spatial pattern

Understanding the structure of forest stands, particularly in Irano-Turanian regions, is essential for effective management and conservation efforts in semi-arid and arid areas. A thorough understanding of forest structure, including species distribution, tree size, and spatial patterns, enables more accurate assessments of ecological status, predictions of forest responses to environmental changes, and ultimately, the adoption of more efficient management decisions. This study aimed to investigate the structure of juniper stands in two one-hectare plots (protected and unprotected) in the Saluk region of North Khorasan province, Iran.

For a comprehensive analysis of the forest stand structure, all trees in each one-hectare plot were assessed. Quantitative parameters such as DBH, total height, and crown diameter in two perpendicular directions were measured. The spatial distribution of trees within each plot was determined by measuring the distance and azimuth of each tree. Statistical analyses were then performed to compare the structural characteristics and spatial patterns between the two plots.

The results showed that the spatial distribution of juniper trees in the unprotected plot was random. While in the protected plot, this pattern changed to a regular one at close distances and to a random one and finally to a clustered pattern as the distance increased. The number of juniper trees per hectare was 84 in the protected plot compared to 31 in the unprotected one. There was no significant difference between the average crown area (12.2 ± 1.1 vs. 13.5 ± 2.8 m2), DBH (16.9 ± 0.7 vs. 16.6 ± 1.4 cm) and height (3.9±0.5 vs. 3.5±0.1m) of juniper trees in protected and unprotected plots. The average crown area of all species in the protected plot (9.5±0.8 m2) showed a significant difference from the unprotected one (6.4±1.0 m2).

Considering the situation of crown cover percentage and the spatial distribution pattern of all trees and also juniper trees in the investigated plots as well as the density of trees which is in the low range of the density of juniper stands reported by other researchers, it is necessary to apply restoration management, development and conservation in these forests.

In forest ecosystems, throughfall, a pivotal component of the hydrological cycle, exhibits spatial variations that have received scant attention. The redistribution of rain beneath the forest canopy gives rise to distinct rainfall patterns, resulting in substantial spatial disparities across diverse forest ecosystems. Forests assume a pivotal role in the water balance of the Zagros ecosystem. However, the increasing trend of afforestation using both native and non-native species, particularly fast-growing ones, necessitates an assessment of its impact on rainfall and its components compared to natural stands. This assessment is crucial as it affects the water cycle significantly. The present study aims to estimate the spatial variability of throughfall in natural stands of Persian oak (Quercus brantii) and afforested areas with Pinus eldarica and Cupressus arizonica in Zagros forests, with a specific focus on Chaghasbez Forest Park in Ilam county.

This study was conducted in Chaghasbez Forest Park in Ilam Province, with the aim of measuring rain components, including throughfall and stemflow, in stands of Persian oak, Pinus eldarica (Eldar pine) and Cupressus arizonica (Silver cedar). Rainfall was measured using five rain gauges located in the open space (outside the canopy) adjacent to the studied stands. Throughfall was measured using 27 collectors in Persian oak stands underneath the canopy, and 36 collectors in each Eldar pine and Silver cedar stand. To minimise measurement errors in throughfall at the stands, after every five rain events, four of the collectors were randomly relocated under the crown of the stand. The remaining collectors were stationed at fixed points throughout the study period. This approach increased the number of samples and reduced the measurement error of throughfall. Geostatistical methods were employed to investigate the spatial patterns and distribution of rainfall, and statistical analyses were conducted using GS+ software (version 5.1.1).

The mean throughfall depths for oak, Eldar pine, and Silver cedar were calculated as 207.32 mm, 129.21 mm, and 152.47 mm, respectively. The results indicate that the throughfall percentage of oak is higher than that of Eldar pine and Silver cedar. The average leaf area index (LAI) and the percentage of canopy gap of the studied stands were 1.4 m²/m² (CV= 53%) and 43.85% for Persian oak stands, 1.04 m²/m² (CV= 88.78 %) and 57.04% (CV= 46.26%) for Eldar pine, and 1.2 m²/m² (CV= 80.78%) and 54.71% (CV= 52.47%) for Silver cedar. The spatial pattern analysis of throughfall using variogram analysis revealed that under the canopy of Persian oak (RSS= 0.021, C0= 0.001, and r²= 0.51) and Silver cedar (RSS= 0.0, C0= 0.125, and r²= 0.92), the distribution is anisotropic with a strong spatial structure. Conversely, under the canopy of Eldar pine, the distribution exhibited isotropic characteristics with an average spatial structure (RSS= 0.102, C0= 0.54, and r²= 0.66). The analysis identified the exponential, linear, and spherical variogram models as the most suitable for Persian oak, Eldar pine, and Silver cedar, respectively.

This study found that the spatial continuity range of throughfall was estimated to be 10.8 metres in eldar pine, 8 metres in silver cedar, and 2.4 metres in Persian oak. A review of the literature revealed that the type of forest, tree density, and biomass can affect the spatial change and correlation structure of throughfall. Consequently, it is imperative to take into account the distinct characteristics of the forest type when investigating the spatial patterns of throughfall and their ecological ramifications. Subsequent research, which involves a comparison of the spatial correlation structure of throughfall in evergreen and deciduous forests, is expected to provide a more precise understanding of this subject.

The spatial pattern of landscape elements significantly influences tourists' experiences and preferences. The distribution, diversity, and arrangement of features such as natural covers, land use types, access routes, and visual landscapes directly affect the attractiveness of tourist destinations. Tourists, depending on individual preferences, are attracted to environments with distinct spatial characteristics, such as pristine natural landscapes, historical-cultural regions, or well-structured and diverse urban settings. Understanding the relationship between landscape spatial patterns and tourist preferences can enhance tourism planning, improve the quality of tourist experiences, and support the sustainable development of tourism destinations.  This study investigates the relationship between landscape patterns and tourist spatial preferences in Chehelchay Minudasht Forest Park, Golestan Province. A combination of subjective (6 criteria) and objective (6 criteria) metrics was identified and prioritized to evaluate tourist preferences. Six landscape metrics were selected to assess spatial patterns, and their relationships were analyzed using rank logistic regression. Results revealed that morphological characteristics of landscape elements (MSI) inversely correlate with density, diversity, complexity, continuity, and form. Metrics such as Edge Density (ED) and Mean Patch Fractal Dimension (MPFD) showed significant relationships with these concepts. . The criteria of distance and depth of view were the only ones to show a significant negative relationship with the metric of Class Area (CA), indicating that with the increase in spatial extent of a landscape element, the visual depth and perspective as perceived by users decreases. The findings suggest that tourist preferences are oriented towards areas featuring natural forms, extensive spatial continuity in vegetation cover and landform, and the presence of water bodies. In contrast, regions with high edge density (ED) and above-average shape complexity (MSI) exhibited the lowest levels of tourist presence. This indicates that tourists tend to avoid locations with excessive visual complexity, which typically reflect a high degree of fragmentation and anthropogenic alteration of landscape structure.

Introduction and Goal:

The decreasing trend of precipitation in many regions of the country, including the northwestern provinces, has made it more necessary to investigate new methodologies to complete the databases of the country's watersheds. In this regard, understanding the changes in precipitation barycenters, as an emerging concept, that indicates the long-term spatial distribution of regional precipitation is especially important for the administration of watershed management issues such as reducing drought effect, flood control, and water resource conservation. To this end, the present study analyzes the precipitation barycenter and its relationship with the spatial distribution of the rain gauge network in Ardabil Province.

To calculate the precipitation amount, the statistics of 49 meteorological stations during the statistical period of 45 years (1971-2016) were used. Based on the principle of station extraction and considering the rationality of the lowest density and uniformity, five stations were determined as the minimum possible number. Then, densities of 10, 20, 30, and 40 stations were extracted randomly to compare the distribution of precipitation centroids with the density of the station network. The statistics above were used to implement the gravity center model, calculate the standard deviation ellipse in the ArcMap 10.8 software environment, and conventional correlation analysis on monthly, seasonal, and annual time scales using XLSTAT.

The results showed that in spring (April to June), the direction of movement of the precipitation barycenter was significantly different and the movement distance was 18.17 km. In summer (July to September), the precipitation barycenter mainly moved 20.18 km to the north. In autumn (October to December), the precipitation barycenter mainly moves 20.49 km to the south and has the longest movement distance among the seasons. In winter (December to March), the precipitation barycenter moves in different directions and has the smallest movement distance (8.35). The annual precipitation barycenter migrated mostly in the southeast direction. The maximum migration of barycenter for 1979 was towards the northwest with 111.78 km. Besides, the annual precipitation barycenter in Ardabil Province in the three decades of 1971-1981 migrated mostly to the northwest and in the other decades to the southeast. The stational network density was positively correlated with changes in the precipitation barycenter (CCA = 0.65 at a significance level of 5%).

Conclusion and Suggestion:

The highest conventional correlation coefficient of 0.80 was obtained for the density of 40 stations among different densities of 5, 10, 20, 30, 40, and 50, and the lowest coefficient of 0.04 was obtained for the minimum density of 5 stations. Based on the results of this study, changes in the movement of precipitation patterns that can be effective in drought and wet periods were identified. It is suggested that the relationship between climate change and elevation factors with spatial-temporal changes in the precipitation center of gravity be investigated.

Recognized as the hosts of a wide variety of formative processes, deserts represent vital ecosystems within Iran's natural landscape. On the other hand, wind erosion exerts particularly significant influence on such arid regions, playing a key role in shaping the environment while posing serious environmental risks. Moreover, wind-driven movement of active and semi-active sand dunes decreases the comfort levels for local inhabitants, putting agricultural lands, settlements, and transportation routes at risks. Consequently, studying the dynamic behavior and variability of wind-driven sediments, especially in arid and desert regions, is of great importance. While UAVs (Unmanned Aerial Vehicles) may not fully replace traditional methods of spatial data collection, their unique capabilities allow them to be integral to the map-making process, offering more economical alternatives. Analyzing statistical summaries within the study timeframe facilitates an understanding of the spatial and temporal patterns of the sand dunes. As with many natural phenomena, wind erosion and sand dune dynamics can be complex and elusive; therefore, the investigation of their various impacts requires the application of contemporary methods such as statistical analysis. In this regard, this study mainly sought to develop a conceptual framework that outlines the patterns of sand features in the study area and elaborates on their interrelationships.

This study was conducted in an area covering approximately 200 hectares of sand dunes in the southern region of Mezinan Kalate, located in western Sabzevar city. The area features various sand formations, including Nebkha and Barkhan. To analyze the spatial patterns of the complications observed, the exact locations of such complications were identified, followed by an assessment of their distribution patterns. The paired univariate function (g(r)) was then employed to investigate the distribution patterns of different complications and their impacts on similar types. Additionally, the bivariate pairwise correlation function (g12(r)) was utilized to explore the interactions among various complications in the study area. Initially, a general assessment of the region was conducted through a field visit, followed by aerial photography using a drone to collect the required data regarding the complications from the study area. After analyzing the images, an orthophoto was generated. Then, a point map was created for spatial locations via ArcGIS 10.2, detailing the distribution of sand dunes and vegetation within the study area. Furthermore, the Kolmogorov-Smirnov test was applied to evaluate the normality of the statistical data. Finally, data processing and spatial analysis were carried out using the Programita software, which involved univariate and bivariate correlation functions, along with O-ring functions. The software employed a Monte Carlo simulation with 199 repetitions, achieving a 95% confidence level and a 5% significance level for the random distribution of the two species investigated.

The diagram illustrating the distribution pattern of sand dunes employs the O-ring function, utilizing the g(r) function values to analyze the spatial arrangement of the dunes. Findings from the application of this univariate function indicated that Barkhans did not display a significant spatial pattern. The finding is supported by the O(r) function, reaffirming that the spatial arrangement of Barkhans lacks any significance. The results of the g(r) function in examining the spatial pattern of Nebkhas via univariate functions revealed that within distances ranging from zero to 270 meters, the spatial pattern of the species was characterized by cumulative or clustered shape, and that no significant pattern was detected beyond 270 meters. Similarly, the results of O(r) function suggested that the spatial arrangement of Nebkhas formed clusters within the 0 to 270 meters range, with no significant pattern being observed beyond 250 meters. Additionally, the results obtained from the bivariate function g12(r) showed a negative correlation between these two elements up to about 500 meters, demonstrating their opposing influences on each other's formation and distribution. This finding is consistent with the distribution map of the two elements. The bivariate function O12(r) was also used to validate the results found in g12(r), yielding consistent outcomes with those derived from the pairwise correlation analysis.

The findings obtained from the spatial analysis of sand dunes and Nebkha indicated that the distribution of sand dunes in this area was intricate, while the arrangement of Nebkhas remained inconsistent. Together, these factors adversely impacted the formation and development of both phenomena. This situation may arise from the phenomena’s similar requirements for the establishment, specifically the availability of sand. It may also be driven by the presence of certain favorable environmental conditions.

determining the spatial distribution pattern of species in their environment is regarded as an important aspect of quantitative plant ecology. On the other hand, evaluating vegetation and arid land reclamation attempts requires awareness of the type of distribution pattern. Moreover, the study of plant distribution patterns significantly contributes to the assessment of the plants’ environmental uniformity or heterogeneity, reproduction type, distribution, competition, and behavioral patterns, helping to determine appropriate methods for measuring quantitative properties of vegetation such as coverage and density. However, studies on the distribution patterns of plant species are mainly focused on forest and rangeland ecosystems, and desert ecosystems are under-researched in this regard. Therefore, this study sought to determine the distribution pattern of ten halophyte species in eastern Iran's desert ecosystems using quadrate methods and the probability distribution function.​

This study was carried out in the halophyte habitats in the rangeland and desert ecosystems of Ferdows, Khosf, and Zirkouh in South Khorasan province and Zabol in Sistan and Baluchistan province. After visiting the study area and identifying its dominant species, the sampling of the region’s vegetation habitats was performed in the spring of 2022 using a random systematic method.To this end, sixty 4*4-meter quadrats were placed in the key area of each habitat, where the density of the dominant species was calculated by the counting method.Then, after measuring the density of ten species of dominant halophytes in each habitat under study, the mean and variance of species density were calculated.After that, Index of Dispersion (ID), Lexis’s Index (IL), Charlier’s Index (ICh), Index of Cluster Size (ICS), Green’s Index (GI), Index of Cluster Frequency (ICF), Index of Mean Crowding (IMC), Index of Patchiness (IP), Morisita’s Index, (IM) and Standardized Morisita (Ip) were calculated based on mean , variance (), and sampling plot number (n).Moreover, coefficients a and b distribution patterns were determined for ten halophyte species based on Taylor’s power law model or the linear logarithmic relationship between mean  and variance . In addition, Iwao’s patchiness regression model was used to calculate the relationship between the mean ( ) and the Index of Mean Crowding (IMC), based on which α and β coefficients were determined. Finally, invers K indices of negative binomial distribution and deviation from the Poisson distribution (ID) were determined, and the fit of plant density data was examined regarding three discreet statistical distributions, including Poisson, binomial, and negative binomial distributions.

The results of the analysis of quadrate indices and probability distribution function revealed that Salsloa tomenosa, Suaeda Monoica, Salsloa kali, Aeluropus Littoralis, and Tamarix Stricta had a clumped pattern, Sedilitzia Rosmarinus and Haloxylon Ammodendron followed a random pattern, and Salsola richteri, Hammada Salicornica, and Tamarix aphylla enjoyed a uniform pattern. Moreover, Aeluropus littoralis was found to have the highest amount of all the indices (except ICF).On the other hand, the results of the analysis for IP and IM indices were close to each other. Furthermore, according to the halophyte species density data obtained from the analysis of the probability distribution function, Aeluropus littoralis and Suaeda monoica were the only species that followed the negative binomial distribution which indicates a clumped pattern. On the other hand, Sedilitzia rosmarinus and Haloxylon ammodendron were the only species that followed the Poisson distribution which indicates a random pattern. Moreover, Salsola richteri, Hammada Salicornica, and Tamarix aphylla were found to have followed both Poisson and binomial distribution functions. However, based on the linear relationship between mean logarithm and variance logarithm (R2adj = 0.94, P <0/0001) and the linear relationship between the mean and Index of Mean Crowding (IMC) of density data (R2adj = 0.94, p <0/0001), the overall distribution pattern of the studied halophyte species was identified to have a clumped pattern.

This study used quadrate, regression, and possibility distribution methods to identify the plants’ distribution patterns. Accordingly, the results of the quadrate method indicated that out of the ten species studied, six species had a clumped pattern and four species enjoyed a uniform pattern. Moreover, almost all the methods used in the study area showed that Aeluropus littoralis and Suaeda monoica followed the clumped distribution pattern. On the other hand, Tamarix stricta were found to exert a negative influence on the soil due to salt accumulation and possibly prevent the growth and germination of the surrounding plants, thus contributing to the plant’s patchiness. The findings of the study also revealed that Sedilitzia rosmarinus and Haloxylon ammodendron followed a random distribution pattern. On the other hand, while a random distribution pattern is rarely observed in natural ecosystems, the distribution of seeds through wind and livestock, and germination and rapid reproduction of the Haloxylon ammodendronin the regional sites of the study area may be regarded as possible reasons for the random distribution of the species.The results of the analysis of regression methods suggested that the halophyte species generally followed a clumped distribution pattern, indicating the patchiness of nutritional sources and the soil’s physical and chemical properties such as moisture, salinity, and texture. It should be noted soil moisture and salinity are considered the main constraining factors of plant communities in desert ecosystems that affect the physiological and morphological properties of halophyte and psammophyte plants and limit their distribution, probably contributing to the heterogeneous distribution of plant species. Therefore, the effects of environmental stress on the vegetative and functional properties of plant species and their distribution pattern should be taken into account in developing desert greening and saline land reclamation plans.

This research aimed to quantify the structure of juniper and pistachio forest stands. To achieve this, two one-hectare sample plots were randomly selected: Pistacia atlantica in the Eslami Island region and Juniperus excelsa M. Bieb. in the Kaghazkonan region. Quantitative measurements included diameter at breast height (DBH), collar diameter, tree height, and crown diameter for all trees. The spatial pattern of the two stands was analyzed using the distance-azimuth method, and structural diversity was assessed in terms of species mingling, tree dimensions, and spatial position based on the four nearest neighbors method. The results showed that the most abundant species were P. atlantica and Ephedra major in plot 1, and J. excelsa and Cotoneaster nummularioides in plot 2. The average DBH and canopy cover were 22 cm and 569.5 m² in plot 1, and 4 cm and 1195 m² in plot 2, respectively. Species mingling was low in plot 1 (0.31), while plot 2 had higher mingling (0.5). Additionally, crown area differentiation was high, while height differentiation was intermediate in both stands. The mean distances between trees, 7.4 m in plot 1 and 2.8 m in plot 2, indicated sparse and dense stands, respectively. The assessment of structural diversity showed high values for both stands, with plot 2 (0.539) having significantly higher diversity than plot 1 (0.459). This highlights the importance of species mixture in the structural diversity of forest stands. This information serves as an important tool for silvicultural interventions, monitoring, and evaluating forest stand management effectiveness.

Hot spots are often associated with places where an abnormal process has occurred. Accordingly, their identification can help experts and managers to scrutinize the state of health and sustainability, from an ecological point of view. The present study was therefore conducted to analyze the spatial autocorrelation and identify hot spots of 11 landscape metrics, the new Runoff Landscape Index (RLI), and its related factors in 28 watersheds of Ardabil province. The average positive values of the z score obtained from Moran's index indicate the presence of spatial correlation in the studied watersheds. In addition, the results of local Moran's showed that the landscape metrics have a structured spatial pattern and are not randomly distributed. A completely unipolar pattern was obtained for land cover factor (λC), soil factor (λK), and RLI. Furthermore, the negative values of the local Moran's index for the topographic factor (λS) proved the scattered pattern. Spatial distribution of hot and cold spots, using the Getis-Ord-Gi index, showed no significant pattern in the λC of Ahmadkandi, Akbardavod, Deru, Mashiran, Firozabad, Lai, Nir, and Hir watersheds. Cold spots were observed in the Eiril, Namin, and Nanehkaran watersheds at the 90% confidence level and the rest of watersheds had hot spots at a 95% confidence level. The RLIs of Ahmadkandi, Akbardavod, Deru, Mashiran, Firozabad, Lai, Nir, and Hir watersheds lack a significant pattern, and the rest of watersheds showed the hot spots at a 95% confidence level.

The structure of forest stands changes over time and under the influence of local disturbances, these changes are referred as the dynamics of forest stands. Changes in the structure of forest stands result in the formation of development phases. The purpose of this study was to identify the structural characteristics of natural beech forests during the stage of growing up volume in the Kheyroud forest. For this purpose, three one-hectare sample plots with structural features of growing up volume stage were selected and the location, diameter and height of all trees within each sample plot with DBH N 7.5 cm were measured. The structural properties of this stage were investigated using a set of indices based on the nearest neighbors. Based on the results, the mean values of uniform angles and Clark and Evans indices were 0.49 and 0.96, respectively, which indicated a random clumped spatial pattern of trees at this stage. The results of the mingling index showed that the tendency of beech trees to mix with other species was low. The results of diameter differentiation index indicated a clear difference and height differentiation index showed a moderate difference in dimensions of trees with each other. In general, using the nearest neighbor indices showed that these indices have a high ability to detect the differentiation of forest stands in the growing up volume stage and thus are useful tools for forest management.

Estimators of distance sampling methods based on random spatial pattern of trees are bias in non-random spatial pattern. The purpose of this study was to evaluate the effect of spatial pattern of oak trees on the results of quantitative characteristics estimation of three different stands by nearest-individual method estimators in Chaharzabar  forests in Islamabad, west of Kermanshah province. For this purpose, three stands were selected in the area and within each stand half one hectare plot was identified. After full callipering of trees in the stands, according to completely randomized design, 30 samples with  nearest-individual method in each stand carried out. Then, spatial pattern, density, canopy cover and tree height were calculated with nearest-individual sampling method. Results showed that from the three studied stands, two stands had random spatial pattern and one had clumped pattern. Of  five estimators of nearest –individual method based on acceptable accuracy criteria (range ± 10%) for estimate density of trees, the formula proposed by Byth and Ripley in the random spatial pattern and the formula suggested by Batcheler and Bell in aggregate pattern were the most appropriate estimators. In order to estimate trees canopy cover percentage, the formulas suggested by Byth and Ripley, Cottam et al. and Morisita in the random spatial pattern were appropriate. However,  none of them were appropriate to estimate the canopy percentage of trees in clumped spatial pattern. To estimate the height of the trees, since the height was calculated independently of the estimators, it was found that estimation of the tree height by this sampling method yielded good results in both random and clumped patterns. Finally, it can be concluded that the spatial pattern of the trees was effective on the estimators of the nearest-individual distance sampling method.

Nowaday, forest structure issue is one of the main ecological debates in forest science. Determination of forest structure characteristics is essential for investigating stands changing process, silviculture interventions and revival operations planning. In order to investigate the structure of Ghale-Gol forests in Khorramabad, a set of indices such as Clark and Evans and uniform angle indices, mingling, domination and differentiation were used based on the nearest neighbors. In so doing, 80 circular sample sizes with 12 (acer) areas were collected in the field using a random sampling pattern and these plots were analyzed by Crancod (Ver.1.4) software. Based on the results, the average of Clark and Evans and uniform angle indices were calculated 0.936 and 0.449, respectively. These results showed that the samples have a random distribution with the tendency to be uniform. Also, the result obtained from the average of mingling index was 0.181 that indicated low species mixture. In an investigation on the diversity of tree dimensions, the average of domination and differentiation indices of the crown area were 0.449 and 0.519, respectively. This in turn shows that neighboring trees had a clear difference with each other in terms of the crown area. As the results showed, in the Zagros forests which often consist of wide and pure oak stands, using small sample size reduced time and cost of field survey, recordation of the sample size position, trees and shrubs accurately.  Surveying and monitoring different forest features are more probably suitable for quantification of forests structure.

The tree species regeneration is a critical process in the population dynamics of forests and significantly influences the composition of forest communities. Quantitative analysis of tree regeneration may provide baseline information for conservation and management strategies. Zagros oak forests have been subjected to dramatic changes in forest regeneration, cover and structure in recent decades. Zagros forests have critical national importance. These forests capture over one third of the country’s annual precipitation, and are the headwaters for 40% of the country’s rivers and streams which provide water to the dry central plateau of Iran. Given the national and regional importance of Zagros forests, it is extremely useful for restoration management to evaluate spatial distribution of tree regeneration. Disturbing of ecosystems, changes the dynamic of species and ecosystem processes. Ecosystems are therefore moving in a self-organizing way towards a more efficient use of energy/nutrients to the total energy input. This self-organizing of the ecosystem is an inherent feature of non-linear interacting systems. Techniques used to study non-linear systems could be able to quantify the structure of complex objects and spatial dynamic of plants.

The mathematical features of spatially complex systems are often fractal. Fractal has the potential to exposure a new way to understand and analyze such natural spatial phenomena, which are not smooth, but rough and fragmented to self-similarity. We investigated the spatial patterns of tree regeneration density and diversity in 126 plots (100 m2). The study was conducted at a preserved area (12 years) in Zagros forest of western Iran. We applied autocorelation methods to examine the spatial structure in distribution of regeneration. Fractal analysis was also used to characterize the complexity of the spatial patterns.

We found that preservation favored density and diversity of tree regeneration in this area. On the whole the variables have weak autocorrelation but regeneration density of C.microcarpa, total regeneration density, regeneration height and Shannon index are the variables which have the most autocorrelation. On the other hand, fractal dimension, representing the unpredictability of spatial patterns, is high for trees and regeneration. This implies that although spatial dependence exists, it is generally fairly weak.

These results revealed the scattered and homogeneous spatial distribution of trees and their regeneration. Indeed, our results showed a recovery of regeneration but not the spatial structure of it. It seems that conservation efforts must be continue to complete the recovery of regeneration and their spatial structure.

The importance of study on the structure of mixed stands is not less than that of studies on beech stands. For this purpose, nine sample plots, each one ha, were established in the control compartment of district four in Loveh forest. After recording the general characteristics of the stand, 100% inventory was done in the plots. Coordination and diameter at breast height (dbh) of all woody species with dbh larger than 7.5cm were measured. Spatial pattern of species was mapped using PAST software. Moreover, the locations of the stands were determined in the structure triangle. Results showed that the studied stands were three-storied uneven-aged and composed of 12 woody species with the highest abundance of hornbeam. Mean stem number was 384ha-1, height of trees varied between 3.6 and 34.7 m and large and extra-large trees of Lime and Chestnut-leaved oak with a total height of more than 25m appeared in the upper story. Mean basal area, total volume and dead wood volume accounted to 36.1 m2ha-1, 420.6 m3ha-1 and 17 m3ha-1, respectively. Spatial pattern of the trees was generally cluster. All nine plots were located on the upper part of the structure triangle indicating abundance of old and large trees which were far from the theoretical irregular structure. Considering this structure, immediate application of group selection method is too early in such stands; we suggest starting with silvicultural interventions and moving towards irregular structure, and later establishment of young generation keeping tree diversity and sustainability in mind.

Hyrcanian forests are rare and unique ecosystems and their sustainability is essential. Gaps, as part of a general process, help to establish and stabilize the structure of the Hyrcanian forests and the dynamism of its society. This study seeks to identify possible differences in the gap characteristics in the two managed and intact compartments. For this purpose, compartments No. 114 (intact) and No. 115 (managed) from district one of Livan-Banafshtapeh forestry plan in Golestan province of Iran were selected to compare some gap characteristics (gap fraction, distribution of gap sizes, number of gaps per hectare and status of gapmaker trees). In these compartments, all gaps>100 m2 caused by mortality of at least one tree with remnants of the gapmaker or detectable tree stumps, were identified and recorded. The results showed that the gap fraction in the intact and managed compartments was 10.7% and 6.3%, respectively. The average number of gaps varied from 1.4 ha-1 in the managed to 2.9 ha-1 in the intact compartment. The spatial pattern of gaps was randomly spaced up to a distance of 30 (managed) and 40 (intact) meters and then reached the cluster pattern. The differences between the characteristics in the two compartments were not statistically significant and management did not have a significant effect on these variables. However, no significant differences between the two compartments were due to the low harvest intensity in the managed compartment. The biodiversity of Hyrcanian forests must always be taken into account so that it is not endangered by mismanagement; otherwise irreparable effects on the ecosystem of the managed compartment may occur.

Taradeh, Kerman province, has valuable forest stands that are under pressure from local communities. In this study, after making forest survey, plot area was selected as ​​1500 m2 and 50 samples were collected systematically with in a grid of 100 m×100 m. In each plot, the plant species were recorded along with diameter at breast height, tree height, crown diameter, number of trees per hectare, large and small crown diameters, regeneration count, the distance between plot center and the nearest tree, and distance to neighboring trees. Results showed that the forests under study are mixed and include Prosopis cineraria, Prosopis farcta, Tamarix stricta, Lysium shawii, and Calligonum comosum as the main species. The mean density of Prosopis cineraria and other species were 10.6 and 37.2 tree.ha-1 and canopy cover were 308 and 1088.3 m2.ha-1, respectively. The height and diameter of P. cineraria trees were in the range of 5.5-14.3 m and 16-100 cm respectively, and its regeneration density was 1.26 tree.ha-1. The structure of the forest was uneven-aged and two-layered which in overstory was occupied by P. cineraria trees. The distribution pattern of P. cineraria trees was clumped which may be influenced by type and size of the seeds, dispersion method, human interference, habitat constraints, and livestock grazing. Due to the lack of trees in low diameter classes and lack of regeneration, tree planting and preservation is recommended, especially in occupied lands.

This study aimed to evaluate the structural characteristics of Quercus macranthera forests in the Arasbaran region, Hatam Mashe Si, Meshgin-Shahr. To achieve this, all trees and shrubs were full calipered in three one-hectare plots. Additionally, the structural characteristics were measured using the nearest neighbor’s method. To measure intensity of trees, several indices like nearest neighbor distance index (density of trees), uniform angle index and Clark and Evans index (variety of location), Mingling index and Shannon-Wiener index (tree diversity in diameter classes), diameter and height differentiation indices (dimensional differences of trees), and complex structural diversity index (tree diversity) were used. The results showed that Q. macranthera represented a relatively homogeneous structure in its main site, and the mean of distance to the neighbors was 2.59 m. The results of uniform angle and Clark and Evans indices showed that the spatial pattern of trees was regular. Mingling and Shannon-Wiener indices showed a low tendency of Q. macranthera to mix with other tree species so that the majority of trees were Q. macranthera. The height and diameter differentiation indices illustrated that the dimensions of the trees had a slight difference. According to complex structural diversity index, tree diversity was at the medium level. It can be concluded that the Q. macranthera communities have a homogeneous structure in a study region with a low mixture and single canopy layer. The information can provide the opportunity to monitor future changes in Q. macranthera communities in this region. To promote ecosystem stability, it is suggested to create heterogeneity of stand structure and support other tree species in this area.

This research aimed to evaluate the spatial patterns of water quality and its controlling factors in the Mazandaran coastal ecosystem during winter using the multivariate analysis methods.

Water quality parameters such as nutrients, temperature, conductivity, salinity, DO, pH, chlorophyll-a and turbidity were measured monthly in 16 stations (44 layers) along 4 transects (Amirabad, Babolsar, Noushahr and Ramsar). To evaluate the data, several multivariate statistical methods were used including discriminant function analysis, cluster and factor analysis as well as correlation test.

Results of cluster analysis showed that the sampling sites (44 layers) were classified into 4 groups. Based on discriminant analysis, 93.20% of the sampling sites correctly classified. Factor analysis extracted 4 principal components that explained 74.05% of the total variance. Based on these analyses, organic phosphorus, organic nitrogen, turbidity, chlorophyll-a and temperature were the most effective parameters on the spatial variation of water quality.

This study suggested that the number of sampling locations could be reduced to 3 transects including Amirabad, Babolsar and west coasts (Noushahr and Ramsar) and 2 stations (one surface layer and one deep layer). Transport of nutrients from land, sea floor and fish cage culture were the most effective factors on spatial patterns of water quality in Mazandaran coasts. Based on the results, multivariate statistical methods are also introduced as one of the useful methods for identifying the spatial pattern of water quality.

The ecological importance of deadwoods has led to an ever-increasing collection of related information to be taken into account in management plans. Considering the key role of deadwoods in forest ecosystem, the present study investigated some of the most important characteristics of deadwoods, including number, volume and spatial distribution pattern in a natural forest with beech dominance. For this purpose, two managed and unmanaged regions were selected from Gorazbon district of Kheyrudkenar forest in the vicinity of Noshahr as the study area and full calipering inventory of deadwoods was done. Moreover, species, diameter and height of standing deadwoods and in the case of fallen deadwoods, characteristics such as species, median diameter and their length were recorded and measured. In order to study the spatial pattern of the deadwood, the position of each deadwood was obtained by azimuth distance method using a laser distance finder and subsequently analyzed by univariate O-rings statistic functions. The results showed that the frequency of deadwoods were in the managed area more than of the unmanaged area, whereas the volume of deadwoods in unmanaged area was more. The highest number and volume of deadwoods were in low-diameter class of the managed area and in large and very large class of the unmanaged area respectively. The O-ring statistic showed that the spatial pattern of whole deadwoods in the managed and unmanaged area was completely random. Thus it can be stated that disturbances in studied area were in small scale. The amount of deadwood especially in managed area is not enough and its increasing is one of the requirements that with regarding to disturbance and structure pattern should be considered.