نشریه علوم محیطی
سال سوم شماره 3 (پیاپی 11، بهار 1385)

Determining the structure of mangrove forests on the basis of the vertical and horizontal stand profiles is considered both as a managing feature and as an approach for utilization or protection. The mangrove forests in the study area at Koolaghan, Tiyab and Kolahi region cover 41,258 hectares and form one of the five mangrove protected areas on the Hormozgan Province shoreline. Hormozgan mangroves are covered by an association of pure and uneven-aged grey mangrove trees (Avicennia marina). The study area is distributed over the area with the latitude 26˚52'50''- 27˚10' 54'' and longitude of 56˚23'37''-56˚ 59' 8''. Four linear transacts were used to determine the structure of the mangrove forests in this area. A quadrate sample plot with 100 m2 in each transect has been used as the measuring unit with random–systematic distribution. In each plot, the height and steed diameter of trees as well as the height and diameter of crowns were measured. Furthermore, 1 m2 micro plots were used to measure the quantity of aerial roots, shed leaves and seedlings. In this way, the growth parameters of 345 trees from 39 sampling plots were studied. The results show that the average intensity of this mangrove stand is 1,014.71 trees per hectare, the average tree height is 190.41 cm and the average stem diameter 10.514 cm. The average heights and diameters oftree's crowns were measured at 151.74 cm and 230.74 cm, respectively. In a like manner, the average area of crown was calculated at 6.01 m2. The number of aerial breathing roots was established as 197.50 per cubic meter with an average height of 11.24 cm. The number of leaves shed on the forest floor was 119.34 per cubic meter with an average area equal to 6.95cm2. Statistical studies showed that plots of the Koolaghan region are homogeneous, nevertheless there are significant differences in other sampling plots among the transects of some parameters such as tree height, crown height, crown diameter, crown area and stem diameter, with a 95% certainty. However, we couldnt find any difference in some parameters such as tree density and coverage percentage, so all the areas studied were homogeneous in these parameters.

A census of water fowl and wader migratory birds in the Gilan wetlands is carried out every year at the same time, with a census of the mid-winter migratory waterfowl birds conducted by the International Wetlands Organization from 5-24 January. Results of the direct census conducted during the years 2003, 2004 and 2005 show that the size of the bird population in the Gilan wetlands is declining. But, as a percentage of the total bird population, the number of migratory birds in Boojagh National Park has increased to 23.9%. Ducks (Anatidae) had the highest population in the site with 15,580 individual birds, which is 7.6 times higher than the census result for the year 2003 and 8.3 times higher than in 2004. This increasing is very noticeable among surface feeding ducks with 14,984 birds.

There is concern about the harmful effect on human and animal health of excessive nitrate concentrations in edible plants. Numerous studies have been made throughout the world on nitrate accumulation, especially in vegetable plants. Therefore, studies are necessary to assess the local nitrate content of vegetable crops in major production areas. The soil, water and vegetable nitrate level were studied in Northern Baraan (20 Km East of Esfahan in the old alluvial plain of the Zayandeh-roud River in Central Iran) for two years. The vegetables selected consisted of: leafy and stem vegetables including leek, dill, fenugreek (Trigonell), spinach, mint, sparsely and chinese parsley; root vegetables including onion, potato and tomato; and fruit vegetables including the commonly grown of cantaloupe melons and cucumber. For each plant, three fields with similar cultural management were selected. In each field, at the beginning and end of the growing season, the top 0-30 cm of soil and irrigation well-water were sampled in three replicates. Also, edible plant parts were sampled in three replicates, in the morning and afternoon. Soil nitrate concentrations in most of the vegetable fields were higher than permissible levels, showing excessive nitrogen fertilizer application. The results showed that nitrate concentration over 75% and 79% of the soil study area was higher than the permissible level of 20 mg/kg in the first and second years, respectively. The nitrate concentration of most of the irrigation well-water was higher than the permissible range of 10 mg/l, which is the threshold limit for direct human and animal consumption and for land irrigation. The highest nitrate content in stem and leafy vegetables was found in sparsely (mean of 2121 mg/kg), and onion (mean of 238 mg/kg). The lowest nitrate concentration in leafy vegetables was found in spinach (mean of 20.8 mg/kg) and cucumber (mean of 89 mg/kg). The ranges of nitrate concentration in stem and leafy vegetables were 4 to 6,297 mg/kg and in root vegetables were 17.3 to 872.4 mg/kg fresh weight. The nitrate content of all stem and leafy vegetables except spinach, bulb and of fruit vegetables, except cucumber, were higher than permissible limits. In leafy, bulbous and fruit vegetables nitrate concentrations were higher than the permissible concentration level of 67-mg/kg fresh weight. The effect of the time of plant sampling in the morning and afternoon on nitrate content was significant. Timing of sampling shows that the nitrate level in stem and leafy vegetables were significantly lower in the afternoon than in the morning and nitrate content decreased during the day.

This experiment was conducted in order to evaluate the resistance of fifteen native onion cultivars against Thrips tabaci. These cultivars consisted of Ghermez Azarshahr, Kazbar, Tarom, Shenat Abhar, Gholi Gheseh Zanjan, Sefid Qom, Sefid Khomein, Dorche Isfahan, Sefid Kashan, Meshkan Fars, Eghlid Fars, Sefid and Ghermez Neishabour, Sefid and Sooraty Kordestan. The cultivars were grown in a randomized complete block (RCB) design with three replications over two consecutive years. The number of Thrips, leaf temperature and color, leaf thickness, damage rate and leaf angle were all measured in this experiment. The results indicated that cultivars were significantly different in terms of the number of Thrips and the damage rate at the 1% level. Meshkan Fars, Sefid Kordestan and Sefid Qom cultivars were resistant and Sooraty Kordestan, Gholi Gheseh Zanjan cultivars were sensitive against Thrips tabaci. Also, the angle between the two central leaves of resistant cultivars (Sefid Kordestan and Sefid Qom) was considerably greater than the others. In the case of leaf temperature, color and thickness, the results showed no significant differences between cultivars. To control Thrips tabaci (especially in Iran) growers mainly use dangerous pesticides in large quantities. The usage of resistant cultivars is one of the major components in integrated pest management (IPM) for decreasing pesticides use.

The Northwest of Iran, covering the three provinces of Ardabil, East Azerbaijan and West Azerbaijan, is a special area that, due to its particular geographical and climatic conditions has a rich biodiversity. The present study was conducted with the aim of studying the habitat, substrate type, feeding, conservation and distribution of lizards in this area from 2003 to now. Our results have revealed that there are 20 lizard species belonging to 13 genera and 5 families in this area. Lacertid lizards have the highest species diversity with 12 species. We also found that high ranges of habitats with a different substrate types are inhabited by lizard species. The number of species in pine regions compared with other types of area is considerably greater. The conservation status of lizards is unknown and requires further study.

This experiment was conducted with the aim of investigating the effect of using n-3 HUFA enriched Artemia Nauplii and newly hatched Artemia as a starter food for Caspian salmon (Salmo trutta caspius) larvae compared with artificial food. It was conducted in three treatments: artificial food, newly hatched Artemia nauplii and n-3 HUFA enriched Artemia nauplii during 15 days. Larvae fed with newly hatched Artemia nauplii did not show any significant difference in growth rate compared to larvae fed with n-3 HUFA enriched Artemia nauplii (P³0/05). However, both of these groups showed a better growth rate compared to larvae fed on artificial food. Larvae fed with newly hatched Artemia nauplii show no significant difference in survival compared with larvae fed with n-3 HUFA enriched Artemia nauplii (P ³ 0/05). However, both of these groups showed a better survival compared to larvae fed on artificial food. Overall, larvae fed with newly-hatched Artemia nauplii had a better performance and it was selected as a starter food for Caspian salmon larvae.

Greenway planning is one of the most important tools for increasing quality of life for residents. Green space and greenways are essential to maintain urban environment quality and considerably increase aesthetic values of it. Protecting ecology of specific natural system, providing recreational opportunities for people in metropolitan and rural space, increasing economic benefits and protecting heritage and cultural values are some of the advantages of greenway planning. Developing and extending of Tehran to the Alborz Mountain and its piedmont has made cause extermination of open and green space, gardens, valuable valleys and piedmont and irreversible changing in this area. Building houses, bridges and roads in buffer zones and even bed of river in north of Tehran simultaneously leisure time uses has disturbed the natural trend in area and has changed landscape in this valuable ecological regions. So, preparing plans for valleys as greenways can improve environmental conditions in the area while it can use for recreational manner for residents. This paper review greenway’s literature and history and attempt to introduce this planning tool with aim of improving conditions of valleys in north of Tehran with a focus of Darakeh Valley.

Striped hyenas are unique and vital components of certain ecosystems. As the species is located on the top of the food pyramid, information about its biological needs can be useful at the same time for the conservation of other species. Recent environmental destructions have generally led to major habitat loss, and so protection of the hyenas’ habitats is regarded as very important. As such, habitat management based on evaluation is strongly recommended as a practical solution. A habitat evaluation for the striped hyena (Hyaena hyaena) was conducted in Khojir National Park, located in the southwest of Tehran. The park is 11,570 ha in size and was divided into three sections for the purposes of the evaluation. Habitat conditions were evaluated in three sections of the park using the Habitat Evaluation Procedure (HEP) and the Ranking Variable Approach (RVA). Both methods provided the highest Habitat Suitability Indices (HSI) for section 3. A maximum HIS of 0.87 was found for which 3,654 habitat units were available.