جستجوی مقالات مرتبط با کلیدواژه « zagros » در نشریات گروه « جنگلداری »

Monitoring the nutrients of tree leaves is crucial for understanding their physiological responses to environmental stresses. This study monitored the status of leaf nutrients in Persian oak trees (Quercus brantii Lindl.) affected by crown dieback during the years 2019-2021.

Two sites, one northern and one southern, were selected in the Mele-Siah area. Five healthy trees and five declining trees were identified at each site. From each tree, 20 mature and healthy leaves were collected and taken to the laboratory to measure the concentration of nitrogen, phosphorus, potassium, calcium, and magnesium elements. Leaf sampling was conducted annually in August over three years. Soil sampling was also conducted during the growing season over three years, with a hole dug on the southern side of each tree crown to measure soil moisture in two horizons.

The results showed that the amount of leaf nitrogen was highest (1.48%) in 2019 and lowest (1%) in 2020, and it was higher in healthy trees (1.30%) than in declining trees (1.22%). The amount of phosphorus was higher in the northern site in all years. The amount of potassium was highest (2.22%) in 2019 and lowest (0.58%) in 2020. The amounts of leaf calcium and magnesium were highest (1.8% and 2.36% respectively) in 2019 and lowest (0.57% and 0.69% respectively) in 2021. Furthermore, the amount of calcium was higher in the northern site (1.29%) than in the southern site (0.99%). The highest amount of calcium was found in declining trees (1.465%) in the northern site and in healthy trees (1.241%) in the southern site. The results also showed that soil moisture was higher in the northern site in all sampling years and was associated with annual changes, which affected the changes in leaf nutrients over different years.

Considering the differences in soil moisture, soil acidity, and salinity of the studied sites, as well as temporal changes in the concentration of leaf elements caused by climate changes, it can be concluded that the crown dieback of Persian oak trees is related to the physiological mechanisms involved in water and nutrient absorption.

One of the basic parameters in forest management is the detailed knowledge of the trees’ growing stock for planning, which is operational by forest inventory. Excessive human interference and dependence on the forests have changed their natural structure. Although the circumstances of wood harvesting are not provided in these forests, their role is essential in soil and water conservation, the livelihood of local people, and environment improvement. Sampling methods must be accurate, inexpensive, and easily implementable in the wild. This study presents a new sampling method, called a branching transect, in the Iranian Zagros forests and similar forests. Features of the new method include proper accuracy, easy implementation in nature, simplicity of statistical calculations, and low cost. The number of trees per hectare (density) in a forest stand represents the existing situation, and its monitoring is very important to know the changes in forest stands. The use of distance sampling methods, especially in open forests, has grown in recent years due to the reduction of inventory costs and optimal accuracy. The research mainly aims to evaluate the efficiency of a proposed distance method (a branched sampling line) with easy implementation and good accuracy in a 100 × 100 m network and the GIS environment.

The studied area is located in the southwestern part of the Manshet and Qalarang protected area in Ilam County. First, 100% inventory was applied in a 90-hectare area of the studied forest, and then 10 and 20-m sampling lines with branches of up to a maximum of 20 m (90 sampling points) were used for this study. In this method, a transect is used that includes some sub-transects. The length of the main transect, sub-transect, the number of trees measured in each sub-transect, and the number of sub-branches in this method are changeable based on the homogeneity, heterogeneity, density, and structure of the forest and are determined according to the forest and expert opinions. In general, less numbers of sub-branches and trees can be considered when the forest is denser or more homogeneous. It is better to consider more sub-branches in dense forests, such as Zagros forests so that a wider area can be covered under inventory and an acceptable number of trees can be examined in transects. Due to the density and heterogeneity of the studied forest area, 20-meter transects with 2, 4, and 6 sub-branches were used in this study. To reach the study goal of the comparison among distance sampling methods, the results of these samplings should be compared to a real amount to have the final judgment on their benefits and weaknesses. Accordingly, the results were compared to 100% inventory in the study area. In 100% inventory, geographical features and the measured quantities for each tree were entered into the GIS environment. This research is the first to use the sampling method of a sample line with 2, 4, and 6 m lateral branches. To evaluate the methods, they compared with 100% inventory based on the accuracy rate and t-test.

The normality of data was tested through the chi-square test, and the unpaired Student`s t-test was used to compare the average numbers and canopy of trees in a hectare, resulting from real amount sampling (100% inventory). Based on the whole amount of trees in the area (12079( and the whole area of the canopy of trees (62.32 m2), the real average amount of trees per hectare and the real average value of the canopy area per hectare were calculated as 141 and 3704, respectively 12). The 6-branched two-tree sample line with 141 trees per hectare and the four-branched one-tree sample line method with a canopy of 3815 m2 per hectare showed the best results compared to the real mean. The analysis showed that most of the used sampling methods  (the branched sampling line with six different patterns 6b2t- 6b1t- 2b1t- 2b2t- 4b2t-4b1t) yielded acceptable results for the evaluation of open forests. However, the branched sampling line method in most networks showed a lower statistical error and was closer to the real value in terms of the mean number of trees per hectare.

Totally, the branched sampling line has an accuracy percentage within 10% to estimate the number of trees per hectare in most networks. In terms of the mean number of trees per hectare, this method was not significantly different from the actual value with a probability of 95% and was more accurate than the other distance methods tested in this research. Considering the low percentage of sampling errors, acceptable accuracy, and easy implementation in nature, the branched sampling line was evaluated as a more suitable method than the other approaches. Due to the novelty of the presented sampling method, there was no case for comparison, in other words, transect branching has not been applied in other areas that can be compared with the results of this study. Finally, the results of this review for the parameters of the number and area of canopy of trees per hectare and its comparison with the actual value and flexibility of this method (changeability of the number of branches, number of trees in each branch, and the length of the main and sub-transects) demonstrate that it is a proper sampling method in dense and even normal forests.

Using landscape metrics, it is possible to study the quantification of spatial patterns of environmental elements and changes in their extent at different scales. The result of this study can lead to a good understanding of how the landscape changes, which is required for sustainable management and planning. Due to the importance of the subject, the purpose of this study is to use remote sensing and evaluate the efficiency of landscape metrics in analyzing changes in forest areas and land cover in part of theNorthernZagros forest areas. 

Land cover map related to different years (1998, 2009, 2020) was prepared through supervised classification of satellite images and visual interpretation of Google Earth images and field visits. The ArcGIS Patch Analyst extension and FRAGSTAT software were used in order to monitor and evaluate the landscape metrics. Nine landscape metrics including four metrics of the number of patches (NP), patch density (PD), percentage of each class (PLAND) and area of each class (CA) at the class level and five metrics at the landscape level including number of patches (NP), Mean Patch Size (MPS), Shannon Diversity Index (SHDI), Largest patch Index (LPI), Continuity (contag) were calculated.

The results of measuring the area of the class and the percentage of each class in the period of 1998, 2009, 2020 at the class level showed a decrease in the forest area and an increase in the percentage of residential and agricultural cover during the period; So that in 1998, the forest cover was 78.82% of the area, and in 2020, this amount decreased to 77.36% (The area of forests has decreased by 0.066% annually during 22 years). During the period, we have seen an increase in the number of residential patches (13-17) and agricultural patches (19-42) and a decrease in the number of forest patches (21-18). The comparison of the patch density metric also shows the increase of this metric in all the land covers except the forest. The results of the survey at the surface of the land show an increase in the number of patches and the Shannon diversity index and a decrease in the continuity index, the mean patch size and the largest patch size metrices.

The results of this study show the expansion of residential areas and agricultural uses and the reduction of forest areas, which indicates the destruction of the integrity of the land due to the increase in the number and classes of man-made areas (residential and agricultural).

In the present study, the crown dieback of Persian oak trees was monitored over a period of four years (2019 to 2022) in order to determine the characteristics of oak trees that are sensitive to crown dieback in the Mele-Siah forests of Ilam. Two plots, with varying areas in order to include 100 oak trees, were selected on the northern and southern slopes. The characteristics of each tree, including the diameter at breast height, tree height, and the large and small diameters of the crown, were measured and recorded. The crown dieback of each tree was evaluated based on the percentage of crown dieback over the course of four years at the end of the summer season, and the trees were divided into four classes of crown dieback. The results showed that there is variation within the species in terms of the extent of crown dieback. On the northern slope, the majority of trees were in the declining and less than 50% crown dieback classes, while on the southern slope, the majority of trees were in the healthy and more than 50% crown dieback classes. The healthy class had the lowest average diameter at breast height, height, and crown area, while the higher crown dieback classes had higher averages for these characteristics. Additionally, the results showed that there is variation within the species in terms of the annual variability of crown dieback intensity. In the northern site, 17 trees and in the southern site, 14 trees were moved from the healthy and low crown dieback classes to the higher crown dieback classes. The results indicated that the transplanted trees had larger diameters at breast height, heights, and crown areas compared to the trees in the same class that were not transplanted. It was concluded that trees with larger dimensions in terms of diameter at breast height, height, and crown area, which are also older, are more sensitive to dieback. Conversely, trees with less crown variability or greater crown health have greater adaptability or tolerance to drought conditions, which can be used to produce resilient seedlings for the restoration of dieback-affected forests. The findings of this study can be utilized in the identification and protective management of forest trees that have not yet experienced decline or are situated near affected trees and stands.

One of the main destruction factors of oak forests is the oak leaf roller Tortrix viridana L. which causes a lot of damage to these woods by feeding leaves and buds of oak trees. The purpose of study was to investigate the population changes of this pest in different altitudes. This research was conducted in 2018 in Perdanan and Mirabad. In each region, in three elevation classes, transects with 100 meters’ intervals, and in each elevation class, 30 individuals of Quercus infectoria Olivier, which were located along the specific transect and in terms of appearance approximately similar, measured. In each tree, four branches were selected in four main directions (each direction of a length of 50 cm) and the pest larvae counted and the diameter of the branches were measured. Data were analyzed by SPSS 18 software and comparison of means was performed using Duncan's multiple range test. Results showed that according to the climatic diversity of two regions, the number of T. viridana larvae in the Perdanan was higher than Mirabad. Also, the number of larvae was recorded for both areas in the 1200-1300 meters’ elevation, which shows that the favorable conditions for larvae activity. The elevation class had no effect on distribution of pest in directions of the tree crown. The highest number of larvae in all three elevation classes was recorded in the eastern direction of the tree and its lowest amount were recorded in the west direction.

The occurrence of fires is one of the important factors that determine the different characteristics of many terrestrial ecosystems. For a long time, fires have severely affected forest areas, and sometimes their negative effects remain for several years after the occurrence of the fire, so that the state of vegetation does not return to its previous state. The aim of this study is to model the restoration of vegetation in Zagros forests (Ilam province) following fire.

We used various climatic and environmental data as independent variables (vegetation at the time of fire (NDVI+1), burn severity index, temperature and precipitation anomaly, average temperature, annual precipitation, slope, aspect, and elevation) and NDVI +5 as dependent variable for the modeling (using random forest, decision tree and gradient boosting) the vegetation recovery following fire. Landsat satellite images were used to prepare indices indicating vegetation density status and burn severity, and after preprocessing the images, these indices were prepared by spectral ratio. Climatic variables (precipitation, average temperature, minimum temperature and maximum temperature) were also estimated according to the regression relationships between these variables and the elevation in the study area. Finally, three machine learning algorithms, including decision tree, random forest, and gradient boosting, were used for modeling, and also the accuracy of these models were evaluated.

The results showed that among the various variables investigated, the annual precipitation, average annual temperature, normalized vegetation difference index (NDVI) and burn intensity index at the time of fire were the most important factors affecting the vegetation restoration post fire in these forests. The precipitation and temperature were the most important factors affecting the restoration among the mentioned factors. Also, the results showed that among the different models, the gradient boosting algorithm with R2 = 0.66 models vegetation restoration better than other models. In this model, the climatic factors were the most important in the vegetation recovery.

According the relationships between the NDVI and other studied factors and the results of the modeling; it is possible to explain the effective role of climate factors in the vegetation restoration in the study area.

Drought in Zagros, which is one of the most important ecosystems in Iran, is a big challenge. Remote sensing has a unique application in diagnosis, monitoring and management of natural resources. The purpose of this study is to investigate and analyze the drought situation in the middle and southern Zagros basin based on atmospheric general circulation models and neural network in relation to remote sensing indices NDVI, VCI, TCI, VHI, DDI, EVI, NDWI and SAVI. At first the Modis satellite time series images were used in a 20-year period. First the mentioned indicators were produced from MOD021KM products of Terra sensor from 2000 to 2019. Then amount of precipitation were estimated by using of statistical-dynamic model MP5 under RCP 2.6, RCP 4.5 and RCP 8.5 scenarios and neural network and Remote sensing indicators during the period from 2020 to 2039, And then the state of droughts was investigated in 2 periods of 20 years based on the SPI method (2000-2019) and based on RCP scenarios and remote sensing methods and neural networks for the next 20 years (2021-2039). The results showed that both in the period of 2000-2019 and 2020-2039, the high areas of the studied area have and will have severe and very severe wet year. Also, the spatial analysis of droughts and remote sensing indices of the second period has depicted an irregular pattern in all indices, and only in NDVI and SAVI indices, the spatial analysis of droughts has been able to present a relatively regular pattern

The goal of this study is to see how well the forest canopy density (FCD) model and the GLAMA mobile ‎app estimate the canopy cover density of Zagros forests in Sardasht province. Landsat 9 Operational Land ‎Imager-2 (OLI-2) in 2022 was employed for this purpose. Four indices were created to run the model: 1- Advanced ‎Vegetation Index, 2- Bare Soil Index, 3- Shadow Index, and 4- Thermal Index. The Scaled Shadow Index and Vegetation Density index were then computed by integrating and synthesizing indices one and two, as well as indices three and four, and the FCD model map was created by combining these two indices. The created model was validated using GLAMA mobile app and ‎hemispherical photographs. For this purpose, 100 square sample plots in Sardasht city with varying canopy ‎cover were chosen, and photographs of the canopy cover were taken at five positions on each sample ‎plot. The overall accuracy of the FCD model generated for Sardasht Province was 76%, with a Kappa ‎coefficient of 0.697. Furthermore, the correlation results demonstrate a strong (R2‎ = 0.985) and significant ‎‎(p-value = <0.0001) correlation between the average canopy cover index values estimated by ‎hemispherical photography using GLAMA software and the values acquired by the FCD model. According ‎to the findings of this study, the FCD model developed using Landsat 9 satellite data and the GLAMA ‎mobile app performs very well in estimating forest land canopy density in Zagros forests.

Wildfires are one of the most important challenges of natural resources management causing a lot of damages to these natural ecosystems, annually. Although, reportedly almost all of the wildfires are human caused in the Zagros region, environmental factors play a key role in fire spreading and burned area.  Hence, the aim of this study was to determine the relationship between burned area and physiographic factors (slope, aspect and elevation) from 2001 to 2018 using Moderate Resolution Imaging Spectro-radiometer (MODIS) fire data.

MODIS burned area data were collected for the statistical period of 2001-2018 with the resolution of 500m include spatial and temporal information of fire incidents. Then the physiographic maps including slope (five classes), aspect (five classes) and elevation (six classes) maps of study area were prepared, using a 90m DEM. Kolmogorov–Smirnov test was used to check the normal distribution of the data. Since the data did not follow the normal distribution, non-parametric tests such as Kruskal–Wallis and Mann–Whitney U tests were used for comparing the statistical differences between the median of burned area in different classes of physiographic factors. Furthermore, the specific burned area (SBA) index were calculated by overlaying the layers of burned area, vegetation type (rangeland and forest) and physiographic factors to remove the effect of the surface area of physiographic classes.

The results showed that the larger burned area was observed in the larger physiographic classes. In other words, the surface area of physiographic classes is the most effective factor on burned area. However, the values of specific burned area (SBA) in each classes showed a different result. In both vegetation types, the value of specific burned area index was highest in the elevation class of 500-1000m and the eastern aspect. Furthermore, the value of SBA was highest in slope class of 15-30% and more than 80% in rangelands and forests, respectively. Since the value of SBA index is not dependent to the extent of relevant physiographic classes, it could be used to indicate the natural potential of each physiographic classes for fire spreading in different regions.

It was concluded that the specific burned area in comparison with burned area is a more appropriate index for investigating the effects of physiographic factors on fire spreading.

A comprehensive study of vegetation changes requires consideration of all influential factors in the ecosystem. The Zagros forests, as one of Iran's most important forest ecosystems, contain diversified vegetation including trees, shrubs, and herbaceous species. Therefore, accurate identification of vegetation and knowledge of their ecological role can help in protecting natural resources and sustainable development. The aim of this study was to investigate the changes in herbaceous vegetation in the Hashtadpahloo forests of Lorestan province.

For this purpose, after physiognomic typing of the region, 21 multi-scales, modified Whittaker plots were randomly selected in pure oak type (Quercus brantii Lindl.), Mixed oak and Acer type (Quercus brantii Lindl., Acer monspessulanum L.), Shrubs and cushion plants type (Daphne mucronata Royle, Cotoneaster morulus Pojark), and rangeland type (grassland and rangeland species). Species richness, canopy cover of tree species, Physiographic factors such as slope, aspect and altitude were measured at 250 m2 (25×10) plots, and presence and cover percentage of each herbaceous plant was recorded at o.25 m2 plots. (0.25 × 1. Furthermore a combined soil samples were taken at 0–30 cm depths to determine soil properties. After measuring plant diversity indices such as Margalf, Mannick and Shannon Wiener indices and some physical and chemical characteristics of soil in laboratory, principle component analysis (PCA) was used to indicate the most important environmental factors affecting diversity indices in different types.

The results showed that there were significant differences among different vegetation types with respect to Menhinick and Margalef richness indices, aspect, slope, altitude, and canopy cover (p<0.05). While Simpson's and Pylo's indicators of diversity, dominance, and evenness had no significant differences among different types. The highest Menhinick and Margalef richness indices were observed in pure oak type, whereas rangeland type had the lowest richness indices and canopy cover and the highest slope and altitude. In addition, the soil variables absorbable potassium and magnesium had a significant correlation with the values of Manchinic, Margalf, Simpson, and Shannon-Weiner indices. Based on the PCA results, dominance, diversity, and species richness indices (constituent variables of the first component), edaphic factors (constituent variables of the second component), and eventually Physiographic factors such as slope, aspect, and altitude with canopy cover (constituent variables of the third component), describe the highest percentage of changes in the herbaceous community of the region respectively.

As a result, it can be acknowledged that due to the wide spread of Zagros forests, simultaneous attention to the three components of forest types, physiography and soil can favorably reflect the changes in the vegetation of the herbaceous vegetation of the Zagros, and they can be used in the management of these forests.

Water and soil protection, providing living conditions for human communities and production of by-products are the most important performances and characteristics of Zagros forests. About one third of the total population of the country lives in the Zagros region and more than 70% of the total nomads of the country are in this area; in terms of livestock, 50% of the country's livestock are located in this area. Unfortunately, today the Zagros forests degradation is happening for various human and ecological reasons. Due to the importance of degradation in the Zagros forests and the unfavorable conditions of this ecosystem, the present study was conducted with the aim of geographical modeling of forest degradation factors in the Khorramabad basin.

Based on studies, five main causes of degradation were identified, including overgrazing, nomadic migration routes, distribution of residences, distribution of access roads and farming under the forest canopy. For each factor, a digital map was prepared and normalized by fuzzy method in ArcGIS. Fuzzy layers were weighted by AHP and degradation potential layer was obtained by WLC method. In order to validate this layer, five classes were considered and in each class 12 sample plots of 35 × 35 m were implemented and two factors of farming under the forest canopy and tree decline were examined and measured. Then, based on the numerical values of the forest degradation potential layer (as a response variable) and the field surveys of five degradation factors (as independent variables) at 30 random points, the modeling was performed by geographically weighted regression method.

The results of weighting the factors affecting forest degradation showed that the two factors of farming under the forest canopy and overgrazing are more important than other factors. Based on geographical modeling, the results of forest degradation prediction in the sample points showed that the residuals standard deviation without any specific spatial pattern are distributed throughout the forest. The continuous forest degradation prediction map also showed that there is potential for degradation in all parts of the forest, but with different intensities. There are three critical points on this map that should be given special attention in the management of these forests.

Various researchers have often used classical regression methods to model and investigate the factors affecting forest degradation, but this study has used geographical regression and many georeferencing errors of predictive data are automatically eliminated. Therefore, this method can be used with more confidence and used to prepare prediction maps.

The purpose of this study was to monitor changes in the structural characteristics of a pollarded oak forest in Baneh county of Kurdistan province, Iran. Fifty-nine permanent sample plots were recovered for 14 years (2005-2019). In each plot, the diameter at breast height (dbh) for all trees (dbh ≥ 5 cm) was measured. Woody species less than 5 cm in dbh were recorded as regeneration in two height classes less than and greater than 2 meters by species and form (coppice and seedling). Total height and crown area for two trees in each sample plot (i.e., the nearest tree to the center of the plot and the largest tree in terms of dbh in the plot) were measured. The results showed that the difference between the beginning and the end of the studied period was significant in terms of the distribution pattern of trees in diameter classes (p<0.01); while there was no significant difference in the distribution pattern of trees in the total height and canopy area classes. The average annual increment of diameter, height and crown area in oak trees (excluding species) was 2.41 mm, 12.59 cm and 0.73 m2, respectively. A comparison of the current diameter distribution curve with the expected diameter distribution showed that the number of trees in diameter classes lower than 12.5 cm was less than the expected value, indicating poor regeneration. In order to reveal the consequences of pollarding as a traditional silvopastoral system and to make appropriate management decisions in order to improve the condition of pollarded oak forests, the use of permanent sample plots is suggested as a suitable method for studying the changes in structural indices of these forests.

Zagros forests are one of the most important vegetation areas in Iran that play an important role in protecting water and soil resources. Over the past decade, the decline of some tree species in these forests, including oak, has raised serious concerns about the endangerment of these forests. Climate change, site poverty, absorption of heavy metals from dust, reduced nutrient uptake and site factors are an important factor of this phenomenon. The present study was carried out to investigate the effect of nutrition spraying on controlling the drying process of oak trees (Quercus brantii Lindl.) and compensating their needs through foliar application.

This research was carried out in Monj region of Lordegan city in Chaharmahal and Bakhtiari province. Thirty oak trees (including 15 coppice and 15 Single stem trees) were selected in one of the areas with drought. Trees in each vegetative form were divided into three health classes including healthy, diback and drought up to 50% of the crown. In total, this study had three treatments including vegetative form (two levels), health (three levels), sampling time (two levels) and five replications. Foliar spraying (three per thousand) was carried out during the full growth of leaves from early June to July with an interval of 10 days in three shifts.

The results showed that the amount of high macronutrient elements including potassium, phosphorus and nitrogen at the beginning of the growing season were 1.22, 0.27 and 0.998 percent, against the end of the growing season that were 0.17, 0.24 and 1.11 percent, respectively, that was a significant difference at the level of 95% confidence. The amount of these elements in coppice and Single stem trees in healthy trees was more than two classes of drought, but this difference was not significant statistically.

In general, macronutrients can stop the decay of oak trees by increasing the ability of trees to withstand environmental stresses. In between, the role of phosphorus and potassium was important in increasing the resistance of trees to environmental stresses and stopping the drying process.

This study was done to investigate the effect of slope aspect and crown dieback intensity on the nutrient status of leaves of Persian oak trees influenced by dieback and site soil in the forests of Ilam province. For this purpose, the Forest area of Melah-Siah was considered and two one-hectare areas on the northern and southern aspects with almost the same altitude levels were selected. In each selected area, 10 trees were sampled in two intensities of healthy and dieback affected. Leaf samples were collected from the four main sides of tree crown and the middle part of the crown and from their terminal branches. Furthermore, from the south side of the selected trees, soil samples were prepared from two depths. Collected samples were transferred to the laboratory for analysis of OC, N, P, K, Ca and Mg.  The results showed that the slope-aspect and crown dieback intensities have significant effects on the amount of phosphorus, calcium and magnesium in Persian oak tree leaves. So that, the amount of leaf phosphorus in the northern site was higher than the southern site. Leaf calcium and magnesium concentrations were higher in the north site than the south site and in dieback-affected trees than the healthy trees. Also, the amount of soil organic carbon was significantly affected by slope aspect. The OC content in depth of 0-20 cm, in the northern site was less than the southern site. The amount of pH, CaCO3 and soil moisture in the depth of 0-20 cm and soil moisture in the depth of 20-50 cm were also changed under the slope aspect. It was concluded that leaf nutrients had more changes than soil elements under the influence of considered factors and the amount of these changes was more attributed to the slope-aspect. The studied Persian oak trees with different crown dieback degrees had a similar situation in terms of soil macro elements, but had different conditions in terms of leaf macro elements. Considering the differences between their habitats in terms of soil moisture and pH, it can be said that the dieback severity of tree crowns is related to physiological mechanisms in trees for absorbing water and nutrients.

Land degradation and environmental heterogeneities are factors that affect forest ecosystems worldwide and their characteristics. Despite the significant role of soil seed bank to the rehabilitation of degraded plant communities, the floristic studies in many terrestrial ecosystems have focused only on aboveground vegetation. This study carried out to investigate the effect of land-use change from forest to agriculture and long-term and short-term abundance of this disturbance on aboveground vegetation and soil seed bank in Cheghasabz forest park in Ilam County. A total of 66 sample plots (1 m × 1 m) were established using a random systematic method to measure the aboveground vegetation. For soil seed bank, around each of the sample plots, a sample 20 cm × 20 cm area to a depth of 10 cm randomly collected. The seedling emergence method (in greenhouse) and the Braun-Blanquet cover-abundance scale was used to study of soil seed bank and vegetation, repectively. The results showed that in all three studied areas, the number of species in the soil seed bank decreased compared to aboveground vegetation. The dominant life form in the three studied areas were therophytes for both the soil seed bank and aboveground vegetation. The phytocorya distribution of plant species in all land uses also showed that the elements of Irano-Turanian and Iran-Touran-Mediterranean are dominant for both soil seed bank and aboveground vegetation. The density of soil seed bank decreased significantly in agricultural land use. Along DCA axes, based on soil seed bank and aboveground vegetation two distinct vegetation composition separated. The first group includes plots of the soil seed bank and aboveground vegetation in long-term abandoned lands and forest stands, and the second group consisted of seed bank and vegetation of short-term abandoned lands. Long-term abandonment from agriculture as a management measure and relying on the seed bank can be efficient in restoration of vegetation and returning to pre-disturbance conditions.

Among climatic factors, temperature and precipitation are of two particular importance, which directly and indirectly affects the uptake and transport of minerals. In order to study the relationship between climatic variables and chemical element concentrations in two groups of healthy and declined Iranian oak trees, three healthy trees and three declined trees were cut in Dadabad habitat of Khorramabad. A disk was selected from each tree. Then, growth rings over the last 35 years were determined including three five-years and two 10-years pieces. The samples were cut and extracted by using the wet digestion method, and the concentration of different elements (Ca, K, Mg, Fe, Na, Zn, Cu, Pb, Ni, Si, Cr) was measured by using atomic absorption apparatus. The result showed that there was no significant difference between concentration elements of healthy and declined wood trees. The Pearson correlation between concentration elements and the average of seasonal temperature and rainfall was significant; in healthy trees, potassium with autumn rainfall (-0.931), magnesium with winter rainfall (0.959) as well as spring temperature (-0.969) and summer (-0.967) had significant correlations, and in declined trees, potassium with spring temperature (-0.961) and summer (-0.949), calcium with autumn (-0.953), silicon with autumn (-0.686) and lead with spring (0.966) temperatures had significant correlations. The difference between element concentrations of two groups of trees regrading climatic factors can be caused by the difference between genetics and physiological characteristics of trees, environmental physiography (especially light regulation and moisture regime), and physiology of uptake.

Nowadays, the oak decline is the most important challenge in the Zagros forests for the last decade. Concerning the importance of soil physical, chemical, and biological properties in the forest ecosystems performance, the impacts of oak decline on soil characteristics were studied. In spring, two declined stands and two healthy stands of Brant`s oak (Quercus brantii Lindl.) with one ha area (100×100 m) in the north and south aspects were selected and then soil samples were collected systematically from 0-10 cm depth. Next, soil texture, reaction, EC, moisture content, organic carbon, nitrogen, potassium, and phosphorus content of collected soils were analyzed. Furthermore, basal soil microbial respiration, induced soil microbial respiration, and nitrification potential were measured. The results showed that pH, organic material and carbon, and nitrogen did not have any significant difference between the declined and healthy stands. On the other hand, EC (around 28-29 %), moisture (around 3-4 times), potassium (around two times), and phosphorus (around 4-5 times) content were considerably higher in the healthy stands. Furthermore, the highest induced microbial respiration were recorded in southern (2.06) and northern healthy stands (1.67) and southern decline stand (1.38 mg CO2.100g-1.dm.h-1), respectively while we did not find any reasonable trend for basal respiration. Nitrification potential did not response to oak decline occurrence. Although soil nutrient significantly declined in response to oak decline, it can be supposed that dried leaves and branches can repair deficiency of soil organic material to some extent in the declined stands but over time, as trees weaken, soil quality will decline. Finally, monitoring of soil fauna and soil enzymes can be suggested for future research.

Joint-point method is one of the distance sampling methods for forest inventory. For estimation of tree density with joint-point sampling method two estimator suggested by Batcheler and also Engeman et al. that biased in nonrandom spatial pattern. Aim of this study was presentation a new unbiased and most efficiency estimator for this method. Forty-four sample size for each of six sampling methods: Circle plot (10ar as true value), Nearest individual method, nearest neighbor method, Compound method, second nearest neighbor method and Joint-point method in forests of Sorkheh dizeh Dalahoo of Kermanshah province with systematic random design (100m*100m) carried out. After that trees density of forest stand calculated with 10 estimators of above methods and new estimator. Then calculated density with new estimator compared with Batcheler and Engeman et al. estimators and other estimators in different spatial patterns (regular, random and aggregate) by precision and accuracy criteria. The results showed that this new estimator was not only most efficient than Batcheler and Engeman et al. estimators but also was best than other estimators.

Among the various components of vegetation, root system plays an important role in stabilizing, soil reinforcement and preventing erosion. This study aimed to investigate the effect of oak decline phenomenon on root mechanical characteristics of Brant`s oak (Quercus brantii Lindl.) in Dinarkuh forests, Ilam province. Considering DBH distribution of the trees in the study site, five trees were randomly selected in small DBH (15 to 35 cm) and large DBH (35 to 55 cm) classes within three treatments of healthy, moderate decline, and severe decline. Root samples were collected from each tree by digging near the tree and then tensile test were performed in the laboratory. The results showed that the root diameter-force strength relation was positive power-law and the root diameter-tensile strength relationship was negative power-law. Results of the covariance analysis for tensile force and strength showed that there is no significant difference between tensile force and strength among treatments of small DBH class, while in large DBH class, root tensile force and strength of healthy trees were significantly higher than trees with severe decline. Based on the decline, tensile force of the trees in the treatment of severe decline compared to the healthy trees, so force decreased by 11.3% in the small DBH and 22.7% in the large DBH classes. Also, these values ​​for tensile strength showed a decrease of 13.4% and 19.7%, respectively. The findings of this study show how the effect of forest decline on the root tensile force and strength values ​​leads to a better knowledge of the controlling soil erosion in the Zagros ecosystems.

The decline of forest trees has always been one of the main problems of various ecosystems. Today’s, this phenomenon is occurring in the natural resources and forests of Zagros, and has a wider dimension every day. Various biotic and abiotic factors have been identified and introduced in different countries as the main factor or factors affecting the weakness, dryness and death of oak trees. But in Iran, the factor or main factors of the trees decline in the Zagros forest have not yet been determined accurately. The incidence and severity of this phenomenon in recent years due to the importance of forests in the province of Ilam from the viewpoint of in environmental issues and their becoming generous to oak decline, have been investigated. For this purpose, in the present study, in the multi-criteria decision-making space and the use of the AHP hierarchical process, six main criteria and a total of 28 sub-criteria were evaluated. The weight of each criteria and sub-criteria was computed by distributing 30 special questionnaires of forest specialist and obtaining opinions from experts group and using Expert Choice software version 11. The results showed that the highest weight was for drought and climate change (0.289), and the lowest weight for the quantitative and qualitative criteria of the tree and its forestry characteristics (0.097). Other criteria In order of importance were; pests and diseases (0.194), human and animal factors (0.192), air pollution (0.123) and site quality of habitat (0.105).