Evidence has shown that drought-induced crown dieback has significant interaction with soilplant ... more Evidence has shown that drought-induced crown dieback has significant interaction with soilplant water and nutrients relationships, but there isn't sufficient knowledge of the water and nutrients connections in declining Persian oak (Quercus brantii) trees. To investigate the relationships between crown dieback and leaf nutrients concentrations, leaf water content, soil nutrients concentrations and soil moisture, one of the dieback affected stands was selected. This stand was located in Shalam forested area in northern Ilam province, west of Iran. Persian oak trees were evaluated using a crown dieback classification and divided into four classes with four replicates based on the severity of crown dieback. Sampling from leaves of trees and soil was implemented randomly in four sides of tree crown in August. Trees with moderate to severe declining showed reduced leaf water content (WC) and reduced relative leaf water content (RWC). Leaf N and P concentration of declining trees was significantly (p-value <0.05) more than that of healthy trees. The leaf K concentration of declining trees was significantly (p-value <0.10) more than that of the healthy. The leaf N:P amounts of oak trees was statistically different among crown dieback classes. But no significant differences was observed between the healthy and declining trees in terms of soil N, P, K, Ca and Mg concentrations and soil moisture. It was concluded that drought has effects on the nutrients status in the leaves of Persian oak trees and their changing in the declining trees is for resistance to drought condition, improving water use efficiency and possibly performance of vital activities.
Drought-induced crown dieback depends on plant nutrient status. This research examined the leaves... more Drought-induced crown dieback depends on plant nutrient status. This research examined the leaves and roots nutrients of Persian oak trees (Quercus brantii Lindl.) under the effects of drought and tree decline. The leaves and roots of oak trees were sampled randomly on the four main sides of their crown to analyze the N, P, K, Ca, and Mg. In healthy and declining trees, the N, P, and K content in the leaves was higher than in the roots, while the Ca content in the leaves was lower than in roots. The N and P in the roots of healthy trees had decreasing temporal changes, but these elements did not have significant temporal changes in the roots of declining trees. Leaf P showed decreasing temporal changes. The temporal decrease of root N and P and leaf P showed a negative effect of drought on Persian oak trees by reducing their ability to absorb water and nutrients and transfer them to their leaves. The higher concentration of elements in the leaves of oak trees, in addition to showing the decrease in the absorption of elements by the roots from the soil, can indicate a protective mechanism of oak trees against drought stress.
Leafy mistletoes are semi-parasitic plants that have negative impacts on their hosts, but there i... more Leafy mistletoes are semi-parasitic plants that have negative impacts on their hosts, but there is inadequate knowledge about the impacts of Loranthus europaeus Jacq. on Persian oak trees (Quercus brantii Lindl.). This study examined the impacts of L. europaeus Jacq. on morphological and physiological characteristics of Persian oak tree leaves in western Iran. A forested area infested with L. europaeus Jacq. was selected to study. Five infected and five healthy Persian oak trees were selected. Leaf samples were collected from the southern side of infected and healthy tree crowns to quantify and compare the leaf area, leaf weight, and concentrations of leaf minerals. The area and weight of leaves and the amount of leaf K, P, and Ca in healthy trees were statistically more than in infected trees. Leaf N, Mg, Mn, Zn, and Fe contents were not significantly different between healthy and infected trees. The higher amount of leaf area and weight in healthy trees suggested that they had a b...
This research was carried out to compare two oak (Quercus brantii) stands (healthy and affected b... more This research was carried out to compare two oak (Quercus brantii) stands (healthy and affected by oak decline) in respect to characteristics of competitive environments in Shalam Forest, located at north of Ilam province of Iran. The study area was divided into 20 topographical homogeneous units, using GIS method. Considering the dieback rate at the units, five homogeneous units with different dieback rates were selected. After that, six transects (100 m. length) were allocated at each of the units and five points were laid on them at 25 m. intervals, using the systematic random statistical method. The two closest dead and alive trees to the points were identified. Finally, some characteristics of the focal trees around the two selected trees were measured and recorded, including their distance to the focal trees, species, crown diameter and total height. Competitive condition of the focal alive and dead trees in the stands was computed by Hegyi index. The data were analyzed, using ANOVA and t-test statistical methods. Results showed that there was significant difference between the homogeneous units in respect to the tree's competition rate. According to the t-test results, competition rate of the dry and almost dry trees was greater than that of the healthy or less dried trees. The lowest and the greatest tree competition rates were found in the homogenous units with lowest and greatest crown dieback rate, respectively. The focal dieback trees had lower crown diameter, total height and distance to the neighboring trees in comparison to the focal healthy trees, whereas the neighboring trees to the focal dieback trees had greater crown diameter, total height and density. It might be concluded that tree's competition rate has direct correlation with stand or tree groups density which varies, depends on available soil moisture content and competitive stress at different parts of the stand. The results of this research can highlight importance of tree competition, dependant on stand density as a predisposing factor [...]
Intraspecific variability in morphological and ecophysiological leaf traits might be theorized to... more Intraspecific variability in morphological and ecophysiological leaf traits might be theorized to be present in declining populations, since they seem to be exposed to stress and plasticity could be advantageous. Here we focused on declining Persian oaks (Quercus brantii Lindl. var. persica (Jaub and Spach) Zohary) in the Zagros Mountains of western Iran, representing the most important tree species of this region. We selected trees with contrasting crown dieback, from healthy to severely defoliated, to investigate the relationships between canopy dieback and leaf morphology, water content and pigments. We also measured esterase and peroxidase, as enzymatic antioxidants and indicators of contrasting genotypes. Trees showing moderate to severe defoliation showed higher leaf mass area (LMA), reduced relative water content (RWC), and lower stomatal density (SD). Increasing LMA indicates a more sclerophyllic structure, according to drier conditions. We did not find significant differences in leaf pigments (chlorophyll a and b, and carotenoids) among crown dieback classes, suggesting that Persian oak trees are able to maintain accurate photochemical efficiency, while reduced RWC and SD suggest hydraulic limitations. Our results do not provide a consistent pattern as regards enzymatic antioxidant defense in Persian oak. Morphological leaf traits would be important drivers of future adaptive evolution in Persian oak, leading to smaller and thicker leaves, which have fitness benefits in dry environments. Nonetheless, drought responses may be critically affecting carbon uptake, as photosynthetic compounds are less effectively used in leaves with higher sclerophylly.
Today, Zagros reforestation is more than ever felt due to human presence and its destructive acti... more Today, Zagros reforestation is more than ever felt due to human presence and its destructive activities. To do this requires observing the scientific principles of silviculture. Of essential restoration activities in these forests can be mentioned the seed planting of indigenous species within their range of development. In this regard, the present research was conducted with the aim of investigate the germination and emergence status of Quercus persica, Pistacia atlantica and Acer cineracens seeds planted in Dalab Ilam forests in 2018. For this, three sites on the northern slope and approximately the same height of 1380 to 1410 meters above sea level were selected. In each site, three trees were considered for each of Q. persica, P. atlantica and A. cineracens species. Under each tree, three holes were drilled between the trunk and the end of the crown for each crown side, and a total of 12 holes. In drilled holes under the trees, the corresponding seeds were planted in the winter 2017. The results of the sampling in the spring 2018 showed that the seeds of Q. persica had the highest emergence rates (22%). The seeds of P. atlantica gained the second rank in terms of germination and emergence (18%). The seeds of A. cineracens had the lowest amount of emergence (0.3%) and the number of emerged seedlings was rare. The highest occurrence rate of Q. persica seedlings was on the northern side of tree crown (32%) and in for P. atlantica was on the southern (32%) and western (30%) sides of the tree crown. The highest rate of seedling emergence of Q. persica (48%) and P. atlantica (51%) was found at nearest distance to tree trunk. Despite planting the seeds of these three tree species in the same conditions in terms of topography, position under the crown and distance from tree trunk, similar results were not obtained which the reason of this can be attributed to their seed characteristics such as seed size and seed vigor.
The aim of the study was to investigate the effects of tree mortality on structural characteristi... more The aim of the study was to investigate the effects of tree mortality on structural characteristics of an oak stand named Shalam Forest, with 670 ha area, located 10 km south east Ilam city of I.R. Iran. The structural characteristics consisted of stand density, basal area, canopy cover density, species composition, silvicultural form and distribution pattern of dead trees density and basal area and different diameter classes. The studied area was divided to 20 homogeneous topographical units in which three circular plots with 1000m2 area were located to measure diameter at breast height (dbh), minimum and maximum diameter of tree's crown, percentage of dried crown, trees origin and silvicultural form of each species separately and record the data. The results showed that the trees and shrubs density was reduced at 15.7%, in which 97.65% belonged to Quercus brantii. Basal area reduced at 14.23%, in which 95.29% belonged to Q. brantii. Mortality was found at most of the diameter ...
This research carried out to study the relationship between tree competition and Persian oak (Que... more This research carried out to study the relationship between tree competition and Persian oak (Quercus brantii) dieback and mortality in different site conditions and stand structures in Shalam oak forest which located in north of Ilam province, western Iran. We divided study area into 20 homogenize units based on topography using GIS. Then we established 6 transect with a length of 100 m in each landform unit and determined 5 random points with interval of 25m on each transect and marked the closest live and dead tree to them. To each focal tree we measured the distance, species, Diameter at breast height, crown diameter, height and crown dieback percent of neighbor trees. Competitive condition of focal live and dead trees was computed by Hegyi index. The results showed that the amount of tree competition varied among units. Also the results of correlation and Principal component analysis (PCA) showed the significant positive and direct relationship between competition and tree dieback amount. The lowest and highest amount of tree dieback was found respectively in units those had the lowest and highest amount of tree competition. Also the amount of tree competition had inverse relationship with crown diameter of focal tree and direct relationship with crown diameter and height of neighbor trees and crown dieback percent of focal trees.
Aim of study: Drought and stand structure are major and interconnected drivers of forest dynamics... more Aim of study: Drought and stand structure are major and interconnected drivers of forest dynamics. Water shortage and tree-to-tree competition may interact under the current climate change scenario, increasing tree mortality. In this study, we aimed to investigate climate trends, site and stand structure effects on tree mortality, with the main hypothesis that drought-induced mortality is higher as competition increases.Area of study: Persian oak forests from Zagros Range, western Iran.Material and Methods: We split the study area into 20 topographical units (TUs), based on aspect, slope and elevation. In each TU, three 0.1 ha plots were established to quantify site and stand characteristics, namely the diameter of all trees and shrubs, stand density and basal area, canopy dieback and mortality. In addition, soil profiles were analyzed to obtain physical and chemical soil properties. Six transects 100 m length were established per TU to measure tree-to-tree competition for alive and...
Evidence has shown that drought-induced crown dieback has significant interaction with soilplant ... more Evidence has shown that drought-induced crown dieback has significant interaction with soilplant water and nutrients relationships, but there isn't sufficient knowledge of the water and nutrients connections in declining Persian oak (Quercus brantii) trees. To investigate the relationships between crown dieback and leaf nutrients concentrations, leaf water content, soil nutrients concentrations and soil moisture, one of the dieback affected stands was selected. This stand was located in Shalam forested area in northern Ilam province, west of Iran. Persian oak trees were evaluated using a crown dieback classification and divided into four classes with four replicates based on the severity of crown dieback. Sampling from leaves of trees and soil was implemented randomly in four sides of tree crown in August. Trees with moderate to severe declining showed reduced leaf water content (WC) and reduced relative leaf water content (RWC). Leaf N and P concentration of declining trees was significantly (p-value <0.05) more than that of healthy trees. The leaf K concentration of declining trees was significantly (p-value <0.10) more than that of the healthy. The leaf N:P amounts of oak trees was statistically different among crown dieback classes. But no significant differences was observed between the healthy and declining trees in terms of soil N, P, K, Ca and Mg concentrations and soil moisture. It was concluded that drought has effects on the nutrients status in the leaves of Persian oak trees and their changing in the declining trees is for resistance to drought condition, improving water use efficiency and possibly performance of vital activities.
Drought-induced crown dieback depends on plant nutrient status. This research examined the leaves... more Drought-induced crown dieback depends on plant nutrient status. This research examined the leaves and roots nutrients of Persian oak trees (Quercus brantii Lindl.) under the effects of drought and tree decline. The leaves and roots of oak trees were sampled randomly on the four main sides of their crown to analyze the N, P, K, Ca, and Mg. In healthy and declining trees, the N, P, and K content in the leaves was higher than in the roots, while the Ca content in the leaves was lower than in roots. The N and P in the roots of healthy trees had decreasing temporal changes, but these elements did not have significant temporal changes in the roots of declining trees. Leaf P showed decreasing temporal changes. The temporal decrease of root N and P and leaf P showed a negative effect of drought on Persian oak trees by reducing their ability to absorb water and nutrients and transfer them to their leaves. The higher concentration of elements in the leaves of oak trees, in addition to showing the decrease in the absorption of elements by the roots from the soil, can indicate a protective mechanism of oak trees against drought stress.
Leafy mistletoes are semi-parasitic plants that have negative impacts on their hosts, but there i... more Leafy mistletoes are semi-parasitic plants that have negative impacts on their hosts, but there is inadequate knowledge about the impacts of Loranthus europaeus Jacq. on Persian oak trees (Quercus brantii Lindl.). This study examined the impacts of L. europaeus Jacq. on morphological and physiological characteristics of Persian oak tree leaves in western Iran. A forested area infested with L. europaeus Jacq. was selected to study. Five infected and five healthy Persian oak trees were selected. Leaf samples were collected from the southern side of infected and healthy tree crowns to quantify and compare the leaf area, leaf weight, and concentrations of leaf minerals. The area and weight of leaves and the amount of leaf K, P, and Ca in healthy trees were statistically more than in infected trees. Leaf N, Mg, Mn, Zn, and Fe contents were not significantly different between healthy and infected trees. The higher amount of leaf area and weight in healthy trees suggested that they had a b...
This research was carried out to compare two oak (Quercus brantii) stands (healthy and affected b... more This research was carried out to compare two oak (Quercus brantii) stands (healthy and affected by oak decline) in respect to characteristics of competitive environments in Shalam Forest, located at north of Ilam province of Iran. The study area was divided into 20 topographical homogeneous units, using GIS method. Considering the dieback rate at the units, five homogeneous units with different dieback rates were selected. After that, six transects (100 m. length) were allocated at each of the units and five points were laid on them at 25 m. intervals, using the systematic random statistical method. The two closest dead and alive trees to the points were identified. Finally, some characteristics of the focal trees around the two selected trees were measured and recorded, including their distance to the focal trees, species, crown diameter and total height. Competitive condition of the focal alive and dead trees in the stands was computed by Hegyi index. The data were analyzed, using ANOVA and t-test statistical methods. Results showed that there was significant difference between the homogeneous units in respect to the tree's competition rate. According to the t-test results, competition rate of the dry and almost dry trees was greater than that of the healthy or less dried trees. The lowest and the greatest tree competition rates were found in the homogenous units with lowest and greatest crown dieback rate, respectively. The focal dieback trees had lower crown diameter, total height and distance to the neighboring trees in comparison to the focal healthy trees, whereas the neighboring trees to the focal dieback trees had greater crown diameter, total height and density. It might be concluded that tree's competition rate has direct correlation with stand or tree groups density which varies, depends on available soil moisture content and competitive stress at different parts of the stand. The results of this research can highlight importance of tree competition, dependant on stand density as a predisposing factor [...]
Intraspecific variability in morphological and ecophysiological leaf traits might be theorized to... more Intraspecific variability in morphological and ecophysiological leaf traits might be theorized to be present in declining populations, since they seem to be exposed to stress and plasticity could be advantageous. Here we focused on declining Persian oaks (Quercus brantii Lindl. var. persica (Jaub and Spach) Zohary) in the Zagros Mountains of western Iran, representing the most important tree species of this region. We selected trees with contrasting crown dieback, from healthy to severely defoliated, to investigate the relationships between canopy dieback and leaf morphology, water content and pigments. We also measured esterase and peroxidase, as enzymatic antioxidants and indicators of contrasting genotypes. Trees showing moderate to severe defoliation showed higher leaf mass area (LMA), reduced relative water content (RWC), and lower stomatal density (SD). Increasing LMA indicates a more sclerophyllic structure, according to drier conditions. We did not find significant differences in leaf pigments (chlorophyll a and b, and carotenoids) among crown dieback classes, suggesting that Persian oak trees are able to maintain accurate photochemical efficiency, while reduced RWC and SD suggest hydraulic limitations. Our results do not provide a consistent pattern as regards enzymatic antioxidant defense in Persian oak. Morphological leaf traits would be important drivers of future adaptive evolution in Persian oak, leading to smaller and thicker leaves, which have fitness benefits in dry environments. Nonetheless, drought responses may be critically affecting carbon uptake, as photosynthetic compounds are less effectively used in leaves with higher sclerophylly.
Today, Zagros reforestation is more than ever felt due to human presence and its destructive acti... more Today, Zagros reforestation is more than ever felt due to human presence and its destructive activities. To do this requires observing the scientific principles of silviculture. Of essential restoration activities in these forests can be mentioned the seed planting of indigenous species within their range of development. In this regard, the present research was conducted with the aim of investigate the germination and emergence status of Quercus persica, Pistacia atlantica and Acer cineracens seeds planted in Dalab Ilam forests in 2018. For this, three sites on the northern slope and approximately the same height of 1380 to 1410 meters above sea level were selected. In each site, three trees were considered for each of Q. persica, P. atlantica and A. cineracens species. Under each tree, three holes were drilled between the trunk and the end of the crown for each crown side, and a total of 12 holes. In drilled holes under the trees, the corresponding seeds were planted in the winter 2017. The results of the sampling in the spring 2018 showed that the seeds of Q. persica had the highest emergence rates (22%). The seeds of P. atlantica gained the second rank in terms of germination and emergence (18%). The seeds of A. cineracens had the lowest amount of emergence (0.3%) and the number of emerged seedlings was rare. The highest occurrence rate of Q. persica seedlings was on the northern side of tree crown (32%) and in for P. atlantica was on the southern (32%) and western (30%) sides of the tree crown. The highest rate of seedling emergence of Q. persica (48%) and P. atlantica (51%) was found at nearest distance to tree trunk. Despite planting the seeds of these three tree species in the same conditions in terms of topography, position under the crown and distance from tree trunk, similar results were not obtained which the reason of this can be attributed to their seed characteristics such as seed size and seed vigor.
The aim of the study was to investigate the effects of tree mortality on structural characteristi... more The aim of the study was to investigate the effects of tree mortality on structural characteristics of an oak stand named Shalam Forest, with 670 ha area, located 10 km south east Ilam city of I.R. Iran. The structural characteristics consisted of stand density, basal area, canopy cover density, species composition, silvicultural form and distribution pattern of dead trees density and basal area and different diameter classes. The studied area was divided to 20 homogeneous topographical units in which three circular plots with 1000m2 area were located to measure diameter at breast height (dbh), minimum and maximum diameter of tree's crown, percentage of dried crown, trees origin and silvicultural form of each species separately and record the data. The results showed that the trees and shrubs density was reduced at 15.7%, in which 97.65% belonged to Quercus brantii. Basal area reduced at 14.23%, in which 95.29% belonged to Q. brantii. Mortality was found at most of the diameter ...
This research carried out to study the relationship between tree competition and Persian oak (Que... more This research carried out to study the relationship between tree competition and Persian oak (Quercus brantii) dieback and mortality in different site conditions and stand structures in Shalam oak forest which located in north of Ilam province, western Iran. We divided study area into 20 homogenize units based on topography using GIS. Then we established 6 transect with a length of 100 m in each landform unit and determined 5 random points with interval of 25m on each transect and marked the closest live and dead tree to them. To each focal tree we measured the distance, species, Diameter at breast height, crown diameter, height and crown dieback percent of neighbor trees. Competitive condition of focal live and dead trees was computed by Hegyi index. The results showed that the amount of tree competition varied among units. Also the results of correlation and Principal component analysis (PCA) showed the significant positive and direct relationship between competition and tree dieback amount. The lowest and highest amount of tree dieback was found respectively in units those had the lowest and highest amount of tree competition. Also the amount of tree competition had inverse relationship with crown diameter of focal tree and direct relationship with crown diameter and height of neighbor trees and crown dieback percent of focal trees.
Aim of study: Drought and stand structure are major and interconnected drivers of forest dynamics... more Aim of study: Drought and stand structure are major and interconnected drivers of forest dynamics. Water shortage and tree-to-tree competition may interact under the current climate change scenario, increasing tree mortality. In this study, we aimed to investigate climate trends, site and stand structure effects on tree mortality, with the main hypothesis that drought-induced mortality is higher as competition increases.Area of study: Persian oak forests from Zagros Range, western Iran.Material and Methods: We split the study area into 20 topographical units (TUs), based on aspect, slope and elevation. In each TU, three 0.1 ha plots were established to quantify site and stand characteristics, namely the diameter of all trees and shrubs, stand density and basal area, canopy dieback and mortality. In addition, soil profiles were analyzed to obtain physical and chemical soil properties. Six transects 100 m length were established per TU to measure tree-to-tree competition for alive and...
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