The petrophyte plant communities of high mountain limestone area, the West Caucasus

The paper presents description of new syntaxa of pertrophyte associations from West Caucasus lime­stone massifs. The work is based on the author’s long-term observations between years 1998 and 2003, made in the basins of the rivers Belaya, Bolshaja Laba and Malaya Laba within the National Nature Park «Bol­shoi Tkhach» and limestone massifs of Caucasian State Natural Biosphere Reserve. Original geobotanical rele­veйs have been used for the classification. Collec­tion and material processing involved Braun-Blanqet me­thod. The size of sampling plots varied from 4 to 25 m². The paper is based upon 120 releveés. New syntaxa names have been given in accordance with the Code of Phytosociological Nomenclature (Weber et al., 2000).

Ass. Veronica minutae—Chaerophylletum humilis Onipchenko 2002 is common for upper alpine belt of the Reserve and distributed over mobile calcareous screes at 2400—2800 m alt. occupying small areas of Oshten, Fisht, Pshekha-Su and Yatygvarta mountains. Ass. Helianthemetum cani ass. nov. includes open chionophobic groupings of alpine belt, developing on windward mountain slopes and crests at 2000—2800 m alt., occurs on rocky outcrops and dry sedentary screes, and covers significant areas of Lagonaki Pla­teau, mountains Bolshoi Tkhach, Yatygvarta and Snegovalka Ridge. These open associations preferen­tially occupy slopes of «warm» (southern, southern-west, southern-east) expositions of different abruptness from almost horizontal up to 70° (in average 25°). Ass. Saxifragetum sibiricae typicum Onipchenko et Lubez­nova 2002 includes chionophytic groupings of seden­tary screes, characterized by significant snow accu­mulation in winter, forms patches of vegetation around snowbeds and glaciers of Lagonaki Plateau in the Reserve, occurs sporadically on the studied territory. Ass. Saxifragetum sibiricae arabidetosum caucasicae subass. nov. combines open communities of alpine belt at unstable damp rocky substrates and predominantly occupies abrupt slopes (20—35°) of northern—nor­thern-east exposition of damp, slightly mobile screes close to glaciers at 2000—2700 м alt. on Lagonaki Plateau in the Reserve. Ass. Saxifrago cartilagineae—Asplenietum rutae-murariae ass. nov. occurs on rocks in subalpine belt predominantly on abrupt slopes
(20—90°, average 69°) of different expositions at 1400—1700 m alt. on Lagonaki Plateau in the Reserve. Ass. Valeriana saxicolae—Helianthemetum cani ass. nov. includes plant communities of limestone rocks occupying abrupt slopes (20—70°, in average 53°) of predominantly southern expositions at 2000—2700 m alt. on Lagonaki Plateau, Triu-Yatygvarta massif, mountain Bolshoi Tkhach.