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Activity Number: 254
Type: Contributed
Date/Time: Monday, July 30, 2012 : 2:00 PM to 3:50 PM
Sponsor: Section on Statistics and the Environment
Abstract - #304400
Title: Bayesian Estimates of Shrubs Species Diversity in Arid Rangelands Under Two Grazing Management Systems in Northern Syria
Author(s): Murari Singh*+ and Abdoul Aziz Niane and Paul Struik
Companies: ICARDA and ICARDA and Wageningen University
Address: PO Box 5466, Aleppo, , Syrian Arab Republic
Keywords: Diversity indices ; Bayesian method ; Shannon index ; Simpson index ; Rangelands ; Shrubs

The diversity of shrubs in rangelands of northern Syria is affected by the grazing management systems. Shannon and Simpson indices were used to estimate shrubs diversity. We use three sets of prior for the parameters in the Bayesian approach to estimate the indices and compare with frequentist approach. Prior distribution for the species class proportions was taken as Dirichlete distribution with parameter values judged to normalize the indices best. The Bayesian estimates of the diversity were found larger with smaller standard errors compared to the estimates based on frequentist approach which ignores any prior information. The diversity of the shrub species, measured by each index, under the closed system (no-grazing) was significantly higher than that under the open grazing at each site. Also, the Hammam site has significantly higher diversity compared to Obesian under each system. Further, in comparison with the frequentist approach, the Bayesian approach resulted in lower p-values in all the four cases for Simpson index and in two cases for Shannon index. It is recommended that use of Bayesian approach be exploited in estimation of diversity.

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