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Overgrazing and phosphorus (P) deficiency are two major factors limiting the sustainable development of grassland ecosystems. Exploring plant P utilization and acquisition strategies under grazing can provide a solid basis for determining a reasonable grazing intensity. Both foliar P allocation and root P acquisition are crucial mechanisms for plants to adapt to environmental P availability; however, their changing characteristics and correlation under grazing remain unknown. Here, we investigated foliar P fractions, root P-acquisition traits and gene expression, as well as rhizosphere and bulk soil properties of two dominant plant species, Leymus chinensis (a rhizomatous grass) and Stipa grandis (a bunchgrass), in a field grazing intensity gradient site in Inner Mongolia. Grazing induced different degrees of compensatory growth in the two dominant plant species, increased rhizosphere P availability, and alleviated plant P limitation. Under grazing, the foliar metabolite P of L. chinensis increased, whereas the nucleic acid P of S. grandis increased. Increased P fractions in L. chinensis were positively correlated with increased root exudates and rapid inorganic P absorption. For S. grandis , increased foliar P fractions were positively correlated with more fine roots, more root exudates, and up-regulated expression of genes involved in defense and P metabolism. Overall, efficient root P mobilization and uptake traits, as well as increases in leaf metabolic activity-related P fractions, supported plant compensatory growth under grazing, a process that differed between tiller types. The highest plant productivity and leaf metabolic activity-related P concentrations under medium grazing intensity clarify the underlying basis for sustainable livestock production. • Grazing induces plant compensatory growth and alleviates P limitation. • L. chinensis increases leaf metabolite P while S. grandis increases nucleic acid P. • Plant P-acquisition strategies differ between tiller types. • Root traits correlate with leaf P fractions by enhancing P mobilization and uptake. • Plant P utilization can be an important basis for sustainable grazing management. [ABSTRACT FROM AUTHOR]

• P limitation under grazing was driven by plant compensatory growth and soil P loss. • Available P concentration in the rhizosphere was increased under grazing. • Plant requirement for P stimulated its transition from organic into inorganic P. • LMWOAs and mycorrhizal fungi mobilized the rhizosphere P. • A medium grazing intensity is conducive to grassland's sustainable development. Soil erosion and phosphorus (P) removal due to livestock production have led to a grave depletion of P in grasslands. Accordingly, understanding how plants cope with such P limitation conditions and which P transition processes operate in the soil under different grazing intensities is imperative for better scientific management of grazed grasslands. Here, we conducted a field experiment that tested the impact of different grazing intensities (light, medium, and heavy) and a control (no grazing) on P-related dynamics in a typical temperate grassland site in Inner Mongolia, China. The increased N:P ratio in leaves of dominant plant species and higher annual primary production (APP) of vegetation that generally ensued under grazing indicated that plants' compensatory growth in response to grazing pressure was a factor contributing to P limitation. Plants' P requirement for growth stimulated P transition in the rhizosphere via the mobilization of low-molecular-weight organic acids (LMWOAs) and mycorrhizal fungi. Specifically, LMWOAs promoted the conversion of stable P into organic P, and mycorrhizal fungi converted that organic P into labile P in the rhizosphere. This P transition process is jointly affected by changes to key soil physiochemical properties and the altered P input from excrement caused by herbivores. Altogether, these results suggest that grazing increases the biological vitality of the soil and accelerates the transition of P in the rhizosphere; and a medium grazing intensity may be more suitable for agricultural production because it provides the highest APP and a more biologically dynamic soil environment. [ABSTRACT FROM AUTHOR]

Plants have different physiological characteristics as the season changes, grazing management in compliance with plant growth and development characteristics may provide new ideas for sustainable livestock development. However, there has been little research on seasonal grazing and plants physiological responses under it. Here, we studied a typical steppe ecosystem of Inner Mongolia, with Leymus chinensis as the dominant species, in five grazing treatments: continuous grazing, seasonal grazing (which started in spring or in early and late summer), and no grazing (the control). We analyzed growth and resistance of L. chinensis in the five treatments by measuring annual primary productivity, morphological traits and various physiological processes. Compared with continuous grazing, seasonal grazing significantly alleviated grassland degradation. The plants were less affected by stress under spring grazing, with net photosynthesis and non-photochemical quenching closer to the control values and with a lower malondialdehyde content. The annual primary production of plants under grazing started in the early and late summer were 3–4 times the value under continuous grazing. Regrowth under early-summer grazing was greatly improved, and stress resistance was stronger with a higher proline content and high antioxidant enzyme activity. And nutrient accumulation at the end of the growing season such as abundant soluble sugars were transferred from aboveground tissue to the roots in September under late-summer grazing, which benefited regrowth the next year. All these physiological processes were regulated by hormonal changes. Our results highlight how plants response grazing stress in different growing seasons and suggest that seasonal grazing can improve the stress resistance and regrowth capacity of forage vegetation, and applying this knowledge can promote more sustainable grazing practices. • Plants adjusted its Morphological and physiological traits in response to grazing ➢ Plant regrowth in the next year affected by nutrient accumulation and transfer. • Different responses of plants under grazing were regulated by various hormones. • Seasonal grazing alleviated grazing stress and promote regrowth of plants. • Grazing started in June was the most suitable grazing regime for production. [ABSTRACT FROM AUTHOR]

Grazing has a profound impact on the availability of soil resources like carbon (C), nitrogen (N), and phosphorus (P) in grasslands. These changes can potentially make it difficult to meet microbial elemental demands, thus affecting microbial C use efficiency (CUE) and soil C dynamics. Nevertheless, it remains unclear how soil microbes respond to stoichiometric imbalances and their consequent effect on microbial CUE. In this study, we investigated the stoichiometry of soil labile resources, microbial biomass, extracellular enzymes, as well as the microbial community composition and microbial CUE, microbial respiration, microbial quotient (q MB), and soil organic carbon (SOC) changes, at sites with four grazing intensities (no grazing, light, medium, and heavy grazing) in a temperate steppe of northern China. Grazing led to decreased stoichiometric imbalances between soil labile resources and microbial biomass, thereby exacerbating limitations of available C on soil microbes. To alleviate this limitation of C, microbes raised the microbial threshold elemental ratios and microbial biomass, and increased fungi dominance rather than increased activities of C-, N-, and P- acquiring enzymes due to increased microbial own growth. Microbes also improved microbial CUE, q MB, and microbial respiration while decreasing SOC under increasing grazing intensity. These integrated adaptations denote that grazing can reduce SOC which is closely affected by soil microbial C utilization induced by resource change conditions despite the increased microbial biomass contribution to SOC. These findings illustrate the regulation of stoichiometric imbalances in soil C dynamics driven by microbes under grazing and improve our understanding of how stoichiometric changes influences soil C flows in semi-arid grassland. [Display omitted] • Grazing lowered stoichiometric imbalances but increased microbial C limitation. • Microbes decreased C-, N-, P-acquiring enzymes for limiting nutrients acquisition. • Microbes increased their biomass, threshold elemental ratios, and fungi:bacteria. • Aggravated grazing induced increased CUE, q MB, and microbial own growth. • Adaptative pathways of microbes resulted a decline of SOC. [ABSTRACT FROM AUTHOR]

Aims: Litter decomposition affects soil organic carbon storage, and nutrient addition alters exogenous nutrient availability in soil, thereby affecting the endogenous nutrient concentration and extracellular enzyme activity in litter. However, how above- and belowground litter decomposition responds to nutrient addition is not fully understood. Methods: We conducted a 7-yr field experiment with 5 levels (0, 1, 2.5, 5, and 12.5 g P m−2 yr−1) of phosphorus fertilization (P). Starting in the 6th year, we determine litter decomposition, nutrient elements, and enzyme activity to explore the response mechanisms of above- and belowground litter decomposition to P addition. Results: All levels of P addition increased the rate of aboveground litter decomposition, but only 2.5 g P m−2 yr−1 increased that of belowground litter. P addition increased the litter initial P and Mn contents, while decreased the C/P and N/P ratios of aboveground litter, which stimulated the activities of β-1,4-glucosidase and β-1,4-N-acetylglucosaminidase, thereby increasing the aboveground litter decomposition rate. The belowground litter decomposition was mainly inhibited by lignin content, and 2.5 g P m−2 yr−1 addition significantly decreased lignin content and increased the phenol oxidase activity, thereby accelerating the decomposition. P addition promoted the accumulation of P and the release of cellulose from aboveground litter and promoted the accumulation of calcium and the release of carbon from belowground litter. Conclusions: Different mechanisms of above- and belowground litter decomposition under P addition were driven by litter quality and enzyme activity, but moderate P addition increased semiarid grassland litter decomposition, which may contribute to low soil C sequestration. [ABSTRACT FROM AUTHOR]

Summary: Phosphorus (P) fertilization can alleviate a soil P deficiency in grassland ecosystems. Understanding plant functional traits that enhance P uptake can improve grassland management.We measured impacts of P addition on soil chemical and microbial properties, net photosynthetic rate (Pn) and nonstructural carbohydrate concentrations ([NSC]), and root P‐uptake rate (PUR), morphology, anatomy, and exudation of two dominant grass species: Leymus chinensis (C3) and Cleistogenes squarrosa (C4).For L. chinensis, PUR and Pn showed a nonlinear correlation. Growing more adventitious roots compensated for the decrease in P transport per unit root length, so that it maintained a high PUR. For C. squarrosa, PUR and Pn presented a linear correlation. Increased Pn was associated with modifications in root morphology, which further enhanced its PUR and a greater surplus of photosynthate and significantly stimulated root exudation (proxied by leaf [Mn]), which had a greater impact on rhizosheath micro‐environment and microbial PLFAs.Our results present correlations between the PUR and the Pn of L. chinensis and C. squarrosa and reveal that NSC appeared to drive the modifications of root morphology and exudation; they provide more objective basis for more efficient P‐input in grasslands to address the urgent problem of P deficiency. [ABSTRACT FROM AUTHOR]

The ability of plants to efficiently supply nitrogen (N) to their shoots is critical for reconstructing photosynthetic tissues after defoliation events. We conducted an indoor defoliation experiment and used 13C and 15 N labeling to investigate the photosynthetic carbon (C) allocation, the relationships between C allocation and N uptake, and the contribution of N reallocation for regrowth. Leymus chinensis increased the amount of belowground 13C to the low defoliation (LD) treatment, but allocated less 13C belowground in response to the medium (MD) and high defoliation (HD) treatments, these changes were related to photosynthetic C fixation. Moreover, there was no evidence of a trade-off in C allocation between root exudates and roots, because their direct sources of C differed. The uptake rate of 15 N was the greatest in the LD treatment, when the C invested belowground was maximal. MD treatment increased specific root length and specific root area, which augmented the N uptake. Crucially, defoliation increased the N reallocation from roots to shoots, likely due to the greater N demand of shoot. Altogether, our results show that N supply was governed by N uptake and reallocation for Leymus chinensis after low defoliation. [ABSTRACT FROM AUTHOR]

Intensifying nitrogen (N) deposition disturbs the growth of grassland plants due to an imbalance between their carbon (C) and N metabolism. However, it's unclear how plant physiological strategies restore balance. We investigated the effects of multiple N addition levels (0–25 g N m−2 yr−1) on the coordination of C and N metabolism in a dominant grass (Leymus chinensis) in a semiarid grassland in northern China. To do so, we evaluated photosynthetic parameters, leaf N allocation, C- and N-based metabolites, and metabolic enzymes. We found that a moderate N level (10 g N m−2 yr−1) promoted carboxylation and electron transport by allocating more N to the photosynthetic apparatus and increasing ribulose bisphosphate carboxylase/oxygenase activity, thereby increasing photosynthetic capacity. The highest N level (25 g N m−2 yr−1) promoted N investment in nonphotosynthetic pathways and increased the free amino acids in the leaves. N addition stimulated the accumulation of C and N compounds across organs by activating sucrose phosphate synthase, nitrate reductase, and glutamine synthetase. This enhancement triggered a transformation of primary metabolites (nonstructural carbohydrates, proteins, amino acids) to secondary metabolites (flavonoids, phenols, and alkaloids) for temporary storage or as defense compounds. Citric acid, as the C skeleton for enhanced N metabolism, decreased significantly, and malic acid increased by catalysis of phosphoenolpyruvate carboxylase. Our findings show the adaptability of L. chinensis to different N-addition levels by adjusting its allocations of C and N metabolic compounds and confirm the roles of C and N coordination by grassland plants in these adaptations. • Plants solve C–N imbalance caused by N deposition through physiological adaptations. • Moderate N addition promoted plants' photosynthesis by adjusting leaf N allocation. • High N addition increased plant's N assimilation to avoid excess N damage. • Enhanced N assimilation promoted conversion from primary-to secondary metabolites. • Increased C demand of N metabolism was satisfied by citric acid as C skeleton. [ABSTRACT FROM AUTHOR]

The three-dimensional nature of agrophotovoltaic systems (APV) accounts for the needs of photovoltaic power generation and agricultural production. The combination can solve conflicts among utilization of resources, ecological protection, and agricultural production to achieve low-carbon economic development. However, the economically respond (crop yield and quality) of different species under the decreased light available system is still unclear. To provide insights, we compared agrophotovoltaic and traditional ecosystems to explore the economic feasibility of planting Bupleurum chinense (B. chinense) and Medicago sativa (M. sativa) from the perspectives of light utilization, photosynthetic responses, and land use. The combined system improved the land equivalent ratio, net income and species quality of B. chinense and M. sativa. Both species showed high plasticity, and maintained growth and development by regulating their morphology and photosynthetic parameters. B. chinense in the APV increased its light use efficiency, photosynthetic rate, and root biomass by increasing its height, electron transfer flux, and up-regulating a photosystem I protein (PsaA). M. sativa in the APV allocated more energy to photochemical reactions to improve photosynthetic capacity. It captured and utilized the limited light by reducing leaf mass per unit area and dark respiration, increasing the chlorophyll content, and down-regulating a photosystem II protein (PsbD). Our results showed the importance of species selection based on morphological and photosynthetic responses and provide insights into the selection of appropriate species, efficient resource utilization, and sustainable economic development based on APV. [Display omitted] • Bupleurum chinense and Medicago sativa maintained biomass accumulation and quality. • Bupleurum chinense increased photosynthesis by adjusting electron flux and PsaA. • Medicago sativa increased light capture area and protected photosystem II activity. • The agrophotovoltaic ecosystem increased the land use efficiency of both species. • Bupleurum chinense was more adaptable and improved economic benefits most. [ABSTRACT FROM AUTHOR]

Ecological security (ES) can express the health and integrity of regional ecosystems; hence, a better understanding of regional ES levels and their influencing factors can help to specify sustainable ecological management policies. Levels of ES in the West Liao River Basin were computed for the years of 2000 to 2020 at both the grid and county scale by using the pressure–state–response model, with ecosystem services also included in the assessment system. From 2000 to 2020, the area of both the forests and grasslands increased, due to the Grain for Green Project, which augmented net primary productivity (NPP), an ecosystem production service, and enhanced the overall habitat quality of the basin and promoted improvements to the regional ecological environment. The ES levels in most areas of the West Liao River Basin were improved over time, in that >90% of its area was above the middle level in 2020. The coordinates of "very insecure" moved to the basin's southeast, while "very secure" moved to its northwest, which indicated serious ES problems in the southeast of the basin. When compared with the most economically developed areas or remote areas having societal progress and human activities, generally the moderately developed areas have better ES levels. Further, human factors are more important to ES than natural factors, though all driving factors had enhanced impacts on the change in ES via their interactive effects. By determining the ES levels of the basin, four ecological management zones were then derived for it. We identified the main environmental problems in each ecological management zones and put forward the corresponding management measures, which would make the results more useful for supporting resource management and ecological protection of ecologically fragile areas in the agriculture and pasture interlaced landscape of northern China. • Ecological security levels were improved in most areas of the West Liao River Basin. • Moderately developed areas have better ecological security levels. • From 2000 until 2020, the gravity center of ecological security changed. • Human factors are more important to ecological security than natural factors. • Including ecosystem services can better quantify the ecological security status. [ABSTRACT FROM AUTHOR]

Anthropogenic activities have made phosphorus (P) a new sustainability issue globally. To better understand the mechanisms of soil P dynamics responding to inorganic P fertilization (0–12.5 g P m−2yr−1), we conducted a 2-year field experiment in a temperate grassland in northern China. The P fertilizer was added once per year before the growth period as NaH 2 PO 4. We randomly collected topsoil samples (0–10 cm) and analyzed the soil properties, microbial community, and extracellular enzyme activities, and quantified the soil P fractions using solution 31P nuclear magnetic resonance (31P NMR) spectroscopy. P application promoted transformation from organic P to inorganic P driven by microbial carbon (C) demand and regulated by altered soil properties and microbial characteristics. P addition decreased orthophosphate diesters, especially DNA, due to increased hydrolysis under increased soil pH. This may increase hydrolysates such as α - glycerophosphate and choline phosphate. Orthophosphate monoesters, especially myo -inositol hexaphosphate, also decreased following increased P availability. This could be explained by increased alkaline phosphatase activity and reduced sorption due to a decreased metal (Ca, Al, and Fe) content. Furthermore, P fertilization increased soil NH 4 +-N, thereby increasing the growth of phosphonate-solubilizing microorganisms (Bacillus, Streptomyces, Bradyrhizobium, Mesorhizobium, Penicillium, Aspergillus , and Fusarium). Their increased growth also contributed to inorganic P solubilization and organic P mineralization due to their P-solubilizing specificity. Together, these factors increased inorganic P, especially orthophosphate, which was temporarily immobilized in microbial cells, to regulate the soil-solution P supply, and created a potentially available P sink in the grassland. • Microbial C demand drove transformations from organic P to inorganic P. • Increased soil pH stimulated the hydrolysis of diesters, especially DNA. • Monoesters decreased due to altered alkaline phosphatase activity and metal content. • Soil NH 4 +-N stimulated the growth of phosphonate-solubilizing microorganisms. • Orthophosphate immobilized in microbes regulated the soil solution's P supply. [ABSTRACT FROM AUTHOR]

Anthropogenic activities have increased ecosystem phosphorus (P) inputs and have affected terrestrial ecosystem carbon (C) cycles. However, the fate of soil organic C (SOC) under P addition remains elusive, and the potential mechanisms underlying plant-microbial linkages mediated SOC formation and decomposition are poorly understood. Here, we conducted a field P fertilization experiment to explore the effects on SOC dynamics in a typical temperate grassland in northern China. P addition increased soil P availability and pH, thereby stimulating plant nutrient uptake and growth, leading to higher C inputs to soils via plant biomass (shoots, litter and roots). However, P addition exacerbated microbial N limitation, altered microbial community composition (with a lower fungal to bacterial ratio), shifted microbial life-history strategies, which transitioned from the K -strategy (Acidobacteria, Chloroflexi, and Verrucomicrobia dominant) to the r - strategy (Proteobacteria, Bacteroidetes, and Firmicutes dominant), and modulated their functional characteristics. All of these factors regulated microbial substrate preferences and changed the C components that undergo decomposition. These changes ultimately accelerated the utilization of active C, hampered passive C decomposition, and helped to create a longer-term stable C sink in the grassland. • P addition decreased active C and increased passive C and this resulted in a net increase of SOC. • Increased plant productivity and litter quality improved plant C inputs to the soil. • Altered microbial characteristics regulated their substrate preference, thus stimulating active C loss. • Decreased soil metallic elements may partially weaken the stability of SOC. • Accumulated passive C would be beneficial in creating a longer-term stable C sink. [ABSTRACT FROM AUTHOR]

Carbon (C) assimilation and allocation play a crucial role in determining plant responses to environmental stress such as herbivory. However, the pattern how these grasses allocate assimilated C under increasing herbivory intensity hasn't been fully understand. In this study, we quantified photosynthetic C assimilation and allocation of newly assimilated C among tissues and metabolic processes (structural growth, storage, and defense) under different grazing intensities using 13C tracing of a dominant grass species, Leymus chinensis. Light grazing promoted utilization of newly-assimilated 13C (more than 90% 13C allocated to aboveground tissues on first day after labeling), photosynthetic rate, and reduced mean residence time of 13C of L. chinensis. The photosynthetic capacity and regulation of chlorophyll fluorescence thereby C assimilation were constrained under medium and heavy grazing. Light grazing also increased accumulation of non-structural carbohydrates (NSC) in stems for energy supply to leaf regeneration. As herbivory pressure increased, 13C tracing showed preferential allocation of newly assimilated C to belowground tissues (16–27% 13C on first day after labeling), while upregulating leaf defenses by increasing secondary metabolites and in root storage by NSC accumulation. Although the significant changes showed in C allocation to storage and secondary metabolism of L. chinensis , there are no difference in structural growth (defined as structural biomass= biomass - NSC – secondary metabolites) among grazing intensities. Overall, L. chinensis adopted a conservative C-allocation strategy (upregulated C storage and secondary metabolism) that emphasized long-term survival under increasing herbivory. Light grazing was an optimal grazing intensity that promoted structural growth and C allocation of L. chinensis , which could sustain and even increase grassland productivity. These characteristics of the plant's C allocation strategy provide new insights into the C budget of grassland ecosystems and increase our understanding of the role of C fixation and partitioning when plants respond to environmental challenges. [Display omitted] • Carbon (C) assimilation and allocation was evaluated by 13C tracing technique. • More 13C allocated to aboveground tissues for photosynthesis under light grazing. • Light grazing promoted C fixation and turnover of leaves and NSC storage of stems. • Under grazing pressure L. chinensis increased NSC storage across organs. • The production of SM increased in leaves as increasing herbivory pressure. [ABSTRACT FROM AUTHOR]

• Light grazing was more conductive to the decomposition of shoot litter. • Phenols of shoot litter mainly lost in the first growing season by leaching. • Snow cover promoted litter decomposition in the non-growing season. • Nutrients enrichment was the dominant factor in the second growing season. • Medium grazing could promote refractory substances decomposition in root litter. Grazing can affect the grassland microclimate, soil properties, and litter quality, thereby affecting litter decomposition. However, it is still unclear which grazing intensity provides the most suitable environment for litter decomposition, and which factors play the dominant role in shoot and root litter decomposition. To investigate the effect of grazing on shoot and root litter decomposition, and the dominant factors in each decomposition period, we conducted a 17-month (from May 2016 to September 2017) litter bag experiment under five grazing intensities (control, light grazing, medium grazing, heavy grazing, and extremely heavy grazing, based on local grazing pressure standard) in a temperate grassland in Inner Mongolia, China. We divided the litter decomposition process into three stages according to the seasons. In the first growing season, the decomposition rate of shoot litter was faster under light grazing, probably because better soil environment was beneficial for microbes, and the high precipitation promoted leaching loss of soluble components. In the non-growing season, snow cover played an important role in litter decomposition. In the second growing season, the accumulation of macroelements (nitrogen, N; phosphorus, P) and microelements (magnesium, Mg; manganese, Mn) accelerated litter decomposition. Heavy and extremely heavy grazing intensities promoted the breakdown of cellulose in shoot litter. Medium grazing intensity could promote refractory substances decomposition in root litter. But the mass loss rate of root litter was inhibited by grazing, which was regulated by MBC/MBN. Our results indicate that different grazing intensities had different effects on the decomposition of shoot and root litter. At each stage of decomposition, the dominant factors of shoot and root litter decomposition were different and directly or indirectly affected by grazing and season. [ABSTRACT FROM AUTHOR]

The productivity of terrestrial ecosystems is limited by soil fertility, such assoil phosphorus (P). The decomposition of litter is the main process that affects nutrient cycling. To understand the characteristics of litter decomposition and nutrient release under P addition, we conducted a 2-year litter bag experiment at P addition rates (0–12.5 g P m−2 yr−1). All litter decomposed faster during the second growing season due to highly concentrated precipitation, and Stipa grandis litter decomposed faster (1.02–1.63 times) than Leymus chinensis under P treatments. The decomposition of L. chinensis and mixed litter was more thoroughly at 1 g P m−2 yr−1, while S. grandis decomposed more under 5 g P m−2 yr−1. P addition promoted nitrogen (N) and P immobilization and all litter reached its maximum at 12.5 g P m−2 yr−1. Phosphorus addition increased β-glucosidase production at 5 g P m−2 yr−1, but leucine aminopeptidase production was promoted at high P. The ratio of leucine aminopeptidase to phosphatase increased over time, indicating the N deficiency and P saturation during late stages of decomposition. Our results show that Inner Mongolia's grasslands was limited by P availability and that precipitation was important in the region's decomposition processes. • P addition sped decomposition of S. grandis but not L. chinensis and mixed litter. • The decomposition of S. grandis was more sensitive to nutrient availability. • P addition promoted the immobilization of N and P in the litter. • The dominant enzyme shifted from P-acquiring enzyme to N-acquiring enzyme. • Increased precipitation changed the normal pattern of litter decomposition. [ABSTRACT FROM AUTHOR]

• Light grazing was more conductive to the decomposition of shoot litter. • Phenols of shoot litter mainly lost in the first growing season by leaching. • Snow cover promoted litter decomposition in the non-growing season. • Nutrients enrichment was the dominant factor in the second growing season. • Medium grazing could promote refractory substances decomposition in root litter. Grazing can affect the grassland microclimate, soil properties, and litter quality, thereby affecting litter decomposition. However, it is still unclear which grazing intensity provides the most suitable environment for litter decomposition, and which factors play the dominant role in shoot and root litter decomposition. To investigate the effect of grazing on shoot and root litter decomposition, and the dominant factors in each decomposition period, we conducted a 17-month (from May 2016 to September 2017) litter bag experiment under five grazing intensities (control, light grazing, medium grazing, heavy grazing, and extremely heavy grazing, based on local grazing pressure standard) in a temperate grassland in Inner Mongolia, China. We divided the litter decomposition process into three stages according to the seasons. In the first growing season, the decomposition rate of shoot litter was faster under light grazing, probably because better soil environment was beneficial for microbes, and the high precipitation promoted leaching loss of soluble components. In the non-growing season, snow cover played an important role in litter decomposition. In the second growing season, the accumulation of macroelements (nitrogen, N; phosphorus, P) and microelements (magnesium, Mg; manganese, Mn) accelerated litter decomposition. Heavy and extremely heavy grazing intensities promoted the breakdown of cellulose in shoot litter. Medium grazing intensity could promote refractory substances decomposition in root litter. But the mass loss rate of root litter was inhibited by grazing, which was regulated by MBC/MBN. Our results indicate that different grazing intensities had different effects on the decomposition of shoot and root litter. At each stage of decomposition, the dominant factors of shoot and root litter decomposition were different and directly or indirectly affected by grazing and season. [ABSTRACT FROM AUTHOR]

Zoysia matrella [L.] Merr. is a widely cultivated warm-season turf grass in subtropical and tropical areas. Dwarf varieties of Z. matrella are attractive to growers because they often reduce lawn mowing frequencies. In this study, we describe a dwarf mutant of Z. matrella induced from the 60Co-γ-irradiated calluses. We conducted morphological test and physiological, biochemical and transcriptional analyses to reveal the dwarfing mechanism in the mutant. Phenotypically, the dwarf mutant showed shorter stems, wider leaves, lower canopy height, and a darker green color than the wild type (WT) control under the greenhouse conditions. Physiologically, we found that the phenotypic changes of the dwarf mutant were associated with the physiological responses in catalase, guaiacol peroxidase, superoxide dismutase, soluble protein, lignin, chlorophyll, and electric conductivity. Of the four endogenous hormones measured in leaves, both indole-3-acetic acid and abscisic acid contents were decreased in the mutant, whereas the contents of gibberellin and brassinosteroid showed no difference between the mutant and the WT control. A transcriptomic comparison between the dwarf mutant and the WT leaves revealed 360 differentially-expressed genes (DEGs), including 62 up-regulated and 298 down-regulated unigenes. The major DEGs related to auxin transportation (e.g., PIN-FORMED1) and cell wall development (i.e., CELLULOSE SYNTHASE1) and expansin homologous genes were all down-regulated, indicating their potential contribution to the phenotypic changes observed in the dwarf mutant. Overall, the results provide information to facilitate a better understanding of the dwarfing mechanism in grasses at physiological and transcript levels. In addition, the results suggest that manipulation of auxin biosynthetic pathway genes can be an effective approach for dwarfing breeding of turf grasses. [ABSTRACT FROM AUTHOR]