English abstract
In Oman, the vast majority of the plant species found in developed landscapes are exotic species from other parts of the world. These species showcase abundant floral displays and verdant green foliage; they also tend to consume a large quantity of the limited precious natural resources in Oman, in particular, water. This study of Omani native plants, which consisted of four sections, aims to partially address the issue of the underuse of native Omani plants. The first section compiled a list of possible specimens for the developed landscapes of Oman from existing literature on Omani native plants. These consisted of 171 plants of 49 families divided into six groups: trees, large shrubs, small shrubs, perennials-annuals, climbers, and succulents. The second section tested the tolerance of three Omani native plant species, Dodonaea viscosa, Ipomoea pes-caprae, and Ziziphus spina-christi, to the abiotic stress combination of heat and drought. Plants were subjected to four different drought treatments in two locations for the heat treatments. No plants died from the treatments, but no plants showed complete tolerance to the combined treatments. Dodonaea viscosa was found to adapt to the drought treatments, but only in the cooler temperatures averaging around 30 °C. Ziziphus spina-christi performed well in the heat, but only when there was sufficient irrigation. Ipomoea pes-caprae produced the most new growth and its highest Carbon dioxide assimilation levels in the greenhouse locations. three plants showed adaptability to both locations and all treatments. The third section further tested the tolerance of Dodonaea viscosa, Ipomoea pes-caprae, and Ziziphus spina-christi, to the abiotic stress combination of heat and salinity. Plants were subjected to four different salinity treatments in two locations for the heat treatments. The combination of the heat in the field location and the higher two salinity levels proved fatal for Dodonaea viscosa; however, the plant adapted to the salinity treatments in the cooler temperatures of the greenhouse location. Ziziphus spina-christi had the highest levels of photosynthesis in the greenhouse, but larger growth on plants in the field. Ipomoea pes-caprae had its greatest Carbon dioxide assimilation rates and the most new and densest growth in the greenhouse. All three species showed adaptability to the high temperatures in the field, but with varying degree of
resilience to the combination with high salinity levels. These two separate experiments demonstrated that the three species tested could survive in many of the demanding environments that Oman's developed landscapes provide. The fourth section of the study monitored seven native Omani plant species, Anogeissus dhofarica, Adansonia digitata, Delonix elata, Ipomoea pes caprae, Prosopsis cineraria, Tamarindus indica, and Ziziphus spina-christi, for the effects they have on their microclimates in the wild as well as in developed landscapes. Most species had denser growth in the developed landscape and changed the microclimates of their canopies by reducing temperatures, increasing relative humidity, reducing light, and reducing wind speed. These effects also carried through to below canopy zones due to their shading through insolation abatement. Overall, this experiment showed that these Omani native plant species have the ability to impact their surrounding microclimates in a positive way. The study further showed that while some species had more of an impact in their natural settings, others had more of an impact in the developed landscape. In either case, all the species studied proved they could be functional additions to the developed landscapes of Oman
