Cyclic and linear trajectories of ecosystem evolution on sand dunes in Siberian taiga: A comprehensive analysis.

Extensive unforested sandy areas on the margins of floodplains and riverbeds, formed by dunes, barchans, and accumulation berms, are a ubiquitous feature across northern Eurasia and Alaska. These dynamic landscapes, which bear witness to the complex Holocene and modern climatic fluctuations, provide a unique opportunity to study ecosystem evolution. Within this heterogeneous assemblage, active dunes, characterized by their very sparse plant communities, contrast sharply with the surrounding taiga (boreal) forests common for the stabilized dunes. This juxtaposition makes these regions to natural laboratories to study vegetation succession and soil development. Through a comprehensive analysis of climate, geomorphology, vegetation, soil properties, and microbiome composition, we elucidate the intricacies of cyclic and linear ecosystem evolution within a representative sandy area located along the lower Nadym River in Siberia, approximately 100 km south of the Arctic Circle. The shift in the Holocene wind regime and the slow development of vegetation under harsh climatic conditions promoted cyclical ecosystem dynamics that precluded the attainment of a steady state. This cyclical trajectory is exemplified by Arenosols, characterized by extremely sparse vegetation and undifferentiated horizons. Conversely, accelerated vegetation growth within wind-protected enclaves on marginally stabilized soils facilitated sand stabilization and subsequent pedogenesis towards Podzols. Based on soil acidification due to litter input (mainly needles, lichens, and mosses) and the succession of microbial communities, we investigated constraints on carbon and nutrient availability during the initial stages of pedogenesis. In summary, the comprehensive study of initial ecosystem development on sand dunes within taiga forests has facilitated the elucidation of both common phases and spatiotemporal dynamics of vegetation and soil succession. This analysis has further clarified the existence of both cyclic and linear trajectories within the successional processes of ecosystem evolution.

Contribution to knowledge of the oribatid mite genus Symbioribates (Acari, Oribatida, Symbioribatidae), with descriptions of two new arboreal species from Vietnam.

The family Symbioribatidae is recorded in Vietnam for the first time. Two new arboreal species of SymbioribatesS. bimorphus sp. nov. and S. tripartitus sp. nov.are described, based on adults (males and females) collected from tree branches of Dipterocarpus alatus in Cat Tien National Park, Vietnam; the former species is sexually dimorphic, the latter species is the first non-sexually dimorphic representative within the genus. The generic diagnosis is presented. An identification key, distribution and habitats to the known representatives of Symbioribates are provided.

Ontogenetic instars of the oribatid mite Spatiodamaeus kalugaensis sp. nov. (Acari, Oribatida, Damaeidae) from Russia.

A new species of the genus Spatiodamaeus (Oribatida, Damaeidae) is described from Russia, based on adult and juvenile instars collected from bark of Acer platanoides and soil-litter of mixed and broadleaf forests in European part of Russia and Western Siberia. The adult of Spatiodamaeus kalugaensis sp. nov. is similar to S. nortoni (Bayartogtokh, 2004) comb. nov. in having epimeral neotrichy but differs from the latter by the presence of the parastigmatic tubercle Sa, the form of the parastigmatic tubercle Sp and the notogastral setae c1, c2, and the barbulation of the rostral, epimeral, anogenital, and notogastral setae of p-series. Comparisons between juvenile instars of the new species and the known juveniles of Spatiodamaeus and Epidamaeus are presented.

Taxonomic contribution to the knowledge of the oribatid mite family Scheloribatidae (Acari, Oribatida), with description of three new species from Vietnam.

Three new oribatid mite species of the family Scheloribatidae (Oribatida)Dometorina (Dometorina) robusta sp. nov., Phylloribatula latiseta sp. nov., Scheloribates (Scheloribates) paraflagellisetosus sp. nov.are described, based on adults collected from tree branches of Dipterocarpus alatus in southern Vietnam. Representatives of Dometorina (Dometorina) and Phylloribatula are recorded in the Vietnamese fauna for the first time. An identification key to the known species of Phylloribatula is provided.

Neoribates alius Fujikawa, 2007, a junior synonym of Neoribates pallidus Aoki, 1988 (Acari, Oribatida, Parakalummidae).

The morphology of adult instars of two oribatid mites of the genus Neoribates, N. pallidus Aoki, 1988 and N. alius Fujikawa, 2007, is analyzed. Comparisons were based on holotype and paratypes (for N. alius) and specimens identified by the original author (for N. pallidus). Both species were described from Japan. Neoribates alius is recognized as a junior subjective synonym of N. pallidus.