Despite the essential role of micronutrients in plant metabolic processes and carbon cycle, the mechanisms by which micronutrients regulate plant community traits remain poorly understood. Here, we used a long-term experiment to explore the potential mechanisms of plant community micronutrients and traits along a precipitation gradient. Our results showed that plants shifted toward lateral growth and asexual reproduction over time. From 1985 to 2022, the plant community Fe content increased by 18.8% in the north but declined by 25.2% in the south of the typical steppe. Furthermore, plant community growth and reproduction were sensitive to both micronutrient contents and uptake efficiencies in the north of the typical steppe. While plant community Mn and Zn contents enhanced growth longitudinally, Zn and Fe uptake efficiencies hindered sexual reproduction. Furthermore, soil moisture and GDP per capita were the key drivers of micronutrient variation in the north and south of the typical steppe, respectively. Precipitation fluctuations primarily regulated community traits across all sites. In the arid site, micronutrient-driven shifts in reproduction stabilized the soil carbon stock by balancing biomass allocation. These findings can help us to better understand the coupling of plant micronutrients, traits, and soil carbon stocks, thereby providing the basis for a scientific grassland conservation strategy under global change scenarios.

Lycium barbarum is a promising high-quality woody forage, with crude protein concentration up to 30% and rich in secondary metabolites. This study investigated the effects of L. barbarum inclusion into an alfalfa-tall fescue mixture on in vitro dry matter digestibility (IVDMD), total gas production (TGP), fermentation characteristics, production of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), and global warming potential (GWP). Three cultivars, ‘Ningqicai (NQC) No.1’, ‘Ningqi (NQ) No.9’, ‘Qixin (QX) No.2’, were included at 4%, 8%, and 12% levels of the substrate with 7 replicates. After 72 h of incubation, the highest IVDMD among the three cultivars was observed at 4% compared with the control group. Although TGP and GWP at 4% inclusion were comparable to the control across all three cultivars (P > 0.05), they exhibited a quadratic increase (P < 0.05) with higher substitution levels for ‘NQC No.1’ and a quadratic decrease (P < 0.05) for ‘NQ No.9’. These variations corresponded with the productions of CO2 and CH4, and ammonia nitrogen (AN) and volatile fatty acids (VFA). For ‘QX No.2’, CO2 and CH4 production, the acetate to propionate ratio, and GWP were significantly lower than the control at the 12% level (P < 0.05). L. barbarum inclusion increased N2O production across all treatments (P < 0.05). Overall, 4%, 8%, and 12% were suggested potential for ‘NQC No.1’, ‘NQ No.9’ and ‘QX No.2’, respectively, which increased IVDMD and fermentation characteristics, and reduced CO2, CH4, and N2O productions. These findings suggest that L. barbarum can be used as a novel woody forage for ruminants, offering high degradability and low GWP at optimal inclusion levels.

Purpose The incorporation of crop residues is regarded as an important practice for increasing agricultural productivity. However, the impact of different residue types on the yield and quality of forage crops remains unclear. This study examines the effect of common vetch (CV), alfalfa (AF), and maize (MZ) residues on plant growth and quality of forage crops in controlled dryland conditions. Methods A two-phase greenhouse experiment was conducted to cultivate each crop, incorporating its harvested biomass as residue, and to evaluate their effects on soil nitrogen content, growth, and qualitative attributes of subsequent forage crops. Results Crop residues, particularly alfalfa residue (AF), significantly improved the growth indices and quality of forage crops. The AF residue increased plant height of common vetch, alfalfa, and maize by 47.65

Soil nitrogen (N) mineralization is a key process in the cycling of N and is sensitive to ongoing human activities and climate changes. However, little is known about how grazing and N inputs separately and/or jointly affect the soil net N mineralization of grassland ecosystems across large temporal scales in the context of climate change. Here, we conducted a 4-year in situ measurement campaign of soil net N mineralization within a long-term grazing and N addition treatments in a semi-arid grassland. We found an alternating seasonal pattern of soil N transformation between mineralization and immobilization. Relative to normal year, peak N mineralization was advanced one month in the wet year, but peak N immobilization was delayed one month in the dry year. Precipitation-induced changes in soil temperature and moisture determined the seasonal dynamics of N mineralization in wet and dry years. The effects of grazing and N addition on soil N mineralization were temporally dependent. At the seasonal scale, N addition significantly accelerated soil N mineralization and immobilization in the peak growing season and the period after the peak growing season, respectively. Dry climate weakened the response of peak soil N transformation to N addition. Grazing broadly had no effect on soil N transformation during most of the experimental period, except for some events during the wet years. At the interannual scale, grazing, N addition and their interactions had no influences on cumulative net N mineralization. Further analysis showed that the interannual variation in soil N mineralization was driven by the previous year’s annual precipitation rather than the current year. Our results suggest that grazing and N addition could stabilize the soil N cycling in semi-arid grasslands over long-term time scales. Moreover, they emphasize the importance of precipitation legacy effects on soil N cycling, and thus for ecosystem productivity.

Cultivated forages are widely planted in arid and semi-arid agro-pastoral regions to increase livestock carrying capacity and thereby relieve excessive grazing pressure. The effect of grazing on soil N2O emissions in different types of sown pasture converted from cropland remains unclear. Stands of annual (tillage) and perennial (no-tillage) forage species were established in a saline cropland area of northwest China in a 4-year experiment to investigate the effect of utilization method (grazing vs. haying) on soil N2O emissions during the growing seasons. Grazing did not differ from haying in cumulative soil N2O flux during the growing seasons in the annual forages but had 11 % lesser (P < 0.05) cumulative N2O flux in the second year in the perennial forages. The positive effects of soil compaction and the manure return from grazing sheep on soil N2O emissions may be counteracted or even outweighed by the negative effects of enhanced soil nutrient uptake due to sheep intake. A negative correlation (r = 0.55, P < 0.05) between soil N2O flux and soil water content was found in the perennial forages, but not in the annual forages. The varying regression slopes of soil N2O emissions vs. soil organic carbon content in the annual forages differed (P < 0.05) between grazing and haying. The multiple linear regression results indicated that soil temperature accounted for >= 60 % of the temporal variation in soil N2O flux. Grazing significantly increased the mean forage yield by 44 % and 14 % and mean crude protein (CP) yield by 81 % and 11 % over that of haying, and decreased the mean hay-scaled soil N2O emission (NEIhay, kg of N2O kg(-1) of dry forage yield) by 36 % and 20 % and mean CP-scaled soil N2O emission (NEICP, kg of N2O kg(-1) of CP yield) by 49 % and 17 % over that of haying, in the annual and perennial stands, respectively, from 2014 to 2017. In conclusion, grazing reduced the soil N2O emission intensity (NEI) by increasing forage yield in annual sown pasture but by reducing soil N2O emission in perennial pasture. Therefore, grazing is one of the optimal approachs to improve forage yield while mitigating soil N2O emissions in sown pasture in continental arid regions.

Abstract Ongoing human activities and climate change threaten global grasslands, where plant nutrients are essential for ecosystem stability. However, long-term assessments (1985–2022) of above- and below-ground nutrient trade-offs remain limited. Here, we conducted a 37-year study along the precipitation gradient (267–441 mm) to investigate the dynamics and trade-offs of plant carbon (C), nitrogen (N) and phosphorus (P). Our study found that with increasing local precipitation, above-ground C, N and P contents increased, while below-ground C content declined. The long-term response of plant nutrients varied spatially; the drier north (267 mm) and central region (334 mm) showed increased above-ground C but decreased N and P over time, whereas the opposite pattern occurred in the wetter south (441 mm). Additionally, the trade-off values of plant C, N and P stocks increased with local precipitation, and temporal stability of the N and P trade-off values was lowest in the drier north. Finally, precipitation fluctuation, fertilizer input and per capita GDP were identified as the key drivers of plant above- and below-ground nutrient dynamics in the northern, central and southern regions, respectively. With increasing local precipitation, the effect of climate on trade-off values shifts from negative to positive, whereas the effect of human activities shifts from positive to negative. Our findings highlight that the long-term response of plant nutrients is regulated by local precipitation patterns, through which the precipitation gradient has reshaped plant nutrient regulation by shifting the dominant driver from climatic to human activities factors.

Livestock husbandry is a primary anthropogenic source of global greenhouse gas (GHG) emissions. The Qinghai-Tibetan Plateau (QTP), an important geography for animal husbandry in China, and is therefore a significant contributor to the global GHG budget. Therefore, this study employs the life cycle assessment method to comprehensively assess the effect of yak grazing on GHG balance and enhance our understanding and monitoring of GHG budgeting in the alpine ecosystem. The results show that yak grazing alters the GHG balance of alpine meadow ecosystems from sink to source (Critical value = 1.3 yak/ha). Sequestration of CO2 in soil organic matter is the most significant contributor to the GHG balance in both grazed and ungrazed grassland. In grazed grassland, enteric fermentation and livestock manure and its management (dung and urine patches, manure heaps, night pens, and dry stored manure combustion) are important contributors to the total GHG balance, where implementing mitigation practices that target reductions of enteric fermentation and improve manure management can help to alleviate these emissions. Due to the unique geographical and biophysical environment of the QTP, solar and wind energy are viable emission-free alternatives to dry manure consumption, and livestock enclosure has the potential to restore soil organic carbon stocks by increasing sequestration of atmospheric CO2. In conclusion, our findings suggest that successful implementation of targeted emission reduction measures is conducive to the sustainable development of animal husbandry, while also maintaining a balance with ecosystem functions under the multifaceted ecological landscape of QTP.

Population dynamics may fluctuate dramatically over time in response to changing climate conditions. Thus, assessing how trade-offs in growth and reproduction of plant population respond to climate change may be key for predicting and conserving complex communities, especially in the context of different precipitation. Here, using a long-term experiment along the precipitation gradient, we investigated trade-offs in growth and reproduction of dominant species, Artemisia capillaris and companion species, Aster altaicus, as well as their climate-driven mechanisms. The impact of A. capillaris and A. altaicus on community above-ground biomass (AGB) and species richness (SR) were also evaluated. Our findings indicate that, over the past 37 years, A. capillaris exhibited lateral growth and asexual reproduction across the three sites. In contrast, A. altaicus tended to grow vertically and reproduce sexually, with a significant increase in its AGB. Moreover, the influence of climate fluctuation, characterized by variations in temperature and precipitation over specific time scales, on the two populations diminished from north to south. Long-term average climate, reflecting mean temperature and precipitation, and current climate conditions during the sampling year primarily influenced changes in A. capillaris and A. altaicus in south, respectively. Additionally, from north to south, the contribution of A. altaicus to community AGB and SR increased, while the contribution of A. capillaris to community AGB and SR decreased. Community AGB increased as the coupling index between A. capillaris and A. altaicus intensified. These findings can help us to better understand the coupling of plant traits, populations and communities, aid in the protection of grasslands under future climate change scenarios.

Livestock production faces the challenge of feed shortage due to the escalating demand for livestock products and the continued degradation of grasslands. The cultivation of annual forage crops may be an alternative option in the forthcoming decades. However, the impact of grassland utilization method (grazing vs. mowing) on forage yield and associated soil greenhouse gas (GHG) emissions of annual sown pastures remains uncertain. A 4-year experiment was conducted in a saline-alkali cropland with irrigation of 560 mm yr-1 in Northwest China. Annual forage crops were rotationally sown to elucidate the impact of grassland utilization methods on forage productivity (hay, crude protein (CP)) and soil GHG (CO2, N2O, and CH4) fluxes, aiming to optimize the trade-off between forage production and soil GHG emissions. Results show that compared to mowing, grazing increased the mean yields of hay and CP by 44.7 % and 50.2 %, respectively; however, grazing had no significant impact on the cumulative soil N2O emissions and CH4 uptake but significantly reduced cumulative soil CO2 emissions during the last two study years. For both grazing and mowing, soil water content was the primary influencing factor of soil N2O emissions, and soil temperature was the primary influencing factor of soil CH4 uptakes and CO2 emissions. Cumulative soil N2O emissions and CH4 uptakes had upward trends with the increasing forage hay and CP yields under grazing. Cumulative soil CO2 emission under mowing had a downward-curving relationship with the hay and CP yields. Overall, compared to mowing, grazing decreased hay and CP yield-scaled soil GHG intensity by 36.3 % and 38.6 % respectively. Grazing presents an effective strategy for optimizing forage production and environmental performance of annual cereal grasses in arid regions.

Grazing is widely used in mountain land, which changes soil structure through feeding, trampling, excreta return, redistributing solar radiation, surface runoff, and then affects soil moisture (SM) and soil elements. However, research of interaction between topography and exclusion duration on relationship between soil and vegetation characteristics is scarce. The study was carried out to explore effect of topography and livestock exclusion duration on soil properties, correlation between soil and vegetation characteristics. The results showed that: (i) SM peaked at 3 years of exclusion. Water use efficiency, soil organic carbon, soil phosphorus, soil available nitrogen and soil available phosphorus were found to be directly proportional to duration of livestock exclusion and inversely correlated with slope. Soil nitrogen and N/P were directly proportional to duration of livestock exclusion and slope. C/N was inversely correlated with duration of livestock exclusion and slope. C/P was directly proportional to duration of livestock exclusion, and the change with slope was not obvious. Soil properties in sunny slope were greater than in shady slope. (ii) Aspect and slope positively affected the relationship between soil properties and aboveground biomass significantly. The effects of livestock exclusion on relationship between aboveground biomass, plant species richness and soil properties were insignificant. (iii) Livestock exclusion of sunny slope is more beneficial to soil nutrient accumulation than shady slope. Livestock exclusion played an opposite role to topography in regulating the relationship between soil and vegetation characteristics. Therefore, grazing management on complex topography is conducive to regulating soil nutrients and further coordinating vegetation growth.

Unreasonable grazing activities cause grassland degradation, and the most visible sign of degradation is a decrease in productivity. The dominant species not only carry the majority of the community’s biomass, but they also use specific adaptive strategies to deal with grazing pressure. However, more research focuses on a single influence at the community level, ignoring dominant species’ trait responses to multiple environmental variables, as well as trait-based mechanisms of biomass formation. We based it on a grazing experimental platform on an alpine typical steppe. Through situ sampling with a time span of 20 years, we defined various distances from the pasture entrance as the various grazing intensity and chose the dominant species of Agropyron cristatum (A. cristatum) and Stipa purpurea (S. purpurea) to assess how long-term specific grazing management methods shape plant traits and balance their impact on biomass. The findings revealed that long-term moderate grazing increased the population density of A. cristatum and S. purpurea, whereas high-intensity grazing reduced A. cristatum biomass and flattened it while keeping S. purpurea biomass stable and more huge. Grazing in both seasonal pastures widens their crowns on a temporal and spatial (pasture) scale. High-intensity grazing encourages investment in A. cristatum height and density, while warm-season light grazing encourages investment in density in S. purpurea. Cold-season grazing has no effect on S. purpurea. The main factors influencing A. cristatum and S. purpurea traits are climate and soil nutrient availability. In cold-season pastures, A. cristatum and S. purpurea growth traits are strongly correlated with climate, whereas warm-season grazing weakens this correlation. Population density and climate both significantly increase biomass; warm-season grazing promotes A. cristatum density; and S. purpurea density is unaffected by any variables. Soil available nutrients and growth traits have a positive effect on the biomass of A. cristatum and S. purpurea. These findings imply that differences in growth and reproductive traits between plant populations play an important role in biomass maintenance and that different plants may adapt to grazing disturbances by improving specific traits. It is recommended to implement seasonal fence grazing based on the traits of plant community dominant species, matching animal feeding habits and plant growth phenology, in order to promote degraded grasslands restoration and grassland productivity sustainability.

Silage maize (Zea mays L.) is a prominent forage crop in arid regions where water scarcity and the need for optimized nitrogen (N) fertilizer use pose significant challenges to agricultural productivity and sustainability. Interseeding leguminous cover crops with silage maize can enhance sustainable soil development and improve N management through biological N fixation. However, the competition interactions between silage maize and cover crops under constrained water-N conditions remains uncertain. This study conducted a three-year field experiment of interseeding leguminous cover crops with silage maize under varying drip fertigation conditions. The treatments included three types of leguminous cover crops-red clover (TP, Trifolium pretense L.), common vetch (VS, Vicia sativa L.), and hairy vetch (VV, Vicia villosa Roth)-combined with two N application rates (N1: 120 kg N ha(- 1) and N2: 180 kg N ha(- 1) and two irrigation levels (W1: 75 % of ET(c )and W2: 100 % ETc ). The results showed that interseeding did not significantly inhabit plant height, stem diameter, and relative leaf chlorophyll content of silage maize compared to no covers (P>0.05). Under identical water and N conditions, the hay yield of maize interseeded with VV was significantly higher by 15.3 %-21.9 % compared to no covers (P<0.05), and the hay yield of the interseeding system vetch was significantly higher by 22.7 %-28.4 % (P<0.05). Specifically, under VV, W2N1 decreased actual evapotranspiration (ETa) by 2.1 %-12.9 % (P >0.05), and increased water use efficiency (WUE) by 8.6 %-12.5 % (P>0.05) and nitrogen partial factor productivity (PFPN) by 24.1 %-43.3 % (P<0.05) compared to W2N2. Dry matter of cover crops, which contributed to the increases in PFPN and WUE, ranged from 0.8 to1.2 Mg ha (- 1). Structural equation modeling indicated that the N application was the most important influencing the interseeding system. In conclusion, a 100 % ET(c )irrigation amount and a 120 kg N ha(- 1)N application rate in a silage maize-hairy vetch interseeding system can effectively increase forage yield and enhance water and N utilization efficiencies in the arid region.

Managed grazing is the most widespread and economically significant form of grassland utilization worldwide. Accurate quantification of the spatiotemporal distribution of grazing intensity (GI) is crucial for promoting sustainable management of livestock-grassland ecosystems. However, a reliable method for dynamically monitoring GI and quantifying key proxies under real-world grazing conditions is still lacking. In this study, we developed a practical approach to estimate GI using sequential unmanned aerial vehicle (UAV) monitoring and evaluated its feasibility in a typical household pasture on the Qinghai–Tibetan Plateau, China. Our findings show that: (1) yak dung is clearly identifiable in UAV image, although detection accuracy decreases with increasing flight altitude (from 100% at 2 m to 93.16% at 20 m); (2) yak dung density serves as a feasible proxy for GI, effectively capturing its temporal and spatial variability; (3) yak dung density reflects cumulative GI from May to September, and its representativeness increases with the length of accumulation. The proposed approach is characterized by high frequency, accuracy, and efficiency. It is well-suited for studying animal behavior and evaluating livestock–resource relationships, thereby providing valuable insights for sustainable grassland ecosystem management.

Soil nutrients are essential for ecosystem function and food production. However, the long-term dynamics and ecological drivers of soil macro- and microelements, as well as their relationships, remain virtually unknown, especially in varying precipitation contexts. Here, we conducted a long-term experiment in typical steppes to explore the universal and differential mechanisms of soil macro- and microelements along the precipitation gradient. Our results showed decreases in soil Zn and Fe stocks, alongside increases in Cu, SOC, and STN stocks over time. From north to south, the temporal stability of SOC, STN, Cu and Zn stocks generally increased. Additionally, compared to the humid site, soil macronutrients showed stronger coupling with micronutrients at the arid site, especially Fe, followed by Mn, Zn, Cu. The sensitivity of soil macro- and microelements to climate change and human activities were correlated with the local background precipitation. Precipitation fluctuation, GDP per capita and current precipitation were significant factors contributing to the variation in soil macro- and microelements stock in the north, center and south. Climate explained 46%, 19%, and 16% of nutrient coupling variation in the north, center, and south sites, respectively. Across all sites, human activities explained 74% of variation. Altogether, our findings provide an overview of long-term soil macro- and microelement distribution, their coupling relationships, and driving factors under different precipitation contexts, which is important for grassland management and food production in future global change scenarios.

Soil ecological stoichiometry play vital roles in regulating structure and function of grassland ecosystems. However, the long-term dynamics of soil nutrient elements and their underlying driving mechanisms remain poorly understood, particularly in the context of changing precipitation patterns. Here, we conducted a longterm experiment to assess temporal-spatial dynamics and mechanisms of soil ecological stoichiometry along the precipitation gradient. Over the past 37 years, our results indicated a significant overall increase in soil organic carbon (SOC) and total nitrogen (STN) contents, accompanied by a decrease in soil total phosphorus (STP) content across the three sites. The sensitivity of SOC, STN, C:P, and N:P to climate change decreased significantly as local precipitation increased, while the sensitivity of SOC, STN, and C:N to local precipitation declined significantly over time. From north to south, STP content increased on average by 1.03 %, 1.16 % and 1.68 % in 1985, 2002 and 2022, respectively. Additionally, the coupling strength of SOC, STN and STP decreased with increasing local precipitation from 1985 to 2002. Furthermore, the interaction between climate and soil properties explained 18 % and 22 % of the variation in temporal stability and contents of SOC, STN and STP, climate was the most critical factor affecting spatial stability of SOC, STN and STP. Among them, average precipitation, plant phylogenetic diversity and soil moisture were key indicators of temporal-spatial variability in soil C:N:P stoichiometry. Our findings provide an overview of biogeographical nutrient cycles under different temporal and spatial contexts, which is critical for grassland management and conservation in future global change scenarios.

Agriculture in the 21st century faces the dual challenges of increasing productivity while mitigating its impact on climate change. Nitrogen fertilizers are indispensable for increasing agricultural productivity, but hasten climate warming through greenhouse gas emissions. This study examined the effects of intercropping Cicer milkvetch (Astragalus cicer L.) with Smooth bromegrass (Bromus inermis Leyss.) and Ryegrass (Lolium perenne) at different nitrogen rates (300, 225, 150, and 75 kg ha-1) on hay yield, forage quality, and greenhouse gas emissions. The decrease in nitrogen fertilizer resulted in a linear decline in the yield and quality of monoculture grasses. However, milkvetch+bromegrass and milkvetch+ryegrass intercrops with 150 kg nitrogen ha-1 achieved highest hay yield (9.05-9.12 and 8.17-8.88 t ha-1), crude protein (1.39-1.43 and 1.18-1.23 t ha-1), and relative feed value yield (20.70-20.73 and 19.63-21.33 t ha-1) in 2021-2022, respectively. Legume-grass intercrops presented a good trade-off between environmental sustainability and yield benefits compared to monoculture pastures, indicated by lower greenhouse gas emissions, greenhouse gas intensity, and global warming potential. Milkvetch+bromegrass and milkvetch+ryegrass intercrops with 150 kg nitrogen ha-1 reduced cumulative nitrous oxide emissions by 59.11-62.92 % and 56.23-58.24 %, global warming potential by 59.83-64.02 % and 55.32-59.55 %, and greenhouse gas intensity based on hay yield by 70.96-78.47 % and 67.16-75.47 %, and based on crude protein yield by 83.14-88.12 % and 69.41-83.44 % compared to grass monocultures with nitrogen rate of 300 kg ha-1 in 2021 and 2022, respectively. Pasture fields acted as net methane sinks. Soil inorganic nitrogen and water contents were the primary regulating factors of greenhouse gas fluxes. Overall, legume-grass intercropping, specifically milkvetch+bromegrass with 150 kg nitrogen ha-1, represents a climatesustainable strategy for enhancing forage productivity in arid regions.

Context: Oat (Avena sativa L.) serves as a crucial forage crop, but its production in arid regions, particularly in the Hexi Corridor of Northwest China, is often constrained by inefficient nitrogen (N) use and low quality. Overapplication of N and inconsistent mowing schedules contribute to low N use efficiency (NUE) and suboptimal aboveground dry matter and quality. Objective: This study hypothesized that optimizing N application rate and mowing frequency could enhance forage nutritive value while improving NUE. Methods: A four-year field experiment was conducted using subsurface drip fertigation with four N application rates (0, 90, 180, and 270 kg N ha-1) and four mowing frequencies: M1 (milky stage), M2 (jointing and milky stages), M3 (jointing, booting and milky stages), and M4 (jointing, booting, grain-filling, and milky stages). Results: Results showed that N application, mowing frequency (M) and their interaction (N x M) significantly affected dry matter, regeneration, crude protein (CP) content and NUE (P < 0.05). Dry matter increased with N application, while CP plateaued at 180 kg N ha-1 . No significant differences in aboveground dry matter or CP were observed between 180 and 270 kg N ha-1 (P < 0.05). NUE declined linearly with increasing N application rates. Dry matter and CP followed a unimodal pattern with mowing frequency, peaking at M3. The combination N180M3 produced the highest dry matter and CP over four years. Additionally, accumulated dry matter and CP increased with effective cumulative temperature, while NUE showed a quadratic relationship. Conclusions: Applying 180 kg N ha-1 and mowing at jointing, booting and milky stages provided the best balance of aboveground dry matter, quality, and NUE. Significance: Appropriate mowing frequency and nitrogen application improved growth and quality of oat.

Grasslands have important ecological and economic functions. However, climate change and overgrazing contribute to the deterioration of such functions, and maintaining a balance of forage-livestock is critical to mitigate this effect. In this study, we evaluated the dose-response relationship between Bacillus subtilis (B. subtilis) field spray on an alpine meadow and the chemical composition of forage, digestibility and rumen bacterial populations in Tibetan sheep. Specifically, four treatment blocks were divided into 4 paddocks, which were sprayed with 1 g/L, 2 g/L and 5 g/L B. subtilis suspension, and an equal volume of water as control, respectively, and the treatment dose was 200 mL/ m2. Thirty-two 1-year-old Tibetan sheep (wethers) with a body weight of 30 +/- 0.23 kg were rotationally grazed among 4 blocks, each containing different B. subtilis concentrations, with a 7-day grazing period in each block. The crude protein content in herbage increased with the rise in B. subtilis spraying concentration (P < 0.01), meanwhile, crude fiber contents were negatively correlated (P < 0.01); The apparent digestibility of crude protein, neutral detergent fiber and ether extract were higher (P < 0.05) for sheep feeding on herbage sprayed with B. subtilis than for sheep fed with control, while it was enhanced with increasing spray concentration; B. subtilis had a lower fecal nitrogen (N) as a proportion of N intake (P < 0.05) and urinary N as a proportion of N intake (P < 0.05) than that of control, which was negatively correlated with the spray concentration gradient; The fecal energy and urinary energy output were different (P < 0.05) among diets. Methane/ dry matter intake and methane energy/ gross energy were reduced (P < 0.05) compared with sheep fed with the control, and the maximum spray volume was the lowest; Sheep offered the B. subtilis-sprayed diet had a lower ruminal pH (P < 0.05), which reduced with the increase in spraying concentration and with the rising content of volatile fatty acids (P < 0.05). The acetate: propionate ratio was different (P < 0.05) among diets, with the lowest value at a spray concentration of 2 g/L; The field spray of B. subtilis increased the relative abundances of total bacteria, and the bacteria associated with fiber degradation (P < 0.05), and reduced those of fungi, protozoans and methanogens. In conclusion, the foliar application of B. subtilis on natural grassland could improve the nutritional value of herbage, and the growth performance and apparent feed digestibility in Tibetan sheep.

Grazing is widely used in more than one-forth of global terrestrial ecosystems, with three quarters are distributed on complex topography. Grazing and topography have both resulted in degradation of approximately 49 % of natural grasslands. However, research on the interaction between topography and livestock exclusion on grassland characteristics is scarce. This study was carried out on a typical steppe to explore the effect of topography and enclosure year on vegetation characteristics. Aboveground biomass, and species richness were examined for three different enclosure years (0, 3, and 6 years), on four slopes (0 degrees, 15 degrees, 30 degrees, and 45 degrees slope), and three aspects (flat, shady and sunny). The results indicated that: The aboveground biomass on the 0 degrees slope had a greater value after 6 years of the enclosure. Aboveground biomass increased with the increasing enclosure year, while it decreased with increasing slope except enclosure for 0 year on shady slope. Aboveground biomass on the shady slopes was greater than on the sunny slopes. Species richness of community and perennial plants increased with increasing slope and enclosure year. The annual plants richness inversely correlated with slope and enclosure year. All plant diversity indexes increased with increasing enclosure year. Margalef and Shannonwiener indexes decreased with increasing slope, while Simpson and Pielou indexes increased. This paper demonstrates that aspect, slope and enclosure affect aboveground biomass by affecting other vegetation characteristics. In conclusion, grassland production can be improved with moderate livestock exclusion under different topography.

Introduction of alpine grasses to low altitude regions has long been a crucial strategy for enriching germplasm diversity, cultivating and acclimating high-quality species, enhancing ecosystem resilience and adaptability, as well as facilitating ecosystem restoration. However, there is an urgent need to investigate the impacts of planting Gramineae seeds on greenhouse gas (GHG) emissions, particularly during the critical stage of early plant growth. In this study, four species of grass seeds (Stipa breviflora, Poa pratensis, Achnatherum splendens, Elymus nutans) were collected from 19 high-altitude regions surrounding the Qinghai-Tibet Plateau and sown at low-altitude. Measurements of GHG emissions at early seedling growth in the mesocosm experiment using static chamber method showed a strong increase in the cumulative emissions of CO2 (5.71%-9.19%) and N2O (11.36%-13.64%) (p < 0.05), as well as an elevated CH4 uptake (2.75%-5.50%) in sites where the four grass species were introduced, compared to bare soil. Consequently, there was a substantial rise in global warming potential (13.87%-16.33%) (p < 0.05) at grass-introduced sites. Redundancy analysis showed that seed traits, plant biomass, and seedling emergence percentage were the main driving biotic factors of three GHGs fluxes. Our study unveils the potential risk of escalating GHG emissions induced by introducing high altitude grasses to low altitude bare soil, elucidating the mechanism through linking seed traits with seedling establishment and environmental feedback. Furthermore, this offers a new perspective for assessing the impact of grass introduction on ecological environment of introduced site.