Hulless barley (Hordeum vulgare L. var. nudum) is one of the most important crops in the Qinghai-Tibet Plateau. Soil salinity seriously affects its cultivation. To investigate the mechanism of salt stress response during seed germination, two contrasting hulless barley genotypes were selected to first investigate the molecular mechanism of seed salinity response during the germination stage using RNA-sequencing and isobaric tags for relative and absolute quantitation technologies. Compared to the salt-sensitive landrace lk621, the salt-tolerant one lk573 germinated normally under salt stress. The changes in hormone contents also differed between lk621 and lk573. In lk573, 1597 differentially expressed genes (DEGs) and 171 differentially expressed proteins (DEPs) were specifically detected at 4 h after salt stress, and correspondingly, 2748 and 328 specifically detected at 16 h. Most specific DEGs in lk573 were involved in response to oxidative stress, biosynthetic process, protein localization, and vesicle-mediated transport, and most specific DEPs were assigned to an oxidation-reduction process, carbohydrate metabolic process, and protein phosphorylation. There were 96 genes specifically differentially expressed at both transcriptomic and proteomic levels in lk573. These results revealed the molecular mechanism of salt tolerance and provided candidate genes for further study and salt-tolerant improvement in hulless barley.

To reveal the effects of different land-use types on soil enzyme activities, soil samples were collected from 0–10, 10–20 and 20–30 cm soil layers to compare and analyze soil β-glucosidase (BG), urease (URE), protease (PROT) and catalase (CAT) activities in farmland (FL), abandoned land (AL) and three plantation forests: Platycladus orientalis (L.) Franco (PO), Robinia pseudoacacia L. (RP) and Quercus variabilis Bl. (QV) in the rocky mountainous region of North China. The results showed that the soil enzyme activities varied significantly under different land-use types, and the interannual mean values of FL and PO were remarkably higher than those of other land uses in the 0–30 cm soil layer, in which the soil BG and URE activities of FL were 22% and 12% higher than those of AL, and 428% and 179% higher than those of QV, respectively; the soil PROT and CAT activities of PO were 66% and 23% higher than those of AL, and 479% and 113% higher than those of QV, respectively. Soil BG, URE and PROT activities were all higher in June and lower in December, while soil CAT activity was slightly lower in June. The soil enzymatic activities all showed a notable decrease with the depth of the soil layer. Soil BG, URE, PROT and CAT activities were remarkably (p < 0.01) or significantly (p < 0.05) positively correlated with available nitrogen, available phosphorus, available potassium, dissolved organic carbon (DOC), NO₃⁻-N, soil organic carbon, water content, clay and silt volume fraction, and significantly negatively correlated with sand volume fraction. Soil DOC and pH were important factors influencing soil enzymatic activity, implying that changes in soil enzymatic activity under different land-use types may be the result of a combination of temperature, moisture and plant type. In conclusion, PO plantations are conducive to improving the physicochemical and biological properties of soil and enhance soil fertility, which is a reasonable land-use method to achieve sustainable development in the rocky mountainous region of North China.

Climate warming has led to more frequent soil freeze–thaw (FT) events in high-latitude and high-altitude regions, leading to significant pulse releases of greenhouse gasses (GHGs) such as nitrous oxide (N₂O) and carbon dioxide (CO₂) into the atmosphere. These pulse emissions exhibit unpredictable spatiotemporal variability, which are influenced by soil type, soil moisture and FT temperature. This study employed controlled laboratory experiments to investigate the effects of varying FT intensities (−10 °C/10 °C, −5 °C/5 °C, and a control at 0 °C/0 °C) and soil moisture levels (30%, 60%, and 90% water-filled pore space, WFPS) on the dynamics of soil N₂O and CO₂ emissions (measured daily), and the availability of carbon and nitrogen, microbial biomass, and enzyme activities (measured weekly) in the soils collected from two forest stands in the Changbai mountains of northeast China, a broadleaf and Korean pine (Pinus koraiensis Sieb. et Zucc.) mixed forest (BKPF) and an adjacent secondary white birch (Betula platyphylla Suk.) forest (WBF), where FT events frequently occur. Our findings reveal that a high FT intensity (−10 °C/10 °C) significantly increased N₂O and CO₂ emissions from BKPF and WBF soils. With increasing soil moisture, soil CO₂ emissions peaked at 60% WFPS, while soil N₂O emissions were the highest at 90% WFPS. Notably, pulse emissions of N₂O were particularly intense under a high FT intensity and high moisture (i.e., 90% WFPS) in WBF soils, persisting for nearly 8 days during FT cycles. The emissions of N₂O and CO₂ under varying FT and moisture conditions are intricately regulated by soil substrate dynamics, including dissolved organic carbon, nitrogen mineralization, and nitrate concentrations. The results improve the understanding of the high variability of soil GHG emissions during the FT process and its underlying mechanisms, which are inadequately considered in current ecological and land surface process models. Consequently, it would contribute valuable insights into the interaction between soil GHG emissions and climate change in high-latitude and high-altitude zones.

The Grain for Green Program (GGP) initiated by Chinese government significantly impacts mitigating environmental degradation. Soil water resources probably constrain large-scale vegetation restoration projects in arid and semi-arid regions. Characterizing soil water dynamics after the GGP’s implementation is essential in assessing whether vegetation restoration can be sustained as part of ecological restoration. In this study, four sites were selected for field investigation: original natural grassland (NG) and grassland that was reconverted from cropland 12 years (12-year site), 8 years (8-year site), and 6 years (6-year site) before. Soil water at five depths was measured continuously at 10 min intervals at four sites. The findings showed that less rainfall infiltrated a deeper soil layer as the time after restoration augmented, and the 12-year site had the shallowest infiltration depth and soil water storage. Younger restored grassland (8-year and 6-year sites) had a higher soil water content than older restored grassland (12-year site) and NG. The soil water content decreased steadily with restoration age after an immediate initial rise, and the highest soil moisture was in the 8-year site. The results suggest that soil water dynamics varied with GGP and a soil water deficit could be formed after the GGP’s implementation for 12 years in semi-arid grassland.

Active soil substances, which can indicate environmental changes sensitively, have the fastest turnover rate. Vegetation diversity and soil bio-physicochemical properties according to five elevations classes (800 m, 1000 m, 1100 m, 1200 m, and 1500 m a.s.l.) in the Southern Taihang Mountain were investigated. Soil ammonium-N (NH₄⁺—N), nitrate-N (NO₃⁻—N), microbial biomass carbon (MBC), and nitrogen (MBN), as well as soil urease (URE) and sucrose (SUC) activities were determined. The results showed that elevation gradients, soil layers, and their interaction had significant effects on most of the active soil substances. With the rise of elevation, soil NO₃⁻—N, inorganic N, MBC, and MBN contents, as well as SUC activity and SUC/MBC ratio basically showed an inverted V-shaped distribution trend and reached the peak value at 1100 m (p < 0.05). Soil URE showed a fluctuating upward trend and reached the peak value at 1500 m (p < 0.05), and the URE/MBC ratio showed a straight upward trend. With the depth of soil layer, the contents of active soil substances tended to decrease, showing a phenomenon of surface aggregation. Active soil substances were correlated with plant community diversity indexes, soil water content, pH, available N, and available phosphorus contents, and available N was the main factor affecting active soil substances, which could explain 34.4% of the variation. In summary, at the intermediate slope of 1100 m, soil moisture and tightness were suitable for soil microbial activity and plant growth, the highest contents of active soil substances, indicating a fast turnover of soil carbon and nitrogen. The present study enriched our understanding of soil carbon and nitrogen turnover mechanisms in the mountain ecosystem.

Static chambers combined with isotopic (δ¹³C and δ¹⁸O) and flux (CO₂ and CH₄) measurements were applied, to explore the effects of mosses and long-term nitrogen (N) addition at two levels (22.5 and 45 kg N ha⁻¹ yr⁻¹) on δ¹³C and δ¹⁸O values of respired CO₂ across three autumn seasons under a temperate forest (northeastern China) and their relationships with CO₂ and CH₄ fluxes and with soil properties. Mosses generally depleted δ¹³C and enriched δ¹⁸O in respired CO₂, likely by altering soil microenvironments or/and substrate use. The effect of N addition on the δ¹³C and δ¹⁸O values of respired CO₂ varied with years, and its interaction with mosses had no effects on the isotopic values. The removal of mosses decreased CO₂ fluxes and the addition of N at a high dose increased CH₄ fluxes. The δ¹³C and δ¹⁸O values of respired CO₂ decreased at soil moisture levels below and above an optimum, and the moisture-dependent effect became more pronounced for the δ¹⁸O than for the δ¹³C. The results of structural equation modeling showed that 70% of the variability of δ¹³C values of respired CO_2. was accounted for by the N addition, mosses, soil moisture, and CH₄ and CO₂ fluxes, while only 22% of the variability of δ¹⁸O values of respired CO₂ was explained by these factors. The results highlight that moss–soil interaction drives the isotopic shifts, which is modulated by N availability. Soil moisture regulates the δ¹⁸O values of respired CO₂, but its drivers remain poorly understood. Future work should target processes influencing the δ¹⁸O shifts of respired CO₂ and deep soil property interactions.