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.