Psammophyte vegetation of the Bargusin depression (Republic of Buryatia)

Abstract

Modern aeolian landscapes occupy large territories in Transbaikalia. The Barguzin depression bottom is an area with sandy lands (Ivanov, 1960). This depression is one of the largest around the Lake Baikal (Florensov et al., 1965). Its internal field are accumulative surfaces, formed by Pleistocene sands, so-called “kujtuns” (Forest, Suvinsky, Lower, and Upper), are located as stripes of variable width, replacing each other from the north-west to the south-east (Fig. 2 A-D). Aeolian processes are most dynamic on weakly sod and bare sands: in the lower part of the Argada river, in the basins of Ina, Ulan-Burga, Zhargalanty rivers, and in the marginal parts of the steppe “kuytuns” (Fig. 3, 4). The results of aeolian processes are dunes and ridge-basin relief. This publication continues the series of papers (Dulepova, Korolyuk, 2013, 2015; Dulepova, 2016) on psammophytic vegetation of Baikal Siberia (Irkutsk region, the Republic of Buryatia, and the Trans-Baikal region). The paper is based on the analysis of 116 geobotanical relevés obtained in the course of the field studies in 2009–2014 in the Barguzinsky and Kurumkansky districts of the Republic of Buryatia. Four relevés are taken from the literature (Shchipek et al., 2002). Three diagnostic species of the class Brometea korotkiji Hilbig et Koroljuk 2000 (Bromopsis korotkiji, Corispermum sibiricum, Carex sabulosa) occur on the studied sandy lands. Among species of the order Oxytropidetalia lanatae Brzeg et Wika 2001 (Brzeg, Wika, 2001) such species as Artemisia ledebouriana, Chamaerhodos grandiflora, Oxytropis lanata have high constancy and often dominate in communities. When comparing new syntaxa with the previously described alliances (Oxytropidion lanatae Hilbig et Koroljuk 2000, Aconogonion chlorochryseum Dulepova et Korolyuk 2013 and Festucion dahuricae Dulepova et Korolyuk 2015) it was found that they are closer to the alliance Festucion dahuricae. However, Artemisia xanthochroa, Caragana buriatica, Festuca dahurica, Thymus baicalensis, and Ulmus pumila, commom in the Selenga river middle mountains, are absent in the study area (Korolyuk, 2017). The psammophytic fraction of the flora of the study area is not very peculiar. Only two endemic species (Oxytropis bargusinensis and Aconogonon bargusinense) are recorded on the sands of the Barguzin depression. 5 associations, 3 subassociations and 3 communities of the class Brometea korotkiji and 1 association of the class Cleistogenetea squarrosae Mirk. et al. ex Korotkov et al. 1991 (Table 1) are established as new. Association Bromopsietum korotkiji ass. nov. hoc loco (Table 2, rel. 6–17). Nomenclature type (holotypus hoc loco): Table 2, relevé 6 (field number — nd10-200), Republic of Buryatia, Kurumkansky district, 2 km southwest of the village of Kharamodun, the convex peak of dune), 54.18734° N, 110.48333° E., altitude 473 m a.s.l., 31/07/2010, author — N. A. Dulepova (Fig. 5). Diagnostic species: Bromopsis korotkiji (dom.). Association Aconogonetum bargusinensis ass. nov. hoc loco (Table 2, rel. 18–25). Nomenclature type (holotypus hoc loco): Table 2, relevé 18 (field number — 10-591), Republic of Buryatia, Barguzinsky district, 7 km south of the village Urzhil, an elevated sandy terrace of the Ulan-Burga river, 53.87645° N, 110.32410° E, altitude 628 m a.s.l., 28/07/2010, ­author — A. Yu. Korolyuk. (Fig. 6, 7). Diagnostic species: Aconogonon bargusinense (dom.) Association Oxytropido lanatae–Caricetum sabulosae ass. nov. hoc loco (Table 2, rel. 26–37). Nomenclature type (holotypus hoc loco): Table 2, relevé 26 (field number — nd10-339), Republic of Buryatia, Kurumkansky district, 8.3 km southwest of the village of Kharamodun, an elevated sandy terrace of the Argada river, 54.12156° N, 110.45382 E, altitude 514 m a.s.l., 17/08/2010, author — N. A. Dulepova. Diagnostic species: Carex sabulosa (dom.) Association Oxytropido lanatae–Bromopsietum korotkiji ass. nov. hoc loco (Table 3, rel. 1–30). Nomenclature type (holotype hoc loco): Table 3, relevé 1 (field number — nd09-040), Republic of Buryatia, Kurumkansky district, side of the river valley Argada in 4–5 km south-west from village Argada, the lower part of the high sandy terrace, 54.20118° N, 110.64804° E, altitude 537 m a.s.l., 05/07/2009, author — N. A. Dulepova. Diagnosed by species of class and order. Subassociation B.k.–O.l. typicum subass. nov. hoc loco (Table 3, rel. 1–8. Nomenclature type (holotypus hoc loco): Table 3, relevé 1. Diagnostic features are those of association. Subassociation B.k.–O.l. chamaerhodetosum grandiflorae subass. nov. hoc loco (Table 3, rel. 9–19). Nomenclature type (holotypus hoc loco): Table 3, relevé 9 (field number — 09-176), Republic of Buryatia, Kurumkansky district, side of the valley of the Argada river 4–5 km southwest of the village Argada, upper convex part of high sandy terrace, 54.20235° N, 110.64528° E, altitude 570 m a.s.l., 05/07/2009, author — A.Yu. Korolyuk. Diagnostic species: Chamaerhodos grandiflora (dom.). Subassociation B.k.–O.l. artemisietosum ledebourianae subass. nov. hoc loco (Table 3, rel. 20–30). Nomenclature type (holotypus hoc loco): Table 3, relevé 20 (field number — nd10-325), Republic of Buryatia, Kurumkansky district, 8.3 km south-west of the village of Kharamodun, the upper third of the high sandy terrace of the Argada river, 54.12157° N, 110.48679° E, altitude 557 m a.s.l., 17/08/2010, ­author — N. A. Dulepova. Diagnostic species: Artemisia ledebouriana (dom.), Orobanche coerulescens, Stellaria dichotoma, Vincetoxicum sibiricum. Association Artemisio frigido–Oxytropidetum bargusinensis ass. nov. hoc loco (Table 3, rel. 41–46). Nomenclature type (holotypus hoc loco): Table 3, relevé 41 (field number — 10-566), Republic of Buryatia, Barguzinsky district, 4 km north-west of Bodon village, Suvinsky kujtun, flat elongated blowing trough, 53.71945° N, 110.04983° E, altitude 566 m a.s.l., 27/07/2010, author — A. Yu. Korolyuk. Diagnostic species: Bupleurum bicaule, Iris humilis, Youngia tenuifolia, Oxytropis bargusinensis. According to cluster analysis (Fig. 9) of data from Baikal Siberia, Mongolia, Tuva, and Inner Mongolia (China) the diversity of psammophytic vegetation is mainly determined by the sand land geography, which is reflected at the alliance, order, and class levels. The dynamics of overgrowth of sands is well traced at the association, subassociation, and community levels. Cluster analysis confirmed the attribution of most of the described syntaxa from the Barguzin and Selenga basins in the alliance Festucion dahuricae.