فهرست مطالب sh. asgari

Monitoring the nutrients of tree leaves is crucial for understanding their physiological responses to environmental stresses. This study monitored the status of leaf nutrients in Persian oak trees (Quercus brantii Lindl.) affected by crown dieback during the years 2019-2021.

Two sites, one northern and one southern, were selected in the Mele-Siah area. Five healthy trees and five declining trees were identified at each site. From each tree, 20 mature and healthy leaves were collected and taken to the laboratory to measure the concentration of nitrogen, phosphorus, potassium, calcium, and magnesium elements. Leaf sampling was conducted annually in August over three years. Soil sampling was also conducted during the growing season over three years, with a hole dug on the southern side of each tree crown to measure soil moisture in two horizons.

The results showed that the amount of leaf nitrogen was highest (1.48%) in 2019 and lowest (1%) in 2020, and it was higher in healthy trees (1.30%) than in declining trees (1.22%). The amount of phosphorus was higher in the northern site in all years. The amount of potassium was highest (2.22%) in 2019 and lowest (0.58%) in 2020. The amounts of leaf calcium and magnesium were highest (1.8% and 2.36% respectively) in 2019 and lowest (0.57% and 0.69% respectively) in 2021. Furthermore, the amount of calcium was higher in the northern site (1.29%) than in the southern site (0.99%). The highest amount of calcium was found in declining trees (1.465%) in the northern site and in healthy trees (1.241%) in the southern site. The results also showed that soil moisture was higher in the northern site in all sampling years and was associated with annual changes, which affected the changes in leaf nutrients over different years.

Considering the differences in soil moisture, soil acidity, and salinity of the studied sites, as well as temporal changes in the concentration of leaf elements caused by climate changes, it can be concluded that the crown dieback of Persian oak trees is related to the physiological mechanisms involved in water and nutrient absorption.

The purpose of this study was to investigate some environmental factors of Zagros forest dieback. In this regard, raster layers of elevation, slope, aspect, hillshade, toposhape and the land formation of Zagros forests in Ilam province were prepared. The distribution map of live and dieback forest cover were also prepared, using Landsat 8 panchromatic images. Then, the percentage of dieback forest cover in each  specific class of the studied factors was calculated, using geographic information system (GIS). Results showed that 2.37% of the forest cover area is dieback canopy. The difference in the percentage of dieback forest cover between landforms was negligible. Maximum and minimum dieback areas of forest cover were in southern aspects (2.7%) and northern aspects (1.73%), slope class 0%-20% (2.6%) and more than 80% (1.52%), elevation less than 1300 m (3.36%) and more than 1700 m (0.52%), hillshade class 0-102 (2.56%) and 255-204 (0.82%), Gachsaran formation (5.08%) and Asmari-Shahbazan formation (0.96%), respectively. As a result, the amount of dieback in the southern slopes was 35.9% higher than the northern, in low hillshade was 68% more than high hillshade and in low elevations was 84.5% higher than high elevations. It seems that the higher ratio of crown dieback was occurred in the less hillshade and at low elevations, due to higher temperatures and lower soil moisture in these areas, which indicates the effective role of recent droughts in intensifying the process of forest dieback.

Chronic ankle instability is a common injury in athletes that leads to postural control disorders. The aim of this study was to compare the effect of external focus of attention and postural task alone on center of pressure sway in athletes with chronic ankle instability and healthy athletes during dual task training.

This cross-sectional study was performed on 29 male volleyball athletes with a referral from a specialist and 29 healthy athletes matched with the affected group in terms of age, height and weight. Subjects in the two groups were on the balance board with single-leg and double-leg stance, standing in the center of the force plate for 60 seconds and performing postural tasks alone and with external focus. The degree of displacement of the pressure center was measured to investigate the variables of standard deviation of amplitude and mean velocity.

In double-leg stance, standard deviation of amplitude in medio-lateral (14.2±2.1) and anterior-posterior (16.7±3.3), mean velocity in medio-lateral (39.2±9.8) and anterior-posterior (40.7 ± 6.1) directions in patients during external focus were significantly less than the standard deviation of amplitude in medio-lateral (12.2±1.5) and anterior-posterior (13.9±2.4), mean velocity in medio-lateral (46.2±13.1) and anterior-posterior (48.4±9.6) directions during the single task. In single-leg stance, standard deviation of amplitude in medio-lateral (16.1±2.1) and anterior-posterior (13.1±1.7), mean velocity in medio-lateral (42.2±13.3) and anterior-posterior (40.7±8.6) directions in patients during external focus were significantly less than the standard deviation of amplitude in medio-lateral (11.1±2.1) and anterior-posterior (17.4±3.3), mean velocity in medio-lateral (47.8±16.6) and anterior-posterior (55.2±17.4) directions during the single task.

The results of the study showed that external focus task leads to distraction from postural control and reduces postural sway in athletes with chronic ankle instability.

Several studies showed that increasing the total available time for parasitoid causes biases in parameter estimation of functional response experiments. Hence direct observations are required for unbias estimating of handling time. In addition there is some difference among geographical populations of parasitoid. Therefore in this study, two populations of Trissolcus vassilievi (Mayr), (Tabriz and Varamin) were chosen and time allocated for different activities were recorded by direct observations. The time budget of a female parasitoid (24h-old fertile females of the 3rd generation) was divided to four components including drumming, parasitism, host marking and performing actions and duration of each behavior was recorded for three hours in an experimental arena.Time spent for whole clutch was 1071±70.25, 4288.6±293.26, 874.2±60.38 and 972.0±133.89 seconds in Tabriz wasps and 1237.2±94.03, 4911.6±365.72, 935±87.08 and 1136.8±69.20 seconds in Varamin wasps, for above respect of behaviors. Furthermore, per capita times assigned for above behaviors were 31.87±1.16, 127.64±2.18, 26.02±0.83 and 28.93±6.75 seconds for Tabriz wasps and 31.40±0.83, 124.66±1.88, 23.73±0.77 and 28.85±6.05 seconds for Varamin wasps respectively. Handling time increased slowly until the end of the experiment. It was concluded that the classical functional response experiments should be accompanied by direct recording of insect behavior and parasitoids/predators should be allowed to determine the patch time themselves in a host arena. Otherwise, handling time will be overestimated due to time wasted by predator/parasitoid during satiation or depletion of egg reservoires.

Introduction Geometric Characteristics of watersheds are very important in study and assessment of floods. They play the most significant role in hydrologic assessment of the missing data on watersheds. Watershed diversity in our country is a major obstacle to the correct assessment of flood forecasting in terms of climatic conditions, vegetation, soil, geology and lack of hydrometric stations. Flood is a natural phenomenon which nations adopted as an inevitable event. However, flood event, size and frequency result from several changing factors in terms of climatic, natural and geographical conditions in areas. This is why the relation between rainfall and runoff is noticeably different in every basin. Not only every basin but also every sub-basin has its unique conditions which must be independently discussed. Since at present we can’t change atmospheric elements in order to prevent these harmful phenomena, we should seek any alternative and solution on the earth and especially in watershed basins. In this regard, areas that have high potentials in creating floods should be identified. Therefore, the first step to reduce flood danger is flood managing in its origin, that is, watersheds. Certainly, we need to identify flood-producing areas within the basin because it isn’t possible to perform executive and reparatory operations across the basin due to the large extent and spread of the watersheds, and even if it isn’t studied precisely, peak debit can be intensified by changing the synchronization of peak debit in sub-basins. At present, the flood phenomenon in our country is the result of disturbing natural balance and geographical conditions (physical and morphological) in flood-producing areas rather than the incidence of heavy precipitation, which is why common rainfalls cause flowing floods. Factors like vegetation wastage due to improper knowledge of present resources management, lack of places for it in great policy makings and economical conditions dominant on this scope and overusing natural capacities of existing resources provided conditions under which occasionally we see flood-producing and its destructive effects and losing millions of tons of rich soil. Therefore, one of the main challenges in managing our country and Ilam province is to relatively reduce and control flood dangers, and one of the approaches in reducing flood damage is zoning the flood-producing potentials of watersheds. Materials and Methods In this study, we used topography maps 1:50000 of Armed Forces Geographical Organization, geological map 1:250000, vegetation Atlas, land use, area soil and the studies done in the basin level and multi-variable statistical methods of factor analysis and cluster analysis by SPSS software and Arc GIS software package. We obtained rainfall statistics from Ilam province Weather Bureau and Iran Meteorology Organization and obtained debit statistics from the Ministry of Power (Tamab). In this research, Konjancham watershed was classified into 29 sub-basins. In view of the objectives of this study, the maximum instant debit, daily rainfall, date of basin floods during the statistical period of 1995-2007 were selected. And for other indexes used in this study, at first we calculated the effective indexes in producing flood like geometric variables, physiographic, permeability and climatic variables for Konjancham watershed sub-basins by Arc GIS software. Then they were analyzed using statistical factors and cluster analysis methods by SPSS statistical software. Results and Discussion In this study, Konjancham watershed in Ilam province is divided into 29 sub-basins and the intensity of flood producing of sub-basins is classified into five classes. Considering the purposes of this study, instant peak flow rate, daily rainfall and the date of basin floods during statistical period of 1995-2007 are selected. Using Arc GIS software, we calculated 28 geometric, physiographic, permeability and climatic parameters such as area, perimeter, length and slope of the main stream, length and slope of the watershed, concentration time, form of coefficient and precipitation variables, vegetation canopy, CN, flow rate and etc.. Statistical methods of cluster and factor analysis were used to determine the flood potential in the sub-basins of Konjancham watershed and the data for 28 sub-basins variables were processed by SPSS statistical software and summarized in the form of 5 major factors (form, stream, slope, drainage and runoff) and finally, the flood producing potentials zoning map was drawn in five levels: low, moderate, relatively low, relatively high and high. In addition, qualitative variables effective in occurrence of flood have been descriptively analyzed within Konjancham river sub-basins. Conclusion The results indicate that the form factor with specific value of 9.75 is the most important factor in the studied basin flood production. Factors like stream, slope, drainage and runoff with specific values of 6.55, 3.45, 2.51 and 2.26 respectively are grouped into the next ranks in terms of priority. Then according to the factor score, the region was divided into 5 parts including high, relatively high, moderate, relatively low and low flood producing, and as a result, the zoning map of flood producing potentials was drawn in GIS for sub-basins and a descriptive analysis of qualitative variables effective on flood occurrence was done in Konjancham river basin.

The biological parameters of cabbage aphid, Brevicoryne brassicae (L.) was studied in the laboratory conditions under the three constant temperatures (20, 25 and 30 ºC), RH 60±5% and a photoperiod of 16:8 (L:D) using 40 first instar nymphs. Among nymphs, 40%, 55% and 10% of them completed their nymphal period in 20, 25 and 30 ºC, respectively and developed to adult stage. In 30 ºC, the most biological acitivities of aphid were disrupted and the most individuals (nymphs and adults) were killed. Most developmental periods, longevity and the amount of reproduction in 20 ºC were significantly greater than other temperatures. In temperatures 20, 25 and 30 ºC the last individual of a cohort died in age of 33, 29 and 16 days, respectively. The life expectancy of cabbage aphid in the first day of experiment was 13.93, 10.50 and 7.19, respectively according to the mentioned temperatures. There was a little difference between net reproduction rates in temperatures 20 and 25 ºC (16.74 and 15.92, respectively). Net reproduction rate was reduced extremely in temperature 30 ºC (1.75). The intrinsic rate of the increase in the temperatures 20, 25 and 30 ºC were 0.187, 0.226 and 0.042, respectively. The results indicated that 25 ºC was the optimal temperature for biological activities of B. brassicae and its highest population growth was observed at this temperature.