Spatial pattern of Populus euphratica Oliv. using K, L, G and J functions in Maroon, Behbahan

Recognition of spatial pattern of plant species is essential to check the canopy position, regeneration, forest dynamics and identify biological relationships in an ecosystem. One of the main goals in analyzing the spatial pattern of trees in forest ecosystems is to discover more meaningful relationships between trees and their environment. For this purpose, special analytical methods are used to quantify the spatial pattern of plant communities. The aim of this study was to determine the spatial pattern of Populus euphratica Oliv. using various K, L, G and J functions and the ability of these functions in determining details spatial pattern of the species in riparian forests of Maroon, Behbahan.

Two stands of Populus euphratica including Pure and mixed were studied and callipered. Position (distance and azimuth) of all individuals with DBH larger than 5 cm was set. Spatial pattern of Populus euphratica in both pure and mixed stands was determined using Ripley's K function, L, G and J functions. For explanatory analysis in analysis of point statistics, the assumption test of complete randomness of points was considered. The usual hypothesis test in point analysis statistics was applied based on simulation tests such as the Monte Carlo significance test. This test was repeated 999 times so that the probability of the first type of error is at least close to 5%. Also, in order to check the homogeneity and heterogeneity of the studied areas, the Kolmogorov-Smirnov test was used, and R software (Var3.2.2) was used to analyze the distribution pattern.

Findings: 

The results related to the analysis of the spatial distribution pattern of the Populus using Ripley's K function in the pure stand indicate that the distribution pattern of the Populus up to a distance of approximately 150m is clumped and from this distance onwards, the pattern has changed to randomness and then to uniformity. A significant clumped pattern can be seen in the mixed stand up to a distance of about 125m. The results of the analysis of the heterogeneous L function in the pure stand show the spatial pattern of the field up to a distance of about 150m, a significant clump. In the mixed stand up to a distance of 125m, the pattern is aggregated and from this distance onwards, the pattern changes towards randomness and then significantly towards uniformity. The inhomogeneous function G in the pure stand of Populus up to a distance of about 100m shows a clumped pattern with a low slope. In the mixed stand of Populus from the initial intervals onwards, the curve with a low slope indicates a medium aggregated pattern. The value of the J index in the pure stand is equal to 1 up to a distance of about 30m, and the uniform state curve shows the existence of a random pattern up to this distance. The value of the index is less than 1 from the distance of 30 to about 75m with an almost steep slope, which indicates a relatively strong clumped pattern. In the mixed stand, the value of the index is less than 1 up to a distance of about 60m, with a steeper slope, and shows a strong clumped pattern.

All functions for two stands have confirmed similar results which are clumped up to a distance of about 100 meters. The J function provided more detail of the spatial pattern. Generally, the functions endorsed a type of ecological dependency between the Populus euphratica individuals.