IRANIAN JOURNAL OF NATURAL RESOURCES
Year:2004 | Volume:56 | Issue:4|Papers Count:17

Studying landslide triggering factors and zoning of their hazards can effectively help in reducing the damages. This research was an effort in this regard, studying landslide triggering factors and mass movement hazard zoning for the Germichay watershed, zoned by both Multiple Regression (MR) and Analytical Hierarchy Process (AHP) methods. Finally, a regional model has been presented. Methodologically, first the landslide triggering factors of the area were studied; then, the most important factors along with their priority arrangement including lithology, slope, land use, lineament factors, precipitation, aspect and altitude were investigated. Next, the map of landslide distribution was prepared. In MR method, four factors were examined, and the map of their homogeneous units was prepared using GIS. In order to quantify the factors and give them weights, landslides percentage in different units was determined. Employing the stepwise regression method, the zoning model was found after omitting the precipitation factor. In AHP method, the above mentioned seven factors were used where the proposed factors were compared in pair, with their weights being then determined. Moreover, cumulative curve was used to classify the above factors, and the landslide value (%) was then determined for ranking. Eventually, according to the weight earned by each factor as well as rank values, the zoning model was finalized. Comparing the results of these two methods, it was found that the AHP method is clearly more accurate and reliable than the MR method as the former contained more variables as well as a rational classification without any expert's bias/interference. Therefore, the AHP model was eventually evantually selected as the final model.

The current critical situation of natural resources in Iran resulted from overuse of these resources. In spite of performing watershed management projects during past forty years, natural resources have been degraded. In addition, enough appropriate researches have not been conducted to evaluate the effectiveness and the reasons for failure of these projects. In this research, the watershed management project in Menderjan sub-catchment of Zayandehrood basin was evaluated, from preparing and proposing to operational stages by quantitative and qualitative methods. Basic data were collected by investigating the projects documents, direct visiting, filling out questioner, and interviewing settlers of the watershed. Finally, effective factors in operation of project were categorized in seven groups. Each of these groups was divided into subgroup factors, which were scoried by weight according to some parameters. The results showed that the situation of proposed plan and lacks of economic assessment were the most important influencing factors in operation of project. According to the invented model, the final score calculated by the method mentioned was 29 (out of 110), which indicates weak operation for this project.

This study has revealed that Isfahan region is a fluvial environment rather than an alluvial fan. Morphology of the region shows a mid channel bar and island. In the past, after Zyandehrud entered Isfahan, it was divided into two branches due to impact against Atomic energy mountains, decreasing bed slope, as well as remarkably widening the riverbed. The above feature has accumulated considerable amount of sedimentation in front of Atomic energy mountains and has formed the mid channel bar. Topographic map of Isfahan, indicates a talweg in northern part of the region. This talweg is known as the old branch of Zayandehrud. Increasing sedimentary load and uplifting of the river bed has eliminated this branch from Zayandehrud.

In erosion and soil conservation projects, lithological characteristics of drainage basin are very important. Sensitivity of different rocks to erosion is different and some of the geological materials are very sensitive to erosion and sediment yield. Sensitivity of rocks and sediments to weathering and erosion are dependent on different factors, some of which are related to the nature of geological materials and the others related to the surrounding environment. In small drainage basins, the nature of geological materials is more important than the factors related to the surrounding environment. Different factors such as geomorphology, climate, vegetation cover, human effect, etc. are effective on erosion. The investigation of all effective factors is difficult and complex. Therefore, the effective factors should be listed according to their (decreasing) importance in erosion, and then the most effective factors should be studied. As a result, the homogeneous land units with the size suitable for investigation will be obtained by crossing these factors, and the relationship between effective factors and sediment yield data will also be reached. The area studied was Latian Drainage Basin and its sub-catchments. By primary field investigation, it was found that among all effective factors on erosion, geological materials, slope and climate were the most effective ones in the area. Then, the maps of three mentioned factors were prepared and were overlain to obtain land units map of the area. Next, sensitivity of formations and rocks to erosion was obtained in each land unit; for pre-Quaternary consolidated geological materials, Rock Mass Strength Classification of Selby (1980) and for Quaternary sediments and pre-Quaternary unconsolidated geological materials, K factor in USLE model were used for qualitative approach. For quantifying sensitivity of geological materials to erosion, sediment yield data of hydrometric stations in Latian Drainage Basin were used.

To determine a suitable method, based on precision and cost, of inventory in Western oak forests, a random-systematic sampling with circle shape (already used, in the region) as well as transect method (recommended method in these kinds of forests) were selected for comparison. Parameters evaluated were number per hectare, crown cover and basal area (suitable parameters for these forest types).Considering all the sampling factors, a grid of 100×100 m and plot areas of 2000m2 were determined for random-systematic sampling. Length of transect was determined as 50m in transect method.To compare the results of these two sampling methods with the real population statistical parameters, a 100% inventory was taken over a 37.03-hectare area while using both methods over the same area.The results show that the population mean was similar to those of samplings for all parameters, the means being within the range of confidence intervals. However in both sampling methods and in all cases, the inventory errors were greater than those at the acceptalbe level (10%).To compare the related costs, the total man-hour employed in each method was evaluated. Total time used in transect method was 714 minutes and in random-systematic method it was 3027.5 minutes.With respect to precision, random-systematic sampling with circle shape plots is of less error than transect method in all cases.To precisely evaluate the two methods, the product of E2 (Square of sampling error) times T (total inventory time) was used. This ceofficienct was less in transect method than in randome-systematic sampling with circle shape plots in all cases.

In the present study it was tried to introduce the most relevant method of data collection from Aras-baran natural forests. To achieve this, a random systematic sampling network of 150×300 m dimensions including 140 sampling plots along with three sampling methods including circular, quadratic and transect methods were empolyed. The obtained data from the study sites were used to evaluate factors of basal area per hectare , number of trees in hectare ,and sampling time in plot as well as in transects. Duncans and t.tests revealed no significance between mean basal area and number of trees per hectare in eny of these three methods. But mean sampling time for circular and quadratic plots as well as transects demonstrated significant difference. To determine the optimum sampling method equation A=E %2 × T was used. Where, E% is peresentage of sampling error and T sampling time. Finally, the study pointed out that the transect sampling method was the most appropriate for Aras-baran natural forests.

A vast area of Iranian forests plain near the Caspian Sea have been converted into paddy soils. The special management practices required for rice cultivation have changed the physico-chemical and micro-morphological properties of these soil. During the course of this study, it was intended to show these changes taken place in foomanat region. An adjacent pair of pedons in the forest land and paddy field in this area was selected. Morphological and physico-chemical studies were carried out. Microscopical studies on the thin sections and finally comparison between the pair of pedons were performed. These changes in physico-chemical soil properties mainly included decrease in soil organic matter, change in volume and type of voids, creation of reducing conditions, soil aggregates, and damage of its structure. Micro-morphological changes included impregnative diffuse sesquiocidic nodules, friargillan infillings and subsequently producing the condition for fragipan formation. Therefore, in this region, conversion of forest soils to paddy soils provided special soil properties, which make it impossible to carry out reforestation even with the original species.

Diversity and assemblage structure of selected soil invertebrates including Earthworm, Collembula, Diplopoda, Isopoda, Chilopoda, Protura, Pseudoscorpions, Araneas, Symphyla, Diplura, Pauropoda, Opiliones, other insects and their larvae were examined in different soil layers of beech, hornbeam and oak-hornbeam forest types of Neka in north of Iran (Caspian forests). Biomass of invertebrates were monthly sampled for one year using core soil sampler (81 cm2cross section) to a depth of 30 cm including litter, fragmented organic matter, 0-10 cm, 10-20 cm and 20-30 cm mineral layers. Presence of invertebrates in soil layers of beech, hornbeam and oak-hornbeam forest types were compared. Variability of invertebrate biomass in soil layers of beech, hornbeam and oak-hornbeam forest types was quantified as the diversity and equitability indices using Simpson and Shannon formula. Invertebrate assemblage structures in soil layers of beech, hornbeam and oak-hornbeam forest types were illustrated with rank-frequency diagrams. Forest types and soil layers were ordinated using PCA. Presence of invertebrates in soil layers was different, an indication of variability in vertical distribution of their biomass. An increase in soil depth was associated with a decrease in diversity and equitability indices of soil invertebrates. Diversity and equitability indices of soil invertebrates in beech forest type were higher than those in hornbeam and oak-hornbeam forest types. Assemblage structure of invertebrates among soil layers was different, but it was similar among forest types. PCA showed that forest types and soil layers were respectively divided into three and two different groups. In general, diversity and variability in soil organic layers were higher than those in mineral layers; this should be considered in management and protection of forest biodiversity.

In this study zoning for the management plan of Kavir National Park (419613 ha, SE of Tehran, Iran) has been implemented. Ecological and socio-economic resources were initially surveyed and mapped (scale 1:50000). Then data analysis as well as integration with system analysis approach was performed. As a result 863 micro-ecosystems were mapped. Ecological capability of mapping unit (MU) was evaluated for:restricted nature reserve, protected area, extensive use, intensive use, rehabilitation, domestic use and culture-historical, with the aid of specified ecological park management models. Finally with coordination of socio-economic data and ecological capability of MU, priority, ranking and arrangements of zones were mapped.The results show that %15.95 of allocated zones is suitable for restricted nature reseve, %33.63 for protected area zone, %35.85 for extensive use zone, %7.82 for intensive use zone, %1.27 for rehabilitation zone, %2.47 for domestic use zone, and finally%3.01 for culture-historical zone.

Chemical characteristics of raw material influence the development of technologies and methods of pulping. Wheat straw as an available and abundant agricultural residue has been used in some developing countries as an alternative material in papermaking, and this indicates its importance as fibrous raw material. Wheat straw which was used in this study was obtained from the Research Farm of Faculty of Agriculture at Mashhed University. In this study, materials soluble in cold water, in hot water, in 1% NaOH, in acetone, as well as lignin, cellulose, and ash contents were determined according to TAPPI Standard Methods. Various parts of wheat stalk investigated in this study included whole straw, first inter-node (from top), second inter-node and third inter-node (bottom) of stalk, nodes and leaves separately. The results of this study indicated that ash content, cold water solubility, hot water solubility, 1% NaOH solubility and extractive content from leaves were the highest. The amount of these materials decreased from top to the bottom of stalk. Ash content and materials soluble in cold water, hot water and 1% NaOH were higher in nodes than inter-node. Cellulose and lignin contents of stalks increased from top to the bottom.

The objectives of this study were to determine the influence of wood density on the physical and mechanical properties of commercial hard boards, as well as the acoustical property of the insulation board. The commercial fiberboard was manufactured under the same conditions as in Babolsar- and Iran- fiber companies. It was found that the sound absorption of insulation board containing 95% low density wood fibers were 1.7-5.6 times higher than that of insulation board which contained 95% high density wood fibers. The mechanical properties (static bending and tensile strength perpendicular to the surface) of hardboard containing 95% high density wood fiber were 1.4-1.7 times higher. Water absorption was 7.3 and thickness swelling was 0.8 times higher than that for panels made of 95% low density wood fibers. Therefore, low and high density wood species are recommended to be utilized in insulation-board and in hard- board manufacturing, respectively.

This research was carried out to investigate the chemical treatment conditions to produce CMP utilizing wheat straw. Fiber biometry as well as chemical characteristics of wheat straw was evaluated. Then chemical treatment involving two chemicals; sodium hydroxide (NaOH) and sodium sulfite (Na2SO3) buffered with sodium carbonate (Na2CO3) was done. Chemical charge was comprised 6, 8 and 10 percent (based on oven dry weight of straw) with treatment time being 20, 30 and 40 minutes. Treatment temperatures of 95–98°C at atmospheric pressure and L:W=10:1 were selected. Regarding the results, sulfite treatments showed higher yield, screen reject and refining energy consumption as compared with sodium hydroxide treatment, because NaOH is more reactive than Na2SO3. NaOH dissolved more lignin and polysaccharides during treatment, decreased pulp yield and caused better and easier fiber separation leading toless screen reject produced. Considering pulp properties and treatment conditions, 6 treatments including 30 minute treatments, various chemicals and chemical charges were selected to handsheet. Selected pulps were refined up to 350±25 ml.CSF freeness prior to making handsheets. Strength of papers produced from NaOH treatment was significantly higher than that of papers produced from sulfite treatment with chemical charges have showing direct effect on all paper strengths except burst strength.

Anisotropy of three types of Iranian particleboards was estimated as the ratio of Young s moduli, velocities of bulk waves (shear and longitudinal waves) and of acoustic invariant. The ultrasonic through-transmission method was used to measure the ultrasonic velocities in principle symmetry axis. Young s moduli were determined with the 4-point static bending test. The results show that the velocity parallel to the production direction is higher than that in perpendicular direction and is lowest through thickness because particles are directed in production direction. The structure of particleboard influences ultrasonic velocities, so the anisotropy behavior of particleboard can be explained by the ratios of ultrasonic velocities. The used different methods for description of anisotropy by ultrasonic parameters and static modulus of elasticity show to be in good agreement.

Soil physical properties have an important role on vegetation growth in rangelands through affecting the development of root system. The goal of this research was to investigate the trampling effect of livestock grazing on soil physical properties and range vegetation cover. The experiment was conducted on three range condition sites (reference, key and critical area) in Lar rangelands during grazing season from 2000 to 2001. The results of the experiment showed that soil moisture reduced from reference area to critical area as well as through grazing season in both 0-15 and 15-30 cm depths. Soil bulk density increased during grazing season and was the lowest in reference area and the highest in critical site. Through the grazing season bulk density was higher at 0-15 cm compared to 15-30 cm. Reference site had the highest soil porosity while the porosity reduced both in key and critical area. As the grazing season continued soil porosity reduced in all sites in both 0-15 and 15-30 cm soil depths. Soil infiltration rate decreased and mechanical resistance increased in all experimental sites as the grazing period continued. The proportion of grass was the highest in vegetation composition in reference area while it reduced to as low as 1 percent in critical site. The total vegetation covers of 7 percent (93 percent of bare soil) at the end of the grazing season made the soil very vulnerable to water and wind erosions at critical site.