IRANIAN JOURNAL OF NATURAL RESOURCES
Year:2002 | Volume:55 | Issue:2|Papers Count:13

Erosion is a phenomenon during which soil and sediment materials are transferred by such damaging factors as water and wind. The type of erosion, of course, is different in various climates. As an example, in wet and semi-wet areas, water erosion is more likely than wind erosion. In turn, wind erosion is the main reason for damaging and transferring soil and sediment materials in arid and semi-arid zones, which can cover talented lands and bring about indispensable damage to land administrators. Wind erosion in arid zones is one of the most important processes of desertification, which is considered in different forms and in various models. One of the main methods is FAO-UNEP method, which is considered the most complete and comprehensive method for desertification up to now. However, analysis made on the wind erosion process showed that some of its criteria had deficiencies that were reviewed, and some of them, that were suitable for studying area were selected and applied. Another method that was presented for evaluating the intensity of desertification is ICD, in which more attention is paid to special conditions of the area biomes. An analysis made on this method indicated that the number of criteria considered for evaluating the wind erosion were not sufficient, and due to small scale of the method (1:250000), the available criteria were evaluated qualitatively and in the overall form. From the analysis made on both methods, suitable factors were selected in order to determine the intensity of the region’s wind erosion, giving value to each of the standards and sub-factors in the form of a desertification model. After determining working units (geomoprphologic facies), all criteria and sub-factors were evaluated in each facies and then across the region. Among the whole area understudy (616.81km2), about 118.2km2 (19.16 percent) was found to be in very high class, about 316.81 km2 (51.36 percent) in high class and 181.8km2 (29.48 percent) in middle class intensity of wind erosion.

Application of vegetation indices derived from Landsat Thematic Mapper imagery to estimate rangeland vegetation canopy cover percentage of Jahan-Nama protected area was assessed. Stratified random sampling was designed and 370 sample plots on 37 sample units were allocated in the field using Global positioning System (GPS). Landsat Thematic Mapper image, dated on 1998, was geometrically corrected with RMS error of less than 0.98-pixel size. Corresponding mean values of 9-pixel elements belonging to sample units for all created indices were extracted. Corresponding field measurements have been regressed against TM data, as an independent variable, and 69 vegetation index values created by different combination of TM bands as dependent varibables. Their statistical models have been developed. Results show that if canopy cover percentage without its arrangement in classes is entered in the regression analysis, landsat data are unable to detect their changes. The results also show that landsat data are capable of detecting high canopy cover percentage classes when field data are categorized. Regression analyses show promising results in estimating canopy cover percentage of rangeland vegetation. The index, (TM5- TM3)/(TM5+TM3), shows high correlation (0.99) with the first canopy cover class (71.9- 88.1%), (TM3-TM7)/(TM3+TM7) and (TM6)/(TM3+TM5) show high correlation with the second class (58.6-71.9%). Having more than 0.85 regression coefficient. (TM6)/(TM7-TM2) demonstrates high correlation with the third canopy class having 45.2-58.6 percent canopy coverage. For the last class, no index is introduced, because of any significant correlation between canopy cover and all involved indices.

Different methods are proposed and used for pedological studies in natural resources research by different experts. Some of these methods are: geology, geomorphology, land evaluation, land suitability and vegetation methods. The aim of this research is to see how pedological studies by geomorphology methods are scientifically and economically suitable. For this purpose, six sub-catchments of Taleghan watershed located in the upper, middle and lower parts of the watershed were chosen. Each two sub-catchments were almost face to face and in opposite aspects (southern and northern aspects). Then, six photogeological investigations, field checks, and geomorphology maps of six sub-catchments were prepared on which geomorphological units, facies, types and sub-types were shown. Then, in each geomorphological facies, several soil profiles were made and soil samples were taken from them and the samples were analysed physically and chemically in the lab. Geomorphological studies have shown that nearly all sub-catchments consists of mountain unit (some sub-catchments, such as Shahrak-Taleghan, also consist of hill unit). Erosion processes including water erosion and physical weathering and in part chemical weathering prevail in the area and have developed numerous geomorphological facies. The results of laboratory soil analyses have shown that the geomorphology method can differentiate the boundaries of different soil groups with high accuracy.

Floodwater spreading system is an efficient and appropriate method for optimization of runoff utilization, particularly in arid and semirid regions. Beside the reduction of flood damages, this technique is also useful for artificial recharge, rangeland rehabilitation, and desertification control. The objective of this research was to evaluate the efficiency of Moghar floodwater spreading system which was designed and performed for artificial recharge of groundwater and for improving groundwater quality in the region. First, data on piezometric wells were collected. Then, infiltration rate as well as the physical properties of both sediments deposited in different strips and those of the natural soil of the area were determined. Groundwater samples from different irrigation wells as well as the flood water entered the system were taken and their chemical characteristics were evaluated. The results indicated that more than 100,000 tons of fine sediments with mean thickness of 43 cm and mostly containg silt-sized particles were deposited in the system. From the frist to fifth strip, the amount of sand content in the sediments decreased whereas the clay content increased. Consequently, the infiltration rate decreased from 1.35 cm/h in the first strip to 0.65 cm/h in the fifth one. Due to the formation of a thick and dense crust in different strips, their infiltration rate is not high. The second time flooding occurred in 1375 and seems to have had the highest influence on rising the groundwater level. Reduction of infiltration, evaporation of a very good quality floodwater, overuse of groundwater resources by farmers particularly in dry seasons, and the occurence of recent severe drought lowered the efficiency of this system. It seems that a great portion of water entering the system would be lost through evaporation if no measure is taken for reducing the floodwater turbidity. In conclusion it is highly recommended that an integrated watershed management system is implemented in the area in order to reduce the turbidity of floodwater, which in turn increases the profitabity of the system.

Unstable ecological conditions of north Iran forests coineided with metamorphism and unstable sociological and economical conditions of forest dwellers and these have confronted forests with more and more destruction. Cooporatives of forest – dwellers were establisied with the aim of proper exploilation and reclamation of destructed north Iran forests in Gilan province. The cooporatives which mainly undertok the lands under forestry projects, were basically coosidered as economic institutes which were responsible for protection and reclamation of forests. From this point of view, with respect to forests ecological limitations the need for establishment of logical relation between econonical exploilation and ecological conditions was emphasized. The attraction of contribution of forests villagers in forest exploitation and management policy. In the past some objections have been occurred between forest management projects and villagers. Therefore, transferriy of these land, to cooperatives has been the beginning for prevention of these objections. But at the some time, the forest-dwellers cooperatives, in framework of economic institutes, should follow economical laws and be beneficial and should have economical stability. In fact, a logical relationship should exist between environmental vales and economical values. In this paper it is attempted to investigate the power and profit of cooperatives from economical point of view. In addition, the possible relationship between ecological potential and economical feasibility will be considered.

The physical and anatomical properties of Fagus orientalis (wood and bark) and their variations in three heights and radial directon in the trunk of tree were analysed in this study. Three Fagus orientalis trees were cut down at "Shenrood forest" in west of Lahijan (Siahkal). From each tree, 3 disks from the bottom, middle and top of the tree trunk were selected. The Specimens were prepared from these disks to measure the main properties, such as moisture content, dry specific gravity, total shrinkage and fiber length, fiber efficiency, L/D ratio.Then, data from 3 heights and radial direction in the trunk were statistically analysed. The results show that there was little change in the moisture content of wood radial direction, but it increased from bottom to top of the tree when the three heights were compared. The specific gravity and total volumetric shrinkage of wood in radial direction decreased from pith to bark and from bottom to top of the tree whereas there were little change in fiber length, fiber efficiency and L/D ratio of wood. There were also little change in moisture content, dry specific gravity, volumertric shrinkage and fiber length of bark in longitudinal direction of tree trunk, but fiber efficiency of the bark in the middle part and its L/D ration in the lower part of tree trunk were higher than other parts.

Soda pulping of old jute bags was studied. Moreover, Fiber length and diameter, lumen diameter and cellwall thickness were measured. Average yield and Kappa number of soda pulps were found to be 55.4% and 34.7, respectively. Different pulping conditions were compared and optimum pulping conditions were selected at 14, 16, 18% alkali and 20 min cooking time. Then, 60 g/m2 hand sheets were made. Burst index of hand sheet was measured at 4.73, 5.78 and 4.78 kPa.m2/g for 14, 16 and 18% alkali charge, respectively. Tear index was measured at 10.98, 10.83 and 11.65 mNm2/g for 14, 16 and 18% alkali charge, respectively. Breaking length was measured at 4.4185, 4.6390 and 4.3900 km for 14, 16 and 18% alkali charge, respectively. Folding endurance was also measured. Statistical analysis indicated that alkali charge did not affect breaking length significantly. However, it influenced tear index, burst index, and folding endurance significantly.

With regard to the important role of benthos invertebrates in aquatic ecosystems, the purpose of this research was to study about them in Gomishan wetland. The sampling was done by Ekman Grab from the sediments of the wetland bottom within 5 chosen stations for 12 continous months (from Esfand 1377 until Bahman 1378). The specimens were stained by Rose Bengal solvent and then were identified and counted in separate groups of macro-and meio-benthos. Among the macro-benthos, the highest density was observed in Pyrgula caspia species. After that, more density was seen respectively in Abra ovata, Cerastoderma sp., Balanus sp., Nereis diversicolar, Mytilaster lineatus and Dreissena sp. Among the meio-benthos, the highest density was seen in Foraminifera and then respectively in Ostracoda, Nematoda and Bivalve larvae. The indices of diversity and distribution were calculated and are given in this article.

A study was conducted to determine some ecological and biological characters, including age, growth and reproduction in migratory population of roach, Rutilus rutilus caspicus, in Anzali wetland from early November 1999 to early December 2000. The sampling was done monthly but in the peak of spawning migration (late February to mid April) it was done weekly. Sex ratio in the population was 1:17♂:1♀ Although the sex ratio was not significantly different even at 10% level but the sex ratio for each separate age group were significantly different at 0.5%. The correlation between total length, age, body weight, and scale radius were significant (P<0.001). Based on the back– calculation, the maximum growth rate was in ages 1 and 2. Instantaneous growth rate were the highest at ages 1 and 2. Gonadosmatic index (GSI) was age-dependent. The peaks for GSI curves were; late February and early March for the males and females. The eggs diameter varied from 0.95 mm to 1.3 mm. The absolute fecundity was related to age.

This project was conducted in Selkeh and Espand International wetlands. The study area in Selkeh and Espand are 78 and 45 ha., respectively. In Selkeh wetland, 57 speacies and in Espand 39 species were identified. The monthly average of waterfowl and wader birds were 5021 and 2695, respectively. Also, avereage density of birds in Selkeh and Espand wetlands were 64 and 60 birds per ha., respectively. During the study period common teal (Anas crecca) was the major species in both areas. The major population in Selkeh was autumn, wintering & spring migrants and for Espand it was winter migrant only. The number of species, population size, biodiversity indices of Menhinick, Simpson and Shanon Wiener diversity and evenness in Selkeh habitat were higher. However, in Espand habitat, only Marga indices were more in number comparedto the other habitat.

Biodiversity is one of the prominent characteristics of Golestan National Park in north of Iran which made the park one of the biosphere reserves in all over the world. Occurrence of several fires (67 fires from 1957 to 1999) in this park can reduce the floristic richness and disturb the sustainability of the environment and lower its world wide importance. To investigate the consequence of fire and changes that usually take place in vegetation structure in ecological succession, the 720 ha Takhti Yeylagh area located in southern part of the park was selected. This area had fire in August 1995. In this study, canopy cover, phytomass and diversity were investigated and compared, for both fired and control areas. The analysis showed that canopy percentage and phytomass in the fired and control areas had significant differences and their amount increased significantly in the fired area, whereas the diversity of the two areas had no significant difference. Also, this research indicated significant increase in Gramineae likes Stipa pennata, Festuca valessiana, Avena wiestii and Aegilops tauschii in the fired area compared to surrounding control area, but woody species like Acanthophyllum pugens, Rosa persica, Cotoneaster ovatus and Onobrychis cornuta had considerable decrease. Due to the increase in annual species (especially Gramineae) and decrease in woody species, it can be concluded that fire is a preventing parameter in dynamic evolution of ecosystem towards climax, and that the dominance of Gramineae can increase the chance fire in the future.

Along with the increasing use of the country's rangelands, the need for their reclamation and preservation is of prime importance. Due to the vast expanse of the rangelands, using machines for this purpose is unavoidable. For proper use of machines and achievement of high productivity in rangelands, suitable studies and research work are required. Despite the existence of millions of hectares of rangelands and their economic as well as environmental importance, studies on rangeland's appropriate machine utilization in the country are few and scientific work in this area is scarce. Of all the mechanized operations practiced in agricultural production, including soil preparation, planting, plant protection, and harvesting, the most common one in rangeland work is the planting operation. Hence, scientific study of rangeland planting machinery, especially seedling planters is of prime importance. In this investigation, conducted as a factorial experiment based on a randomized complete block design, three dependent variables were measured. These include depth of furrow created by the planter, spacing precision in planting of Atriplex seedling, and plant establishment as indices for monitoring the quality of planting operations. Independent variables in this study include: disk coulter (with and without coulter), depth of work (20 and 30 cm), and forward speed (2.8 and 5 km/h). Statistical analysis of the data indicated that depth of work and the use of disk coulter had significant effects on the depth of the furrow created by the planter. Moreover, plant spacing precision was significantly affected by the interaction between depth of work and forward speed, while there was no significant effect on plant establishment. Removing of the coulter and using higher depth of work resulted in deeper furrows compared with the other treatments; 24.3 and 26.3 cm deep respectively. However, use of the coulter and planting at a shallower depth created furrows of 20.5 and 18.4 cm deep, respectively. In the final analysis for the factors under consideration, forward speed of 5 km/h at 20 cm depth of work were found to be a better combination and is thus recommended.