This name is a synonym of Deschampsia cespitosa subsp. macrothyrsa (Tatew. & Ohwi) Tzvelev.
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 407761) with original publication details: Canad. J. Bot. 41: 740 1963.
This name was in version 1 of The Plant List, record kew-407761.