The 2008 Joint Meeting of the Society for Range Management and the America Forage and Grassland Council.

Tuesday, January 29, 2008
20

Herbaceous Biomass Dynamics in the Arid Zone of Uzbekistan

Wolfgang Pitroff, Livestock Systems Research, Idar-Oberstein, Germany, José Ramón Arévalo, Departamento de Ecología, Universidad de La Laguna, La Laguna, Spain, Bakhtiyor Mardonov, Uzbek Academy of Sciences, Samarkand, Uzbekistan, and Gustave Gintzburger, INRA, Montpellier, France.

Rangeland-based livestock production is the major agricultural use in most of Uzbekistan. After independence, range management practices changed radically and the objective of this study was to analyze the seasonal and temporal dynamics of herbaceous biomass. Herbaceous biomass was determined on 5 distinct range sites representative of over 90% of the rangeland resources currently utilized in this country. Annuals were collected in 1 square meter quadrats, repeated five times at randomly placed locations in the sampling area. All collections were made in spring, repeated for 4 years from 2002 to 2005. Between 12 and 62 species were identified for each site. All sampling sites had similar degree of grazing utilization, with one exception. The effects of grazing intensity, as far as they could be ascertained, are discussed. Above-ground and below-ground biomass were analyzed in linear mixed models after extensive data transformation because of deviation from normality. Number of species found varied strongly between years. Location, species and year were highly significant factors determining above ground biomass. Year was not a significant factor in determining below-ground biomass, but location and species were highly significant. The interaction between location and species was highly significant for both variables, and this interaction appeared to be conditioned by year. Precipitation was used as a covariate in all analyses. Its effect was not significant, but it was retained in the model to adjust the main effects appropriately. The pattern of species richness is discussed in the context of an ordination analysis based on cover conducted on the same sites.

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