Soil salinization is a significant obstacle to improving natural grasslands, also affecting farmland productivity. The main distribution area of high salinity soils is primarily located in western China, with a significant presence in the Qinghai–Tibet Plateau (QTP). Siberian wildrye (Elymus sibiricus L.) has been widely used in ecological restoration and reseeding in the QTP, due to its strong salt and alkali resistance. To comprehensively evaluate its salt tolerance and to screen salt-tolerant and salt-sensitive germplasm resources, 50 wild E. sibiricus accessions were assessed through the measurement of several physiological parameters. These included the relative water content (RWC); relative electrical conductivity (REC); malondialdehyde content (MDA); proline content (Pro); and Na⁺/K⁺ ratio after 14 days of salt stress treatment (200 mmol L⁻¹ NaCl). Through principal component analysis (PCA) based on both material sources and physiological indexing, it was found that the salt damage score (SDS) and RWC had a strong positive correlation (p < 0.05), in opposition to other indices. The positive indicators were REC, Pro, Na⁺/K⁺, and MDA, and the negative indicators were RWC and SDS. Ultimately, by combining the results of the conventional membership function analysis and the weighted membership function analysis based on major components, three salt-tolerant accessions—including XJ013-28, NM021-13 and XJ012-17—and four salt-sensitive accessions, including XZ008-20, QH013-8, XZ009-20, and QH005-35, were screened out. These results could be effectively used to assess the effects of salt stress on Siberian wildrye and its related species. This study provides a reference for the discovery and breeding of salt-tolerant cultivars among the Elymus species.

Kengyilia melanthera is one of the most important forages, and has received significant attention as a desirable ecological pioneer grass for conserving grasslands and mitigating degradation pressure in a region. It is widely distributed in the alpine sandy meadow zone of the Eastern Qinghai–Tibet Plateau (QTP). Therefore, determining the optimal harvest time of this species is critical. A two-year field experiment (2016–2017) was utilized in this study to evaluate the impact of eight harvest times on the seed yield and quality of K. melanthera ‘Aba’. The results show that the fresh weight (FW), dry weight (DW), seed yield (SY), thousand-grain weight (TGW), accelerated aging germination percentage (AAGP), and dehydrogenase activity (DA) of seeds increased with the extension of harvest time in two trial years, while the water content (WC) of seeds decreased. In both trial years, the germination percentage (GEP), germination potential (GP), and acid phosphatase activity (APA) of seeds increased initially and then decreased with the extension of harvest time. The comprehensive evaluation of the membership function and hierarchical clustering revealed that the 30th day after peak anthesis was the optimal harvest time for both 2016 and 2017. During this time, FW, DW, SY, TGW, AAGP, DA, WC, GEP, GP, and APA reached their optimal value, with 0.815 g, 0.518 g, 1773.67 kg·hm⁻², 143.81%, 66%, 16.23 µg·mL⁻¹, 36.01%, 87%, 85%, and 2.50 nmol·min⁻¹ in 2016 and 0.805 g, 0.515 g, 1847.42 kg·hm⁻², 133.96%, 65%, 16.52 µg·mL⁻¹, 36.04%, 86.5%, 83.5%, and 2.55 nmol·min⁻¹ in 2017, respectively. This study uncovers several high-efficiency and long-term technological solutions for cultivating high yields and quality production of K. melanthera in East QTP.