جستجوی مقالات مرتبط با کلیدواژه « similarity index » در نشریات گروه « آب و خاک »

Precipitation is a parameter related to climate and research on it is facing problems due to the lack of continuous data. Accurate planning and management of water resources depends on the availability of continuous and accurate precipitation data at meteorological stations. Hence, estimation of missing rainfall data is important in order to obtain more reliable results. Various imputation methods have been proposed and developed by researchers to estimate missing values in daily and monthly rainfall data. In most situations, spatial interpolation techniques such as normal ratio and inverse distance methods are used for estimating missing rainfall values at a particular target station based on the available rainfall values recorded at the neighboring stations. Moreover, these two methods are found to be very useful in the case where the neighboring stations are very close and highly correlated with the target stations. In this study, several modifications and improvements have been proposed to these methods in order to estimate the missing rainfall values at the target station using the information from the nearby stations. The methods have been tested with different percentages of missing rainfall values and also with a radius range of 75 km to 150 km in the catchment area of South Balochestan. The result indicate that the performance of these modified methods improved the estimation of missing rainfall values at the target station based on the similarity index (S-index), mean absolute error (MAE) and coefficient of correlation (R).

Surveying of soils along a toposequence is a primary key for identification of the spatial variability and development of soils that have been performed continuously at a certain direction. The main objective of this study is to assess both clay mineralogy and Sorensen similarity index to describe the genesis and development of soils in Fasarood region. In this context, three major physiographical units were recognized in this area (i.e., Colluvial fan, Piedmont plain and Flood plain). Moreover, nine presentative pedons were digged according to physiographical map units in the direction of NW to SE. Typic Endoaquepts and Oxyaquic Haplustepts are identified as dominant soils in the flood plain in which the redoximorphic and gleyzation processes have been occurred. Fluventic Haplustepts and Typic Calciustepts were recognized in the piedmont plain along with an irregular decrease in organic-carbon content as well as calcic horizon, caused by erosion and sedimentation, respectively. Typic Ustorthents is the major soil of Colluvial fan that have more than 60% coarse fragment in subsurface horizon. The results revealed that smectite, illite, cholorite, palygorskite and kaolinite were dominating minerals in colluvial fan, piedmont plain and flood plain. According to the similarity index, 0.5, 0.54, 0.55, 0.74 and 0.74 were achieved for order, suborder, great group, sub group, and family levels, respectively. Generally, similarity index could better describe soil variation in different slope position than clay mineralogy due to its quantity approach.

Geopedology is a systematic approach of geomorphic analysis for soil mapping which focuses the field operation mainly on sample area. The purpose of this study is to determine the credibility of generalization of the results of geopedological approach for similar landforms in the Borujen region, using diversity and similarity indices in a soil taxonomic hierarchical structure. After a primary interpretation of the study area on air photos (1:20000 scale), the largest delineation of Pi111 geomorphic unit was selected and 19 pedons with an approximate 125 m interval were excavated, described and sampled. The credibility of generalizing the results of the geopedological approach for the studied unit was tested by comparison with 15 pedons in a similar unit outside the sample area, named the validation area. Results showed that as the category decreases from order to soil family, the Shannon's diversity index increases in both the sample and validation areas. A significant difference at 95% confidence level was observed for pedodiversity mean values of two areas at family level. Soil diversity also remains high through the soil taxonomic hierarchy when we change the understanding level and consider the horizon/genetic diversity in both the sample and validation areas. Jaccard index and proportional similarity also indicated that up to subgroup level, the geopedological approach can be used for generalization of the similar geomorphic unit results and it does not have a good efficiency for lower soil taxonomic levels (family and series). Therefore, the use of landform phases and also phases of soil families and/or series for each of landform phases is recommended to increase the accuracy of geopedological results.

It is important to investigate the genetic diversity and evaluate symbiotic effectiveness of the indigenous rhizobial population. It helps understand the responses of indigenous isolates to different rhizobial inoculants. In spite of the importance of bacterial diversity, there are a few scientific reports about it in Iranian soils. Genetic diversity of 150 isolates of Sinorhizobium isolated from Hamadan soils was studied by using PCR / RFLP 16S-23S rDNA technique. The results showed that all isolates clustered in three different groups. Group (I) formed 122 isolates and they were quite similar to Sinorhizobium meliloti from viewpoint of genetic characteristics. Twenty five isolates were clustered in Group (II) and they belonged to Sinorhizobium medicae. Group (III) had two isolates and they were new species and quite different from the other groups. Shannon diversity index was different within eleven different land units (Medium gradient mountains, Level lands, Plateau, Foot slopes, Depressions and Composite land) and there was a correlation between Shannon index and some soil properties. Difference in Similarity index showed that Sinorhizobium groups in each land unit were different.