The availability of suitable native plant species for local animal husbandry development and ecological restoration is limited on the Qinghai-Tibetan Plateau. Therefore, comparisons of the ecological adaptability of native species to alternative habitats and their introduction into new habitats are of high importance. This study is aimed at identifying the alteration in morphological and physiological characteristics by measuring photosynthetic physiology, nutrient content, and growth associated with adaptation of plants to conditions at different altitudes 2450, 2950, 3100, and 3300 m above sea level (a. s. l.) on the plateau. Seeds of the dominant grass, Elymus nutans, were collected from locations at these altitudes and grown at a test location of 2950 m a. s. l. Results indicated that altitude had no significant effect on plant height and root depth. However, the leaf area and total root surface area of plants derived from 2950 and 3300 m a. s. l. showed a parabolic response, being greater than those of plants derived from the lowest (2450 m) and highest (3300 m a. s. l.). Total (root plus shoot) dry matter reduced progressively from 2450 to 3300 m a. s. l, while root : shoot ratio increased progressively with altitude. Seed yield of plants originating from the test altitude (2950 m a. s. l) was significantly higher than at any other altitude, being 20% lower at 2450 m, and 38% and 58% less in populations originating from the higher altitudes (3100 and 3300 m a. s. l.). There was also a parabolic decline in response of Elymus nutans germplasm from 3100, 3300, and 2450 m, compared with plants from 2950 m a. s. l., to photosynthetic rate, total N, soluble sugar, and starch contents. Germplasm from 2450 m a. s. l. had significantly lower shoot and higher root carbon content, lower shoot nitrogen, and lower root carbon-to-nitrogen ratio compared with plants derived from the other three altitudes. It is suggested that the stable, genetically determined morphological and physiological features of ecotypes showed parabolic responses which means these ecotypes have become adapted to local habitats, whereas parameters such as dry matter, total root : shoot ratio, photosynthetic rate, and intercellular CO₂ concentration of plants reflected phenotypic linear response to current abiotic conditions. It is postulated that introduced ecotypes from 2450, 3100, and 3300 m could adapt to the environment at 2950 m a. s. l. gradually. We conclude that the increased thermal regime experienced by plants introduced from high altitude to low altitude may facilitate the increased growth of Elymus nutans subtypes. It is important to preserve local strains of native species, or ecotypes, for reintroduction into degraded environments and to maintain the greatest ecosystem stability in the northeastern Tibetan Plateau.

Elymus sibiricus L. is a perennial forage species that has potential to serve as a forage source in livestock grazing systems. However, E. sibiricus has been shown to have a rapid and substantial reduction of aboveground biomass and seed yield after 3 or 4 years and an accelerated aging process. To determine possible aging mechanisms, we planted E. sibiricus seeds in triplicate blocks in 2012, 2015, and 2016, respectively, and harvested samples of leaves and roots at the jointing and heading stages in 2018 and 2019 to determine oxidative indices and endogenous hormones. The fresh aboveground biomass of 4- and 5-year old plants declined by 34.2% and 52.4% respectively compared with 3-year old plants, and the seed yield declined by 12.7% and 34.1%, respectively. The water content in leaves was 51.7%, 43.3%, and 35.6%, and net photosynthesis was 7.73, 6.35, and 2.08 µmol/m²·s in 3-, 4-, and 5-year old plants, respectively. The superoxide anion radical generation rate in leaves and roots did not show any aging pattern. There was a non-significant increase in malondialdehyde concentration with plant age, particularly in leaves and roots at the heading stage in 2019. The superoxide dismutase activity showed a declining trend with age of plant roots at the jointing stage in both 2018 and 2019. The peroxidase activity declined with plant age in both leaves and roots, for example, and the catalase activity in roots 4- and 7-year old plants declined by 13.8% and 0.85%, respectively, compared to 3-year old plants at the heading stage in 2018. Therefore, the reduced capacity of the antioxidant system may lead to oxidative stress during plant aging process. Overall, the concentrations of plant hormones, auxin (IAA), gibberellin (GA), zeatin (ZT), and abscisic acid (ABA) were significantly lower in roots than in leaves. The IAA concentration in leaves and roots exhibited different patterns with plant age. The ZT concentrations in leaves of 3-year old plants was 2.39- and 2.62-fold of those in 4- and 7-year old plants, respectively at the jointing stage, and in roots, the concentration declined with plant age. The changes in the GA concentration with plant age varied between the physiological stages and between years. The ABA concentrations appeared to increase with plant age, particularly in leaves. In conclusion, the aging process of E. sibiricus was apparently associated with an increase in oxidative stress, a decrease of ZT and an increase of ABA, particularly in roots. These findings highlight the effects of plant age on the antioxidant and endogenous hormone activity of E. sibiricus. However, these plant age-related trends showed variations between plant physiological stages and between harvest years that needs to be researched in the future to develop strategies to manage this forage species.

Industrial parks in China are centers of intensive chemical manufacturing and other industrial activities, often concentrated in relatively small areas. This concentration increases the risk of soil pollution both within the parks and in surrounding areas. The soils of the Tibetan Plateau, known for their high sensitivity to environmental changes, are particularly vulnerable to human activity. In this study, we examined the concentrations (mg/kg) of 10 metal elements (As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Se, and Zn) in soils at depths of 0–10 cm, 10–20 cm, and 20–30 cm from the surface at three distances (500 m, 1000 m, and 1500 m from the park boundary) on the east, south, west, and north sides of the Tianzhu Industrial Park on the Qinghai-Tibet Plateau. The concentrations of As, Cr, Mn, and Pb were close to the standard reference values for the Qinghai-Tibet Plateau, while Cu, Ni, Se, and Zn levels were found to be 1.6-2.2 times higher than the reference values. Cd and Hg concentrations were particularly concerning, at 8.0 and 6.5 times higher than reference values, respectively. The potential ecological risk indexes indicated persistent risk levels for Cd and Se across various directions and distances. Variations in soil depth and direction were observed for the concentrations of As, Cd, Hg, Pb, Se, and Zn, underscoring the need for regular or long-term monitoring. Cd, in particular, presents a significant hazard due to its high concentration and its propensity for uptake by plants in the study area.

Introduction: The alpine meadows of the Tibetan Plateau play a crucial role in the grassland ecosystem. However, due to the rapid growth and strong competitiveness of broad-leaved grasses, the nutritional resources and living space available for Gramineae species are severely restricted in this region. Broad-leaved grasses and noxious weeds have evolved into dominant population, severely limiting grassland production in alpine meadows. A shortage of premium seeds limits grassland ecosystem restoration efforts. Elymus nutans is regarded as a pioneer plant for restoring degraded grassland into meadows dominated by grasses, and for developing cultivated grassland in the Tibetan Plateau region, and the demand for native seeds of E. nutans is increasing.Methods: Therefore, this study investigated the effect of combinations of four levels of a broad-leaved grass inhibitor (0, 0.9, 1.5, and 2.1 kg·hm^-2) crossed with four levels of nitrogen fertilizer (0, 75, 150, and 225 kg·hm^-2) on seed production of E. nutans in Gannan alpine meadow of the Qinghai-Tibet Plateau.Results: We observed that the grass inhibitor significantly (p < 0.05) influenced on fertile tillers (FT), spikelets per fertile tiller (SFT), seeds per spikelet (SS) and panicle length (PL), but not florets per spikelet (FS) (p = 0.145). Nitrogen fertilizer significantly influenced on FT, FS, SS, and PL (p < 0.001), but not SFT (p = 0.068). The interaction of the grass inhibitor and nitrogen fertilizer had no significant effect on any of these seed yield components (p > 0.05). Both the grass inhibitor and nitrogen fertilizer significantly influenced all indicators of seed production (p < 0.001), increasing their values in a dose-dependent manner. Moreover, their interaction proved significant for all indicators (p < 0.001), except for actual seed yield (p > 0.05), demonstrating their synergistic effects. The maximum thousand seed weight (4.66 g) and actual seed yield (365 kg·hm^-2) were observed at the highest doss of 2.1 kg·hm^-2 of grass inhibitor and 225 kg·hm^-2 of nitrogen fertilizer, which were 1.85-fold and 2.94-fold of the control, respectively. Furthermore, significantly positive correlations were observed among seed yield and all yield components. Pathway analysis showed that FT made significant direct contributions to the seed yield.Discussion: This approach (using broad-leaved grass inhibitors and nitrogen fertilizer) effectively reduced competition from broad-leaved grasses and increased the proportion of E. nutans in the plant community composition, thus alleviating the shortage of E. nutans seeds for grassland ecological restoration.

Qinghai-Tibet Plateau was a clean environment in the past. Zinc (Zn) and cadmium (Cd) present in soils now. We postulated that the dominant native grass Elymus nutans is tolerant to Zn and Cd. We investigated the effects of Cd-Zn interactions on seed germination, seedling growth, physiological stress, and their uptake in plants of E. nutans. Two ecotypes, Population1 (POP1, altitude 2450 m) and Population2 (POP2, 3300 m), were selected from alpine grassland of Qinghai-Tibet Plateau. Germination and growth parameters were measured after Cd as CdSO₄ · 8H₂O (15–100 mg l⁻¹) and Zn as ZnSO4 · 7H₂O (40–300 mg l⁻¹) were applied. Zn and Cd affected the germination and early seedling growth of both ecotypes. Below 50 mg l⁻¹, Zn promoted seed germination and plant growth, while 300 mg l⁻¹ Zn significantly inhibited it. All levels of Cd had an inhibitory effect. Zn and Cd affected the POP2 above-ground dry weight more than POP1 and reduced root growth more than shoot growth. The measurement of metal accumulation showed that Zn application suppressed Cd accumulation in plants under the lower Cd (< 20 mg l⁻¹) treatments, while above 20 mg l⁻¹, Cd had an antagonistic effect on Zn uptake. Cadmium and Zn alone or in combination induced oxidative stress. The results suggest that responses to Cd and Zn and their interactions vary with concentration: moderate levels of heavy metals activated the species’ protective system, but higher concentrations destroyed it. We concluded that this species has differing abilities to tolerate Zn and Cd related to their original habitats.

Under intensified global climate change and anthropogenic pressures, alpine ecosystems confront unprecedented stress. The degradation of alpine meadows has caused significant declines in productivity and in the abundance of high-quality forage species. This study aims to explore the effects of phosphorus (P) application and reseeding of Medicago ruthenica (L.) Trautv. on the biomass and quality of forage in degraded alpine meadows, and to identify the key soil factors influencing forage growth. Three reseeding rates (V₁: low, V₂: medium, V₃: high) and three P levels (P₀: none, P₁: low, P₂: high) were established in this experiment. The factors were arranged in a completely randomized design, resulting in nine distinct treatment combinations, that is V₁P₀, V₁P₁, V₁P₂, V₂P₀, V₂P₁, V₂P₂, V₃P₀, V₃P₁, and V₃P₂. The results showed that the interaction between the reseeding and P addition exerts a significant effect on the biomass of M. ruthenica, forbs, and aboveground biomass (p < 0.05). Additionally, the interaction between the reseeding and P addition had a significant effect on crude protein content (p < 0.05). Phosphorus addition and the interaction between the reseeding and P addition had a significant effect on ether extract content (p < 0.05). However, it is only reseeding that can significantly influence the neutral detergent fiber content (p < 0.05). Grey correlation analysis revealed that the V₃P₂ treatment optimized both forage biomass and nutritional quality. Hierarchical partitioning further identified soil total nitrogen as the factor that contributed the most to forage biomass and quality following reseeding and phosphorus application.