IRANIAN JOURNAL OF RANGE AND DESERT RESEARCH
Year:2002 | Volume:- | Issue:6|Papers Count:6

Seven distance measure techniques; Random pairs, closest individual, Angle order, nearest neighbor, point-centered quarter. Wandering quarter and Joint point-nearest neighbor were employed for estimating of Artemisia sieberi and Stipa hohenackeriana population's density in a shrub-Grass vegetation Type. The study was conducted in the steppic zone of south west of Tehran (Roud-e-shoor) in 1995.A representative area of the vegetation type was chosen for applying the techniques. The actual density or check was resulted by counting the population individuals on a 0.5 ha.site. Consumed times were measured for each method. The pielou's and Dice's indices were applied to determine the forms of population distribution patterns. A t-test was used for comparison the means with each other and actual density. The indices of distribution patterns showed that both Artemisia sieberi and Stipa hohenackeriana were contagious populations.In Artemisia sieberi population, the nearest nieber, closest indivilual and random pairs methods estimated the density near to the check and statistically, there were not any significant difference (a =5%) between them and check. Random pairs method estimation was more accurate than nearest niebor and closest individual.In Stipa hohenackeriana population the random pairs, nearest nieghbor and Joint point -nearest nieghbor methods estimated the density near the check and statistically were not any significant difference but the nearest neighbor method consumed less time. The two methods of random pairs and nearest neighbor estimathed the density of populations of the species more accuracy and faster.

The effects of planting methods for plant establishment of grass were studied in this work. Three important grass species in Iranian rangelands are Agropyron elengatum, A. desertorum and Bromus tomentellus. The investigated planting methods were broadcasting, shallow drilling and deep drilling. The experiment was carried out in split plot experimental design. The main factors were planting methods and the sub factors were grass species. They were planted in three replications and in two years. In broadcasting, a 28-blade disk covered the seeds. A Rau experimental planter was used in shallow and deep drilling methods. In shallow drilling method furrow openers were not used on planter. For deep drilling furrow openers were installed on planter. This study was carried out in 1997and 1998.In the broadcasting planting method, the seedling was not established properly. The best seedling establishment was in shallow drilling method. The seedlings were established intermediate in deep drilling method.

Determination of the suitable irrigation period for establishment of Calligonum comosom was objective of the study. The experiment was conducted in the vixinity of 50 km of west Iranshahr. Annual precipitation of the study area which is located on 580 m altitude was 100mm during three years of the study. The split split plot design with four replications was used for this experiment, in which the main plots were two date for plantination, November and February, sub plots were plantation methods, seed and cutting, and sub sub plots were irrigation periods with four levels, 15, 20, 25 and 30 days intervals.'Number of established stands was used as the main critrion for determination of the success of the treatments. For that the number of seedling mortality was counted for each and all treatments on a monthly basis within the year.Results showed that the differences between planting dates and planting methods are significant. For irrigation period levels however no significant difference could be found. Seeding was more successful than cutting.

A general model was developed to explain the interrelationships of soil saturation percentage , mean annual precipitation, and population density on growth and vulgarity of planted Haloxylon trees by Rahbar (1988). Soil saturation percent is an easy measure to determine the water (rain) availability to plants.The main recommendation of the model is thinning the stands in accordance with the above named factors. Calibrating the general model for several regions, and optimizing the stands of Haloxylon plantation in Kashan area are the main objectives of the present study.Six density treatment were selected; two densities more than estimated number based on the model and two less than the estimated number, and the control. The treatments consisted of T1=329, T2=366, T3=410(estimated number), T4=452 , T5=490, and existing density as the control, T6= 557, trees per hectar. The treatments have been compared in a Randomized Complete Blocke Design, with four replications, since autumn of 1992 on nine-year-old trees.After thinning practices, height (H) and crown diameter (CD) of the remained trees were measured. This was repeated during the growth periods in five years.Since the CD increment between the first and the last measurement was 40% more than H increment, therefore, a size index (SI) model of the form [H. (CD2)] , which was constructed by graphical trial and error, was found to distinguish the best among the 6 treatments.The growth percentage of H, CD and SI between the first and the last measurement were recorded. The analysis of variance of the factors showed that there is no significant differences between the H , but differences between the CD and SI is significant at I and 5 percent of significant levels respectively.Comparison of CD and SI mean between the treatments indicated that the highest significant growth rate belonged to Ts (group A), and lowest belonged to T6 (group.C); T2 , T3 and T4 is grouped under AB , and Tt is belonged to group of BC. This result implies that in Kashan area, decreasing of density more than Ts is not suitable.The results indicated necessity of thinnig of Haloxylon plantation in Kashan for revival the vigor and increase of trees growth; it is also indicated the relative accuracy and correctness of the general equation for identifying the optimized population density of Haloxylon plantation. By using the results of this project, not only the vigor of trees will revived, but also, because of higher increment of CD growth, the goals of soil conservation will be gaind and prepare the direct access of domesticated to trimming of trees and also prepared a lots of fuel woods for nomadic people.

A study was conducted to determine the capabilities of the successive numerical Landsat data for assessment and monitoring of land use. Kashan plain with 7230 km2 of area, which is located in an arid zone of the central part of IRAN, selected as the site of investigation. It seemed to be a region prone to desertification processes. Two sorts of Landsat data: MSS (1976), TM (1998) and the supplementary information such as the soil and topography and land cover maps were collected.After preprocessing, the images were classified on the base of the field and subsidiary data. For Mss data, the Mss1, Mss2 and Mss3 were merged and showed the best correlation with field samples. In TM data, merging the TM3, Tm4 and Tm5 showed the best correlation. The classification performed by the minimum distance algorithm.Five land classes were distinguished with the overall precision of 65% and 75% for Mss and TM respectively. Detection of the changes between two maps showed a decrease of the area under range, bare and salt flats as much as 7.4%, 18.3% and 1.5% respectively, and an increase in cultivated and forest land use by the factor of 0.5% and 20.7% respectively. some referral to reliable documents determined the good agreement between the results and the real occurrence, except for the cultivated lands, that was significantly under estimated. It is concluded that thematic maps, which have released by image processing in a time series, could be compared and some general and useful results will be expected. Access to the same time field data of image acquisition time can promote the precision.