To understand the nutrient absorption and adaptability of plant species that initially colonize mounds and the influences of the plateau zokor on the diversity of the plant community after 4 years' period, a series of experiments was conducted in an alpine meadow on the Qinghai-Tibetan Plateau. The contents of C and N and the flow of N in pioneer species were measured and tracked using the 15N isotope tracer method, and the species diversity on 4-year-old mounds was investigated. The results showed that (1) plateau zokors could influence the plant species on the mounds by creating gaps in the grassland; (2) Elymus nutans and Elsholtzia feddei, with high rates and efficiencies of nutrient absorption and transportation, were more competitive on the newly formed mounds than other species; (3) Elymus nutans played a dominant role in the plant community of the mounds; and (4) plateau zokors did not change the plant diversity after 4 years' period. These findings indicated that species colonizing the mounds experienced a process of competition when gaps were created by the rodents, that species with greater capabilities for resource acquisition and utilization had stronger competitiveness and vice versa, and that after a few years, the plant diversity on the mounds was almost similar to that of the undisturbed grassland.
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A new habitat for many inhabitants is created as a result of glacier retreating or spoil-heap construction and these sites provide a unique experimental field for studying primary succession. The general aim of the study was to characterize oribatid fauna established in the first stage of successional process - colonization phase - on new land surfaces, e.g. deglaciated areas and post-industrial dumps. Five microhabitats in the front of two outlets (Nigardsbreen and Austerdalbreen ) of the Jostedal Glacier (SW Norway) and four reclaimed and non-reclaimed post-industrial dumps (Southern Poland) were chosen to study an earliest successional stage. Moderately diverse oribatid fauna was developed on glacier forelands or post-industrial dumps within a few years. Pioneer oribatid communities were not initially similar, especially in species composition. The pool of oribatid species, which were capable of performing the role of colonists, was broad. Fifteen species were found as dominants on nine studied plots. Oppiella nova (Oudemans, 1902) and Lauroppia neerlandica (Oudemans, 1900) were associated with the glacier foreland at Nigardsbreen, whereas Oromurcia bicuspidata Thor 1930 and Trichoribates novus (Sellnick, 1928) were typical of the foreland at Austerdalbreen. Colonizer species appearing within the first years of colonization on the non-reclaimed and reclaimed dumps were also different. Small species of weak sclerotization, representatives of the family Brachychtoniidae (e. g. Sellnickochthonius immaculatus Forsslund, 1942 and Liochthonius piluliferus (Forsslund, 1942) dominated on the non-reclaimed dumps, whereas Ctenobelba obsoleta (C.L. Koch, 1841), Scheloribates laevigatus (C.L. Koch, 1836) and Scutovertex sculptus Michael, 1879, bigger species of strong sclerotization, were the most numerous on the reclaimed dumps. Only Tectocepheus velatus (Michael, 1880) occurred as a dominant at most sites. Parthenogenetic species as well as bisexual successfully invaded glacier foreland and post-industrial dumps. The phenomenon of random colonization in the pioneer stages is well proved on glacier forelands and dumps. However, the process is possibly non-random and depends on the characteristics of an individual species. Although oribatids are known as slow colonizers of new habitats, they were the most numerous group of mites at some sites on glacier forelands and on reclaimed dumps. It is well evidenced that the reclamation measures carried out on post-industrial dumps introduces an element of randomness in the succession of oribatid fauna.
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