfa ll above the long-term average from winter to spring that elucidates the trend of change detected in the di versity "t the close of the decade. Il is concluded that, the di versity of biotops (spatial heterogeneity in habitats) in the area is the influential base for the biodi versity and is greatly affected by human impacts. Concurrently, the changes in the climate and the associated environmental degradation of notably soil resources, are more of cyclic (recurring) phenomena, whi ch reflects specific feedback effects on biodiversity in the region.