Soil salinity is a major abiotic stress that severely limits plant growth and productivity worldwide, particularly under changing climate conditions. Silicon (Si) has emerged as a promising approach for improving plant tolerance to salinity stress; however, its integrated physiological effects in perennial forage grasses remain insufficiently understood. This study investigated the role of Si in alleviating salinity stress in Agropyron cristatum × A. desertorum cv. Hycrest-Mengnong under controlled conditions. Plants were exposed to 0, 100, and 200 mM NaCl with or without Si application, and growth, physiological, biochemical, and ionic responses were evaluated. Salinity stress significantly reduced plant height, biomass, leaf area, photosynthetic performance, chlorophyll content, and PSII efficiency, with the strongest inhibitory effects observed at 200 mM NaCl. Salinity also increased oxidative damage, as indicated by higher malondialdehyde (MDA) content, promoted proline accumulation associated with osmotic adjustment, enhanced antioxidant enzyme activities, and disrupted ionic homeostasis through excessive Na⁺ accumulation and reduced K⁺/Na⁺ ratio. Si application markedly alleviated these adverse effects by improving growth, maintaining photosynthetic efficiency and chlorophyll stability, enhancing antioxidant defense, promoting osmotic adjustment, and regulating ion balance through reduced Na⁺ accumulation and improved K⁺ retention. These findings demonstrate that Si enhances salinity tolerance through coordinated regulation of physiological, biochemical, and ionic mechanisms. The study provides a mechanistic framework for understanding Si-mediated salinity tolerance in perennial forage grasses and highlights the potential application of Si for improving forage productivity under saline conditions.

Livestock grazing has been shown to shape the biodiversity of grasslands, thereby impacting ecosystem stability. Overgrazing may promote the encroachment of shrubs into these habitats through niche partitioning, specifically differences in above-versus below-ground resource usage between woody and herbaceous plants. However, grazing effects on grassland stability remains under-researched, with a paucity of comprehensive empirical studies. In our study, we conducted a seven-year sheep grazing experiment in a desert steppe of northern China. We specifically compared two habitat types: grass-dominated and shrub-encroached, aiming to discern the effects of varying grazing intensities on the stability of aboveground, belowground, and total biomass. Our results indicated that grazing increased the community-weighted mean (CWM) of fast-slow traits and reduced the species asynchrony in grass-dominated habitat, while elevated relative abundance of dominant species and reduced functional dispersion and soil property in shrub-encroached habitat. Increasing grazing intensity diminished the stability of aboveground and belowground biomass within grass-dominated habitat, without significant changes to stability of belowground biomass in shrub-encroached habitat. The CWM Fast-slow traits in grass-dominated habitat and the dominant species abundance of Reaumuria songarica in shrub-encroached habitat were negatively correlated with the stability of aboveground biomass. Thus, while grazing indirectly decreased community stability through elevating CWM Fast-slow traits in grass-dominated habitat, grazing impacted community stability in shrub-encroached habitat via increasing the dominant species abundance of R. songarica, with consequent influences on species asynchrony and stability. Together, our two-habitats experiment highlights the importance of conserving different facets of biodiversity for sustainably providing ecosystem functions and services in arid grazing grasslands.

Plant- and microbial-derived residues constitute the primary sources of soil organic carbon (SOC) in grassland ecosystems. However, their differential responses to chronic nitrogen (N) enrichment and the depth-dependent mechanisms governing their accumulation remain poorly characterized, particularly for water-limited grassland systems. Based on a 13-year field experiment in a semiarid grassland, we quantified the effects of long-term N addition on the accumulation of plant- (lignin phenols) and microbial-derived (amino sugars) residues. We found that N addition significantly increased lignin phenol content and its contribution to SOC in the topsoil, whereas lignin phenols exhibited a hump-shaped response peaking under moderate N levels in the subsoil. Amino sugar concentrations and their relative contribution to SOC increased in both soil layers under N addition but declined at the highest N input. The dominant factors regulating residue accumulation varied with soil depth: in the topsoil, microbial K-/r-traits and community composition primarily explained lignin phenol and amino sugar dynamics, while in the subsoil, mineral-associated protection and microbial composition were the key drivers. These findings underscore the depth-dependent nature of SOC formation pathways and highlight the importance of incorporating both plant- and microbial-derived residues into Earth System Models to improve projections of carbon-climate feedback under changing nitrogen regimes.Read the free for this article on the Journal blog.

Increased atmospheric nitrogen (N) deposition alters the structure and function of soil microbial communities in terrestrial ecosystems, consequently exerting a profound influence on ecosystem processes. However, the effects of N deposition on soil microbial network complexity and its regulation of soil carbon (C) processes in semiarid grassland ecosystems are poorly understood. In this study, based on a 13-year multilevel field N addition experiment in a semiarid grassland on the Loess Plateau, together with metagenomic sequencing and cooccurrence network analysis methods, we observed that the complexity of microbial co-occurrence network, characterized by the number of nodes and edges and the average path length, increased first and then decreased in a nonlinear response to N addition, with thresholds between 4.60 g N m- 2 yr- 1 and 9.20 g N m- 2 yr- 1 in both the topsoil and subsoil. Meanwhile, soil microbial network complexity was significantly positively correlated with plant root traits (e.g., root biomass), soil microbial properties (e.g., fungal community composition and bacterial Shannon diversity and community composition) and most physicochemical properties (e.g., soil water content, NH4+-N, and Fep). Structural equation model analysis (SEM) revealed that the major determinants of the soil microbial network complexity shifted from soil physicochemical properties to bacterial community composition along the N addition gradient. Further analysis revealed that N-induced alterations in microbial network complexity could modulate soil organic C (SOC) formation, preservation, and decomposition by affecting the functional potential of microbial communities. For instance, the microbial network complexity, abundance of functional genes involved in starch and hemicellulose degradation, and microbial C use efficiency decreased significantly under high levels of N addition. These results provide empirical evidence for the close linkages between soil microbial network complexity and soil C processes and highlight the need to disentangle the mechanisms underlying the nonlinear response of soil microbial interactions to atmospheric N deposition to improve soil C projections.

Accelerated flowering, an essential aspect of speed breeding, has become a significant tool to enhance crop improvement programs, especially in changing climates. This review examines how temperature, light quality, and photoperiod regulate flowering time across diverse crops. The mechanisms that drive these factors are being studied at the molecular, physiological, and phenotypic scales, highlighting how changes in light spectrum, photoperiod sensitivity, and temperature regimes can significantly influence flowering patterns. We emphasize the optimization of these factors in controlled environments to achieve accelerated flowering, thereby improving breeding cycles without compromising yield or plant health. The review explores the integration of these strategies into speed breeding platforms for legumes, cereals, and forage species, highlighting the challenges and potential for scaling this technology. This paper also synthesizes current knowledge and identifies understanding gaps to provide insights into strategically manipulating light quality, photoperiod, and temperature to expedite crop development and meet sustainable agriculture's demands.

Nitrogen (N) fertilization is known to impact the capacity of ecosystems to support multiple ecosystem services such as carbon sequestration and nutrient cycling, particularly in nutrient‐limited environments. Yet, little is known about how N fertilization may result in trade‐offs across contrasting soil ecosystem services. Moreover, the contribution of soil microbial networks as mediators of the impacts of fertilization on soil ecosystem services is poorly understood. Here we collected topsoil (0–10 cm) and subsoil (10–20 cm) samples from a 13‐year N addition experiment in a semiarid grassland to investigate how long‐term N additions affect soil multiservices. We found that soil multiservice predominantly exhibited a hump‐shaped response to the increasing levels of N addition across two soil depths. More importantly, changes in the complexity of soil microbial networks were positively correlated with ecosystem multiservices across the two soil depths. This relationship was especially important in explaining topsoil multiservice responses, while in subsoils, multiservices were more strongly associated with abiotic properties than network complexity. This distinction may be attributed to the lower microbial activity and reduced nutrient utilization capacity in subsoils, which allows abiotic factors to play a more dominant role on multiservices. Synthesis . Our results highlight that soil microbial network complexity is highly correlated with multiple ecosystem services in the context of global atmospheric N deposition.

Alpine grassland degradation is a major threat to global carbon cycles, yet the microbial mechanisms driving soil organic carbon (SOC) loss remain poorly understood. Ecological stoichiometry theory provides a framework for understanding how resource imbalances constrain microbial activity and metabolism. Here, we investigated how grassland degradation altered the stoichiometric imbalances between soil microbes and their resources and how microbes coped with such imbalances, as well as the implications of their responses for SOC stock. We established a degradation gradient (non-, light, moderate, and heavy) in both an alpine meadow and an alpine steppe on the Qinghai-Tibet Plateau, China, with analyzing vegetation nutrient storage, soil physicochemical properties, microbial biomass, dissolved organic nutrients, extracellular enzyme activities, and nutrient mineralization rates. Our results showed that C:N stoichiometric imbalance exhibited a hump-shaped response to grassland degradation with a maximum around moderate degradation, while C:P and N:P stoichiometric imbalances significantly decreased with increasing grassland degradation levels in both ecosystems. However, microbial responses were ecosystem-specific: meadow microbes showed strong C:N:P homeostasis, while steppe microbes showed weaker C:N and C:P homeostasis, indicating higher stoichiometric plasticity. Mechanistically, microbes coped with these shifting imbalances by adjusting extracellular enzyme stoichiometry, net N mineralization, and soil microbial respiration. For instance, C:P and N:P stoichiometric imbalances were strongly linked to the relative production of P-acquiring enzymes across both ecosystems, with slightly stronger correlations in meadows. These response mechanisms were significantly correlated with SOC stock, suggesting that microbial metabolic adjustments are a key pathway regulating the 14.8–71.5% decline in SOC stock decline observed during degradation. Our findings provide a mechanistic link between grassland degradation, microbial stoichiometric response, and carbon cycling, highlighting that ecosystem-specific microbial strategies are critical determinants of SOC vulnerability in these sensitive high-altitude ecosystems.

Soil net nitrogen mineralization (Nmin), a microbial-mediated conversion of organic to inorganic N, is critical for grassland productivity and biogeochemical cycling. Enhanced atmospheric N deposition has been shown to substantially increase both plant and soil N content, leading to a major change in Nmin. However, the mechanisms underlying microbial properties, particularly microbial functional genes, which drive the response of Nmin to elevated N deposition are still being discussed. Besides, it is still uncertain whether the relative importance of plant carbon (C) input, microbial properties, and mineral protection in regulating Nmin under continuous N addition would vary with the soil depth. Here, based on a 13-year multi-level field N addition experiment conducted in a typical grassland on the Loess Plateau, we elucidated how N-induced changes in plant C input, soil physicochemical properties, mineral properties, soil microbial community, and the soil Nmin rate (Rmin)-related functional genes drove the responses of Rmin to N addition in the topsoil and subsoil. The results showed that Rmin increased significantly in both topsoil and subsoil with increasing rates of N addition. Such a response was mainly dominated by the rate of soil nitrification. Structural equation modeling (SEM) revealed that a combination of microbial properties (functional genes and diversity) and mineral properties regulated the response of Rmin to N addition at both soil depths, thus leading to changes in the soil N availability. More importantly, the regulatory impacts of microbial and mineral properties on Rmin were depth-dependent: the influences of microbial properties weakened with soil depth, whereas the effects of mineral protection enhanced with soil depth. Collectively, these results highlight the need to incorporate the effects of differential microbial and mineral properties on Rmin at different soil depths into the Earth system models to better predict soil N cycling under further scenarios of N deposition.

A large amount of vegetable waste is often dumped into the environment, causing serious pollution in major market distribution areas. This paper explores the feasibility and optimization of incorporating vegetable waste into dryland fields to improve soil fertility and crop productivity. The experimental design included three quantities of fresh leafy vegetable waste (QVW) buried into the soil: 800, 1600, and 2400 t & sdot;ha- 1 and three covering soil thicknesses (CST): 10, 20, and 30 cm. Zero QVW was the control NW. By planting forage maize for two consecutive years, the variations of soil parameters and aboveground dry biomass (ABM) of maize plants were observed. Compared with the NW, the incorporation led to a distinct decline in soil bulk density (BD) by 2.00-17.41%, an increase in soil moisture (SM), organic carbon (SOC), total nitrogen (TN), and microbial carbon (MBC) by 5.84% -29.72%, 5.93% -50.17%, 16.98% -245.71% and 19.66% -304.08%, respectively. Topsoil conductivity (EC) and soil inorganic nitrogen (IN) were 3.81-9.43 fold and 19.02-88.29 fold that of NW. BD was significantly negatively correlated with the QVW and CST. SM, SOC, TN, and IN increased significantly with the increase of QVW and CST. The topsoil EC was significantly positively correlated with QVW, and negatively correlated with CST. The sequestration rates of SOC and nitrogen were significantly positively correlated with CST. The ABM in the incorporating vegetable waste treatment was 1.59-2.74 fold that of NW. The ABM showed a parabolic relationship with QVW (R2 = 0.97 **), and a linear relationship with CST (R2 = 0.91 **). Conclusively, the optimal QVW was 1346 t & sdot;ha- 1, and the corresponding CST was 30 cm. Excessive QVW can cause topsoil salinization and constrain crop growth. Increasing CST contributes to sequestrating more water and nutrients and mitigating secondary salinization of the soil.

This study examined the effects of different mixed cropping ratios on forage yield, biomass accumulation, distribution, and nitrogen utilization in the Qinghai Lake region. Five mixed ratios of oat and common vetch were established: 1:0 (A.M.), 2:1 (A2V1), 1:1 (A1V1), 1:2 (A1V2), and 0:1 (V.M.), with A representing oats and V representing common vetch, under two nitrogen conditions. The study found that (1) Oats contributed the most to biomass and A1V1 had the highest production. (2) Treatments impact the nitrogen accumulation, A1V1 had higher nitrogen contents of leaves and stem. (3)A1V1 showed the highest nitrogen utilization efficiency. These findings can help improve agricultural practices in the area by promoting more efficient and sustainable farming methods.

为了解生物土壤结皮发育与土壤养分特征的关系,该研究选取处于不同发育阶段和不同盖度的藓结皮(M-crust)和地衣结皮(L-crust),对其结皮层生物体及结皮下层3 cm土壤进行养分分析.结果显示:(1)藓结皮生物体对土壤全氮(TN)、全磷(TP)、铜(Cu)和锌(Zn)的生物富集作用较强,其富集系数分别高达807.4％、175％、122.4％和244.5％,而地衣结皮生物体对TN、TP和钙(Ca)的生物富集作用较强,其富集系数分别高达950.8％、126.2％和208.6％;除Ca外,藓结皮生物体中TP、钠(Na)、钾(K)、Cu、铁(Fe)、镁(Mg)、锰(Mn)和Zn均显著高于地衣结皮.(2)土壤生物结皮盖度与其对应的土壤养分含量之间无显著线性相关关系,但发育有不同盖度藓结皮的土壤其平均TN、TP、Cu、Fe、K、Na和Ca含量均高于地衣结皮.研究表明,不同类型生物土壤结皮对养分吸收、富集效率不同,处于发育后期的藓结皮较发育中期的地衣结皮具有更强的养分累积效应,提高了土壤的养分贮存量,对黄土高原典型草原生态系统的恢复与重建具有潜在的重要影响.

Soil microbes are subject to stoichiometric imbalances, which are the dissimilarities in elemental stoichiometry between microbial biomass and resources. Shifts in dominant plant species co-occur with unparallel changes in the stoichiometry of soil microbial biomass and resources, leading to stoichiometric imbalances. However, how soil microbes deal with stoichiometric imbalances induced by changes in dominant plant species, and what the implications are for soil carbon cycling, remain unknown. Here, we compared the stoichiometric imbalances of five plant patch types with the dominant plant community (Kobresia pygmaea) in a Tibetan alpine grassland to examine how soil microbes respond physiologically to stoichiometric imbalances, thereby affecting soil microbial respiration (SMR). We found that C:N and C:P imbalances varied between plant patches and differed significantly from those in the soil of K. pygmaea. We also found that the regulation of extracellular enzyme production, SMR, potential microbial carbon use efficiency (CUE), net N mineralization, and net ammonification were essential mechanisms for soil microbes to deal with C:N imbalances. Simultaneously, soil microbes dealt with fluctuating C:P imbalances by regulating their net P mineralization and CUE. Further, structural equation modeling revealed that stoichiometric imbalances induced by changes in dominant plant species could indirectly affect SMR by regulating extracellular enzyme stoichiometry and net nutrient mineralization. These results highlight the importance of the stoichiometry of soil microbe/resource interactions in regulating metabolic activities and modifying terrestrial carbon flows in shifting plant communities.

Soil net nitrogen mineralization (Nmin), a microbial-mediated conversion of organic to inorganic N, is critical for grassland productivity and biogeochemical cycling. Enhanced atmospheric N deposition has been shown to substantially increase both plant and soil N content, leading to a major change in Nmin. However, the mechanisms underlying microbial properties, particularly microbial functional genes, which drive the response of Nmin to elevated N deposition are still being discussed. Besides, it is still uncertain whether the relative importance of plant carbon (C) input, microbial properties, and mineral protection in Nmin regulating under continuous N addition would vary with the soil depth. Here, based on a 13-year multi-level field N addition experiment conducted in a typical grassland on the Loess Plateau, we elucidated how N-induced changes in plant C input, soil physicochemical properties, mineral properties, soil microbial community, and soil net N mineralization (Rmin)-related functional genes drove the responses of Rmin to N addition in the topsoil and subsoil. The results showed that Rmin increased significantly in both topsoil and subsoil with increasing rates of N addition. Such a response was mainly dominated by the rate of soil nitrification. Structural equation modeling (SEM) revealed that a combination of microbial properties (functional genes and diversity) and mineral properties regulated the response of Rmin to N addition at both soil depths, thus leading to changes in the soil N availability. More importantly, the regulatory impacts of microbial and mineral properties on Rmin were depth-dependent: the influences of microbial properties weakened with soil depth, whereas the effects of mineral protection enhanced with soil depth. Collectively, these results highlight the need to incorporate the effects of differential microbial and mineral properties on Rmin at different soil depths into the Earth system models to better project soil N cycling under further scenarios of N deposition.

Elevated atmospheric N deposition can profoundly alter soil carbon (C) mineralization (Cmin) and nitrogen (N) mineralization (Nmin), which could severely impact long-term productivity of grassland ecosystem. However, little is known about how N addition, season, and their interaction affect soil Cmin and Nmin rates and their relationships by regulating soil abiotic and biotic factors. Here we investigated the seasonal variations in soil Cmin and Nmin rates and their relationship in response to multi-level N additions in a semiarid grassland in 2014-2015, and further identified direct and indirect pathways by which soil abiotic and biotic factors regulated these variations using structural equation modeling. We documented the statistically significant impacts of N addition and its interaction with season on soil Cmin rates. In contrast, only a significant seasonal effect on the soil Nmin rate was observed. Random forest analysis revealed that across all seasons, dissolved organic carbon (DOC), soil water content (SWC), catalase, urease, sucrase, microbial biomass carbon (MBC), soil organic carbon (SOC) to total nitrogen (TN) ratio, and TN were the most pivotal predictors of the soil Cmin rate. Comparatively, catalase, MBC, DOC, NO3--N, urease, TN, NH4+-N, SWC, and the MBC to microbial biomass nitrogen (MBN) ratio were the most dominant drivers of the soil Nmin rate. SEM results indicated that the identified potential drivers that regulated the soil Cmin and Nmin rates in response to N addition varied seasonally. Additionally, N addition decoupled the soil Cmin and Nmin rates, which was a consistent relationship among most seasons. In summary, our results show that, in this semiarid grassland, current N additions can enhance soil N immobilization across all seasons; however, its impacts on soil C sequestration were seasonally variable. These findings provide evidence that season and its interactions with elevated atmospheric N deposition have important implications for the grassland biogeochemical cycling.

Litter decomposition is a key component of global biogeochemical cycles that affects the availability of soil nutrients for plant productivity. Significant variations in litter decomposability between plant taxa are attributed to diverse functional traits including litter quality, plant nutrient production, and nutrient resorption efficiency which should influence the ecological fitness of plants in the community. However, no reports to date have explored the relationships between litter decomposition and plant community dynamics, that is, plant succession and interspecific competition. We conducted a litter decomposition experiment that focused on 21 plant species in an alpine meadow. The litter decomposition rates of these species were compared with their initial litter quality and nutrient use efficiencies to examine whether the plant litter indicators of the community structures were altered following grazing exclusion. We found that among these 21 plant species, those with higher nutrient use efficiencies had a lower litter decomposition rate. Meanwhile, lower decomposition rates were correlated with higher plant importance values, and this correlation became stronger over time in plant communities following grazing exclusion, except for dominant species. Our results suggested that litter decomposability can be used to predict the changing trajectories of plant communities following grazing exclusion, except for dominant species.

Plant litter is the most important source of soil organic carbon（SOC）, and the quality of litter may affect the amount and stability of newly formed SOC. In this study, we evaluated the effects of decomposition of litters of different quality（AS: Artemisia sacrorum stem, SR: Stipa bungeana root, SL: S. bungeana leaf, SAL: Sophora alopecuroides leaf）, which were selected from the typical grassland of the Loess Plateau in the middle of Gansu Province, on SOC and its stability. According to their chemical composition, litters were divided into high-quality litters（higher soluble components content and lower lignin content） and low-quality litters（lower soluble components content and higher lignin content）. The litters were co-incubated with soil to study the decomposition process and determine how it affected SOC content and stability. Compared with low-quality litters（AS and SR）, high-quality litters（SAL and SL） had a relatively higher decomposition rate due to their higher content of labile components and lower carbon/nitrogen（C/N）. After decomposition for 2 years, the SOC content had increased in each treatment. The increases in SOC and the formation efficiency of new carbon（C） were significantly higher in the high-quality litter treatments than in the low-quality litter treatments. These results indicated that, compared with low-quality litters, high-quality litters made a greater contribution to SOC sequestration after decomposition. The amounts of all soil aggregate components did not vary significantly among treatments. After decomposition for 2years, the SOC content in ＜0. 053 mm soil aggregates was significantly increased in all the treatments. The SOC content and efficiency of new C formation in ＜0. 053 mm soil aggregates were significantly higher in the high-quality litter treatments than in the low-quality litter treatments. Overall, these results show that, compared with lowquality litter, high-quality litter more readily forms stable mineral-associated organic matter after decomposition.