Effects of the Growth Substrate on the Restoration of Stipa capillata L. Populations on Refuse Dumps

A 5-year-long experiment was carried out to assess the possibility of creating a naturelike community of meadow–steppe plant species with the predomination of Stipa capillata L. on the overburden dump of the Vinogradovskii coal pit in Kemerovo oblast. The dump preparation involved leveling the technogenic eluvium and its subsequent covering with (1) a 10-cm layer of fertile topsoil (FTS) taken from heaps of soil removed and piled prior to the dump formation or (2) a 10-cm layer of potentially fertile undersoil (PFUS) consisting of loesslike loam from the overburden dump. A flat site on a sandstone dump with a lithogenically undeveloped soil layer without the application of FTS or PFUS was used as the control. The herbal–seed mixture (HSM) was procured in summer and fall in Bachatskie Sopki regional botanical reserve on steppe slopes, whose vegetation is constituted by meadow–steppe plant communities with the predomination of S. capillata. The experimental and control sites were monitored for 5 years, from 2015 to 2019. The variant with loamy undersoil provides the best conditions for the growth and development of S. capillata: some individuals start blossoming as early as in the first year; in the third year, all plants blossom and fruit; and, in the fifth year, the share of S. capillata in the total productivity amounts to 83.6%. The plants form a thick sod layer and successfully compete with weeds. In the variant with FTS, the share of S. capillata was 4–8% in 2015–2018 and reached 30.1% only in 2019. The suppression of S. capillata in this variant is caused by the high competitiveness of the species Elytrigia repens (L.) Nevski, whose rhizomes were brought to the dump together with FTS from the soil heaps. In the control variant, an S. capillata community was noted in the fifth–fourth years; apparently, it originates from seeds dispersed from the experimental variants.