IRANIAN JOURNAL OF RANGE AND DESERT RESEARCH
Year:2003 | Volume:10 | Issue:4|Papers Count:7

This paper reports the ecological characteristic of the Eurotia ceratoides (L.) C.A. Mey. mainly in terms of autecology. This species normally grows in many stepic and Semi-stepicregions of Iran and as well as in Esfahan. In order to investigate the autecology of the species two different sites were selected based on the Iran vegetation cover map. Thus one site was allocated for the steppic region and the other in the Sim-steppic zones. The most important ecological parameters such as climate condition, topography, geological formation and soil properties were studied in terms of the plant niche. Other plant characteristics such as phonology, morphology, forage yield and chemical compononts were also investigated. The results show that this species can grow in a wide ranges of geological formation and soil properties with different types of textur. Flowering starts from May up to late September. The forage production of this species was measured for the two studied regions and ranged between 34 to 390 kg/ ha respectively. This species is generally resistant to heavy grazing and many diseases. Chemial analysis shows high protein content approximately 10.5 percent

In this study, criterions of climatology, vegetation cover, soil, geology, and geomorphology were used to separate desert and non-desert areas of Tehran Province. First, data layers of each criterion were determined. For example, related to climatology factor, annual precipitation, coefficient of variation, irregularity factor of precipitation, daily mean rainfall intensity, range of absolute monthly and yearly temperature, evaporation was considered. For coverage factor; pesamophyt and xerophyt species or a few variety of plant were surveyed. These indices for all factors were assessed as descripted of research methodology. Supply of numeral maps in GIS for each factor showed there are different area from 7.7% for geology factor to 23.6% of soil factor in Tehran province. The desert Areas for climatology, coverage and geomorphology were 15, 9.3, and 16.1% respectively. Overlaying factors two by two and then all of them showed that; there is different coverage of desert from each factor. The region indication that one of factors introduces it as desert, the others didn't know it as desert. Indicating the region that all factors introduces them as desert is 1% of Tehran Province and 51.7% of all deserts only by one factor introduce for deserts. Thus for Delineating and separating of desert and non-desert areas. We must use all of factors. The regions have more combined factor have more bio- environmental difficulty.

Annual medics having rapid growth rate, various growing habits, form a thick plant growing cover which reduces surface run-off and soil erosion, so it may replaces the wheat-fallow system. This study conducted during 2000-2001 in Lorestan Meteorological and Agriculture Research Station in 30 Km Northeast, Khorramabad Iran, to evaluate the effects of mixed cropping and monocropping of annual medics, fallow and chickpea cropping on surface run-off, soil erosion, moisture conservation and water holding capacity in soil. Results showed that mixed cropping of annual medics having dense plant cover, preformed better than monocropping of the same in reducing surface run-off, soil erosion and increasing moisture conservation and water holding capacity in soil. Fallow system showed the maximum surface run-off, soil erosion among all of the treatments and a 30 mm rain in 12 hours the soil erosion measured was 2.2 ton/ha in the station. Chickpea cropping showed more surface run-off, soil erosion compared with mixed and monocropping of annual medics. On the stages of primary growth, there is no significant difference "in surface run-off, soil erosion" among different cropping system of annual medics, fallow (bare soil) and chickpea by reason of unsuitable plant cover. The rate of surface run-off and soil erosion was high. There is significant difference in reserve moisture of soil on different cropping systems of annual medics cultivars, chickpea cropping and fallow. In the final stage of experiment, treatment of the mixed cropping in two cultivars Medicago truncatula cv. orion and Medicago rigidula cv. rigidula had highest content of the reserve moisture in soil. This treatment increased water infiltration and moisture content in soil. The treatment of chckpea had the least moisture content in soil. There is no significant difference among fallow and monocropping system of annual medics in moisture content of soil. Capacity of moisture retention in soil on mixed cropping treatments of annual medics was higher than the other treatments.

Autecological studies on plant species are conducted to investigate about the relationships between a particular plant and other components of ecosystem. Ecological knowledge about range plant species are essential for rehabilitation, reclamation, and management of rangelands. This study was accomplished to provide information about ecological characteristics of the range plant species of Smirnovia turkestana in sand dunes of Kashan, in Esfahan Province. Some topographic, climatic, and edaphic aspects, as well as the boundaries of the ecological habitats of this species were delineated. Phenological stages and root system of the plant were studied. The names of other species accompanied with the species were listed. The results show that the ecological amplitude of Smirnovia turkestana in Esfahan Province is very limited. Average annual rainfall at its habitats is 80-130 mm. Tests of soil texture indicates that this range plant species grows in sandy soils. This plant mostly prefers sandy soils. A range of 7.85-8.5 was observed for soil pH. Vegetative growth of this plant starts in late February. Its flowering stage starts in early May; and the seeds ripen in June. Some root like organs of the plant grow and distribute horizontally at soil depth of 20 to 50 centimeters. With different distances, new plants regenerate from these roots. The root system keeps the particles of sandy soil together and protects it against wind erosion. This plant also regenerates through the seeds that reproduce. Wind storms, however, often endanger the establishment of seedlings. This plant species has an important role in sand dune fixation and constituting of suitable vegetation in desert ecosystems.

A general model was developed to explain the interrelationships between soil saturation percentage, mean annual precipitation, and population density on growth and vigority of planted Haloxylon trees. Soil saturation percent is an easy measure to determine the water (rain) availability to plants. The main recommendation of the model is thinning the stands in accordance with the above named factors. Calibrating the general model for several regions, and optimizing the stands of Haloxylon Plantation in Sabzevar are the main objective of the present study. Six thinning treatments consisted of T1=247, T2=278, T3=309 (estimated number), T4=340, T5=371, and existing density as the control, T6=500 trees per hectare. The treatments have been compared in a Randomized Complete Block Desing, with four replications, since winter of 1994. After thinning practices, height (H) and crown diameters (CD) of the remained trees were measured. This was repeated ends of each seasonal growth periods in next years. Since the CD increment between the first and the 5th measurement was 4 times more than H increment; therefore, a size index (SI) model of the form [H×(CD)2], which was constructed by trial and error, was found to distinguish the best among the 6 treatments. The growth percentage of H, CD, and SI between the first and the 5th measurement were recorded. The analysis of variance of the factors showed that there are no significant differences between the H, but differences between the CD and SI is significant at 5 and 10 percent of significant levels respectively. Comparison of CD means between the treatments indicated that the high significant growth rates belonged to thinned treatment (T1, T2, T3, T4 and T5, all in group A); and lowest belonged to T6 (control, as group B). Similar comparison on SI indicated that the high significant growth belonged T1, T2, and T3 (all ingroup a); lowest belonged to T6 (control, as group b); T4 and T5 is grouped under ab. The results indicated necessity of thinning of Haloxylon plantation in Sabzevar for revival the vigor and increase of trees growth; it is also indicated accuracy and correctness of the general model for identifyin the optimized population density of Haloxylon plantation.

In order to study "The effect of grazing management on rangelands protection" at first, two communal boundaries named shourik and Hajou located in Aras watershed were selected. These communal boundaries have the same climate and stable environmental factors (height, slope and direction), therefore a scientific comparision was possible. For this purpose factors of plant cover, physiography, weather and climate, geomorphology and the exerted management for rangelands were studied. In this survey geomorphological units were selected as base study and to achieve that, the maps of (slops, height, direction, geology and geomorphology) combined to each other. Plant cover studies were done at the base study by using physiognomy and floristic methods. For study of exerted management for communal boundaries the required information was collected by interview and analized by (Z) exam. Finally the exerted management on Shourik due to consideration the balance between animal and rangelands, applying deferred grazing system, livestock grazing in unique group and existence of and powerful person (a person that others obey him) was introduced as a successful method.