IRANIAN JOURNAL OF RANGE AND DESERT RESEARCH
Year:2003 | Volume:10 | Issue:3|Papers Count:6

The objective of the present study was to evaluate desertification phenomena in North Part of Khorasan province adopting FAO-UNEP as well as Turkmenistan Desert Research Institute specific version methods. However these methods were modified according to local situation. All maps were prepared based on TM and MSS satellite images (1:250000) using geology, topography, vegetation and climatologic maps. Final map of human-induced desertification was set (1:500000). This map reflects development of different classes of desertification along with their respected intensities and causes. Results revealed that about %7.7 of the area could be classified as natural desert composed of sandy, saline and low quality lands. Signs of desertification were not found only in about %5.5 of the territory. In general about %86.5 of total area (61440 Km2) are being affected by desertification with different intensities. The most and the least important factors of desertification were vegetation destruction and wind erosion with 46 and 0.5 percent respectively. Other processes like water erosion (%34.4) and soil salinization (%5.7) had their own effects on the subject. Considering desertification intensity, 46.7 percent of total area is classified as high and very high, %23.8 as medium and %16 as low intensity.

Determination of suitable irrigation period and water volume for haloxylon persicum establishment was the aim of the study. The experiment was conducted in 50 km of west Iranshahr, Iran, characterized by 100 mm annual precipitation and 580 m altitude. The study was run for three years. Seed were planted 1995 and conserved from animal damages. The split split plot design with three replications was used for the experiment, in which Irrigation period with three level of 25, 30 and 35 days was the main plots and water volume with three level of 15, 20 and 25 litters was the sub plots. Irrigation continued for the first year. Plant establishment was a major factor; therefore the seedling mortality was counted on treatments monthly each year. There were no significant differences between treatments in the first year however the shortest irrigation period with largest water volume had the little seedling mortality. During the second year after May, the mortality increased and by the end of this year all seedlings died. It appeared that essential variations in soil surface layer that causes by soil wind erosion, has prevented seedlings establishment.

The hypothesis or main issue of the present paper is to review the possibility of achieving the minimum, expressive, simple and regional criteria and factors that can provide us with the actual review of the desertification process in Iran. In other words, this study attempts to introduce a list of the most efficient assessment criteria for the land degradation in the regions affected by the process of desertification and to provide measurable, accessible and simple factors for the assessment of exact condition of the said criteria: Therefore, by strengthening and updating the watch and observation systems of the country, the more accurate forecast of desertification risk according to the affected climatic conditions or natural environments and increase in percentage of success of the national action programs are more expected. In the process of this important achievement, the complete definition of desertification and its scope, and also its difference with other scientific terms such as desert and land degradation, together with strict and adducible norms for identification of criteria and indicators will be necessary. This paper has also tried to respond properly to the following question of Why the climatic factors can not only be referred in the assessment of desertification process?

The effects of rotational and continuous grazing systems and light, medium and heavy grazing intensities on the phenology of Bromus tomentellus were studied in Homand -e-abesard rangeland research station, which stated in 70 km east of Tehran, in 2002. 30 stands of Bromus tomentellus were selected for investigating of phenology in different times in each treatment. By using the air temperature data The Growing degre- days were calculated for each phenology stage the results showed that the species started its growth from late Eesfand and dried in late Tyr in both grazing systems. There was dormancy from early mordad to late Aban and regrowth periods from late Aban to late Azar for the species. Then it was dormant until the late esfand. Growing degree- days were calculated for vegetative and reproductive stages of heavy and light intensities of rotational grazing system respectively 1262.2 and 1306 celecius degree and for the similar treatments in continuous grazing system attained respectively 1293.8 and 1262.3 celecius degree. There was a thin regression between phenology and soil moisture (p < 5) but a strong one between air temperature and it (p >5 )..The grazing systems and grazing intensities did not affected obviously on phenology.

Autecological study of range plant species to provide basic knowledge for managing rangeland ecosystems is eminently important. This study was conducted to furnish some information about autecological function of two range plant species of Bromus cappadocicus and Bromus stenostachyus in Mazanderan Province of Iran. Some topographic, climatic, and edaphic aspects, as well as the boundaries, of the ecological habitats of these species were delineated. Phenological stages, root system, and the way of presence of each of these two species in the vegetation assemblage were determined. The names of other species accompanied with each of these two species were listed. The results show that the habitats of Bromus cappadocicus in Mazanderan Province are very limited. This species was observed in some scattered patches at slopes of %5-60 and altitudes of 2550-3100 m above sea level, mainly in western and central sections of the province. Average annual rainfall at these habitats is 400-500 mm. Tests of soil texture indicates that this range plant species grows in loamy and loamy silt soils. In the main section of its habitat, at the altitude of 3100 m above sea level, vegetative growth of this plant starts in early April. Its flowering stage starts in mid May; and the seeds ripen in mid June. The root system of this species is fibrous and distributed among particles of shallow soils. Ecological habitats of Bromus stenostachyus are at altitudes of 1500-4000 m above sea level and slopes of %10-70, in central parts of Elborz Mountain in Mazanderan Province. At most of its habitats, this species was observed as first dominant, second dominant, or third dominant species of the vegetation. At the elevations of 3000-4000 m above sea level, however, it grows in scattered patches. Annual rainfall at these areas is 400-500 mm. This range plant prefers loamy and loamy silt soils too. At the altitude of 3100 m above sea level, vegetative growth of this plant starts in early to mid May. Its flowering stage is in mid to late June; and the seed ripening stage is in early to mid July. The root system of this species is fibrous and distributed among particles of shallow soils. The findings of this study suggest that considering the autecological characteristics of these two species is highly essential for managing of such fragile rangeland ecosystems.

Plantation of salt tolerant plants and production of biomass is one of the methods of the utilization of non agricultural saline lands, which has an obvious effect on desert environment amelioration. Since the brackish and saline water resources is available in these regions, and can be used for irrigation, increase or decrease of salts in soil profile is occurred due to water quality. This research was conducted in a saline land, which is subjected to temporary flooding. The study site is closed to a drainage channel, which drains the saline shallow ground water to the Tashk Lake. The main objective was to investigate the adaptability of salt tolerant trees and the effect of saline irrigation water on the salt status of the soil profile. A split plot statistical design with three replications was applied. The quality of water (saline water of the drainage channel, and freshwater of the Kor River) were the major treatments. The minor treatments were the tree species. Salinity of drained water varied from 4.4 to 8.7 dSm-1 from Oct. to Nov. Soil profile was described and sampled before the start of treatments (1989) and after 10 years. The weighted average of EC of the layers has been reduced from 21.5 to 14.1 dSm-1 (35% has decreased). The SAR reduction was from 32.1 to 27.4 (15% decreased). Trend of change of the SAR has been slower than the EC. This may be due to the preferential adsorption of the Na by exchangeable phase, rather than the Ca and Mg. So, the result of leaching has been less effective for these cations and the average of the SAR of the profile has reduced less than the EC.