Reseeding diverse plant communities is a promising strategy for enhancing multiple ecosystem services, grounded in the fundamental assumption that greater biodiversity promotes higher levels of ecosystem functioning. However, current grassland restoration efforts often prioritize a single ecosystem service, which may enhance a limited number of ecosystem services at the cost of others. As a result, there is a lack of compelling evidence illustrating how vegetation reestablishment through reseeding positively impacts grassland ecosystem multifunctionality. To address this gap, we conducted a two-year field reseeding experiment in a degraded semiarid grassland in Northern China, aiming to assess how different levels of plant diversity influence the restoration of multiple grassland ecosystem functions. Our experiment established a plant species richness gradient (1-4 species), with legume forage included in every planting combination and all possible species mixtures fully covered. The results showed that increased species richness, combined with a balanced legume-grass composition significantly enhanced grassland ecosystem multifunctionality. Such positive association was closely related to improved soil functions, which act as a key linkage connecting plant diversity to overall ecosystem service supply. Our findings highlight the importance of adopting a multifunctionality perspective when evaluating the capacity of degraded grasslands to sustain multiple functions and services simultaneously, and provide practical implications for optimizing reseeding strategies in semi-arid degraded grasslands. This study offers a valuable reference for restoration ecology research, particularly as an early-stage assessment that warrants longer-term follow-up monitoring.

A novel Gram stain–positive, endospore-forming, motile, rod-shaped, aerobic bacterial strain, designated PS06T, was isolated from the rhizosphere soil of Stipa breviflora at the Siziwang Banner Research Station in Inner Mongolia, PR China. The strain could grow at 4–40 ℃ (optimum, 37 ℃), at pH 6.0–9.5 (optimum, pH 8.5), and in the presence of 0–5

Seasonal grazing is a common alternative to the rest-rotation grazing management regime. Although that research has been extensive on the impacts of grazing on soil organic carbon (SOC) and nitrogen (N) sequestration, there is limited understanding of the regulatory mechanisms of plant productivity and species on SOC and N sequestration under seasonal grazing. To address this problem, the response of plant properties was quantified in five different seasonal grazing regimes (no grazing control, continuous grazing, early summer and late summer grazing, mid summer and early autumn grazing, late summer and mid autumn grazing) in a semi-arid grassland of North China between 2012 and 2018. The results indicated that early summer and late summer grazing had little damage to the plant communities but reduced the SOC and N sequestration in the 10-20 cm layer, while mid summer and early autumn grazing maintained a relatively high plant productivity but resulted in the losses of SOC and N sequestration in the 0-20 cm layer. The late summer and mid autumn grazing regime enhanced SOC and N sequestration in the 0-20 cm layer by producing higher yields of Stipa krylovii and root biomass. The improved biomass of S. krylovii and roots is an indicator of soil quality evolution in the context of grazing management. It is therefore proposed that the late summer and mid autumn grazing regime, including a two-month rest period, is likely to be a beneficial strategy to conserve both plant communities and soil nutrients for sustainable management of the studied grassland.

Abstract Background Clonal plants can successfully adapt to various ecosystems. A trade-off between sexual and clonal reproduction is generally assumed in clonal plants, which may be influenced both by the characteristics of the plant itself and environmental conditions. Currently, it is unclear how climate change, and specifically warming and increased precipitation, might affect sexual and clonal reproduction in clonal plants. Therefore, this study aimed to investigate both the sexual and clonal reproduction responses of Stipa breviflora to warming and increased precipitation. A controlled experiment was conducted by inducing increases in precipitation (ambient condition, 25% and 50% increases) and warming (ambient temperature, 1.5 °C and 3.0 °C increases). Results Warming significantly influenced both the ratio of reproductive ramet shoot biomass to total shoot biomass, and the ratio of reproductive ramet number to total ramet number. Additionally, the ratio of reproductive ramet shoot biomass to total shoot biomass was also significantly affected by increased precipitation. Increased precipitation benefited sexual reproduction, while effects of warming on reproductive and/or vegetative ramets varied from negative to positive depending on precipitation conditions. There was no relationship between the number or shoot biomass of reproductive ramets and vegetative ramets. Reproductive ramets displayed greater sensitivity to climate change than vegetative ramets. Conclusions The findings of our study suggest that there was no trade-off between sexual and clonal reproduction in S. breviflora. The combined impact of warming and increased precipitation promoted sexual reproduction but did not inhibit clonal reproduction. Clonal plants with the capacity for both sexual and clonal reproduction, may cope with climate change well via clonal reproduction, ensuring their survival.

Long-term restoration practices have been often reported to enhance soil organic carbon (SOC) and nitrogen (N) stocks in grassland ecosystems. However, there is a limited understanding of how vegetation restoration affects SOC and N stocks at different soil depths over short timescales in semi-arid grassland of North China. To address this problem, we conducted a field study to investigate the effects of plant properties on the SOC and N stock changes during a nine-year period of grassland restoration practices (natural recovery; shallow ploughing; harrowing) in a semi-arid grassland of North China. The results revealed that three restoration practices had a positive contribution to SOC and N stocks following nine years of recovery, however, the rates of SOC and N stock changes under mechanical disturbance were lower across the 0-60 cm soil depth when compared with the natural recovery. The biomass of litter, roots, and dominant plant species were the major factors contributing to SOC and N stock changes. Our findings from the nine-year restoration experiment suggested that short-duration natural recovery is likely to be a beneficial strategy for the restoration of both the plant community and the soil nutrients. Our findings elucidate the regulatory mechanisms of dominant plant species on SOC and N stock changes following revegetation and suggest that the overcompensatory growth of dominant species should be fully considered in grassland restoration.

Artificial restoration is an important strategy to restore plant communities and soil nutrients in degraded grassland ecosystems. Despite that research has been extensive on the impacts of vegetation restoration on soil carbon storage, little work has been tried to examine the impacts of artificial restoration on the vertical distribution of soil organic carbon (SOC) storage following revegetation in grassland ecosystems. In this paper, the responses of plant species diversity, litter biomass (LB), aboveground biomass (AGB), the relative biomass of three dominant plant species, and the belowground biomass (BGB) were quantified under five different restoration regimes (natural recovery, harrowing, harrowing plus fertilization, harrowing plus irrigation, harrowing plus fertilization and irrigation), to explore the direct and indirect effects of artificial restoration, mediated by changes in the plant properties following revegetation, on SOC storage in Leymus chinensis steppe, North China. We found that artificial restoration greatly facilitated the recovery of Leymus chinensis but lowered the plant diversity. Irrigation treatment, particularly harrowing plus irrigation, was associated with both higher BGB and LB, which had positive effects on SOC storage at the 30-60 cm soil layer when compared with natural restoration. In addition, artificial restoration had positive but not significant effects on SOC storage in the surface soil layer (0-10 cm) mediated directly by changes in BGB, while it exerted negative indirect effects on SOC storage at the 10-30 cm soil layer through low level of plant species diversity. The loss of two dominant species (Stipa krylovii and Cleistogenes squarrosa) could greatly impact SOC storage not only due to lowered species diversity but also the reduced quality of litter input into soil. It is therefore proposed that maintaining high levels of plant species diversity could help sustain higher soil carbon storage through producing high-quality root and litter. Our findings from the 9-year restoration experiment suggested that natural restoration is a sustainable grassland restoration regime to conserve both plant diversity and soil nutrients over short timescales in semi-arid grasslands in North China. In the long term, SOC storage can be substantially enhanced by artificial restoration, especially under treatments that include irrigation.

Boron (B), an essential element for increasing seed yield and germinability in alfalfa (Medicago sativa L.), plays a vital role in its reproductive processes. However, effects of B stress on physiological and proteomic changes in reproductive organs related to alfalfa seed yield and germinability are poorly understood. In order to gain a better insight into B response or tolerance mechanisms, field trials were designed for B deficiency (0 mg B L−1), B sufficiency (800 mg B L−1), and B surplus (1600 mg B L−1) application during alfalfa flowering to analyze the proteomics and physiological responses of alfalfa 'Aohan' reproductive organs. Results showed that B deficiency weakened the stress-responsive ability in these organs, while B surplus reduced the sugar utilization of 'Aohan' flowers and caused lipid membrane peroxidation in 'Aohan' seeds. In addition, four upregulated stress responsive proteins (ADF-like protein, IMFP, NAD(P)-binding Rossmann-fold protein and NAD-dependent ALDHs) might play pivotal roles in the response of 'Aohan' reproductive organs to conditions of B deficiency and B surplus. All of the above results would be helpful to understand the tolerance mechanisms of alfalfa reproductive organs to both B deficiency and B surplus conditions, and also to give insight into the regulatory role of B in improving seed yield and germinability in alfalfa seed production. In summary, B likely plays a structural and regulatory role in relation to lipid metabolism, carbohydrate metabolism, amino acid metabolism, and signal transduction, thus regulates alfalfa reproductive processes eventually affecting the seed yield and germinability of alfalfa seeds.

Even though a growing amount of information about the effects of livestock grazing on soil microbial communities have accumulated in literature, less is known about the combined response of plants, soil properties, and their interactions with soil microbes. In this study, we used a seven-year controlled grazing experiment to quantify the response of plant and soil properties and their interactions with soil microbial communities to moderate grazing in a semiarid grassland of Northern China. Our results showed that moderate grazing reduced the richness and diversity of soil microbial communities, as well as weakened community interactions. However, bacterial communities and their linkages were more stable under moderate grazing than fungal communities. Changes in aboveground plant biomass, soil water content, NO3--N, and NO3/NH4 ratio dominated grazing effects on soil bacterial communities, while fungal communities were mainly influenced by plant N, soil NO3--N, and NO3/NH4 ratio. Changes in the plant community composition played a key role in driving the composition of the fungal community. Our results provide a new insight into the response of soil microbes to moderate grazing, and suggest that above- and belowground communities should be considered to be precise indicators of the state and characteristics of the grassland ecosystem.

AbstractBackgroundLoss of vigor caused by seed aging adversely affects agricultural production under natural conditions. However, priming is an economical and effective method for improving the vigor of aged seeds. The objective of this study was to test the effectiveness of exogenous ascorbic acid (ASC) and glutathione (GSH) priming in the repairing of aged oat (Avena sativa) seeds, and to test the hypothesis that structural and functional systems in mitochondria were involved in this process.ResultsOat seeds were artificially aged for 20 days at 45 °C, and were primed with solutions (1 mmol L− 1) of ASC, GSH, or ASC + GSH at 20 °C for 0.5 h before or after their aging. Seed germination, antioxidant enzymes in the ASC-GSH cycle, cytochrome c oxidase (COX) and mitochondrial malate dehydrogenase (MDH) activities, and the mitochondrial ultrastructures of the embryonic root cells were markedly improved in aged oat seeds through post-priming with ASC, GSH, or ASC + GSH, while their malondialdehyde and H2O2contents decreased significantly (P < 0.05).ConclusionOur results suggested that priming with ASC, GSH, or ASC + GSH after aging could effectively alleviate aging damage in oat seeds, and that the role of ASC was more effective than GSH, but positive effects of post-priming with ASC and GSH were not superior to post-priming with ASC in repairing aging damage of aged oat seeds. However, pre-priming with ASC, GSH, or ASC + GSH was not effective in oat seeds, suggesting that pre-priming with ASC, GSH, or ASC + GSH could not inhibit the occurrence of aging damage in oat seeds.

Soil microbial communities play a crucial role in ecological restoration, but it is unknown how co-occurrence networks within these communities respond to grazing exclusion. This lack of information was addressed by investigating the effects of eight years of grazing exclusion on microbial networks in an area of Stipa glareosa P. Smirn desert steppe in northern China. Here, we show that fungal networks were more sensitive to grazing exclusion than bacterial networks. Eight years of grazing exclusion decreased the soil fungal community stability via changes in plant composition and reductions in soil total organic carbon, in this case triggering negative effects on the S. glareosa desert steppe. The results provide new insights into the response mechanisms of soil microbes to grazing exclusion and offer possible solutions for management issues in the restoration of degraded desert steppe.

Boron (B) is an essential micronutrient for plant reproductive growth and seed setting. A better understanding of the reasonable application rate of B could provide guidelines for improving seed yield and quality. In this study, we used five B concentrations (0, 400, 800, 1200, and 1600 mg B L-1) to study the effect of foliar application of B on seed yield and quality of alfalfa (Medicago sativa L.) in northern China. Our results indicated that foliar B application increased the pollen number, pollen viability, and dry weight and B concentration of alfalfa reproductive organs. The effect of B on alfalfa seed yield can be attributed to affecting the number of inflorescence and the seeds per pod. Foliar application with 800 mg B L-1 made quantitative and qualitative improvements in seed yield and quality of alfalfa. These results help to explain the positive effects of B on alfalfa seed production.

Siberian wildrye (Elymus sibiricus L.) is a cool-season, perennial bunchgrass widely used to increase forage production of semi-arid grasslands and to restore degraded lands. It is drought and cold tolerant, and has high yield potential and livestock acceptability. However, seed yield is low and variable and there is little information on the physiological processes limiting its seed yield. A split plot experiment was conducted to determine the effect of source-sink treatments under different nitrogen (N) applications on seed weight, seed setting rate, and dry matter and N remobilization during three successive growing seasons. The main plots were N level (0, 90, 180 kg N ha(-1)) and sub plots were source sink treatments (half trimmed and unaltered spikes). Leaf, stem, and spike dry weights and N concentration were measured at anthesis and seed physiological maturity, while seed weight and seed setting rate were measured at seed physiological maturity and milk stage respectively. Stem and spike dry weights were increased, whereas leaf dry weight was decreased between anthesis and maturity. N application significantly increased all plant parts of Siberian wildrye dry weight and seed weight compared with 0 kg N ha(-1) application. The half-spike treatment increased seed weight and seed setting rate across all N levels, and stem dry weight accumulation, but there was no significant influence on N translocation. The results of this study indicate that Siberian wildrye seed yield is source limited since seed weight and seed setting rate were increased in the half-spike treatment with N application. Stem dry weight increased after anthesis suggesting that stems were sinks and competed for assimilates with spikes. Therefore, breeding for increased photosynthesis and partitioning of assimilates from stems to spikes may result in increased and more consistent seed yield.

The critical nitrogen dilution curve (CNDC) is usually used as an efficient method to diagnose nitrogen (N) status of crop plants. However, there is no successfully developed CNDC for forage species seed production. The objectives of this study were to develop an appropriate CNDC in seed production and to manage nitrogen application accurately in seed fields of Siberian wildrye (Elymus sibiricus L.). Two experiments were carried out with N application treatments (0-225 kg N ha(-1)) in two successive growing seasons (2014 and 2015) at Yuershan Farm in Hebei Province, China. Shoot biomass (t ha(-1)), nitrogen concentration (percentage of dry matter), and seed yield (kg ha(-1)) were measured to calculate critical N concentration, development and validation of the CDNC. The CNDC for Siberian wildrye seed production was developed with the equation Nc = 3.00 W-0.32 (determination coefficient 0.97), based on shoot biomass (between 0.9 and 7.1 t ha(-1)) and its N concentration. According to the independent data set grouped by seed yield, the developed CNDC could adequately identify the situations of N-limiting seed yield and N non-limiting seed yield before and during anthesis stage, the optimum seed yield was reached at around NNI = 1. The CNDC developed in this study provides insight to improve N diagnosis and management in Siberian wildrye seed production under rain-fed conditions.

The changes in mitochondrial ultrastructure, antioxidant enzymatic activities, lipid peroxidation and respiratory function of ultra-dried (4% moisture content) and artificially aged (48 days at 45 degrees C) oat (Avena sativa) seeds were measured. The seeds were also primed with polyethylene glycol (PEG) solutions (0 and -1.2 MPa) for 12 hours at 20 degrees C. The results showed that seed vigour, mitochondrial antioxidant enzymes including superoxide dismutase (SOD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR), mitochondrial ultrastructure and their respiratory function in the embryo cells were improved with PEG-priming whilst mitochondrial H2O2 and malondialdehyde (MDA) contents decreased significantly (P < 0.05). This indicated that the effect of PEG-priming on seed vigour was positively related to mitochondrial antioxidant enzymes, mitochondrial ultrastructure and their respiratory function, but was negatively related to mitochondrial H2O2 and MDA contents. Compared with hydro-priming, PEG-priming was found to have a better effect on seed vigour in aged, ultra-dried oat seeds and this was closely correlated with the enhancements of mitochondrial antioxidant and respiratory function accompanying the regeneration of normal mitochondrial ultrastructure. Thus, ultra-dry and stored oat seeds should be primed with PEG solution at the appropriate water potential to alleviate the damage of seed ageing and imbibition.

Alfalfa (Medicago sativa L.) is the most commonly grown forage crop due to its better quality characteristics and high adaptability in China. However, there was 20%-80% hard seeds in alfalfa which could not be identified easily from non hard seeds which would cause the loss of seed utilization value and plant production. This experiment was designed for 121 samples of alfalfa. Seeds were collected according to different regions, harvested year and varieties. 31 samples were artificial matched as hard rates ranging from 20% to 80% to establish a model for hard seed rate by near infrared spectroscopy (NIRS) with Partial Least Square (PLS). The objective of this study was to establish a model and to estimate the efficiency of NIRS for determining hard rate of alfalfa seeds. The results showed that the correlation coefficient (R2(cal)) of calibration model was 0.981 6, root mean square error of cross validation (RMSECV) was 5.32, and the ratio of prediction to deviation (RPD) was 3.58. The forecast model in this experiment presented the satisfied precision. The proposed method using NIRS technology is feasible for identification and classification of hard seed in alfalfa. A new method, as nondestructive testing of hard seed rate, was provided to theoretical basis for fast nondestructive detection of hard seed rates in alfalfa.

This experiment was designed to measure the changes in ultrastructure, antioxidant enzymatic activities and lipid peroxidation in ultra-dried (4% moisture content) and artificially aged (48 days at 45 degrees C) oat (Avena sativa L.) seeds. The seeds were also primed with polyethylene glycol (PEG) solutions (0,-0.3,-0.6,-0.9 and-1.2 MPa) for 12 hours at 20 degrees C. The results showed that seed vigour, antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR), and the ultrastructure of the embryo cells were improved at lower water potential, whilst the malondialdehyde (MDA) contents decreased significantly (P < 0.05). This indicated that the effect of PEG-priming on seed vigour was positively related to antioxidant enzymes and ultrastructure of embryo cells, but was negatively related to MDA content. In terms of ultrastructure, the mitochondria were the most sensitive organelles to PEG-priming. PEG priming at 0 ,-0.3 and -0.6 MPa aggravated the damage of seed ageing, but priming at -0.9 and -1.2 MPa was beneficial. It is therefore recommended that the water potential used for priming with PEG should be less than -0.9 MPa for ultra-dried aged seeds.

Seeds lose their viability when they are exposed to high temperature and moisture content (MC) during storage. The expression and metabolism of proteins plays a critical role in seed resistance to heat stress. However, the proteome response to heat stress in oat (Avena sativa) seeds during storage has not been revealed. To understand mechanisms of heat stress acclimation and tolerance in oat seeds, an integrated physiological and comparative proteomic analysis was performed on oat seeds with different MC during heat stress. Oat seeds with 10% and 16% MC were subjected to high temperatures (35, 45, and 50°C) for 24 and 2 days, respectively, and changes in physiological and biochemical characteristics were analyzed. The results showed that seed vigor decreased significantly with temperature increase from 35 to 50°C. Also, the proline content in 10% MC seeds decreased significantly (p < 0.05) whereas that in 16% MC seeds increased significantly (p < 0.05) during heat treatment from 35 to 50°C. There were no significant differences in malondialdehyde content in 10% MC seeds with temperature from 35 to 50°C, but a significant (p < 0.05) decline occurred in 16% MC seeds at 45°C. Proteome analysis revealed 21 significantly different proteins, including 19 down-regulated and two up-regulated proteins. The down-regulated proteins, notably six heat shock proteins and two ATP synthases, have important roles in the mobilization of carbohydrates and energy, and in the balance between synthesis and degradation of other proteins during seed deterioration. The up-regulation of argininosuccinate synthase participated in proline biosynthesis at 16% MC, which is important for maintaining reactive oxygen species homeostasis for the resistance of heat stress. In summary, heat-responsive protein species and mitochondrial respiratory metabolism were sensitive to high temperature and MC treatment. These studies provide a new insight into acclimation and tolerance to heat stress in oat seeds.

This experiment was designed to determine the relationship between the ultrastructure of the embryo cells and the changes in antioxidant enzymatic activities and lipid peroxidation in oat (Avena sativa L.) seeds with different moisture contents (4, 10 and 16 %) that were aged for 0, 8, 16, 24, 32 and 40 days in 45 °C. The results showed that the declining in the germination percentage and integrity of cell ultrastructure in oat aged seeds were presented during the aged process, and these changes would be enhanced by the higher moisture content. There were consequent changes for biochemical reactions and lipid peroxidation exhibited. For oat seeds with 4 and 10 % moisture content, SOD and CAT were much more sensitive than APX at the early stages of imbibition after mild ageing, the activities of SOD, CAT, APX and MDHAR at 4 h of imbibition decreased significantly (P < 0.05) after being aged from 32 to 40 days. On the contrary, MDA and H2O2 contents both did not increase further. Upon imbibition the activities of DHAR and GR increased after mild ageing, declined after further ageing and maintained a stable level after ageing from 24 to 40 days at those moisture levels. Both activities were higher after ageing at 4 % moisture content than at 10 %. The decline in integrity of ultrastructural cells was related with accumulation of H2O2 during seed ageing, and favoured by the decrease of SOD, CAT, APX and MDHAR activities after imbibition. The activities of antioxidant enzymes and contents of MDA and H2O2 in oat seeds with 16 % moisture content all gradually decreased after ageing from 8 to 40 days, also the ultrastructure of embryo cells was severely damaged. Its ultrastructure was destroyed much more quickly in the seeds with higher moisture content. The level of moisture content could accelerate the seed deterioration, and mitochondrial damages were probably the main reason for oat seed ageing. However, the activities of antioxidant enzymes were the key factor to repair the damage from lipid peroxidation and to maintain the integrity of cell ultrastructure for oat aged seeds during imbibition.