Ecological studies of Ziziphus genus Fars province.

The Ziziphus genus belongs to Rhamnaceae family and has several species and varieties and is one of the most important drought and heat resistant genera which cover an area of about 500000 ha in Fars province. Other than soil and water conservation, erosion prevention and maintaining shelter for wildlife and range species, these species produce very valuable products including fodder, food, industrials and pharmaceuticals. To study the phenological stages of the two main species including Ziziphus spina-christi and Z. nummularia in their natural distribution zones and to gain a better understanding of the ecological characteristics, three regions were chosen in Fars province in 1379 (2000). These zones included Mamassani, Farashband, and Khonj. These habitats were visited in 2-3 week intervals annually from 1379 to 1386 (2000 to 2007). Several trees were marked in each site and were always monitored during four seasons and their phenological stages and characteristics were recorded. These characteristics included: the time of bud break, flowering, fruiting, ripening, fruit and leaf shedding, and several other characteristics. Also the height and crown cover area of the trees were measured. Climatic data were gathered and soil samples were collected and analyzed. Also, the vegetation composition of the areas was studied. The results from phenological data indicated that the growth patterns of different species of Ziziphus genus may alter with the fluctuations of drought and heat in different seasons of the year and usually they have two distinctive growth season and seed production occurs in two times each year. The first stage of flowering of Z. spina-christi is in early spring and the second stage in late summer and early autumn. This species is evergreen in its natural habitats. The other important species, Z. nummularia, is a deciduous small tree and for this reason occupies cooler sites and higher grounds. The flowering and seed production of this species happen two times annually as well. The first stage is in late winter or early spring and the second phase is in mid to late summer and early autunm. However, most phenological characteristics of this species are similar to those of Z. spina-christi. The timing of phenological events is different between regions due to differences in altjtude, rainfall and temperature. The lack of significant differences in terms of growth factors between different regions suggests that these species can grow in different ecological habitats. The results of soil analysis showed that sandy soils and sand texture and gravels and to some extent sandy loam soils are the most suitable sites for both of species and they usually avoid heavy soils in all three regions. Key words: Ziziphus spina-christi, Z. nummularia, phenology, ecology, height, crown cover, soil texture, slope, altitude, Fars province.