Journal of

Background and Objective: the aim of this study was to investigate the effect of different cultivation densities and cutting turns on the wood yield of white poplar (Populus alba L.) trees in eastern part of Dehcheshmeh village in Farsan county. 

Materials and Methods: An area of approximately 5 hectares was divided into 12 more or less uniform and flat terraces. According to the age of the trees, the terraces were divided into two groups: the terraces with young trees (from 6 to 7 years old) and those with older trees (from 15 to 18 years old). The terraces were also labeled either they were uncut, or under the first (cut) or second turn (double-cut) of cutting; and if they were grown in thin or dense cultivation. Number of shoots and the dimensions of the trees were measured using a plot sampling approach. The width of the annual rings of fallen trees was estimated using the photogrammetry method.

 Results: Considering the age of trees as block, a split-plot design indicated that the trees grown in the cut terraces were significantly larger than those in uncut or double-cut terraces in sense of DBH, height, crown height and standing volume. The highest shoot number was observed in double-cut terraces and the highest crown height values were belonged to the uncut and the double-cut terraces. As the cultivations became thinner, the volume and dimensions of the trees increased significantly. The analysis of mean (MAI) and current (CAI) annual increment curves and the point where those curves intercepted, showed that the biological age for the thinned and cut cultivations (the superior treatments) were 12.1 and 13.0 years respectively.

 Conclusion: In the center of poplar cultivation in the province of Chaharmahal-Va-Bakhtiari, it is strongly recommended to cultivate the white poplars in density of less than 100 trees per are, with a single cut, and for 12.5 years of rotation period.

Background and Objectives: Plant ecology is the scientific study of the interactions between plants and environmental factors that determine their distribution and abundance. Ecology provides the necessary framework for an accurate understanding of vegetation dynamics and species distribution, emphasizing the essential role of vegetation within ecosystems. The biodiversity of any habitat plays a crucial role in the stability and health of the natural environment. The assessment of different plant species and their distributions allows important steps to be taken towards biodiversity conservation. Researchers use parametric distribution models, also known as abundance distribution models, to evaluate vegetation diversity and evaluate species diversity. The four main models developed by ecologists include the geometric series model, the lognormal series model, the logarithmic series model, and the broken-stick model, which are used to adjust the distribution of species diversity. The application of parametric models in riparian forests - one of the most diverse and complex plant communities in the world - has provided a new perspective on methods for assessing ecological diversity. Therefore, the aim of this study was to measure biodiversity in the riparian forests of Maroon River in Behbahan district using biodiversity distribution models.

Materials and methods: In this study, transects were laid at 100-meter intervals across the study area to record vegetation. We surveyed 79 sample plots and recorded and analyzed the percentage of tree cover, number of individuals and species composition. The TWINSPAN analysis classified the sampled plots into two ecological groups based on the indicator species Populus euphratica Oliv. and Tamarix arceuthoides Bunge, resulting in 56 and 23 sample plots, respectively. Using the species abundance data and the chi-square test for goodness of fit, we tested the fit of the Geometric, Lognormal, Logarithmic and Broken-Stick parametric models for each ecological group.

Results: The results of the chi-square test showed significant differences between the observed and expected abundance of species in both ecological groups (Populus euphratica and Tamarix arceuthoides), leading to the rejection of the parametric models. However, no significant difference was found between the distribution curve of the observed data and the lognormal distribution curve.

Conclusion: The lognormal model provided the best fit for the distribution of species abundance in both ecological groups, suggesting that these communities are heterogeneous and stable, characterized by species with moderate abundance.