Soil Genesis and Classification
samaneh Tajik; shamsollah ayoubi; mohmmad mehdi darvisihi; hossein khademi
Abstract
Introduction Soil snails constitute an important part of the forest ecosystem and play an essential role in litter decomposition and soil calcium concentration. Snails are known as bioindicators because of narrow distribution, short lifetime, and high sensitivity (22, 24). The abundance and distribution ...
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Introduction Soil snails constitute an important part of the forest ecosystem and play an essential role in litter decomposition and soil calcium concentration. Snails are known as bioindicators because of narrow distribution, short lifetime, and high sensitivity (22, 24). The abundance and distribution of soil snails are dependent on different environmental conditions, such as precipitation, pH, soil calcium, and plant cover. Also, soil properties are mainly related to topographic parameters. Because ecosystem components have complex relationships, we need powerful models to find effective factors and spatial variations of the soil fauna (23). Linear Regression and random forest are popular and applicable models in soil science. Up to the present, no study has investigated the effect of soil parameters on snail abundance using linear regression and random forest. This study was performed to investigate the effect of soil properties and topographic parameters on the abundance of soil snails and their distribution in a part of forest area located in Bahramnia forest, an experimental site in Golestan Province, in the north of Iran. Materials and Methods This study was conducted in Shast Kalate (Bahramnia) forest, an experimental forest of Gorgan University of Agricultural Sciences and Natural Resources, located at the eastern Caspian region, north of Iran (36° 43′ 27″ N latitudes, 54°24′ 57″ E longitudes). 153 soil samples were collected from 0-10 cm; then soil snails were gathered and classified into the Gastropoda taxonomic class group. Soil properties, such as Soil particle size distribution (clay, silt, and sand), soil pH, electrical conductivity (EC), calcium carbonate equivalent (CCE), soil organic carbon (OC), total nitrogen (TN), and Soil microbial respiration (Resp), were measured via laboratory analysis. Also, digital elevation model and satellite images were used to determine the topographic parameters, such as Elevation, slope, slope aspect (Aspect), land surface temperature (land temp) wetness index (WI) and normalized difference vegetation index (NDVI). We used linear regression and nonlinear random forest models for investigating linear and nonlinear relationships between soil properties, topographic parameters, and the abundance of soil snails. Likewise, sensitive analysis was done to find the importance of the input parameters. Results and Discussion The PCA analysis showed that first and second components explain 38 and 21 percent of the variation. In the first component, EC, OC, TN, pH, and silt were the most variable, and in the second component CCE, Clay, OC, sand, and EC were the most important parameters. In both components, topographic parameters had no effect. The PCA graph showed that CCE, sand, and pH had the most correlation with snail abundance and EC, Resp, OC, and TN affected their abundance. The validation results of regression and random forest models showed that random forests have more accuracy (0.49) and low error (1.82). In addition, the sensitive analysis showed that CCE, pH, EC, OC, aspects, elevation, and land temp are the most important parameters on snail abundance. Different studies reported that pH and CCE are effective parameters on snail abundance (20, 17). Also, Ondina., et al. (27) reported that EC has an important effect on soil snail abundance. We hypothesize that topographic parameters affect soil snail nonlinearly and by affecting soil properties. Aspect is one of the topographic parameters that, via an effect on land temperature, land cover, and pH (8), has an important role in soil snails. In this way, elevation, by affecting pH, wetness, land temperature, OC, and TN, affects soil snail abundance (13). Land temperature is the other topographic parameter that is affected by aspect and elevation and had a significant effect on snail abundance by affecting OC and wetness (17). Conclusion Based on the results, nonlinear random forest model had more accuracy than linear regression in predicting snail abundance. Results showed that calcium carbonate equivalent, pH, EC, and organic carbon were the most effective soil priorities on snail abundance. There was no linear relation between soil properties and soil snails, but in the nonlinear model, we found their role. Aspect, elevation, and land temperature were the most effective parameters on snail abundance that probably affected soil properties, such as calcium carbonate and soil moisture.
Hossein Khademi; MohammadIsfahan Amirmohammadi
Abstract
Introduction: Potassium is a macroelement essential for plant growth and its importance in agriculture is well understood. Potassium in clay minerals is an important source of potassium for plants in many soils. No precise information is available on the impact of lime on potassium uptake by plants. ...
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Introduction: Potassium is a macroelement essential for plant growth and its importance in agriculture is well understood. Potassium in clay minerals is an important source of potassium for plants in many soils. No precise information is available on the impact of lime on potassium uptake by plants. Therefore, this study was conducted to investigate the effect of lime on K availability form phlogopite mineral in alfalfa rhizosphere. Materials and Methods: This study was conducted using a completely randomized design with factorial arrangement. Alfalfa was grown in media containing a mixture of quartz sand and phlogopite, different levels of lime (0, 2, 5, 12, 25%) and under two types of nutrient solutions (complete and potassium free) with three replications for a period of six months. Alfalfa shoots and roots were harvested and their potassium concentration was measured. The Data obtained from this experiment was statistically analyzed using SAS software and comparison of means was performed with the LSD test. Results and Discussion: The results showed that both shoot and root biomass was significantly affected by lime. Potassium concentration in shoot and root significantly reduced as the level of lime increased. The amount of soluble calcium increases as the level of lime in medium increases. This is mainly due to the hydrolysis of lime which also reduces the ratio of potassium to calcium and magnesium. This causes a great decline in potassium uptake by plant. Reduced uptake from the root surfaces of the plants in medium containing lime can also be caused by calcium oxalate precipitation on the root surfaces due to the abundance of calcium ions in the the root zone. Despite the fact that the amount of potassium supplied by different media has been the same, plants were not able to absorb equal quantity of potassium. Plants grown in lime-containing pots were indirectly deficient in potassium. Indirect exposure of plant to potassium deficiency means that, despite the high soil available K level, due to physiological reasons, potassium uptake by roots and its transfer to shoots is restricted. This is attributed to the negative effects of high concentration of magnesium and calcium compared to that of potassium in soil. Potassium concentration of plant roots was less than that of the shoots. This is mainly due to higher demand for K in shoots as compared to that in roots. Besides, the ability of plants to transfer potassium from root to shoot is very high. Shoot dry weight in plants with a complete nutrient solution major than the plants with a potassium free nutrient solution. Maximum dry weight was found in plants supplied with the complete nutrient solution with no lime added. In contrast, plants supplied with potassium free nutrient solution grown in pots containing 25% lime had the least dry weight. Lower root biomass could be caused by differences in physical characteristics of the root environment due to the presence of lime. Under potassium free nutrient solution, the amount of potassium uptake was significantly influenced by the amount of lime as such that the least potassium uptake of shoot and root occurred in treatments with %25 lime. The maximum K uptake (145.84 mg/pot) was obtained in plants treated with the complete nutrient solution. There was a highly significant correlation between the shoot dry weight and potassium uptake and also between the shoot dry weight and potassium concentration indicating that the plant shoot yield increases as the K concentration and uptake increase. Conclusion: The results obtained in this study clearly indicate that the presence of lime in the root zone could be a limiting factor for potassium uptake by plants. Although the concentration of potassium in plants was in the sufficient range defined by standards, but potassium uptake significantly reduced as the level of lime in medium increased. The decreasing trend was more obvious in the plants treated with potassium free nutrition solution. Plants treated with potassium free nutrient solution with no lime added to the medium have been able to take up a high amount of potassium. It appears that plant roots can influence on clay minerals to release potassium by the secretion of H+. But the presence of lime in the medium could release high level of Ca2+ ions into the solution, which, in turn, could reduce the release of potassium from phlogopite and its uptake by plants. In general, in media containing micaceous minerals as the only source of potassium, the presence of lime can have a negative impact on potassium release from minerals and its uptake by plants. Therefore, in calcareous soils with high potassium storage, the level of lime should be considered when potassium fertilizer is recommended. Besides, the amendment of highly calcareous soils by organic matters is suggested to improve the soil physical properties in order to have a better K uptake.
M. Karami; S. Ayoubi; H. Khademi
Soil Biology, Biochemistry and Biotechnology
M. Soliemanzadeh; H. Khademi; M. Sepehri
Volume 37, Issue 2 , March 2015, , Pages 59-72
Abstract
Microorganisms play an important role in providing nutrients for plants and also in soil development. This study was carried out to investigate the effect of two strains of Bacillus cereus on the release of potassium and iron from micaceous minerals. An experiment was set up with a completely randomized ...
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Microorganisms play an important role in providing nutrients for plants and also in soil development. This study was carried out to investigate the effect of two strains of Bacillus cereus on the release of potassium and iron from micaceous minerals. An experiment was set up with a completely randomized design and factorial arrangement with three replications. Treatments included two types of mineral (phlogopite and muscovite), two strains of bacteria (PTCC 1247 and PTCC 1665), control and eight time periods. The results indicated that released potassium and iron were highly dependent on the strain of bacterium and also the mineral type. Strain PTCC 1665 could release a higher amount of potassium as compared to PTCC 1247. The amount of released iron increased at the beginning of the experiment but decreased and then increased as time passed. In general, the amount of released iron from phlogopite was higher than that from muscovite.
