نشریه پژوهش های آبخیزداری
پیاپی 86 (بهار 1389)

Unsuitable utilization of Astragalus gosypinus in addition to wrong gum tracaganth extraction are the main reasons of mentioned plants habitat destruction due to remarkable medicinal and industrial values of gum tracaganth as the main minor product of Iranian rangelands. For this، it is of high importance to find and introduce correct methods of gum tracaganth extractiorrent research has been conducted to find the relations between height، basal area، canopy cover and gum tracaganth extraction amount in Astragalus gosypinus. To do this، regression relationships were used to determine above mentioned interrelations and find an acceptable model for gum tracaganth extraction. Results show that there is a good correlation between basal area and canopy cover percentage of Astragalus gosypinus، in different times. despite this high correlation، only changes of canopy cover percentage in different times is detrimental for gum tracaganth amount extraction، that is، more cover percentage leads to higher amounts of gum tracaganth. If the aim is to estimate gum tracaganth extraction rate during a year، yearly analysis model will be of benefit but when gum tracaganth extraction in a short given time is objected using suggested model for the same period will be better. In yearly analysis basal area shows the highest correlation with gum tracaganth extraction rate، while in first time (July)، second time (August)، third time (August) and fourth time (September) analysis models، canopy cover diameter، basal area، canopy cover diameter. Percentage show the highest relationship with gum tracaganth extraction amount، respectively in other word، based on each extraction time model and regarding the obtained relationship it will be possible to have an acceptable estimation of gum tracaganth extraction rate with no damage to this valuable plant.

Assistant Prof. of Research Institute of Forests and Rangelands، Tehran، Z. Jaberolansar، Senior Expert of Esfahan Agricultural and Natural Resources Research Center، Esfahan. Asragalus caragana is a perennial forb from Papilionaceae that is found in semiarid regions of Esfahan province. In order to study the best method of cultivation in dry condition، plant seeds were gathered in watershed station of Chadegan from 1383 to 1384. The seeds were planted during autumn with randomized complete blocks design. Treatments were consisted of seed and fruit sowing within furrows and pitting at the 2. 5 to 5 cm depth. Early spring the number of germinated stands was counted in each plot. Regarding to percentage of germinated plants، The results showed significant difference between kind of seed، sowing method، interaction between seed and sowing method and interaction between seed and depth. The percentage of germination in various treatments was seed sowing 59. 5%، pitting 39%، sowing at the 2. 5 cm depth 36%، interaction between seed and pitting 75%، interaction between seed and 2. 5 cm depth 71%، interaction between pitting and 2. 5 cm depth 42%، interaction between seed، pitting and 2. 5 cm depth 82%. As conclusion، sowing seed at the 2. 5 cm depth with pitting is the best way to cultivate As. caragana.

Application of unit hydrographs as one of flood estimation techniques requires hydrometry stations and observed data collection. Application of watershed physiographical characteristics is therefore supposed as an applicable substitution because of their accessibility and accuracy. The present research has been conducted to regress different shape and time components of unit hydrograph into physiographical characteristics of the some selected watersheds in northern Iran with an area of ca. 177000 km2 extended in Golestan، Mazandaran and Guilan Provinces. For this purpose، 9 physical characteristics of the watersheds and 8 characteristics of unit hydrograph were taken into account. Different statistical analyses of bivariate and multivariate regressions using simple and transformed forms of data، clustering and principle components were applied to study the relationships. The obtained models were evaluated with the help of relative error، root mean square error and efficiency coefficient. The results verified the possibility of development of synthetic unit hydrographs by using watershed physiographical characteristics emphasizing on watershed perimeter for estimation of hydrograph components and watershed mean slope for prediction of time related factors. The priority of bivariate and multivariate models was also ascertained for estimation of time and discharge components of the 2h unit hydrographs، respectively، with an average value of efficiency coefficient of 0. 52 ± 0. 32.

Reclamation is needed on about 130 thousand hectares of saline-sodic soils in the Golestan province. This field experiment was conducted on a saline-sodic soil to compare changes in chemical properties after various treatments. Treatments were: (i) gypsum، (ii) sulphuric acid، (iii) sulphur and (iv) a control. Also، 60 cm of water added to all treatments for leaching. Electrical conductivity (EC)، pH، exchangeable Na+، Na+، Ca+2 and Mg+2 of the soil in the saturated paste extract under each treatments were measured in the 30 cm and 60 cm soil depths after 40 days. All statistical analysis were performed using the SAS software package. Desalinization and desodification processes were observed in all the treatments. Gypsum and sulphuric acid application increased the soluble Ca+2 Mg+2 and decreased the soluble Na+ in the top 60 cm of soil. Therefore، gypsum and sulphuric acid application significantly decreased SAR، EC and pH in the top 60 cm of soil. Sulphur decreased SAR، EC and pH when compared to control in the top 60 cm of soil. But non-significantly decreased these same parameters. In general، for surface soil improvement، gypsum and sulphuric acid application was the most effective of the treatments used.

Environmental data and information could be defined in the formed of fuzzy sets with no defined accurate boundaries. There do not exist any sharply defined boundaries between informational media، and this very specialty better reflects the continuality of natural phenomena. In this research، in the course of preparation of a map of rainfall erosivity in the Namak Lake basin، the accuracies of the several common methods of interpolation Viz: common Kriging، Co-Kriging، Spline، Inverse Distance Weighted، and Fuzzy Kriging have been appraised. The values of EI30 index evaluated through an empirical relationship have been employed as fuzzy numbers. Results reveal “Fuzzy Kriging” (with a mean absolute error of 10. 49) as the most accurate one among all methods. Thin Plate Spline، is on the other hand of the highest mean absolute error. Based upon the map، prepared on the basis of Fuzzy Kriging method minimum and maximum values of EI30 index are recorded as 10. 99 and 233. 73 mega joule mm per ha per hr per year. Rainfall erosivity index values increase towards north of Namak lake basin. The vastest EI30 index area in Namak Lake basin belongs to the values between 80-93 mega joule mm per ha per hr per year with a covering area of 20 percent. Keywords: Geostatistics، Inverse Distance Weighted، Rainfall erosivity index، Co-Kriging،

Nash instantaneous unit hydrograph is frequently used for simulating hydrological response in natural watersheds. The accuracy of estimating the parameters n and k in Nash model directly affect simulation results. This study focuses on the evaluating different methods of estimating the Nash model parameters (n and k) in Jafar-Abad watershed (109 km2) located in Golestan province. Using Different methods such as moment، trial-and-error، Han’s graphical method، time to peak – time to inflection point and Bhunya et al methods، the n and k parameters was calculated using 33 stormevents، and physiographic parameters was used for experimental Nash formula. Then the mean value of n and k، were used for simulation of 4 other storm events as model validation. The efficiency of Nash model results was evaluated by statistical comparison with the observed hydrographs. The results show that using moment and trial-and-error methods in n and k parameters estimation، the Nash model predict direct runoff hydrographs with good accuracy، 76% and 70 % respectively according to the Nash-Sutcliffe criterion. Also the results indicate that other methods give weak results comparing with moment and trial-and-error methods. Thus regionalization of Nash’s model parameters (n and k) by mentioned methods، in similar catchments introduced for development and application of this hydrological model.

Drought is a national calamity that has bad effects on ecological، social and economical divisions. Growing of crowd and increasing of water demand aggravate the effects of drought. Analyzing of drought and attention to it in development programs has much importance، especially in Iran that is an arid and semiarid country. “Hydrological drought” means time periods that discharge of river is not sufficient to supply planned demands. In this research the flow duration curve (FDC) established using Pole-Shaloo station daily discharges for 1957-2001 years. Next، the hydrological drought periods extracted by truncation level method and analyzed. The “interior criterion” method (IC) used to eliminating minor droughts and pooling dependence droughts. Concluded that Johnson and Generalized Pareto distributions was best cases for annual maximum series (AMS) include “duration” and “deficit volume” respectively، based on Q70 truncation level so، type 3 Pearson and Generalized Pareto distributions best cases for annual maximum series (AMS) include “duration” and “deficit volume” respectively، based on Q90 truncation level. Therefore the return periods calculated for historical droughts. The most drought’s return periods was less than 20 years except 1963-1964 drought. For example The 2001 drought’s return period، that enveloped most of regions in Iran، was 20 years based on analyzing of deficit volume. Also drought risk calculated for return periods and water resource projects life. The maximum drought deficit volume is related to primary 11 years and 5 years at the end of time، so that in primary 11 years 57 and 50 percent of droughts was happened in lieu of Q90 and Q70 respectively. Also in 5 years of end of studying period 40 and 20 percent of droughts was happened in lieu of Q90 and Q70 respectively. The minimum amount of drought deficit volume was related to 1966-1974 period، so that equal to zero and 20 percent in lieu of Q90 and Q70. In final part of research، the annual maximum series of deficit volume extracted with respect to 10، 20،30،60،90،120،150 and180 days durations، and the best probability distributions appointed for these. Consequently، the severity-duration-frequency curve furnished.

Various treatments have been suggested for improving seed germination in different plants including agronomic، rangeland، forest and desert species. Our research was conducted to examine different treatments influences on seed germination and initial growth properties (germination percentage، rate of germination، length of radicle and plumule) in two species of Zygophyllaceae; Z. eurepterum and Z. eichwaldii. Five treatments including sulfuric acid (98% for 10 minutes)، potassium nitrate (0. 2 % for 72 hours)، gibberlic acid (250 ppm for 24 hours)، hot water (90 ºC for 10 minutes) and scarification were used. Additionally، distilled water was used as control treatment for results comparison. Factorial experiment with a completely randomized design in four replications was done. Results showed that there were significant difference among treatments in view point of percentage and rate of germination associated with length of plumule at p≤ 0. 01 and length of radicle at p≤ 0. 05. The highest amount of germination was related to scarification and hot water treatments while the lowest one was related to sulfuric acid. Also it was revealed that Z. eichwaldii understudy properties were higher than those of Z. eurepterum.

The purpose of this research was to identify plant species، diversity، life forms and relevant species to different sites in point of view phytogeographical in Lamerd city (27°02’55”-27°53’38”N، 52°36’58”-54°00’36”W). The flora were surveyed in two growing seasons and identified based on relevant references. Then the life forms were determined and their proportions were compared with Raunkiaer’s normal spectrum using Chi-square test. The position of the area related to phytogeographical classification was investigated based on geographical data and reference. We encountered 178 species belonging to 48 families and 124 genuses. According to the results obtained Compositae، Gramineae، Labiatae، Papilionaceae and Chenopodiaceae were important families in point of view of frequency species. The life forms spectrum observed was: therophytes (34. 4%)، hemicryptophytes (27. 2%)، phanerophytes (18. 9%)، camaephytes (14. 4%)، and cryptophytes (5%). Results showed that therophytes were higher than normal spectrum and phanerophytes were less than normal spectrum and the results were in agreement with drought. In geographical distribution point of view، 54 species with the most frequency (30. 4%) belonged to Irano-Toruni site and 26 species (14. 4%) belonged to Sahara-Sendi site. According to results of this study، it can be concluded that the research area is located in Ecoton region.

Nowadays، water resources provision with proper quality is one of the important needs. Additionally available water quantity، water resources pollution and water quality are problems about water provision. This research has been done to investigate the factors of ground water salinity and to present a model for estimating groundwater salinity on the Caspian southern coasts. So، these data were provided: water qualitative experimentations in this area، annual precipitation and evaporation، groundwater depth، surface water salinity، aquifer transmissivity، topography and distance from Caspian Sea. Then، Multivariate Regression method was used by using SPSS software. In this stage، groundwater EC has been entered qua a variable for water salinity or dependent variable and ground water salinity factors have been entered qua independent variables. A linear model and a non-linear model were presented. Then، resultant models efficiency were considered by using these models in the areas that (east of Mazandaran province) their data were not used to present resultant models. Finally، groundwater EC average map was provided by using the presented non-linear model and Geographic Information System in the east of Mazandaran province.