مجله بوم شناسی کاربردی
پیاپی 39 (بهار 1401)

Among the various species of small pelagic fish, Sardinella sindensis (Day ,1878) has high economic and ecological importance and is one of the most important species exploited by fishermen. In recent years, the catch rate of this species has increased, and due to the limited data available on its stock in southern waters, it is not possible to use models based on the complementary data to assess its stock. In the present study, the catch-maximum sustainable yield (CMSY) model was used to determine the stock status of Sardinella sindensis in southern waters. Catch data related to the last 23 years (1997- 2019) were collected and entered into the model to calculate fisheries reference points. The value for B/BMSY by the model was estimated to be more than 1.0 and the value of F/FMSY was less than 1.0, which indicates the healthy stock status of this species in the southern waters of Iran. The maximum sustainable yield (MSY) was estimated to be  86,000 tons. In recent years, the catch rate has been exceeded this amount and has caused the stock to move gradually towards the overfishing zone. Based on the results, it is suggested to control and manage the fishing activities regionally (specially in Hormozgan province) by taking into account the fishery potentials, monitoring the exploitation status with regard to the environmental factors affecting the stocks of this species.

Iranian mangrove forests provides valuable information to prevent genetic erosion in the gene pool of these ecosystems. The aim of this study was to investigate the genetic diversity among mangrove forests located in four different regions of Iran, based on morphological characteristics and microsatellite markers. Cluster analysis of molecular data, using neighbor joining algorithm classified the 60 mangrove trees, sampled from different coastal areas, into four groups. Analysis of molecular variance showed that the majority (77%) of the variance explained by among-population variation and the highest values of genetic diversity parameters including number of effective alleles, Shannon’s information index, and Nei’s genetic diversity were obtained for the Qeshm population, indicating that region is the most diverse population among all the studied populations. Baced on the morphological analyses significant differences were observed between all populations in terms of height, diameter at breast height, collar diameter, leaf size, pneumatophore length and pneumatophore diameter. The present study, provides useful information about genetic diversity of mangrove habitats which can be used in evolutionary studies and conservation efforts for these valuable plant ecosystems.

Do climatic variations and drought magnitude affect large-scale vegetation composition in the Central Zagrosian forests, and to what extent do topographic variables of altitude and aspect play a role in these potential differences? To answer this question, in this research, the flora list of 15 Central Zagros forests was obtained in five plant life forms between the valleys of two rivers, Gerdbisheh and Bazeft, over the distance of 170 km, using 226 half-hectare sample plots. Two-way cluster analysis and multi-reference permutation procedures (MRPP) were used to validate significant differences in plant composition at the landscape level. Subsequently, plant communities were divided into three ecological groups: eastern, central and western. Canonical correspondence analysis (CCA) was used to determine the correlation between changing plant composition and climatic and topographic variables as well as plant life forms. The results showed that forests in the western ecological group are significantly and positively correlated with the De Marton aridity index, while the drought magnitude differentiates the other two ecological groups. Also, altitude had a significant effect on differentiating the eastern and central ecological groups. The main difference between the three ecological groups in terms of plant life forms, was due to the significant correlation of Therophytes, Cryptophytes and Hemicryptophytes with the driest ecological group (eastern). Despite the fact that all the plots were covered with forests, Phanerophytes were not effective in distinguishing ecological groups.

Monitoring the frequency changes of hard and non-degradable ostracod shells can provide valuable information about the past conditions of inland wetlands sediments as a biological index. In this regard, a sediment core with a length of 38 cm was harvested using a static sediment core sampler at the beginning of the delta of Gavkhooni international wetland (Shakh-Kenar station) in April 2019, and the number of ostracod shells were counted in five groups of particle size simultaneously with determining the physical characteristics of sediments (particle size distribution, density, and moisture content). The results show that there is a significant negative correlation coefficient (r = -0.686 to -0.477) between the density of the dominant size groups of ostracods with the percentage of gravel and sand. Also, the results show a significant positive correlation coefficient (r = 0.579 to 0.638) between the density of these groups with the amount of silt and clay.Based on  to the negative correlation of ostracods with coarse particles, it can be inferred that high-energy environmental conditions such as seasonal floods and massive floods during the wet season have potentially reduced the density of ostracods in this region. While the disruption of the natural hydraulic regime of the Zayandehrud River and the lack of heavy  floods in the river delta in the last three  decades have  reduced the environmental energy of the delta and increased the percentage of silt and clay particles, and the density of ostracods.

In this study, the trend of overwintering and breeding populations of the endangered white-headed duck Oxyura leucocephala was studied using 52 years of mid-winter waterbirds census in Iran (1969–2020) and breeding reports of the species in the 2010s. The trend of species population changes was calculated using RTRIM statistical package in R software. Species population in Iran indicates a substantial increase of 21.3% per year and a moderate increase of 4.4% per year over the last ten years. The results showed that the average annual total population of white-headed duck, overwintering in Iran, was 470.4 ± 126.3 over the past 44 years, covering 14 provinces and 45 wetlands. On average, 41.6% of the population was in Mazandaran province, 25.1% in Fars province, 18.6% in Golestan province, 4.4% in Khuzestan province, and 10.3% in other provinces. The breeding population of white-headed duck in Iran was estimated between 103 and 301 pairs, showing that the breeding population of the species in Iran has increased compared to the past decades. In order to protect this species, it is appropriate to develop a coherent and species-oriented action plan based on the climatic and geographical conditions of the wetland habitats of the species at the national level.

Hot spots are often associated with places where an abnormal process has occurred. Accordingly, their identification can help experts and managers to scrutinize the state of health and sustainability, from an ecological point of view. The present study was therefore conducted to analyze the spatial autocorrelation and identify hot spots of 11 landscape metrics, the new Runoff Landscape Index (RLI), and its related factors in 28 watersheds of Ardabil province. The average positive values of the z score obtained from Moran's index indicate the presence of spatial correlation in the studied watersheds. In addition, the results of local Moran's showed that the landscape metrics have a structured spatial pattern and are not randomly distributed. A completely unipolar pattern was obtained for land cover factor (λC), soil factor (λK), and RLI. Furthermore, the negative values of the local Moran's index for the topographic factor (λS) proved the scattered pattern. Spatial distribution of hot and cold spots, using the Getis-Ord-Gi index, showed no significant pattern in the λC of Ahmadkandi, Akbardavod, Deru, Mashiran, Firozabad, Lai, Nir, and Hir watersheds. Cold spots were observed in the Eiril, Namin, and Nanehkaran watersheds at the 90% confidence level and the rest of watersheds had hot spots at a 95% confidence level. The RLIs of Ahmadkandi, Akbardavod, Deru, Mashiran, Firozabad, Lai, Nir, and Hir watersheds lack a significant pattern, and the rest of watersheds showed the hot spots at a 95% confidence level.