Chalky Highlands in Orenburg Oblast, a Unique Habitat for Rare Plant Species and Plant Communities

Resumo

The paper reports on the floristic, geobotanical, and population biology studies conducted during the years 2014–2017 in nine chalky highland areas within the steppe zone of Orenburg oblast, which is characterized by high specificity and a high proportion of rare and endemic species. The floristic studies were performed with the commonly used route method. Environmental significance was assessed on the basis of eight indicators commonly used in sozological works, including floristic and phytocenotic significance, distribution, naturalness, areal decrease, restorability, protection category, and the protection rate. Forty species included in different levels of Red Data Books and 15 endemic species have been detected within the explored areas. The highest number of rare plant species was reported from the Verkhnechibendinsk and Troitskoe chalky mountains (26 species from each area), which are the largest and least disturbed prototype chalk massifs in the region. A high abundance of rare plant species was observed in the Artemisia salsoloides (24 species) and Agropyron desertorium (25 species) communities. Assessment of the environmental significance revealed that the Anabasis cretacea, Nanophyton erinaceum, and Anthemis trotzkiana communities received the highest score for the integral indicator “protection category.” A status assessment for populations of six rare plant species growing in the explored chalky mountains showed that enhancement of the antropogenic burden causes a decrease in the viability of the analyzed populations. It is noted that that four unprotected chalky highland areas and chalk outcrop areas in Orenburg oblast should be provided with protection.