Document Type : Research Paper
Authors
1 Asistant profesour, Department of Rangeland and Watershed Management and Research Group of Drought and Climate Change, Faculty of Natural Resources and Environment, University of Birjand, Birjand, Iran.
2 Assistant professor, Khorasan-e-Razavi Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran.
3 Ph.D gradguate, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran.
Abstract
Abstract
Background and objectives
Plants distribution pattern is one of the most important features of plant communities whose concept is related to the condition of a species and its distribution in a plant community. Awareness of the spatial distribution pattern of plants in each region is one of the basics and requirements for measuring and evaluating vegetation that is important in determining management practices. This study carried out in order to analyze and investigate the distance indices, probability distribution and regression in order to determine the distribution pattern of 17 rangeland species from the dominant species of Southern and Razavi province.
Methodology
Habitats of 17 plant species were identified in four sub-regions: semi-desert, steppe, semi-steppe, and dry forests located in the Irani-Torani vegetation zone in South Khorasan and Khorasan Razavi province. In each habitat, 40 plots of 1×1 m for herbs, 2×2 m for shrubs, 4×4 m for shrubs, and 10×10 m for trees were established along 2 transects (total of 80 plots per habitat). The distribution of species was determined by calculating quadratic indices including Index of Dispersion (ID), Lexis’s Index (IL), Charlier’s Index (ICh) Index of Cluster Size (ICS). Green’s Index (GI), Index of Cluster Frequency (ICF), Index of Mean Crowding (IMC), Index of Patchiness (IP), Morisita’s Index, (IM) and Standardized Morisita (Ip) and probability distribution indices. including Poisson distribution (ID), positive and negative binomial distribution, and Taylor and Iwao’s patchiness regression and Taylor’s power law indices.
Result
Based on the results indices of Morisita’s Index of Cluster Frequency. Standardized Morisita index and Lexis’s Index are close to each other. Stipagrostis, Bromus tomentellus, Acantholimon scirpinum, Stipa barbata, Festuca ovina, Rhamnus pallasii and Cornulaca monacantha species have clumped pattern based on all quadratic indices. Berberis vulgaris, Onobrychis cornuta and Acantholimon scirpinum species have a random distribution pattern based on Green's index and Stachys inflata based on spot and Green's indices. Based on the probability distributions studied on the density data of Festuca ovina, Cornulaca monacantha, Tamarix ramosissima , Astragalus gossypinus and Juniperus polycarpos species, they were following the Poisson distribution which represents a random pattern. Stipa barbata, Festuca ovina and Astragalus squarrosus were the only species that follow only the positive binomial distribution which indicates a uniform pattern. Based on the regression methods, the distribution pattern of the studied plants was clumped. Stachys inflata had a clustered distribution based on all indices. Caligonium polygonoide had a clustered distribution based on all indices except Z and Charlier’s Index (random and uniform, respectively). The results of Morista index, cluster frequency index (ICF), standard Morista index and Lexis index (IL) were close to each other.
Conclusion
In the present study, quadratic indices, regression, and probability distributions were used. Among the methods, quadratic indices predicted 65 % of species clumped, 32 % uniform, and 3 % random distribution. Since the standard Morrisita and Morrisita index are not dependent of N and n, there are better indicators to determine the distribution pattern.
Keywords
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