Topographic and edaphic variables are the main ecological factor determining species spatial variability on mountainous forests. A field study was performed in central Alborz to investigate how the edaphic and topogra...Topographic and edaphic variables are the main ecological factor determining species spatial variability on mountainous forests. A field study was performed in central Alborz to investigate how the edaphic and topographic parameters can affect the tree and shrub communities. Initially, 27 forest stands were identified and the homogeneous units were separated regarding physiognomy. In each single homogeneous unit, one random sample plot （1000 m^2） and totally 43 plots were established. In each plot, the presence and abundance of all trees and shrubs were recorded and four soil samples were taken from depths of 0-5 and 5-20 cm. Concerning classification results, eight different forest communities were identified. The lowest and highest soil pH values were observed in Malus orientalis and pistacia-Amygdalus communities, respectively. The water saturation percent of pure- and mixed Juniperus excelsa and Rhus coriaria was the highest amongst communities. The clay content was the highest in pure J.excelsa. The 0-5 organic matter and Nitrogen content in mixed J. excelsa were significantly higher than pure J. excelsa and other communities. The CCA （Canonical Correspondence Analysis） altitude, precipitation, pH, results indicated that the EC, SP, clay and CaCO3 are the most important factors determine the distribution of trees and shrub in central Alborz.展开更多
This study was conducted in Juniperus excels a stands on the southern slopes of Iran’s Alborz Mountains,to determine the effects of fire and seasonal variations on soil physicochemical properties and enzyme activitie...This study was conducted in Juniperus excels a stands on the southern slopes of Iran’s Alborz Mountains,to determine the effects of fire and seasonal variations on soil physicochemical properties and enzyme activities.A total of 64 composite soil s amples were randomly collected in the spring and fall from two burned and unburned sites at depths of 0-10 and 10-20 cm.The results of a two-way ANOVA analysis indicate that fire increased the organic carbon(OC),total nitrogen(TN),and available phosphorus(P_(ava)) contents of the soil by 16%,59%,and 53%,respectively.Similarly,when burned sites were compared to unburned sites,the activities of acid phosphatase(ACP) and urease enzymes increased by 73% and 12%,respectively.Nevertheless,fire did not affect soil texture,bulk density(BD),pH,electric conductivity(EC),exchangeable potassium(Kexc),or the activities of alkaline phosphatase(ALP) and dehydrogenase.According to two-way ANOVA results,OC,TN,P_(ava),K_(exc),and EC values were significantly higher in the fall,whereas pH and ALP values were significantly higher in the spring.Additionally,phosphorous and dehydrogenase activity were significantly different in selected soil factors at 0-10 and10-20 cm depths.The interaction of fire,season,and soil depth were significant for phosphorous and urease.Moreover,the activity of ALP correlated well with pH(r=0.68),P(r=-0.74),OC(r=-0.53),and TN(r=-0.37),whereas the activity of ACP correlated significantly with OC(r=0.64) and TN(r=0.71).Two years after the fire,soil properties in J.excels a stands had either improved or remained unaffected,returning to pre-fire levels.Additionally,soil chemical properties varied significantly across sampling seasons,which should be considered when comparing and interpreting soil data in future research.展开更多
Khojir national park is one of the oldest protected areas in Iran that is greatly considerable in terms of biodiversity and ecological values.Pistachio(Pistacia atlantica Desf.) communities,which create some woodland ...Khojir national park is one of the oldest protected areas in Iran that is greatly considerable in terms of biodiversity and ecological values.Pistachio(Pistacia atlantica Desf.) communities,which create some woodland in this park,are unique because they grow tolerantly in a dry land,in the vicinity of Tehran capital.This research is about some ecological properties of Pistachio woodlands.The dominant community of the area is Pistacia-Amygdalus lycioides.The density of Pistacia is 86 per hectare.The density of Pistachio trees was greater in the higher elevation than in the lower one.In addition,the collar diameter and the height of trees in the higher class were less.The average density of Pistacia in plots in northern slopes was significantly more than southern slopes(at 5% level),but the average collar diameter of them were more on the southern aspect.The distribution,diameter and height of pistachio trees were not significantly related to the percentage of slope.Among the soil variables,the saturated water percentage(SP),N(total nitrogen) and texture of soil were effective factors which played significant role in ordination of plots containing pistachio.Considering the important role of P.atlantica forest stands in soil and water conservation in Iran,we should attach more importance to their protection and conservation,as well as activities such as road and dam construction,and garden establishment in such unique ecosystems.展开更多
文摘Topographic and edaphic variables are the main ecological factor determining species spatial variability on mountainous forests. A field study was performed in central Alborz to investigate how the edaphic and topographic parameters can affect the tree and shrub communities. Initially, 27 forest stands were identified and the homogeneous units were separated regarding physiognomy. In each single homogeneous unit, one random sample plot （1000 m^2） and totally 43 plots were established. In each plot, the presence and abundance of all trees and shrubs were recorded and four soil samples were taken from depths of 0-5 and 5-20 cm. Concerning classification results, eight different forest communities were identified. The lowest and highest soil pH values were observed in Malus orientalis and pistacia-Amygdalus communities, respectively. The water saturation percent of pure- and mixed Juniperus excelsa and Rhus coriaria was the highest amongst communities. The clay content was the highest in pure J.excelsa. The 0-5 organic matter and Nitrogen content in mixed J. excelsa were significantly higher than pure J. excelsa and other communities. The CCA （Canonical Correspondence Analysis） altitude, precipitation, pH, results indicated that the EC, SP, clay and CaCO3 are the most important factors determine the distribution of trees and shrub in central Alborz.
文摘This study was conducted in Juniperus excels a stands on the southern slopes of Iran’s Alborz Mountains,to determine the effects of fire and seasonal variations on soil physicochemical properties and enzyme activities.A total of 64 composite soil s amples were randomly collected in the spring and fall from two burned and unburned sites at depths of 0-10 and 10-20 cm.The results of a two-way ANOVA analysis indicate that fire increased the organic carbon(OC),total nitrogen(TN),and available phosphorus(P_(ava)) contents of the soil by 16%,59%,and 53%,respectively.Similarly,when burned sites were compared to unburned sites,the activities of acid phosphatase(ACP) and urease enzymes increased by 73% and 12%,respectively.Nevertheless,fire did not affect soil texture,bulk density(BD),pH,electric conductivity(EC),exchangeable potassium(Kexc),or the activities of alkaline phosphatase(ALP) and dehydrogenase.According to two-way ANOVA results,OC,TN,P_(ava),K_(exc),and EC values were significantly higher in the fall,whereas pH and ALP values were significantly higher in the spring.Additionally,phosphorous and dehydrogenase activity were significantly different in selected soil factors at 0-10 and10-20 cm depths.The interaction of fire,season,and soil depth were significant for phosphorous and urease.Moreover,the activity of ALP correlated well with pH(r=0.68),P(r=-0.74),OC(r=-0.53),and TN(r=-0.37),whereas the activity of ACP correlated significantly with OC(r=0.64) and TN(r=0.71).Two years after the fire,soil properties in J.excels a stands had either improved or remained unaffected,returning to pre-fire levels.Additionally,soil chemical properties varied significantly across sampling seasons,which should be considered when comparing and interpreting soil data in future research.
文摘Khojir national park is one of the oldest protected areas in Iran that is greatly considerable in terms of biodiversity and ecological values.Pistachio(Pistacia atlantica Desf.) communities,which create some woodland in this park,are unique because they grow tolerantly in a dry land,in the vicinity of Tehran capital.This research is about some ecological properties of Pistachio woodlands.The dominant community of the area is Pistacia-Amygdalus lycioides.The density of Pistacia is 86 per hectare.The density of Pistachio trees was greater in the higher elevation than in the lower one.In addition,the collar diameter and the height of trees in the higher class were less.The average density of Pistacia in plots in northern slopes was significantly more than southern slopes(at 5% level),but the average collar diameter of them were more on the southern aspect.The distribution,diameter and height of pistachio trees were not significantly related to the percentage of slope.Among the soil variables,the saturated water percentage(SP),N(total nitrogen) and texture of soil were effective factors which played significant role in ordination of plots containing pistachio.Considering the important role of P.atlantica forest stands in soil and water conservation in Iran,we should attach more importance to their protection and conservation,as well as activities such as road and dam construction,and garden establishment in such unique ecosystems.
