فهرست مطالب

  • Volume:2 Issue:1, 2014
  • تاریخ انتشار: 1392/11/12
  • تعداد عناوین: 7
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  • Ali Mohebbi, Mohammad Jafari, Ali Tavili, Seyed Akbar Javadi, Ehsan Zandi Esfahan, Mehdi Ramezani Pages 419-426
    To compare the seed characteristics in accessions of Atriplex canescens under exclosure and non-exclosure conditions, two even-aged sites were selected with an area of 400 ha as the exclosure and 1000 ha as non-exclosure area. To conduct the study, 30 species were randomly selected in autumn 2009 in reference area of the sites and seeds were collected. Some important seed characteristics were studied in the laboratory. Data analysis was conducted using SPSS 17 software and mean comparisons were performed by Duncan''s Multiple Range Tests. Results showed that the winged seeds did not germinate under all studied treatments in both sites. Moreover, maximum seed germination was recorded for the seeds soaked in cold water for 24 hours and placed in the shade for 48 hours. According to the results of the independent t-test, no significant differences were observed for germination percentage, germination rate, and vigor index in both sites at both 1 and 5% probability levels. In other words, the seeds collected from the exclosure and non-exclosure areas were similar in terms of the mentioned characteristics. However, seed yield, 1000-seed weight and seed moisture content showed significant differences at 1% probability level with higher amount in exclosure area.
    Keywords: Quantitative evalution, Exclosure, Water treatment, Grazing
  • Majid Ajorlo, Ramdzani Abdullah Pages 427-440
    Water quality is a serious issue in tropical grasslands that must be addressed to ensure the continuity and sustainability of water resources. This study aimed to assess the stream water quality of tropical grassland under long-term moderate (2.7 animal unit ha-1 y-1 for 34 years) and short-term heavy (5 animal unit ha-1 y-1 for 2 years) grazing systems at catchment and farm scales in Kuala Lumpur, Malaysia. Water samples were collected in the streams of both grazed and ungrazed grasslands monthly throughout the year. Samples were analyzed forpH, EC, DO, NH3-N, COD, TSS, BOD5, fecal coliform (FC) and E. coli. Harkins’ index was used to classify stream water quality status. Mean values of NH3 and FC were similar amongst the streams in both catchment and farm (P>0.05). Mean values of TSS, COD, BOD and pH of streams in grazed grassland were higher than those in streams of ungrazed grassland in both catchment and farm (P<0.05). DO concentration was similar amongst the streams in the catchment or farm(P>0.05). Water quality of the streams in grazed grassland wasclassified as class II, however, the streams in ungrazed grassland had water quality of class I in the catchment. Water quality was not affected by short-term heavy grazing in farm scale. The negative impact of grazing on water quality was prominent in long-term moderately grazed grasslands than short-term heavily grazed grassland.
    Keywords: Heavy Grazing, Moderate Grazing, Quality Index, Rangeland Hydrology
  • Somayeh Mashari Eshghabad, Ebrahim Omidvar, Karim Solaimani Pages 441-453
    Drought is a climatic phenomenon that causes much detrimental influence on ecological environments. This research investigates the performance of meteorological drought indices in different time scales in theTajan basin in Iran. Indices undergone in this study include: Percent Normal Precipitation Index (PNPI), Z-Score Index (ZSI), Standard Precipitation Index (SPI), China Z Index (CZI), Modified CZI (MZCI), and Decile Precipitation Index (DPI). In this study, we used data of annual and monthly precipitation from meteorological stations in the basin. Drought indices were determined at time scales of 1, 3, 6, 9, 12, 18, 24 year of minimum precipitation with very intense drought and the method of correlation coefficients between drought indices values and monthly precipitation. The results showed that DPI was the best index at annual time scale, while at the time scale of 1,6,12 and 24-months, PNPI was the best index. MCZI was the best index for time scales of 9 and 48-months, and the ZCI had the maximum efficiency for a three-month scale.
    Keywords: Drought, Drought indices, Precipitation data, Tajan basin
  • Mehdi Vafakhah, Saeid Janizadeh, Saeid Khosrobeigi Bozchaloei Pages 455-469
    In this study, several data-driven techniques including system identification, adaptive neuro-fuzzy inference system (ANFIS), artificial neural network (ANN) and wavelet-artificial neural network (Wavelet-ANN) models were applied to model rainfall-runoff (RR) relationship. For this purpose, the daily stream flow time series of hydrometric station of Hajighoshan on Gorgan River and the daily rainfall time series belonging to five meteorological stations (Houtan, Maravehtapeh, Tamar, Cheshmehkhan and Tangrah climatologic stations) were used for period of 1983-2007. Root mean square error (RMSE) and correlation coefficient (r) statistics were employed to evaluate the performance of the ANN, ANFIS, ARX and ARMAX models for rainfall-runoff modeling. The results showed that ANFIS models outperformed the system identification, ANN and Wavelet-ANN models. ANFIS model in which preprocessed data using fuzzy interface system was used as input for ANN which could cope with non-linear nature of time series and performed better than others.
    Keywords: ANFIS, ANN, System Identification, Wavelet, ANN, Rainfall, Runoff modeling
  • Shekoofeh Shokrollahi, Hhmid Reza Moradi, Ghasem Ali Dianati Tilaki, Milad Atghaei Pages 471-483
    This research investigates the vegetation of 4600 ha of Polour semi-steppe rangelands in relation to edaphic and physiographical parameters in Mazandaran province. For this purpose, 23 land units were selected from overlaying slope, aspect and elevation maps using geographic information system (GIS). Within each unit, 3 parallel transects with 100 m length, each containing 10 quadrates (according to vegetation variation) were established. Sampling method was Random systematic. Measured soil properties included texture, organic matter, pH, electrical conductivity, nitrogen, phosphor, and litter. Soil and plant data were analyzed with redundancy analysis and SHAZAM 10 package. RDA analysis suggesting that there is a relatively high correspondence between vegetation and environmental factors that explain 93% of the total variance in data set. RDA results showed that soil slope, aspect, soil texture, acidity, phosphor, and litter were the major environmental factors responsible for variations in vegetation patterns. Furthermore, results also showed that for F. ovina and P. bulbosa, acidity and nitrogen, for A. gossypinus, organic matter and salinity and for D. glomerata, nitrogen have the most important role in plant presence and absence probability.
    Keywords: Environmental factors, Polour rangelands, presence, absence probability, redundancy analysis (RDA), soil parameters
  • Seyedeh Fatemeh Hashemi, Seyed Mohammad Hojjati, Hamid Jalilvand, Seyedeh Mohammad Hosseini Nasr Pages 485-497
    The present study was conducted to determine the most appropriate tree species planted in the same ecological condition considering different variables at Darabkola forest, Mazandran Province. For this purpose, the success of planted species (maple, walnut, oak, pine, ash and elm) was assessed according to ninecriteria (soil nitrogen, soil phosphorus, soil potassium, leaf nitrogen, leaf phosphorus, leaf potassium, growth of diameter at breast, diameter at breast, H/D: height/diameter at breast height ratio). Analytical Hierarchy Process (AHP) was used to assess forest stands based on multiple criteria. Results showed that the maximum local priority of average annual growth, and leaf and soil nitrogenwere observed in pine stands, while the highest levels of phosphorus, potassium, and DBH were recorded for maple plantation. The calculated overall priority showed that based on concerning criteria, pine stand had higher growth and nutritional potential compare to the other stands, while other stands ranked as maple> elm> walnut>oak> ash. In conclusion, our findings from AHP suggested that the growth rate and nutrition ofpine and maple stands had more appropriate condition and efficiency than other stands and therefore found suitable for plantingin the study area.
    Keywords: Darabkola, Analytical Hierarchy Process, Overall priority, Soil chemistry, Tree nutrition
  • Saber Khodabandeh, Halemeh Rajabi Pages 499-512
    The effects of fish weight on salinity tolerance were studied in Caspian salmon (Salmo trutta caspius) parr. 180 fish (all with 2 years old but with three weights; 5, 15, 25g) were selected and they reared in freshwater (FW) and brackish water (BW; 13ppt salinity) for 10 days. The mRNA expression of two α-subunit isoforms of Na+, K+-ATPase (α1a and α1b) and NKCC co-transporters were studied in their gill tissue. In all three weight groups, the mRNA levels for the α1a isoforms decreased following BW exposure, whereas α1b levels significantly increased in 15g and 25g groups. In addition, NKCC gene expression were significantly higher in the groups of BW than FW in 15g and 25g weights (P<0.05). The reciprocal expression of Na+, K+-ATPase isoforms (α1a and α1b) during salinity acclimation suggests that they may have different roles in the gill of FW and BW fishes; ion uptake in FW and ion secretion in BW. In conclusion, in the Caspian salmon, between parrs with the same age, the group with the weight of 15g possesses better compatibility with BW than to other groups. After reaching to 25g, fish passed smoltification and they became more compatible with the FW environment and maybe lost its osmoregulation ability in saline or brackish water.
    Keywords: Caspian Salmon, Na+, K+ pump, Osmoregulation