IRANIAN JOURNAL OF NATURAL RESOURCES
Year:2004 | Volume:57 | Issue:1|Papers Count:18

Amount of real volume, estimated volume from relation of v = g × h × ƒ and the existing models with the number of 424 Beech trees in Veisar forest (in altitude of 1000- 2000 m ) were studied statistically. The results obtained from estimated volume test from the relation of v = g × h × ƒ with the real volume of beech in veisar area showes that in Veisar no meaningful statistical difference is observed between real and estimated volume on the basis of hohenadle form factor. Average of real volume and estimated volume on the basis of artificial form factor has a meaningful difference in the level of α =0.001 in the area of Veisar. Average of real volume and estimated volume on the basis of natural form factor in Veisar area showes a meaningful difference in the level of α =0.05 is observed.Results obtained from estimated volume test from the existing models with the real volume of Beech in Veisar area shows that no meaningful statistical difference is observed among average of each of the estimated volumes of Beech. Finally the one factor model of Hohenadle - kernn was selected as the most proper model.

Desert eonstitutes the biggest bioclimatic area in the world. Saxaoul (Haloxylon spp) is one of the most important stabilizers of sand dunes used in for biological combating of desertification. For improving and development of Saxaoul lands, this research was carried out in Bajestan Desert Plants Research Station (Khorasan) during 1998-2001. The results indicated that, there is a significance difference between genotypes for height and cover characteristics. Higher heights were observed in genotypes number 3, 18 and 4 respectively. The most cover was observed in genotypes number 30, 1 and 3. The biggest trunk perimeter belonaed to genotypes number 23, 30, 18 and 21. The most branch height was characteristic of genotypes number 30, 22, 18 and 4 as compared with other genotypes. Branch number in genotype 30, 18, 17 and 21 was more than in other genotypes. In general,, genotypes number 18 (Sistan) and 30 (Semnan) were the most prominent for most characters. However, additional study is necessary for other characters before introducing any genotype for release.

In drainage basins of the northern part of Iran, acombination of natural and human factors have caused numerous landslide-related damages. One of the main strategies for restricting the damage caused by the activity of landslides is to avoid these regions. To accomplish this, landslide hazard zonation map of the area should be prepared. At the beginning, in this research, through field work and review of previous works, the following nine factors were recognized as primary effective factors on landslide occurrence: altitude, slope, aspect, rainfall, land use, geology, distance from road, distance from fault, and distance from hydrographic network. After preparing the map for above-mentioned factors in GIS environment (using Ilwis, Arc/Info, Idrisi and Arc/View softwares), these maps were overlaid with landslide inventory map. Analyses of the results indicated that aspect and distance from hydrographic network have little effect on landslide occurrence in the area. Then, by considering the other seven factors, landslide hazard zonation map of the area was prepared by using the following four methods: Valuing information, Valuing area accumulation, Index overlay, Analytical Hierarchy Process (AHP). The results have shown that in all four methods, the regions in which serious land use changes have occurred, belong to high hazard zones and also the regions of drainage outlet have a high potential for landslide occurrence. After this phase the evaluation of landslide hazard zonation methods and their ranking in separation of hazard classes were done. For doing this, the method of area accumulation ratio in each hazard class was used. It was shown that different hazard zones were better separated through index overlay method.

To study the geomorphological facies of Lut Desert, especially Yardangs which are prominent and rare features in the world, 6 reflective Landsat satellite thematic mapper bands dated 1367 and 1368 as well as colour composites dated 1368 (TM7=red, TM4=green, TM2=blue) were empolyed. In the study some additional information, such as topographic maps (1:50000), ILWIS and ER mapper softewares were also used for Image processing. To enhance the Images, stretching and filtering techniques were applied to study the features as well as land cover types and photomorphic units. Based on the obtained data, 14 different units were distinguished of which five are related to Yardang. The obtained results also have shown the capability of Landsat satellite images in delineation of Desert geomorphological facies. During the study, major characteristics of geomorphologic facies were also identified and mapped.

One of the most important problems in watershed basins is flash runoff which causes sever damages to industrial, urban, and rural areas. Therefore, use of methods, which can utilize short-term data and estimate the runoff threshold as well as water yield of a catchment, is of paramount importance. In this study, in order to ascertain the runofft hreshold in Latian watershed, a portable rainfall simulator was employed. With use of the rainfall simulator, different rainfall intensities with different durations were simulated and the runoff threshold in each experiment measured. Analysis of rainfall simulator data indicated that the effective variables in ascertaining runoff threshold, in order of importance are: rainfall depth, rainfall intensity, vegetation cover, clay and sand percentae as well as slope. A non-linear model was developed for calculating runoff threshold using obtained data. The coefficient of relation between measured runoff threshold and the one estimated by developed model is 0.98. In the next stage of the study, a comparison between rainfall simulator data and data obtained from rainfall-runoff simulation models was made. AWBM model was employed using obtained data from Kasilian, Kardeh, Amameh, Lighvan, Kan and Kameh. Results of runoff as well as estimated parameters with model showed that AWBM could satisfactorily be used to calculate runoff threshold as well as output runoff in each basin. Results also showed that runoff threshold obtained through the model and that through rainfall simulators are comparable and depend on: rainfall depth, rainfall intensity, vegetation cover, clay and sand percentage and slope respectivley.

In this study, two methods of multivariate techniques and CV-Based test were employed for the identification of homogenous regions for low flow frequency analysis. First a group of 17 variables including climatologic, physiographic, geologic and hydrologic factors of 16 recording stations in Atrak river basin were analyzed using component analysis to find homogenous regions. The analysis indicated the high importance of 4 factors namely basin area, annual precipitation, percentage of pervious formation, and slope of the basin. Spatial variations of data were then interpreted with distance-grouping technique resulting in two homogenous regions. In addition, annual low flows of 7, 15, 30 and 60-day duration in each station were calculated and CV-Base test estimated based on the coefficient of variations. Results showed the non-homogeneity of the whole area, however two homogenous areas were determined using cluster analysis.

In this research, main factors in selection of the most suitable forest roads including slope, aspect, soil, volume of tree per hectare as well as ecological capability have been investigated using GIS. Namkhane district in Khyerudkenar Forest (Tehran University Training and Research Forest) at the east of Nowshahr (Mazandaran Province) has been selected as the area of the resaerch. Digital maps were produced and analyzed through GIS and Arcview software. The maps of slope, aspect, soil and volume of tree per hectare were prepared and calssified. Maps were overlaid to obtain ecological capability units. These units were and arranged in tables to divide the research area into different units for road selection. Finally, it was being taken into account decided to select the best area on overlaid map to plan forest road on, with effective factors being taken into account. Designing of the optimal forest road using GIS and Arcview software was concluded and map of road Prepared.

Structure study of natural and less degraded Zagross forests (second important natural forest ecosystem in Iran) while considering degradation proccess in them and exigency of their regeneration is very necessary. In this study, 12 regions of less degraded oak and wild pistachio forests in Ilam province, in several different elevations and conditions were selected . Information items about regional factors as well as forest stand structure such as: dbh, canopy diameter, height were gathered and analysed by use of suitable softwares of STATISTICA and EXCEL. In order to describe the stand structures, tables and graphs releted to canopy, dbh, canopy diameter and height distributions, regeneration, necromass were used and are presented. Results show that, the stands are basically uneven-aged old forests among which Quercus persica with its vigorus existence outcrops as pure or original species of forest type. Other results show that, maximum forest canopy, maximum basal area, and maximum volume per hectare are 35% , 22.6m2 and 46.3m3, respectively. Some of the DBH distribution graphs in the stands indicate an uneven, aged stand, but most of them are old stands of very little regeneration . Results also show that number of dead trees and amount of dry branches in canopy are very good indices for determination of degradation in forests.

In this research, site classification using vegetation composition was carried out for the first time in Zagros forests in western Iran. the research was performed in a section of northern-east forests of Marivan City (Doveyse forest). The study area covered 724 hectares and main tree species in Doveyse forest are oaks including: Oak manna tree (Quercus persica), Gall oak (Quercus infectoria) and Lebanon tree (Quercus libani). At first, releve area was determined using minimal area method (a square of 20 ×20m sides). Then according to approximate distribution pattern of plants, a systematic random rectangular grid was designed with sides of 150 × 300m.Releves were placed in the corners of this grid. A total of 103 releves were located in the forest. Plants in the releves were collected, identified and their abundance noted using corrected Braun-Blanquet table. An overall 137 plant species (16 woody and 121 herbaceous species) were identified. Using TWINSPAN software data (Plant frequencies) were analyzed in two sections namely woody species and herbaceous ones. The site was classified into 4 units according to woody species analysis but this classification was not accepted because the Eigen values of separated classes were low. Herbaceous plant analysis was carried out in 7 stages with site being classified into 4 homogenous units, too. Similarity among units was verified through Sorenson Index and confirmed which lead to the classification being accepted. Finally the map of homogenous units was drawn using Arc-info and Idrisi softwares.

Landsat-ETM+ data from the national park of Khabr in Kerman province, dating May 2000,were analyzed to investigate the potential of this sensor in forest density mapping in arid and semi-arid regions. The quality of the image was initially evaluated. No radiometric error was found. Orthorectification was implemented using ephemeris data, digital elevation model and 14 ground control points. The RMS error was less than half a pixel. The ground truth map allocating 50 percent of the total area was prepared through fieldwork using strip sampling. The best spectral bands were selected based on the divergence between class signatures using sample areas. The supervised, classification utilizing original and synthetic bands (resulted from band arithmetic, principal components analysis and tasseled cap transformation), maximum likelihood (ML), minimum distance to mean (MD), parallelepiped (PPD) and spectral angle mapper (SAM) classifiers, was performed. Within 3 density classes (very thin, thin and semi-dense) MD classifier exhibited the highest overall accuracy and kappa coefficient equal to 47.11% and 0.21 respectively. Signature separability, producer and user accuracies showed that the first and the second classes had the most spectral reflection similarity. By merging these two classes the classification was done again. In this case also, MD classifier showed the highest overall accuracy and kappa coefficient equal to 66.15% and 0.30 respectively. Based on these results, in such regions, low forest canopy increases the role of background reflection. High spatial resolution images and improved classification methods will demonstrate the potential of this application.

The objective in this study was to investigate the effect of a combination of impact modifiers on the mechamical properties as well as morphology of cellulose fiber polypropylene composite. The impact modifier was EPDM (Ethylene – Propylene Dien Copolymer) while the fibers being of alphacellulose and wastepaper origin. The elastomer (modifier) was mixed with composite at 5, 7.5 and 10 percent by weight. The fillers were mixed with Polypropylene at 35% (by weight). Results indicated that notched impact strength, tensile and bending strains increased when the elastomer added, but tensile strength, bending strength and modulus of elasticity decreased. The impact modifier did not affect hardness. Adding the fibers improved tensile strength, bending strength, hardness, and modulus of elasticity, but impact strength, tensile and bending strains decreased. In fact, the highest impact strength was obtained by adding 10% elastomer to the composites, however, the highest values for tensile strength, bending strength, hardness and modulus of elasticity were related to treatments with no elastomer (except the pure polymer) Also, to examine the fibers and polymer interfacial surface as well as dispersion of the fibers within the matrix, the samples were studied through scanning electron microscopy (SEM)

Wood needed in pulping, using chemiomechanical (CMP) and Semichemical Neutral Sulfite Process (NSSC) in Mazanderan Wood and Paper Industries Company is partly provided from forest areas in Sari region. Hornbeam and beech are two main wood species used in a proportion of 75 to 25 by volume in the factory. Double disc refiner with two feeding inlets and one outelt is used for refining, but one refiner disk is perpetually engaged with refining in the process line, for each of the above mentioned pulping processes. The unrefined pulp consistency was 3.5 to 4 percent for both processes, meanwhile pulp yield for CMP and NSSC were obtained as 85 and 75 percent respectively. Freeness of unrefined CMP and NSSC pulp were 400 and 450 CSF as well as for refined CMP and NSSC pulp being 350 and 400 respectively. Fiber diameter, lumen, and wall thickness in CMP refined pulp fibers decreased to 11, 1.5 and 19.5 percent with comparison to the unrefined pulp respectively. Fiber diameter, lumen and wall thickness in NSSC refined pulp fiber also decreased to 14.5, 3 and 24 percent as compared with the unrefined pulp respectively. Microscopic observation in CMP and NSSC refined pulp fiber showed much broken vessel and fibers with less fiber fibrillation in former and less broken fiber with better external fibrillation as well as reduction of fiber wall thickness in latter. Therefore much fiber flattening has taken place in NSSC pulp after refining. Despite more freeness rate in NSSC pulp, fibers in this pulp have had better flexibility after refining. In the same conditions of refining, pulping method has effectively affected refining quality. Observation showed that, better fiber flattening and refining quality belonged to NSSC pulp, so strength of paper made from NSSC pulp will rank higher by comparison.

In a combined species method of carp fish production, the effect of species combination (other culture conditions unchanged) on growth and final yield was tested. A polyculture of silver , common, grass and bighead carp was empolyed. Feeding was established on the basis of natural food. Three combinations (treatment) of the above mentioned fish species were selected respectively consisting of silver carp, common carp, Grass Carp, and Bighead carp, with respective rations as follows: 70%, 15%, 10%, 5% for the first treatment, 60%, 15%, 10%, 15% for the second treatment; and 50%, 15%, 10%, 25% for the third treatment Each treatment was replicated in 3 ponds (9 ponds in in total). Species percentage of Grass Carp and Common Carp has been equal in all treatments. A decrease in silver carp percentage went together with a decrease in Bighead Carp percentage in combinations. Fianl growth differences (P<0.01) for species have only been significant for Bighead carp with other species not having exhibited a significant difference. Also, there was not a significant difference (P<0.01) observed in final yield. Because of severe reduction in individual growth of Bighead Carp in the third treatment (Profitability reduction) along with more final yield in the second treatment as compared with other treatments, species combination percentage in the second treatment resulted in better growth, leading to the best production ponds (with constancy other culture conditions).

Sustainable utilization of rangeland is dependent upon suitable grazing intensity. Due to this fact, in this study, grazing intensities in steppe rangeland of Yazd province were taken into account. The study was performed in Nir Range and Animal Research Station. A randomized complete block design (RCBD) with 3 replications was used for two years (1379-1380). Each block represented four grazing intensities as follows: heavy, moderate, light and control (no grazing). Moderate grazing intensity was defined to be equal to grazing capacity. Heavy and light intensities were defined as either 25 percent higher or lower than the moderate intensity, respectively. The cover and yield in experimental units were assessed for all species each separately at the beginning and end of grazing seasons (for two years). The results indicated that: vegetation cover and composition of the species were not significantly affected by applied grazing intensities (P< 0.05), but heavy grazing intensity reduced vegetation cover of Salsola rigida as well as Stipa barbata. Maximum and minimum yield in these two species were the result of moderate and heavy grazing intensities, respectively. The differences between maximum and minimum yield (S. rigida, S. barbata) were significant (P< 0.05). Total yield in perennial plants was similar to that in the mentioned species. Considering the results in this study, moderate grazing intensity is recommended for sustainable utilization of these rangelands. Because of slow trend of vegetation change in the arid lands, it is recommended that this study be continued for the next ten years.