M. Hatefi; S. H. Sadeghi; R. Efanzadeh; M. Behzadfar
Abstract
Introduction: Freezing-Thawing (FT) cycle is one of the processes that affects runoff generation. It is therefore necessary to control its negative effects due to specific topographic and climatic situation of Iran. However, there is no documented research about positive effects of vegetation cover on ...
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Introduction: Freezing-Thawing (FT) cycle is one of the processes that affects runoff generation. It is therefore necessary to control its negative effects due to specific topographic and climatic situation of Iran. However, there is no documented research about positive effects of vegetation cover on controlling detrimental effects of (FT) cycle yet. The present study aimed to explain the affectability of runoff generation from vegetation cover in small experimental plots under FT cycle. Materials and Methods: In order to conduct this study, the soil was collected from Badranlou region located in 10 km west of Bojnourd in north Khorasan province. In this study, iron plots with Plexiglas walls with high ability to withstand lateral stresses and thermal insulation with dimensions of 0.5×0.5 m and a height of 0.3 m and a gradient of 20 percent in accordance with the general slope of the maternal area of the soil were used. The soil was passed from 4 mm sieve after air drying and then was placed in the prepared plots. Thirty plots were prepared for the entire selected plants species and transferred to the greenhouse and three species of A. trichophorum, M. sativa and L. prenne were planted. The species were then allowed until completing the main part of the phenological stages to maximally mimic the natural conditions governing the region. A FT cycle including three days of freezing and two consequent days of thawing and rainfall simulation with 72 mm h-1 in 30 min in three plots with vegetation cover was formulated similar to the study area situation. The entire experiments were conducted in three replicates. Similar control plots were also arranged for comparison purposes. Runoff components were measured in two minutes (three-time steps after runoff), three minutes (three second steps), five minutes until the end of the incident (three last steps) and five minutes after the end of the event. After measuring and recording the amount of runoff generation at the end of each rain event, the total amount of runoff generation in different treatments of rangeland species under FT cycle was recorded. Results and Discussion: The result showed that the treated plots of M. sativa, A. trichophorum, and L. prenne significantly (p < 0.05) reduced runoff generation by 0.97, 0.72 and 0.32 times compared with control treatments, respectively. The different effects of L. prenne and A. trichophorum species on runoff generation under the freeze-thaw cycles was confirmed. However, M. sativa did not have significant effect in reducing the amount of runoff generation compared with the control. The effect of FT cycle due to performance of ice lenses and formation of active melting layer in the soil surface was controlled owing to the presence of litter and adhesion of the surface layer of soil under treatments of M.sativa, A.trichophorum and L.Prenne. Besides, according to the measurement unlike the M. sativa, the main parts of root in two gramineae species of A. trichophorum and L. prenne were distributed superficially and caused more cohesion and improvement in soil aggregation. The runoff generation reduced in the presence of L. prenne more than the other two species. Based on the different studies, the percentage of fiber in gramineae species is more than broad-leaved species. Therefore, the presence of more fiber in A. trichophorum and L. prenne litters and subsequently their more resilience can be an effective factor in the relative reduction of runoff generation. In addition, the results of the study showed that the presence of vegetation on the soil surface increased the accumulation of fine grains on the soil surface and, if the soil remains intact, increases the stability of the soil structure. The accumulation of fine crops in the soil creates a large network of small roots in the soil and the soil particles become more adhesive. Due to the presence of the small roots in L. prenne species, there is the soil greater adhesion and further reduction of runoff in the presence of this plant. Conclusion: The results of this study verified that plant cultivation can have significant effects on reducing runoff. In this regard, Lolium prenne had maximum benefit on reduction of runoff and soil loss induced by FT cycle due to better formation of superficial root system.
H. Taefi; Reza Erfanzadeh; M. Abedi
Abstract
Introduction: Amongst different habitats, fire is an ecological factor and determinant that affects many physico-chemical soil factors. In addition, among natural disturbances, fire plays an important role in plant diversity conservation and in some areas around the world, the presence of some plant ...
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Introduction: Amongst different habitats, fire is an ecological factor and determinant that affects many physico-chemical soil factors. In addition, among natural disturbances, fire plays an important role in plant diversity conservation and in some areas around the world, the presence of some plant species depends on natural fire. The extension of fire influences on soil is related to the fire severity. In fact, fire severity encompasses of two characteristics: extension and time of burning. On the other hand, fire extension and burning time are affected by humidity, air temperature, wind speed, topographical characteristics. Despite high frequency of fire in natural habitats and high level of fire effectiveness on soil parameters, study of fire impacts on soil characteristics were rarely reported in Iran. In addition, most previous studies were conducted in forest habitats, ignoring the severity of fire on soil.
Materials and Methods: In order to investigate the effect of fire severity on some soil physico-chemical characteristics, Yeylagh Dasht area (rangeland habitats) was selected in southern-east of national Golestan Park with three different plant covers, viz. grass, shrub and cushion. Many fires occurring have been reported in this park in each year. For the current study, we tried to select the habitats in which the fire was occurred at least one year before. A control area without burning with similar ecological parameters was also selected adjacent to the burnt area. in fact unburnt area was isolated by a road from burnt area, unable to extend the fire into unburnt area due to the road. Fire had been occurred in the burnt area in September, 2014. Soil samples with 15 replications in burnt area and 15 replications in unburnt were collected within a depth of 0-5 cm and then transported to the soil laboratory to measure some qualitative soil characteristics i.e. soil organic matter (SOM), particulate organic matter (POM), total nitrogen (TN) and aggregate stability (AS). All statistical analyses were done by R software. Before ANOVAs (one and two-ways) and unpaired t-test, we tested data for normal distribution by Shapiro-Wilk test and homogeneity of variance by Flinger Test.
Results and Discussion: The results of two-way ANOVA showed that the main effect of fire on soil was not significant while the main effect of fire severity and the interaction of fire and fire severity on SOM and POM were significant (Table 1). The results of one-way ANOVA showed that the content of SOM was significantly different between three different treatments in unburnt area (control area) while there were no significant differences between the three treatments (three fire severities) in burning areas. Therefore it can be discussed that the kind of vegetation (grassland, shrub or cushion) could affect SOM while the fire increased the spatial homogeneity of SOM. The same pattern of SOM was occurred for POM in burnt and unburnt areas. However, the results of unpaired t-test showed that POM was drastically decreased after high and intermediate fire severities. Aggregate stability and POM were significantly decreased in the intermediate and high severities of fire (cushion and shrub plant cover). Fire in the intermediate and high severities increased TN (Figure 1). We concluded that fire occurring by plants might be decreased POM and AS significantly. In addition, mineralization probable increased TN after burning. We also compared soil characteristics among three fire severities in burnt area and in unburnt area separately.
Conclusion: This study showed that the variation of soil characteristic was mainly affected by different fire severities. Therefore, we emphasized that fire severity should be considered in the studies of the impact of fire on soil in different habitats. Fire can decrease the spatial heterogeneity of soil parameters among different sites. We showed that soil POM is a characteristic more sensitive than total SOM in confronting with fire.
R. Erfanzadeh; J. Motamedi
Abstract
In this study, Khanghag Sorkh watershed was selected to study on the effect of vegetation and slope changes on soil carbon sequestration. Therefore, three vegetation communities were recognized and soil sampling was done within 0-30 cm depth in two slopes (10-30% and 30-50%). Soil samples were analyzed ...
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In this study, Khanghag Sorkh watershed was selected to study on the effect of vegetation and slope changes on soil carbon sequestration. Therefore, three vegetation communities were recognized and soil sampling was done within 0-30 cm depth in two slopes (10-30% and 30-50%). Soil samples were analyzed to measure carbon sequestration rate and some of other physico-chemical characteristics. The results showed that the soil of Pteropyrum aucheri-Astragalus microcephulus, Astragalus microcephulus-Acanthophyllum microcephalum and Pteropyrum aucheri-Prangus uloptera communities has sequestrated 96.10, 73.84 and 52.85 ton carbon per hectare, respectively. The slope of 10-30% and 30-50% has sequestrated 96.11 and 126.68 ton carbon per hectare, respectively. In general, the slope of 10-30% had higher carbon sequestration compared with the slope of 30-50% with the exception of Pteropyrum aucheri-Astragalus microcephulus community. Our estimations revealed That the soil of Pteropyrum aucheri-Astragalus microcephulus, Astragalus microcephulus-Acanthophyllum microcephalum and Pteropyrum aucheri-Prangus uloptera had ca. 19220$ , 14768 and 10570$ economical values per hectare in respect to carbon fixation, , respectively. An investigation on other edaphic factors showed that most of soil factors were also significantly different between vegetation communities and slope classes (P