干旱区生态环境知识资源中心

Ertaa (Calligonum comosum) and Ghada (Haloxylon persicum) are two important multipurpose indigenous shrubs in the deserts of Saudi Arabia, supplying firewood and fodder to the local populations. Their environmental benefits in connection with sand dune fixation and microenvironment improvement are commendable. Due to over-exploitation and habitat destruction, population of these two shrubs have become severely degraded. This study helps in the development of the appropriate propagation techniques for their regeneration and evaluates their relative growth rate under different irrigation schedules. Productivity in the natural population and biological growth under cultivation were also evaluated. Seeds of Ertaa required no special treatment while the seeds of Ghada showed higher percentage of germination when soaked in cold water for 1 hour. The seeds of Ghada are photoblastic, which require adequate light for germination while those of Ertaa are negatively photoblastic. The growth rate of both species under different irrigation schedule proved that the increase of irrigation frequency may not proportionally influence the growth rate. The estimated productivity of natural stands in Saudi Arabia was much less than the productivity of both species from other parts of the world. The estimated biological growth function under cultivation was found to reasonably match with the natural growth for both species, indicating that both species are in their initial growth stage.