جستجوی مقالات مرتبط با کلیدواژه "mark correlation function" در نشریات گروه "جنگلداری"

Non-native plant species have been introduced to provide various goods and services. Some species have not shown negative effects on the ecosystem, while others cause habitat disturbances. Considering this issue, it is necessary to know these species' positive and negative effects. Paulownia is an exotic industrial tree species, and there are debates on the positive and negative effects of its plantation in forests and non-forest areas among experts and scientists. There are few studies on paulownia invasion behaviour based on the literature review in Iran. This study tries to investigate the competitive behaviour of Paulownia using scientific methods in reforested mixed stands in the educational and research forest of Shast-Kalate. Data were collected in the educational and research forest of Dr. BahramNia (Shast Kalateh) in the two areas. An area of 2.5 hectares of native species mixed with non-native species of Paulownia and another area of 2.5 hectares that only had native species (control). All trees in the study area were recorded. The measured variables for each tree include tree species, diameter at the breast height (DBH), tree height, and crown diameter. All trees with a diameter at the breast height above 5 cm are included in the surveying. The spatial coordinates of all trees were also recorded. The trees included the non-native species of Paulownia fortunei, and the native trees included Acer velutinum bioss, Acer cappadocicum Gled, and Carpinus betulus L. In order to investigate the interaction between species, bivariate O-Ring statistics and bivariate mark correlation functions were used based on distance. The independent T-statistic was used to compare the biometric variables of native species. The graphs obtained from the O-Ring statistic between Paulownia species and native species indicate that the relationships are generally of the attraction or independent type. Also, the mark correlation function results indicate negative and independent interactions based on the DBH and crown diameter and negative for tree height between Paulownia and Acer cappadocicum. Interactions between Paulownia species and Carpinus betulus in all distances were independent based on DBH and negative and independent regarding crown diameter and tree height. Also, positive, negative and independent interactions were seen regarding tree height and crown diameter between Paulownia species and Acer velutinum and attraction and independent interactions were seen in terms of DBH. The independent t-statistics indicate that the average DBH and crown diameter of the Acer cappadocicum Gled in Paulownia mixed plantation is more than the control area, there is no significant difference in tree height. The average DBH and crown diameter of Acer velutinum bioss were higher, and tree height was less in Paulownia mixed plantation compared to the control area. The tree height of the Carpinus betulus L. was higher, and the crown diameter was less in the control than the Paulownia mixed plantation. No significant differences were seen in DBH between the two study areas. Considering Paulownia's growth nature, a higher tree height, DBH, and crown diameter can be expected, and the results confirmed this. In contrast, this growth rate does not exist in native species. On the other hand, the marks used in the mark correlation function include the variables of tree height, DBH and crown diameter, so the negative marked correlation function results can be attributed to this property. In order to introduce a species as invasive, comprehensive research is needed for its effects on the regeneration of native species, composition of vegetation, and soil properties.

Spatial distribution and size of canopy gaps have important implications for light regime and regeneration, and affect species diversity. In this regard, the present study was conducted with the aim of investigating the spatial pattern and structure of harvesting canopy gaps and comparing with natural canopy gaps in mixed beech forests in the Sordar-Anarestan forestry plan located in Chamestan-Noor, Mazandaran. All natural and harvesting canopy gaps were surveyed by a full inventory and gaps area were measured by using of triangles method. In order to spatial analysis, O-ring statistics, variogram analysis and mark correlation function (MCF) were used. The results showed that the most frequency of gaps was related to canopy gaps with area less than 200 m2. The spatial pattern of natural and harvesting gaps was similar and up to a maximum distance of 35 m was clustered and then random. Only the harvesting gaps indicated a spatial structure up to a distance of 168 m. Natural canopy gaps did not have spatial structure and revealed that the gaps are independent of each other in terms of area. Thus, in silvicultural management, disturbance should be created with different areas that unfortunately have been less considered in the study area.

Intraspecific interaction is important because it occurs between the same species individuals that have similar ecological nests. The objective of this study was to evaluate intera-specific interaction of poplar trees (Populus euhratira Olivier.) using mark correlation functions.

The position of all trees with DBH>2.5 cm were recorded in two pure and mixed stands in Behbahan Chaharasyab area with area of 4.5 and 9.1 ha, respectively. Tree height (H), diameter at breast height (DBH), crown diameter (CD) and light crown length (LCL) were measured as mark variables. Point spatial pattern analysis was used to study the spatial pattern and intraspecific interaction. Marked correlation (MCF) function was used to reveal the spatial relationships between the poplar individuals trees in terms of various characteristics such as total tree height, diameter at breast height, crown diameter and light crown length.

The results showed that in pure stand, a significant negative correlation was observed between the DBH of trees at a distance of less than 5 and more than 20 m. Between distances of 5 to 20 m, an independent state was observed between the individuals. There was a positive and negative correlation between the crown diameter of poplar trees from a distance of 5 to 40 m and more than 45 m, respectively. There was a significant positive correlation between the total height and the light crown length of the trees from a distance of 5 to 30 m. At a distance of more than 30 m, the independence was seen between the individuals. In mixed stand, the independence status was observed between DBH of trees up to a distance of 40 meters. A positive correlation was observed at distances greater than 40 m. There was a negative correlation between trees CD at all distances. The independence was seen between H and LCL of trees at most distances.

In pure stand, depending on different distances and marks, various states of interaction including negative, positive and independence were seen between the tree individuals. While in mixed stand, except for the state of negative interaction that was seen in relation to the crown diameter, in other cases, the condition of independence between different individuals was observed in terms of the studied marks. DBH showed similar conditions in both pure and mixed stands. CD showed positive and negative correlations between individuals in pure and mixed stands, respectively. There was a positive correlation between H and LCL of individuals in pure stand while independence was observed in mixed stand. Overall, it is useful to study the interaction between poplar trees to understand the dynamics, growth process and mechanisms that endanger this valuable species.

Intra and interspecific interactions of plants is one of the important processes in establishing spatial structure of plant communities in semi-arid regions. Additionally, the interactions can be applied in management and rehabilitation of vegetation in these regions. This study was aimed to investigate the spatial pattern of wild pistachio (WP) (Pistacia atlantica Desf.) and wild almond (WA) (Amygdalus spp.) in Baneh Research Forest of Fars province to identify their interactions. In two 150 m × 150 m sample plots, the spatial positions of 798 individuals of two species and their crown diameters were measured. Uni- and bivariate g(r), O-ring, D(r) and kmm(r) were applied to explore the spatial patterns of species. The results showed the heterogeneity of spatial patterns of two species individuals, as well as lower density and higher mean crown area of WP. Moreover, WP and WA individuals were located in mixed clusters, although the positive interaction of conspecifics was stronger than heterospecifics. In small scales, density of conspecifics was almost two times more than heterospecifics. Furthermore, the positive interactions of conspecifics resulted in intense intraspecific competition that negatively influenced their crown areas (p < /em> < 0.05) and was more in WA (in 3 m distance between conspecifics, crown areas of WA and WP were 60% and 20% less than mean, respectively). In general, it was concluded that a mutualistic relationship exists between WP and WA in the study area as a result of their facilitative effects. The quantitative results of this study can be used in silvicultural treatments such as plantation.

The spatial distribution analysis of trees in arid and semi-arid regions presents valuable information about their interactions and impacts on one another. This study was aimed to investigate how biometric characteristics of mount Atlas mastic (Pistacia atlantica Desf.) are influenced by their clustered spatial distribution in Zagros vegetation zone. For this purpose, a part of Wild Pistachio Research Site, Fars province, was selected and in addition to registering the position of all trees with > 2.5 cm diameter at breast height (DBH), DBH, height, and crown area of each tree were measured. Wild pistachio trees with DBH > 10 cm and

Intraspecific competition between trees is a key interaction in shaping forest stands and makes analyzing the underlying ecological processes possible. This interaction may affect growth and spatial distribution of trees and result in a specific horizontal and vertical stand structure. For this reason, competition is known as one of the primary processes that influence population size, community structure and its diversity. In order to understand competitive interactions of trees in forests, several methods have been developed to assess spatial scale of competition among individual trees and show the effect of competition their biometric characteristics. Therefore, this study was aimed to investigate the effect of intraspecific competition between Persian oak coppice trees on their biometric attributes in Zagros arid and semi-arid forests using spatial analysis.
A 300 m × 300 m plot purely cover with Persian oaks was selected close to Yasuj city, Kohgiluye - BoyerAhmad province. The point map of all 1113 coppice trees was obtained by azimuth and distance technique. Kolmogorov-Smirnov test was primarily applied to investigate the difference between the distribution of coppice trees and homogeneous Poisson process. Spatial analysis of Persian oak coppice trees was then performed using pair correlation function g(r), O-ring function O(r), and mark correlation function kmm(r). In mark correlation function, biometric characteristics of total height, crown height, diameter at root collar, crown mean diameter and area were implemented as marks. Moreover, Monte Carlo test was used to test the significance of the results.
Comparison with homogeneous Poisson process showed that the observed pattern of Persian oaks was significantly homogeneous (α=0.05). The results of pair correlation function g(r), and O-ring function revealed that there was intraspecific competition between Persian oak coppice trees that was significant up to spatial scale of 5 m (α=0.05).In addition, the results of mark correlation function demonstrated that total height, crown height, and diameter at root collar were very sensitive to intraspecific competition, while crown attributes (i.e. mean diameter and area) showed less sensitivity to competition.
In general, it was concluded that there were competitive interactions between Persian oaks in the studied pure stand that negatively affected their biometric characteristics. Competition between coppice trees negatively influenced their growth, although this negative interaction had less effect on crown attributes as the distance between coppice trees because of their low density (123.7 coppice trees ha-1) reduced the crown competition.

The spatial distribution analysis of woody plants in arid and semi-arid environments explains their interactions and how they influence one another. This study was aimed to evaluate the intraspecific interactions of Eshnan (Seidlitzia rosmarinus) shrubs across a portion of central Iranian arid lands using different summary statistics including pair correlation g(r), O-ring O(r), nearest neighbor distribution D(r), spherical contact distribution Hs(r) and mark correlation kmm(r) functions. A 160 × 160 m2 plot purely covered by Eshnan was selected in Qehi protected area, Isfahan province. The point map of all 989 Eshnan shrubs was obtained by Trimble R8 differential global positioning system with a positional accuracy of 3 mm ± 0.1 ppm. The observed pattern of shrubs showed significant spatial heterogeneity as compared to inhomogeneous Poisson process (α=0.05). The results of g(r) and O(r) revealed the significant aggregation of Eshnan shrubs up to scale of 3 m (α=0.05). The results of D(r) and Hs(r) also showed maximum distance to nearest shrub to be 6 m. It was additionally shown that the distribution of gap sizes was significantly different from random up to this spatial scale. Finally, kmm(r) for height, mean crown diameter, and crown area indicated the aggregation of Eshnan individuals at all scales. In general, positive interactions were concluded to exist amongst Eshnan shrubs at small scales, and they were aggregated due to their intraspecific facilitation effects in the study area.