جستجوی مقالات مرتبط با کلیدواژه « spatial pattern » در نشریات گروه « اکولوژی »

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.

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.

Evaluation of water requirement in designing irrigation systems and water supply in agriculture is important. The aim of this study was to estimate and determine the spatial pattern of water requirement of apple tree using weather stations statistics from 1985 to 2013 in apple tree cultivation areas in Iran. Initially, annual reference evapotranspiration was estimated based on the FAO, Penman-Monteith model, In the following, the stages of growth the summer apple Kohanz crab and autumn apple Red-Delicious were identified. Eto calculation annual results and water requirement of growth stages were identified using ArcGIS10.2 as a spatial pattern for each variety. The results showed that the annual ETo in the North-Eastern and Southern regions of the apple cultivation area cultivar reaches more than 2000 mm. The summer apple Kohanz crab has less water requirement than autumn apple Red-Delicious varieties and the middle stage of growth in apple trees have the highest water requirement. The spatial changes in evapotranspiration and water requirement apple trees are due to altitude factor. From the north to the south and from the West to the East, the apple cultivation areas in Iran increases the amount of water requirement.

Knowing spatial pattern of plant communities is necessary to recognition of forest ecology and management. In order to investigation on the spatial distribution pattern of wild cherry, forest management plan of Hajikola-Tirancoly in Mazandaran Province was selected. The locations of Prunus avium L.individuals with 100% inventory were recorded through GPS equipment in three areas of case study such as: Fagus type, protective area and plantation area. Qualitative characteristic of trees crown (symmetrical or unsymmetrical) and diameter at breast height was recorded. In order to achive spatial structure, landscape analysis and metrics in class level ( with symmetrical and unsymmetrical crown) was applied using Fragstats and Arc Gis softwares. The results indicated that number of Prunus avium L. were 160 trees in our case study. Highest and lowest distance among trees was observed 67 and 121 meters, respectively. The results of metrics analysis showed that the distribution pattern of wild cherry in Fagus type was clumped pattern and protective area was uniform. The results of metrics Shannon- Wieners evenness (uniformity) and Simpson’s diversity showed that the highest diversity and spatial arrangement was in Fagus type.

Knowledge of the spatial patterns of plants distribution is necessary for the measurement and investigation of vegetation. This research was carried out to study and analysis the distribution pattern of Berberi integerrima in Asbchar rangelands of Baladeh Mountains at the Noor County. Sampling method was random- systematic along three transects with 100 meters length within the type of 1400 hectare. 10 random points were selected along each transect with distance of 10 m and were performed measurements. After choosing any random point, were measured its distance to the nearest plant, distance of that plant to nearest neighbor plant and distance of random point to second nearest plant. Using this data was calculated distance indices of distribution (Eberhart, Hopkins, Holgate, Johnson and Zimmer). In addition, in each random point were established 3m2 plots and were counted number of plants at them. With this information were calculated the quadratic indices of distribution (variance mean, green, Lloyd, Morisita and standard Morisita). The results of methods of one hundred percent sampling methdos such as nearest neighbor, K Rieply and Ld showed that distribution pattern of the species is clumped. Between the distance indices of distribution, Johnson and Zimmer, Eberhart and Hopkins with values 2.66, 2.05 and 0.6 respectively and between the quadratic indices, variance mean, green, Morisita and standard Morisita with values 6.88, 0.2, 2.3 and 0.53 respectively showed clumped pattern for this species. Therefore, for determination of the distribution pattern of this species must be used these methods and pay attention to are better methods to clumped pattern of this species when rangeland are reclaiming with this species.

It is so important to know about ecological characteristics of trees of a stand, in forest management. The first step to achieve this knowledge is to recognize the spatial pattern of trees. Therefore, regarding the enviro-economic importance of F. orientalis in hyrcanian forests, this study checked spatial pattern of these trees. In order to do this research, 5 one-hectare plots with homogeneous environmental conditions were inventoried in natural stands of Fagetum in Nave Asalem, Guilan province accidentally. Then, measuring the angle between fagus trees and using indicators of uniform angle index (Wi), Mean directional inedx (Ri), Mean of angles index and Clark-Evans (CE), the spatial pattern in Fagus orientalis was analyzed. The results showed clumpy pattern of the Fagus orientalis trees which is also tended to be random, and using Wi, Ri and CE indicators together provides better results to determine the spatial pattern of trees. Also, using angular indicators, besides the high accuracy due to the lack of need to measure distances between trees, speeds up spatial pattern determination of forest stands.

The regeneration is one of the most important phenomena in forest ecosystems and the most important factor of development and sustainability of forests. Assessment of the regeneration is one of the best criteria for monitoring forest function stability. The aim of this study was to investigate the spatial variability of regeneration diversity and its relationship with tree species diversity in Zagros Forests, Kermanshah (Gahvareh).This study was conducted at 70 hectares of Gahvareh forests. In this area, 67 sample plots (400 m2) were used in a 100 × 100 m sampling grid. In each plot, total number and species of trees and all seedlings which had diameter less than 7.5 cm were recorded. We also recorded asexual regeneration in ¼ plots (100 m2).Then the spatial continuity was described using geostatistics (variogram and cross- variogram). The variograms of variables revealed the presence of spatial autocorrelation except evenness index (Sheldon) of trees and sexual regeneration. They had spatial dependence at large ranges that showed the large distance of dependency and homogeny of condition. In addition, cross-variograms indicated a strong spatial relationship between diversity of sexual regeneration and tree diversity and between diversity and richness of asexual regeneration and tree abundance.

This study aimed to investigate the spatial patterns of Acanthophyllum microcephalum Boiss, Nepeta glomerulosa Boiss and Hertia angustifolia and evaluate the effects of study scale on spatial patterns of three range plant species in Ghale-Gharak research-station located in Shahr-e-Kord. 40 points with a distance of five meters from each other were selected for sampling of vegetation along four 50 m transects using a random-systematic approach. The species spatial patterns were measured by 6 different distance-based methods including Hopkines, Johnson-and-Zimer, Eberhardt, Holgate, Hines and T-Square-index. A 100 m2 reference site (10 by 10 m) was selected to record the species co-ordinates and conduct point pattern analysis. The spatial patterns of the species were determined in 3 scales of 10×10, 5×10 and 5×5 meters to highlight the effects of scale on spatial patterns of vegetation. According to the results, H. angustifolia showed randomized spatial patterns due to its seed dispersal ability. N. glomerulosa and A. microcephalum showed a clustered spatial pattern beacuse their seed are in achene form and fall next to these species. All the 3 species had a clustered pattern when the scale of point pattern analysis was decreased. Identifying these plant spatial patterns and their controlling factors) such as seed dispersal mechanisms of the species and sampling scale) are required to select the best sampling strategy in rangeland assessment programs.

The key factor in understanding the forest ecosystems is forest structure. Spatial arrangement and location of trees are both one of the main components of forest stand structure. This study was carried out in Manesht protected area, Ilam province. In order to determine the ecological groups and spatial patterns of indicator species, we used fixed-area plots method. For data collection, 125 square sampling plots with an area of 400 m2 were selected based on a systematically random method. The plants were classified using TWINSPAN analysis and then spatial pattern was analyzed by indices of ratio of average to variance, Morisata and standardized Morisata. Four ecological groups were specified and all dispersion indices showed clumped pattern for indicator species of the ecological groups. The results of this study could provide useful information to describe the sustainability of this valuable ecosystem and monitoring protective and rehabilitative practices.

The spatial distribution of benthic foraminiferal assemblage of Nayband Bay and Haleh Estuary, North-West of the Persian Gulf, was explored for the first time during March 2011 to March 2012. The most abundant benthic foraminifera species which were found in the studied area include Ammonia beccarii, Eponides repandus, Quinqueloculina sp., Elphidium sp. The two most abundant species belongs to Rotaliidae family.  The specimen groups presented in the studied area were somehow the same, and their relative abundance did not vary tremendously in sites consisting of foraminifera assemblages.  The relationship between spatial pattern of foraminifera assemblages and ambient factors (i.e. sediment grain size distribution, sediment organic content, heavy metals contents) was measured. Background enrichment indices, contamination factor and contamination degree, were used to assess the health status in the studied area based on Nickel, Lead, Cadmium and Mercury contents of the sediments. Background enrichment indices showed that the health of Jafari Creek has not altered over time due to the constant discharge of industrial wastes to the ecosystem. The concentration of four measured elements was lower than the permitted concentrations announced by NOAA و ISQG.  The BIO-ENV analysis identified a negative relationship -0.32 between the concentration of assessed metals and foraminifera assemblages.

Spatial pattern of trees in forests reveals how trees interact with each other and their environment. Spatial structure of trees in forest ecosystems is affected by environmental heterogeneity that leads to their heterogeneous distribution. This study was aimed to investigate the appropriate methods to analyze spatial pattern of heterogeneous wild pistachio woodlands in Zagros، Iran. A 40-ha pure stand of wild pistachio trees (Pistacia atlantica Desf.) was selected in Wild Pistachio Research Forest in Fars Province for this purpose. The Kolmogrov-Smirnov test of goodness-of-fit of inhomogeneous Poisson point process showed that the distribution of wild pistachio trees was significantly heterogeneous (α=0. 05). Inhomogeneous Ripley''s K-، L-، and G-functions were applied beside their homogeneous forms. Inhomogeneous Ripley''s K- and L-functions showed that wild pistachio trees were primarily clumped and dispersedly distributed thereafter، while g (r) not only showed these results but also well expressed the detailed changes in spatial scale. The results of inappropriate homogeneous functions in the study area showed that all three functions expressed the primary clumping of the trees more than it was and their dispersed pattern as clumped. In general، it was concluded that inhomogeneous functions should be applied to analyze the spatial pattern of heterogeneous wild pistachio trees in the study area and it is recommended to develop g (r) applications due to its more detailed information

The spatial distribution of soil organisms is influenced by the plant cover, thus resulting in a horizontal mosaic of areas subjected to gradients of nutrient availability and microclimatic conditions.This study was conducted to investigate the spatial variability of soil macrofauna in relation to vegetation density in the riparian forest landscape of Karkhe. The vegetation density was determined by calculating the NDVI index. Soil macrofauna were sampled using 200 sampling points along parallel transects (perpendicular to the river). The maximum distance between samples was 0.5 km. Soil macrofauna were extracted from 50 cm×50 cm×25 cm soil monolith by the hand-sorting procedure. Abundance, diversity (Shannon H’ index), richness (Menhinick index) and evenness (Sheldon index) were calculated. Soil macrofauna and NDVI data were analyzed using geostatistics (variogram) in order to describe and quantify the spatial continuity. The variograms were spherical, revealing the presence of spatial autocorrelation. The range of influence was 1724 m for abundance, 1326 m for diversity, 1825 m for richness, 1450 for evenness and 1977 m for NDVI. The kriging maps showed that the NDVI Index and soil macrofauna had spatial variability. The spatial pattern of soil macrofauna abundance and biodiversity were similar to the spatial pattern of vegetation density as shown in the correlation.

Distance methods and their estimators of density may have biased measurements unless the studied stand of trees has a random spatial pattern. This study aimed at assessing the effect of spatial arrangement of wild pistachio trees on the results of density estimation by using the nearest individual sampling method in Zagros woodlands, Iran, and applying a correction factor based on the spatial pattern of trees. A 45 ha clumped stand of wild pistachio trees was selected in Zagros woodlands and two random and dispersed stands with similar density and area were simulated. Distances from the nearest individual and neighbour at 40 sample points in a 100 × 100 m grid were measured in the three stands. The results showed that the nearest individual method with Batcheler estimator could not calculate density correctly in all stands. However, applying the correction factor based on the spatial pattern of the trees, density was measured with no significant difference in terms of the real density of the stands. This study showed that considering the spatial arrangement of trees can improve the results of the nearest individual method with Batcheler estimator in density measurement.

The ecological relationship between trees is important in the sustainable management of forests. Studying this relationship in spatial ecology، different indices are applied that are based on distance to nearest neighbor. The aim of this research was introduction of important indices based on nearest neighbor analysis and their application in the investigation of ecological relationship between Persian oak coppice trees in Zagros forests. A 9 ha plot of these forests in Kohgilouye - BoyerAhmad province was selected that was completely homogeneous. This plot was covered with Persian oak coppice trees that their point map was obtained after registering their spatial location. Five nearest neighbor indices of G (r)، F (r)، J (r)، GF (r) and CE were then applied to study the spatial pattern and relationship of these trees. The results showed that Persian oak coppice trees were located regularly in the homogeneous plot and they were not dependent ecologically. These trees were independent and did not affect the establishment of each other.

Spatial patterns are suitable tools for optimal management in many forested areas. In this research، the effect of conservation on spatial pattern of dominant trees has been studied. To achieving this purpose، protected and non- protected forests were selected in Masal region of Guilan province as the study area. Sampling methods including fixed- area plots and distance methods، such as T- square and compound sampling were used 25 circle sample plots، each with an area 1000 m2and 25 sampling points were taken. Then، tree species in plot samples and the distance of interest were identified and measured. Dispersion indices such as Green، Morisata، standardized Morisata، Hopkins، Eberhart، Johnson and Zimmer، Hines and C were used to analyze the spatial pattern in the areas. All indices related to plot samples indicated the clumped pattern for dominant species in protected and non- protected areas. The results of the distance indices have indicated that destruction changes the spatial pattern of dominant species and these species had different pattern in these areas. Among the distance indices، C and Hines indices revealed differences and they were suitable to describe the spatial pattern of both areas.

Saline soils are common in different ecological sites of Iranian rangelands. Vegetation distributions in saline soils are correlated with soil properties, so recognition of vegetation changes with soil characteristics is necessary for management and restoration of saline rangelands. The aim of this study is to identify main halophyte communities and their relationship with soil properties of rangelands of Sorkhdeh Damghan in Semnan province. Systemathic-randomised taking sample was selected in each homogenous unite of vegetation for both standing vegetation and soil. Cover percentage for vegetation is recorded and soil properties are measured in laboratory. Results of cluster analysis show that there are five halophyte communities. Analysis of variance indicates that all five communities are significantly different according to the soil properties. We also found that species richness and diversity were significantly greater in Hypocylix kerneri-Salsola dendroides than others. Multivariate analysis shows that soil significantly influences the species distribution and any changes causes in soil properties may transfer the vegetation community to others. EC, K, Caco3 and soil texture are the most dominant factors forming vegetation distribution.