Journal of Range and Watershed Managment
Year:2012 | Volume:65 | Issue:1|Papers Count:15

In agriculture, accumulated growing degree - day is commonly used to predict crop development, classify species and hybrids as to maturity data and evaluate climate for crop suitability, but relationships between accumulated degree day and phonological development of range species have received less attention. This research tested the hypothesis that phenological development is related to accumulated degree- day and that these relationships are stable over environment. Therefore this study was conducted in two different field studies on O. melanotricha. One of the most important steps in the design of degree-day system is establishment of the base temperature. For this purpose, seed plants are grown in a controlled environment, at constant temperature (10, 15, 20, and 25’oC) and constant photoperiod, with development rate expressed as a function of temperature. The best fitting line of development rate versus temperature is extrapolated to zero growth. The point at which this line crosses the temperature axis defines the best temperature. Thresholds (base temperature) are different for each species. The linear regression analysis showed highly significant (p=0.01) between rate development and temperature for this species. Degree - day can be easily calculated by using the average daily temperature minus the base temperature. Degree day are totaled over a period of days to determine when a plant has reached a certain phonological stage. Based on the species and condition of this study, plant phenological stages can be predicted from accumulated growing degree-day. Determining relationship between plant phonological development and growing degree-day is especially useful for grazing management.

It is essential to have correct information to determine short-term and long-term capacity of rangelands. Total forage yield cannot be used by livestock due to allowed utilization limit and palatability of species. Varkesh, Khodkavand and Orazan sub- basins of Taleghan region were selected for this research and within key region of each vegetation type, sampling was conducted based on randomized- systematic approach. Four transects of 100 m length was established in each type along and in vertical direction to the slope. Based on vegetation type and uniformity, 10 random plots of 1m2 area were considered and then by clipping and weighting method and considering palatability and allowed utilization limit, available forage yield was calculated. The results showed that among 10 existing types, five types do not have grazing suitability due to weak condition and high sensitivity to soil erosion and were not considered for calculating available forage yield which is mostly related to mountainous and steep slope of the region, low palatability of some class III species (Centaurea virgata and Astragalus aegobromus), sensitivity of soil to erosion and also existence of poisonous species in the region.

The goal of this research is to compare the quality of litter and aerial organs in three rangeland species including Bromus tomentellus, Agropyron tauri and Psathyrostachys fragilis on the basis of nitrogen, phosphorous, potassium, carbon amounts and C/N proportion. After recognition of the species sites in Taleghan Watershed, litter and aerial organs of the mentioned species were collected. Sampling was done in key areas of each site along four transects using randomized-systematic method. Transect length was determined according to the area and variation of the key region.. Ten plots were placed along each transect and the dimensions of sampling plots were selected on the basis of species type and distribution using minimal area method. The obtained results of analysis of variance and comparison of means showed that B. tomentellus has maximum amounts of carbon and C/N proportion in its litter while P. fragilis has maximum amount of phosphorous and finally the maximum amount of nitrogen in litter is related to A. tauri. Meanwhile, P. fragilis showed maximum amounts of nitrogen, carbon and C/N proportion in its areal organs. The highest amounts of phosphorous and potassium are related to B. tomentellus. Totally A. tauri species showed the better condition than other species based on quality of litter and aerial organs.

Change detection is the process of identifying differences in the state of an object or phenomenon by observing it at different times. Soil and topography have long-term changes and can be considered static. However, changes in hydrological response of a watershed over a medium time scale depends on change in the type and distribution of vegetation cover. Over last 50 years, about 3700 floods have occurred in Iran that 53 percent of them have happened in 1992-2002 period due to population growth, change and over use of the land. In this research, MSS and LISSIII images of 1977 and 2007 related to Kasilian Watershed were used. After atmospheric corrections, different false color composites of both images were classified with maximum likelihood algorithm. The best kappa coefficient of both images were related to Green band, NDVI and Red band of false color composites as 0.81 and 0.84, respectively. The results showed that over the 30 year study period; about 251.94 hectare of forest area has been decreased.

In arid and semi-arid areas, due to scarcity of surface water, groundwater resources have been considered. Especially in urban areas, due to increasing urbanization and city progress, the need for high-quality water has increased significantly. In this study, physicochemical characteristics of groundwater were studied in Mashhad city. TH, TDS, EC, important parameters, the restrictive cause was known for drinking. Thus, the spatial distribution of these three parameters has been investigated by using interpolation methods. Interpolation methods that investigated in this study, including Deterministic methods (IDW, and LPI) and the Geostatistical (kriging and Cokriging) respectively. After Variogram analysis, the best method selected based on minimum RMSE, the process was used to locate contaminant. The results showed that the correlation was strong spatial parameters and Geostatistical methods to Deterministic methods indicating better results and Cokriging the method than other methods interpolation has had a significant advantage. Auxiliary variables used for EC and Cl TH parameters for EC and TDS parameters to increase estimation accuracy. Spatial distribution of pollutants showed that the southeast and northwest regions, based on the standard of drinking water, underground water is undesirable in terms of drinking. That were identified, the landfill area is urban. So due reduce the quality and increase groundwater pollution can be there Mozdoran formation and accumulation of municipal solid waste in these areas.

In order to compare the yield and herbage quality, 11 accessions of Elymus hispidus were surveyed in random complete block design under dry farming conditions, with three replications. Some morphological and chemical traits of each accession were measured. The highest value of genetic coefficient of variation and broadsense heritability was obtained for triats of number of shoot on bush, plant height and flag leaf length while the lowest value was observed for traits of acid detergent fiber and crude protein. Triats of flag leaf length, number of shoot on bush and forage yield showed the most environmental coefficient of variation. The positive correlation with forage yield was obsrved for triats of plant height, internode length, flag leaf length and acid detergent fiber at 5% level and for triat of ashes at 5% level. Crude protein and water solution carbohydrate indicated negative correlation with forage yield at 5% and 1% levels, respectively. The results of correlation between traits were verified by biplot of the first two components from principal component analysis with expression of 66.32 percent of the variation in the data structure. Among accessions studied was significant variation for morphological traits. The obtained results of comparing mean of traits showed that the accessions including 890-5 and 890-6 were better than the others for most of the morphological and chemical traits especially herbage yield and as the suitable genetic material have introduced for rangeland restoration or breeding programs under dryland conditions in Kermanshah province. The results of comparing mean were confirmed by cluster analysis and principal components analysis.

Time of concentration is the time required for all parts of the watershed area to take part in the outflow discharges. Application of Arc GIS software for extracting of physical parameters of river network in some extents has automated this approach. But it should be kept in mind that their evaluation is one of the most important necessities. The purpose of the study is to evaluate the effects of Arc GIS automatic extraction method of river network physical parameters on the empirical equations of shallow concentrated flow travel time and time of concentration. Therefore, as the channel slope that is the intended parameter and extracted using the automated method in this study, was also measured by the field surveys at 21 hydrological homogenous reaches in Deh-Bala rural watershed. Comparison of the measured and extracted slope values showed 26 to 54% error in the automated method depending on two arbitrary selected cell conditioning (500 and 1000 cells to determine outlet cell in raster DEM). Calculation of travel time using five empirical equations including Kirpich (1940), Carter (1961), Espey (1966), Yen-Chow (1983) and Bransby-Williams (1964) by the field and the automatic methods revealed that these equations show different efficiencies based on their structure and sensitivity to the parameters. Comparison of the field and automated methods based on three statistic criteria including R2, RMSE, and average of percent errors (APE) showed that for the 26-54% errors in the slope values in the automated method compared with field surveys measurements; Espey equation presented the best results both in 500 and 100 cell conditions. In the estimation of concentration time it was detected that Espey and Bransby-Williams equations presented the best results, respectively.

Snow accumulations of mountainous areas are the major and reliable sources of hydrological regime and streamflow in the warm seasons. Monitoring of persistency of snow covere area (SCA) in different months and melting process is important in the storage, drought management and forecasting of seasonal runoff. The major objective of this research is determining the relationship between SCA and physiographic parameters. For this purpose, Fasham Watershed was selected and its MODIS data was collected for 2004-2005 period. Then SCA and cloud mask were prepared using the spectral unmixing model in subpixel. In order to obtain of disappear date in each pixel, the watershed was resampled to 500*500 m grid. Physiographic features of each pixel such as elevation, slope and curvature were determined using the digital elevation model and its relationship was investigated with persistence of snow cover. The results showed that the highest and lowest correlation between persistency of SCA and mentioned parameters were attributed to elevation (88%) and slope (5%), respectively. On the other hand, there were weak correlation between aspect and curvature with persistence of snow cover.

In this research, quaternary sediments as the representative areas of different geomorphological facies and reservoir of groundwater and also their relationships were studied. The studied area is pediment and playa in Cheshmeh-Ali, Damghan. The characteristics of quaternary deposits and its bedrock were studied using geological map with the scale of 1:100000 and geoelectric sounding data from 100 and 200 meters depth. For geomorphological studies, digital geological maps with the scale of 1:100000, topography map with the scale of 1:50000 and Landsat satellite images were used and checked by field studies. The results of anion, cation and electrical conductivity analyses of groundwater samples were used as qualitative characteristics. On the basis of dominant ions, four chemical zones were detected in the sediments. Data related to depth were used as quantitative characteristics for groundwater studies. Relative maps were generated and interpreted using Arc View software. Based on the results, dry shallow coarse piedmont sediments are predominant and have 30 OM specific resistivity, coarse piedmont sediments containing carbonate type water have 30 to 100 OM specific resistivity, dry coarse water-spreading facies of piedmont containing little chloride-carbonate type water have 100 to 200 OM specific resistivity, fine to semi coarse sediments of piedmont containing sulfate-chloride type water have 20 to 100 OM specific resistivity, fine sediments of the playa containing saline chloride type water in depth of more than 10 meters have 10 to 20 OM specific resistivity and fine sediments of the playa containing superficial saline chloride type water have less than 10 OM specific resistivity. Consequently, it can be concluded that there is a direct relationship between quaternary deposits characteristics, groundwater properties and geomorphological facies characteristics in the studied region.

Investigation of the relationship between rainfall characteristics with runoff and sediment yield is a fundamental study in designing and operating soil and water conservation practices. In this research, the effect of rainfall types on runoff and sediment yield was studied in the plot scale in the Khamsan Watershed located in Kurdistan province. Time to reach the storm maximum intensity was considered as a rainfall type index, based which all rainfalls divided into two types. Runoff, sediment concentration, sediment load and runoff coefficient were also measured in the 22.1 meter length and 1.83 meter width plot for each storm. The results showed that there was a significant difference between rainfall types at the level of 99 percent. In addition, there were significant differences at level of 99% in the runoff, sediment concentration and sediment load between different types of rainfalls. So those, the mean of runoff volume in the type 1 were significantly more than that of type 2 at the significant level of 5 percent. Also, the sediment load and sediment concentration were significantly more in type 2 storms at the level of less than 5 percent. Moreover, bivariate and multivariate modeling of runoff and sediment yield with rainfall characteristics were done and the results showed that the storm runoff could be predicted by the height of precipitation in type 1, the sediment yield of each storm could be predicted by maximum intensity in ten minute of type 1 storm and the maximum intensity in ten minute and runoff of type 2 storm by maximum value of R2 while minimum values of relative errors of estimation and verification.

Species diversity is important concept in ecology and vegetation management. Protection of biodiversity and applying necessary activities for protection is one of the basic roles in modern societies. To reach to the mentioned goals, this research was performed in Sorkhdeh rangelands of Semnan province to investigate species diversity and affecting environmental factors. Totally, 230 plots established at the study area for sampling of vegetation and 29 environmental factors including climatic, topographic and edaphic factors were measured. Also, 15 vegetation types were recognized in the study area. Shanon-Weaner and Simpson diversity, Paylo evenness, Menhinick and Margalef richness indices were determined for all vegetation types using PAST software. DCA analysis showed gradient length is >3, therefore RDA analysis was appropriate to show the effect of environmental factors on the studied indices. Result of multivariate analysis showed that environmental factors had significant effect on the studied indices (P = 0.001, F = 3.233). Tow diversity indices (Shanon-Weaner and Simpson) were highly correlated with elevation, average of annual and seasonal rainfall and average of annual and seasonal relative humidity. Evenness indicator showed strong relationship with nitrogen and clay percentage. Richness indices (Menhinick and Margalef) had significant correlation with aspect, sand, CaCO3 and K of the soil. The studied indices showed no significant correlation with P and pH of soil. Results of analysis showed that 25.6% of variations in plant diversity; evenness and richness could be interoperated by environmental factors.

One of the most important purposes of hydrology is quantitative prediction of rainfall-runoff process, transferring of runoff to the outlet and determination of peak discharge, time to peak, runoff volume and base time of hydrograph. The present research has done with the goal of study of the role of different temporal bases of rainfall in the accuracy of SCS synthetic unit hydrograph in Tehran and Alborz provinces. Amameh, Kan, Karaj and Taleghan sub-basins were selected, which have 37.2, 197, 76.3 and 65.17 square kilometers area, respectively because of their relatively small size, existence the hydrometery and rain gauge stations; and availability of paired records of flood and storm event. In such manner, 31 flood events and corresponding storms were collected and four parameteres including peak discharge, time to peak, runoff volume and base time of seven rainfall intervals were calculated using SCS synthetic unit hydrograph method. Finally, the calculated and observed direct runoff hydrographs were compared based on relative error percentage method. The results showed that the rainfall intervals of 15 minutes in each studied parameter, had the minimum relative error percentage (maximum accuracy) while rainfall interval of 120 minutes, had the maximum of relative error percentage (minimum accuracy).