Soil science
Zeinab Barati; Hamidreza Owliaie; ebrahim adhami; Mahdi Najafi Ghiri
Abstract
Introduction
Zagros oak forest ecosystem is one of the largest forest ecosystems under destruction in Iran, which is of great importance in terms of water and soil protection. Moisture stress in recent years has caused the deterioration of these forests in a wide area. Iranian oak (Quercus brantii Lindlb.) ...
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Introduction
Zagros oak forest ecosystem is one of the largest forest ecosystems under destruction in Iran, which is of great importance in terms of water and soil protection. Moisture stress in recent years has caused the deterioration of these forests in a wide area. Iranian oak (Quercus brantii Lindlb.) is the main tree species forming these forests. Potassium (K) is considered to be the most important nutrient cation in terms of its quantity in plant tissue and its physiological and biochemical functions. Soil tests measure the quantity of a nutrient element that is extracted from soil by a particular extracting solution. Over the years, many different soil testing methods and extracting solutions were evaluated to identify a technique that provides the most reliable prediction of crop yield response to nutrient application. It was determined that some soil testing procedures are best suited for particular soil types and climatic regions. There has been no research on the general status of K in the soil of Zagros forests, related to oak trees. It is important to introduce appropriate K extractants for extracting available K in these soils. Therefore, this research was carried out to achieve the mentioned goals in some forest areas of this Province.
Materials and Methods
Ten forest areas with dominant coverage of oak trees were selected in different parts of Kohgiluyeh and Boyerahmad Province. The physiochemical properties of the soil samples were determined based on standard methods. Soil pH, texture, electrical conductivity, calcium carbonate equivalent (CCE), organic carbon, and cation exchange capacity (CEC) were identified. The content of K present in different forms was determined by standard methods. Solution K was measured in the saturated extract. Exchangeable K was determined by extraction of 5 g soil sample with 20 mL 1 M NH4OAc (pH 7) for 5 min. Nitric acid-extractable K was measured by extraction of 2.5 g soil sample with 30 mL of boiling 1.0 M HNO3 for 1 h. Non-exchangeable K was calculated as the difference between HNO3-extractable K and NH4OAc-extracteable K. Total K was determined following digestion of 0.5 g soil sample with 10 mL of 48% HF and 1 mL of aqua regia. The 12 extracting solutions were 1M NaCl, 2M NaCl, 0.01M CaCl2, Morgan, AB-DTPA, 1M NH4OAC, 0.25M NH4OAC, 1M MgOAC, 1M NaOAC, 2M HCl, 0.1M HNO3, and 0.025M H2SO4. The K content of leaf samples was determined in 1g of each sample. The samples were dried and then ashed in 450°C for 4 h. 2M HCl was used to digest the samples. Potassium was measured on all filtrated extracts using a Corning 405 flame photometer.
Results and Discussion
The soils are all calcareous (average of 42.9 and 44.7% CCE in surface and subsurface, respectively), with pH in range of 7.0-7.8. The textural classes were sandy clay loam, clay loam, and clay. The range of soluble potassium is between 4.8 to 32.7 with an average of 15.4 mgkg-1, exchangeable potassium from 65.1 to 364 (with an average of 247 mgkg-1, non-exchangeable potassium from 106 to 876 with an average of 515 mgkg-1, structural potassium was from 761 to 7322 with an average of 4026 mgkg-1and total potassium was from 1051 to 8110 with an average of 4493 mgkg-1. Soluble, exchangeable, non-exchangeable, and structural potassium were 0.49, 9.6, 12.1, and 77.8%, of the total K, respectively. Among the 12 tested methods, 1.0 mol/L NH4OAC extracted the highest amount of K (mean 229.3 mgkg-1, ranging 64.9-384.2 mgkg-1) and 1.0 mol/L MgOAC removed the lowest amount of K (mean 53.0 mgkg-1, ranged 19.1-88.0 mgkg-1). Correlation coefficients between K extracted by 12 extractants were positive and significant. Maximum correlation between K leaf and extracted soil K was noticed in AB-DTPA, 0.25M NH4OAC, 1M NaCl, and Morgan-Wolfe (r=0.60, 0.59, 0.56, and 0.55, respectively) and the minimum correlation was noticed in 2M HCl and 0.025 M H2SO4 (r= 0.41 and 0.44, respectively). The amount of potassium in oak leaves (in the range of 0.65% to 1.18%) showed a significant correlation with exchangeable potassium in the soil. The amount of potassium in 50% of the oak leaf samples was less than the critical limit (1%). As a general result, 1M NaCl and 0.25M NH4OAC extractants are recommended for extracting potassium, due to greater correlation, simplicity of the method, and economic considerations.
Conclusion
The results of this research showed that the range of the values of different forms of potassium in different parts of the province had a relatively large difference (6 and 8 times difference in exchangeable and non-exchangeable potassium values). The amounts of available forms of potassium in the western regions of the province with less rainfall were in most cases higher than the more humid eastern regions. The average amount of exchangeable potassium in 60% of the studied areas was less than the critical limit of 250 mgkg-1 soil. Also, the average amount of leaf K in 50 percent of the samples was less than the critical level. Considering the great importance of potassium in the nutrition of oak trees and dealing with environmental stress, especially the shortage of soil moisture, it is recommended to pay more attention to the conditions of this element in the soil of the forest areas of the province. Also, fertilizing and foliar spraying of trees in some forest areas should be considered.
Elham Yazadni; Vahid Hosseini; Kyumars Mohammadi Samani
Abstract
Introduction: Fires are natural processes in many ecosystems, constituting a natural, even vital, component of forests. Fire can change the soil properties depending on its severity. In semi-arid regions, the effects of fire are more vigorous in comparison with other regions. In these regions, forests ...
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Introduction: Fires are natural processes in many ecosystems, constituting a natural, even vital, component of forests. Fire can change the soil properties depending on its severity. In semi-arid regions, the effects of fire are more vigorous in comparison with other regions. In these regions, forests restoration is much more difficult especially in the summer when temperatures reach maximum levels and cause fires that reduce soil nutrients by burning organic matters and vegetation. Since the frequency of fire events in Zagros oak forests have been increasing in recent years, therefore, in this study, the chemical properties of soil investigated immediately after fire. Most wildfires in these forests are surface fires with low-to-moderate severity due to low forest density, great distances between trees and few forest floor plants.
Materials and Methods: The study area is located in Kurdistan Province, western Iran, around Marivan that has been burned in July 2017. One transect was installed on the contour line with 250 m length on the burnt slope. Eight Persian oak trees were selected at 30 meters interval. Two soil samples were collected in each tree from depth of 0-5 cm. The two positions of soil samples including: the first one was 50 cm far from the base trunk and the second one was on the edge of tree crown border. In the control area, eight Persian oak were selected in the adjacent area of burned area with same topographic and plant conditions and soil samples were collected same as burned area. Finally, soil organic carbon (SOC), Total nitrogen (TN), available phosphorus, potassium, calcium, magnesium, pH, and EC were analyzed.
Results and Discussion: The results of this study showed that fire has a significant effect on soil properties, so that organic carbon reduced and amount of available phosphorus, calcium, magnesium and potassium of soil increased in burned soil. Organic carbon decreased significantly (P<0.01) in the burned soil in comparison to control treatment near tree trunk while it did not have any significant difference in the border of tree crown. The lowest Organic carbon was 6.19% in burned soil near tree trunk and the highest 9.15% in unburned soil in the border of tree crown. Total nitrogen did not show any significant difference between all treatments. Phosphorus increased significantly after the fire in the burned soil by comparison with control in the both positions. The increase of available P in soil after fire can be due to added ash as the fire partially and completely combusted plant debris in the soil. The highest phosphorus was 130.08 mg/kg in the burned soil near tree trunk and the lowest was 65.67 mg/kg in soil of control area in the border of tree crown. Cations including Ca, Mg and K were significantly higher near tree trunks in burned soil compared with control area, while only Ca and Mg of soil showed significant differences in the border crown position. The pH of burned soil was 7.62 and 7.05 near tree trunk and border of tree crown, respectively, and it was 7.15 and 6.89 near tree trunk and border of tree crown, respectively, in control area. The EC of burned soil was 1.70 mS/cm and 0.66 mS/cm near tree trunk and border of tree crown, respectively and it was 0.44 mS/cm and 0.54 mS/cm near tree trunk and border of tree crown, respectively in control area. One-way ANOVA showed that two positions of soil samples had significant effect on all soil parameters except nitrogen. In the Zagros oak forests, there are a lot of flammable materials inside stands, which can lead to low and medium intensity fire .According to the results of this study, the amount of organic carbon of burned soil near tree trunk was less than the crown border because of high accumulation of flammable materials and high fire intensity.
Conclusion: In general, it can be concluded that wildfire causes significant changes in chemical properties of forest soils. Changes in the chemical properties of soil between burned soil and control area differed with movement from tree trunk to border of tree crown, so that the amounts of phosphorus, potassium, magnesium, calcium, acidity and electrical conductivity were reduced and the amount of carbon increased. Hence, it seems that properties of soil burned has diffiered by moving from the tree trunk to the border of crown trees probabley because of the differences in the amount of accumulated litter, consequently has an effect on the characteristics of the soil in different postions.
Fatemeh Mehmandoost; Hamidreza Owliaie; Ebrahim Adhami; Reza Naghiha
Abstract
Introduction: Land use changes such as conversion of forest to cultivated lands, significantly affect soil properties and modify soil forming processes. Land use changes can drastically affect the soil environment, which in turn markedly affect soils and soil processes. Human activities that are not ...
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Introduction: Land use changes such as conversion of forest to cultivated lands, significantly affect soil properties and modify soil forming processes. Land use changes can drastically affect the soil environment, which in turn markedly affect soils and soil processes. Human activities that are not associated with proper planning have undesirable effects on natural resources such as soil, including land use change. The results of the investigations in different parts of the world show that changing the use of natural ecosystems to managed ecosystems has destructive effects on soil properties. Cutting off the forest trees and converting pastures into agricultural lands will destroy or disrupt natural ecosystems and reduce the current or future production capacity of the soil. One of the important issues in the world is the destructive effects of agriculture on soil quality. These destructive effects can include a wide range of soil changes including physical properties such as soil compaction, soil water depletion, soil structure destruction and soil texture change, chemical properties such as accumulation of some elements such as N, P, K, and soil salinity, and soil biological properties such as soil microbial population and soil fauna activity changes, soil organic matter reduction and also effect on useful soil enzymes. Land use change from forest to agriculture does not necessarily lead to soil degradation. Land use changes and forest destruction in Yasouj region has increased in last decades. In this study, we investigated the effects of land use change on some soil characteristics in Servak plain, Yasouj region.
Materials and Methods: Servak region is located in 4 km south of Yasouj city. Three main land uses of dense forest, degraded forest, and dry farming were chosen to study the role of land use change on some soil properties.. The elevation of the region varies from 1833 to 1869 m above sea level. Five soil samples (0-20 cm) were taken from each land use. Samples from each land use were taken from almost similar elevation and slope to minimize the effect of topography. Soil samples were transferred to the laboratory, air dried and passed through a 2mm sieve. The chemical and biological analyses were carried out. The determination of soil organic carbon was carried out based on the Walkley-Black chromic acid wet oxidation method. Available K was extracted with 1N ammonium acetate at pH=7 and was determined by flame photometry. The Olsen method was used for the determination of available phosphorus. Total nitrogen was measured using the Kjeldahl method. Soil bacterial communities were counted using culture medium (Nutrient agar. The basal respiration rate was estimated by back-titration of the unreacted NaOH to determine CO2 evolved over 10 h. The substrate-induced respiration was measured by adding 2 ml of 1% glucose to soil samples over 6 h. Soil suspensions were prepared by 10-fold serial dilutions with 1g soil. Counting the soil fungal community was done using a culture medium (Potato dextrose agar) and was prepared by 10-fold serial dilutions. The activity of alkaline and acid phosphate enzymes was measured based on a colorimetric method using p-nitrophenol.
Results and Discussion: The land use change from a dense forest to dry farming has modified many chemical and biological soil properties. The results of analysis of variance and comparison of the means of data obtained from this study showed that as a result of land use change from dense forest to dry farming, Organic matter, total nitrogen, exchangeable potassium, basal and substrate-induced respiration, fungal community, acid phosphatase and alkaline phosphatase enzymes contents were decreased. Also, soil bacterial communities were increased at 1% level in dry farming land use. The amounts of phosphorus did not show any significant difference. In general, it can be concluded that following the degradation of the forest and land use change, the soil organic matter and relevant properties, especially biological indices, are more affected compared to the other properties. Soil organic matter plays a key role in ensuring agroecosystem productivity and the long-term conservation of soil resources.
Conclusions: Large-scale conversion of indigenous forests to cultivated land, driven by long-term agricultural development in the Servak region, has greatly affected the physicochemical and biological properties of the soils. Generally, the conversion of the natural ecosystem to agroecosystems decreased organic carbon content and relevant indices such as basal and substrate-induced respiration, fungal community, acid phosphatase and alkaline phosphatase enzymes contents in the top-soils at depth of 0 to 20 cm. The decrease of organic carbon in cropped farms could be attributed to the enhanced oxidation of soil organic C caused by cultivation. The results of this study showed that any management and type of land use that decreases soil capabilities can reduce soil quality and increase the susceptibility to degradation. So, in order to maintain soil quality, appropriate management practices should be done.
M. Hojjati; M. Asadiyan
Abstract
The presence of livestock within forest stands in north of Iran, as one of the main hindrances for optimal forest managing influence the productivity of that individual forest ecosystem in a waste area. The present study was conducted to investigate the effects of the long lasting presence of cattle ...
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The presence of livestock within forest stands in north of Iran, as one of the main hindrances for optimal forest managing influence the productivity of that individual forest ecosystem in a waste area. The present study was conducted to investigate the effects of the long lasting presence of cattle on soil properties in Hyrcanian forests. The investigated area was a part of Parchinak district, Mazandaran -Sari (in 4 Livestock husbandry campus and adjacent forest stands). Soil samples were collected from soil depths of 0-10 cm, 10-20 cm using coring method (8 cm diameter) in each site randomly (n=5) for determining soil physical, chemical and biological characteristic. Results showed that some soil physical characteristics (bulk density and moisture content) and many soil chemical properties (carbon and organic matter, nitrogen, phosphorus, potassium and calcium) were higher in husbandry area than the adjacent forest stand. Also, Net N mineralization and net nitrification have been observed only in Livestock campus. Our findings indicated a significant impact of livestock presence (input of a huge amount of cattle dung and high soil compaction) on forest soil.
