نشریه پژوهش های آبخیزداری
پیاپی 89 (زمستان 1389)

In agriculture، growing degree day accumulation is commonly used to predict crop development، classify species and hybrids as to maturity data and evaluate climate for crop suitability، but relationships between degree day accumulation and phonological development of range species have received less attention. This research tested the hypothesis that phenological development is related to degree day accumulation and that these relationships are stable over environment. Therefore this study was conducted in two different field studies on Bromus tomentellus. 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 phenological development and management، especially in determining grazing readiness، and in refinement of growth and management simulation models.

Rainfall forecasting as one of the most important climatological parameter has a special importance in water resources management. In other hand، there are some complex nonlinear phrases in the equations which are make precipitation modeling too hard. Therefore nowadays scientists are looking for new approaches to improve the knowledge and predict meteorology parameters، especially precipitation. One of these methods is Artificial Neural Networks (ANN) which is categorized in computational intelligence group. In this study was focused on developing a non-numeric precipitation prediction model using ANN. Using daily precipitation data of Mashhad synoptic station، for 23 years (1982-2004) of March as a month with high humidity and May and December as months with medium humidity. From 713 daily data points، 580 were randomly selected as training and testing data sets. The reminder، were taken to check the validity of the models after training. The new approach ANN type used in this study was a feed forward-back propagation-perceptron، using a gradient decent learning algorithm. Out of many models tried، two topologies with best fit parameters were selected for March، named as GS521 and GS651، GS521 and GS681 for May and GS571 and GS631 for December and MATLAB (7. 01) environment was employed to accomplish this study. After applying fitness statically factors، it was founded in the best models R، RMSE and MAE were founded equal 0. 89، 0. 14 (mm) and 1. 15 (mm) for March، 0. 85، 0. 14 (mm) and 1. 16 (mm) for May and 0. 86، 0. 15 (mm) and 1. 17 (mm) for December، respectively.

Tow important characteristics of arid and semi arid regions are wind and wind erosion which accelerate desertification process. Farmlands are on of the major sources of soil particles detachment and consequent erosion. Windbreak is an effective tool in reducing wind speed and making microclimates in its windward and leeward. Plain of Hussein-Abad Sarbisheh is located under an arid climate condition and Sistan 120-days wind has destructive influence on soil and yield of agricultural fields. In this research، live windbreaks (Zea mays and Sorghum bicolor) were created in different patterns and densities at three replications. Wind speed was monitored in definite distances from windward and leeward of windbreak. Results of data analysis from wind speed monitoring was revealed that triangular arrangement in three densities (i. e.، density of 60 cm in rows) is the most effective pattern in density of windbreak to reduce wind speed and protect high distance from leeward of windbreak and offer this windbreak as effective windbreak in Hussein Abad plain.

One of the proper strategies to preserve and revive qanats is harmonic improvement and development of the utilization systems with qanat natural conditions. One of the most suitable strategies is artificial recharge of qanats aquifer with use of runoff water harvesting systems. In this paper in order to identify the suitable sites for qanats recharge، determined the suitable sites of runoff water harvesting by means of Geographical Information System (GIS) in watershed Kalat of Gonabad. For this purpose modeled and evaluated generation of runoff potential with consideration of spatial variations in characteristics such as soil، land use، rainfall and slope information in GIS. With integrate layers in GIS، computed the ratio of area qanat recharge sites to area runoff concentrating sites and site for distributed stored water. The results show that 68. 4 percent of the Kalat watershed area has a high and very high potential for generation surface runoff، whereas only 2. 8 percent of total area have suitability of high and very high for qanats recharge and distance of Qanat is the only cramp factor for this purpose. In addition to the Geographic Information System could be an efficiency and useful tool to determine proper sites for Qanat recharge.

This study was done for the purpose of investigation on the effect of Haloxylon-planted different age’s levels with consideration interval of planting time، on the physical and chemical properties of soil in Ardestan area. For this purpose، sampling was done as randomized-systematic in three Haloxylon-planted areas (8، 15 & 23 year ages) and one adjacent control area. Soil sampling was taken in each control area in two-120m transects with 30m intervals at two depth (0-30 & 30-60 cm). Soil samples were investigated in the laboratory. After importing the data، in spss، ANOVA، and Duncan test were used. The result showed that Haloxylon did not affect on the soil texture. Lime، gypsum، k & p significantly، but there were significant effects on pH، EC، Mg and N in Haloxylon-planted areas with different ages. Therefore، from this study can conclude that the soil physical properties unaffected by the planting of Haloxylon، but it causes the changing of some chemical properties of soil in different depths.

Nowadays، soil erosion is one of the main problems in catchment areas in the agriculture and natural resources point of view، in which destroy the lands and reduces the soil productivity. Soil erosion potential of Aseman Abad plain، Ilam province is determined using Erosion Index in geographic information system in this research. In this study، after data collection، the maps of slope، lithology and land use of the area were prepared. Each map subdivided to seven classes based on their amount and effect on erosion. By combining these maps and considering erosion index، the erosion potential priority map was prepared. Finally، using curve number model، the runoff potential map of the basin was prepared and by combining this map with the erosion potential priority map، the erosion potential map of the basin was obtained. Results showed that more than 52 percent of the basin، having 6019 hectares area، has high erosion potential. These areas are composed of quaternary deposits، terraces and young alluviums which are susceptible to erosion and located near to the exit of the basin. These areas have the first priority protection programs for erosion control.

The genus Artemisia of family Asteraceae has a wide distribution in Iran. Five species of this genus are distributed in Kashan، located in the central part of Iran. For further identification purposes، anatomical of structure of A. scoparia، A. biennis A. persica، A. aucheri and A. oliveriana were studied. Plant materials were fixed in FAA and trasversed sections were prepared by hand and observations were carried out by light microscope. Foliar mesophil type is Isobilateral and also subsidiary stomata cell are anemosyttic. In adaxial and abaxial surfaces of leaves there are two types of trichomes; glandular without stalk and nonglandular، types of simple with multicellular stalk، T shape، long trichome with two arms. Collanchima، fiber cells، colateral vascular bundles، cambium layer were observed in stem section. Secretory duct were observed in root of Artemisia scoparia. A. biennis، was different from other species in some anatomical characters other species in some anatomical characters

Rainfall erosivity is usually represented by indices based on rainfall characteristics. So far، many rainfall erosivity indices have been developed، out of which the R index (EI30 in the model of RUSLE) is the most acceptable one. By calculating the EI30 in various points، erosivity maps can be produced for the country، some provinces or any other parts of the country. In this study، erosivity map for Lorestan Province was produced using this index. In order to estimate this index for regions lacking data from recording rain gauges، regression analysis was used. Thus the EI30 index and a few easily obtainable rainfall erosivity indices were calculated for 13 recording rain gauges with long term and intensive rainfall data. A regression analysis was then carried out between EI30 index and other indices. The best regression equation was established using Modified Fournier index (MF) with determination coefficient and standard error of estimate of 0. 955 and 112، respectively. To mapping rainfall erosivity، all of rain gauges (both having rainfall intensity and daily rainfall depth records) existed in the province and that of the surrounding regions were then assessed، and 61 rain gauges having more than 15 year daily rainfall data were selected. The EI30 were then estimated for the selected ones using the regression equation. Mean، Maximum، Minimum and coefficient of variation of the rain gauges were 594. 94، 2257. 3، 98. 54 Mj-mm-ha-1hr-1year-1 and 66. 38 percent. For converting point erosivity data to a map، a number of common interpolation methods were assessed and in order to select the suitable one، cross- validatin method were used. from the interpolation methods، Co Kriging was found to be the most suitable in terms of low error measures based on cross validation. Therefore rainfall erosivity map were produced for Lorestan Province using Co Kriging.

Due to its economic and environmental impacts، soil erosion has been a major concern to farmers، engineers and policy makers in recent years. So for fighting and subsequent to that success in controlling soil erosion action is necessary to knowledge and awareness of the effective factors on erosion، and the intensity of its impact on specifics and finally in the areas of soil erosion and yield sediment. But due to the complexity of soil erosion، number of indices and criteria involved in it and also lack of and efficient model in the country makes it a very difficult، complex، cost and time-consuming task. So introducing relevant indicates with higher accuracy and time saving to apply for water erosion prone areas are very important. Slope is one of the main factors responsible for this phenomenon and considerable efforts have been made to model it in the previous works. The relationship between percent of erosion and slope was studied in the study region. In other words different classes of the slope erosion risk evaluating a danger to the slopes of the erosion are clear. GIS & RS were used to facilitate the research. Also statistical tests such as Chi-square were considered for the final conclusion. Finally it was resulted that slopes between 20 to 40 percent have been mostly affected by the erosion. Meanwhile، in the gentle slopes، light erosion and in the upper slope existence of rock and lack of soil caused to the lower erosion rate. In this way، it was denoted that as the slope increase، soil erosion increases primarily and then will decrease. Also the slope and the weights assigned to each erosion rate classes based on quantitative geomorphologic approach، specific sediment discharge، erosional facies in 1% is significant. Therefore it can be classified in the preliminary zone erosion in areas of southern Alborz without sufficient data for complementary studies

The aim of this research is generating rockfall hazard zonation map by using of overlay index method in Salavatabad saddle that is located in Sanandaj southeastern، Kurdistan province. The first، in this research، we using of field search، local interview and review on carried out studied in the outside and inside of Iran، eight factors effective was recognized on rock falls. These factors include; slope degree، slope aspect، slope curvature، elevation، distance to road، distance to fault، litology and land use. After recognizing، we act to processing with Arc view 3. 2 and ERDAS imagine 8. 5 software. Thirty four Sensitive slopes were used as prone slopes to rock fall data (Dependent variable). For statistical analysis، be used of likelihood ratio statistical analysis. At this research، the value of each various class between 0 and 1 is determined. As for، the chart be obtained from overlay distribution rockfall map with information layers، the each of class of each layer that had more frequent density، 10 value and other classes with aspect of value of rockfall frequent density in class itself، was determined as unit of 100 value. With transmit this coefficient to each class and wights based on the charts as effective factors with rockfalls and expert opinions، the hazard zonation susceptibility of rockfall was generated in Salvatabad saddle regional with five classes. For Verification، rockfall point’s map was overlaid with hazard map. For more confidence، first each of effective variables removed then hazard Zonation map was generated and at last this map was verificated. Result have shown that percent of verification without slope degree is 75. 81 percent، without slope aspect is 78. 50 percent، without elevation of sea is 72. 16 percent، without litology is 74. 64 percent، without distance from road is 76. 23 percent، without distance from fault is 73. 56 percent، without curvature is 64. 00 percent، without landuse is 74. 23 percent and by all variables the percent of verification is 81. 44 so، it is high and acceptable..