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.
