The impacts of management and site conditions on the phytodiversity of the upper montane and subalpine belts in the Central Greater Caucasus
Tephnadze, Nato; Abdaladze, Otar; Nakhutsrishvili, George; Simmering, Dietmar; Waldhardt, Rainer; Otte, Annette
Land management and land-use change, together with site conditions and their changes over time, impact the diversity of grasslands and related habitats. The relative importance of these determinants for the species composition of agricultural land is unknown in the Central Greater Caucasus (global biodiversity hotspot), where the population mainly depends on the agricultural sector and socio-economic processes have led to recent changes in land management. Therefore we studied the species composition of (i) grasslands nearby villages, (ii) cultivated and recently abandoned potato fields, and (iii) Hippophae scrubs, which occupy abandoned grasslands. In total we recorded 183 relevés, located nearby villages, with a standardized plot size of 25 m2. For each plot, site-specific parameters (topography, aspect, soil physical, and chemical properties) were recorded. Indicator species analysis (ISA) clearly differentiated species composition of the four main vegetation groups (hay meadows, pastures, arable land and Hippophae scrubs). ISA, TWINSPAN (level I) and DCA ordination differentiated grasslands according to land use type (hay meadows and pastures). Level II and III of TWINSPAN division differentiated the relevés according to site conditions, which was supported by MANOVA analysis for the third level. Forward selection and partial CCA revealed that 'Land use type', 'Topography', 'Aspect' and 'Soil properties' explained 24.8% of the total variation in floristic composition. Soil physical and chemical parameters were the most important determinants for species composition. The 'Land use type', 'Topography' and 'Aspect' had almost equal and relatively low explanatory values. Multivariate GRM revealed that 'Land-use type', 'Slope inclination', 'PCAL' and 'spatial component' had significant effects on the species richness and diversity indices (Shannon, Evenness). Considerable differences in the species composition of cultivated and recently abandoned potato fields, as well as in Hippophae scrubs located either nearby hay meadows or pastures were revealed by DCA ordination and ISA.