A New Species of the Genus Scincella Mittleman, 1950 (Squamata: Scincidae)from Sichuan Province, Southwest China, with a Diagnostic Key of Scincella Species in China

The genus Scincella Mittleman,1950 of the family Scincidae currently includes 38 species."To date,however,taxonomic assessment remains challenging.Here,phylogenetic analyses based on DNA sequences of four mitochondrial genes supported a putative new species from Sichuan Province,Southwest China,as an independent lineage.Uncorrected genetic distance of 16S rRNA between the new species and closest congener was 8%,and the population was morphologically distinguishable from all other known congeners.We herein describe the Scincella population as anew species based on both phylogeny and comparative morphology.The new species can be distinguished from its congeners by a combination of the following morphological characters:(1)body slender,mediumsized,snout-vent length 35.0-62.1 mm;(2)infralabials seven,rarely eight;(3)supraciliaries 5-7;(4)tympanum deeply sunk without lobules;(5)midbody scale-row counts 27-30;(6)dorsal scales smooth and enlarged,paravertebral scale-row counts 60-75,ventral scalerow counts 46-59,gulars 25-30;(7)upper edge of lateral longitudinal stripes relatively straight with six rows of dorsal scales in middle;(8)number of enlarged,undivided lamellae beneath fingerⅣ9-11,number of enlarged,undivided lamellae beneath toeⅣ13-16;(9)ventral side of tail densely ornamented with dark brown or black spots;and(10)grayish-brown discontinuous regular dorsal stripes 5-7,distinct black dorsolateral stripes,starting from posterior corner of eye and continuing to lateral side of tail.A diagnostic key to all Scincella members from China is also provided The new species is currently only known from Wenchuan and Lixian counties,Sichuan Province,China,and brings the number of Scincella species in China to 12.This study emphasizes the incompleteness of knowledge on herpetodiversity in China.

不确定条件下创业投资激励政策的选择与优化

创业投资是重要的创新资本,为了得出驱动创业投资主动配置资源支持创新的激励策略,基于风险补贴与税收优惠的激励政策,构建了创业投资期权博弈模型,研究了创新性创业企业的价值不确定条件下创业投资激励政策的实施效果。结果表明:当创新项目价值不确定性小于阈值时,在加快创业投资机构的投资决策方面,税收优惠政策效果更好,反之,两种政策效果相同;当创业企业价值不确定性小于阈值时,在提高创业投资机构投资规模方面,风险补贴政策效果更好,反之,两种政策效果相同。

氧化物钙钛矿的光催化研究进展:CO_(2)还原、水裂解、固氮

在寻求可再生能源供应及解决环境问题的迫切需求下,光电、光催化、电催化等领域中多种技术被开发以解决这一迫切问题。其中,光催化技术因其可将清洁太阳能转化为化学燃料的优越能力而备受关注。在层出不穷的光催化材料中,具有阳离子可替代性的钙钛矿氧化物(ABO_3)在电子信息、太阳能电池和光催化等领域具有极大的潜力。由于这类材料具有活性高、成本低、稳定性好、结构易调控等独特性能,钙钛矿氧化物光催化剂在水分解、二氧化碳还原转化、固氮等方面取得了广泛的应用。本文综述了光催化的结构与合成方法,重点介绍了光催化的应用,最后展望了光催化的未来发展前景。

Analgesic effect of intrathecal bumetanide is accompanied by changes in spinal sodium-potassium-chloride co-transporter 1 and potassium-chloride co-transporter 2 expression in a rat model of incisional pain

Accumulating evidence has demonstrated that the sodium-potassium-chloride co-transporter 1 and potassium-chloride co-transporter 2 have a role in the modulation of pain transmission at the spinal level through chloride regulation in the pain pathway and by effecting neuronal excitability and pain sensitization. The present study aimed to investigate the analgesic effect of the speciifc sodium-potassium-chloride co-transporter 1 inhibitor bumetanide, and the change in spinal sodium-potassium-chloride co-transporter 1 and potassium-chloride co-transporter 2 expression in a rat model of incisional pain. Results showed that intrathecal bumetanide could decrease cumulative pain scores, and could increase thermal and mechanical pain thresholds in a rat model of incisional pain. Sodium-potassium-chloride co-transporter 1 expression in-creased in neurons from dorsal root ganglion and the deep laminae of the ipsilateral dorsal horn following incision. By contrast, potassium-chloride co-transporter 2 expression decreased in neurons of the deep laminae from the ipsilateral dorsal horn. These ifndings suggest that spinal sodium-potassium-chloride co-transporter 1 expression was up-regulated and spinal potassi-um-chloride co-transporter 2 expression was down-regulated following incision. Intrathecal bumetanide has analgesic effects on incisional pain through inhibition of sodium-potassi-um-chloride co-transporter 1.

Deformation and failure modes of composite foundation with sub-embankment plain concrete piles

With the development of high-speed railway in China, composite foundation with rigid piles has become a stamdard solution of meeting the high requirements of stability and post-construction settlement of embankment on soft subgrade. Among several im- provement pattems, plain concrete piles have been extensively used to treat soft ground supported embankment. To investigate the deformation and failure modes of unimproved soft ground and soft ground reinforced by sub-embankment plain concrete piles, and to learn the influences of track and vehicle load, the effect of pile spacing, as well as the compression moduli of soil layers and upper load condition on the failure modes, a series of centrifuge model tests were performed. Test results indicate that the dis- placement of unimproved soft ground under the embankment increases continuously as embankment, track and train loading, and slip circle failure takes place. The deformation law of soft ground reinforced by sub-embankment plain concrete piles depends on pile spacing, compression modulus of the soft ground, and loading conditions. It was also found that plain concrete piles show displacement and failure patterns depending on its location, compression modulus of soft soil around the pile, and loading condi- tions. Furthermore, the evaluation of improved ground stability as well as the model test procedure is also presented.

Enhanced active site extraction from perovskite LaCoO_(3) using encapsulated PdO for efficient CO_(2) methanation

The extraction of metallic nanoparticles from perovskite-type oxides(ABO_(3)) under mild reducing conditions is a novel way to prepare well-dispersed supported catalysts(B/AOd). Herein, we found that the encapsulated PdO in perovskite LaCoO_3(PdO@LaCoO_3) could facilitate the phase transformation of the perovskite structure at a low temperature owing to both strong H2 spillover of Pd and intimate interaction between the encapsulated PdO and LaCoO_(3). The pure LaCoO_(3) without PdO was relatively inert to CO_(2) hydrogenation(CO_(2) conversion <4%). In contrast, PdO@LaCoO_(3) exhibited excellent CO_(2) methanation performance with 62.3% CO_(2) conversion and >99% CH4 selectivity. The characterization results demonstrated that the catalytically active Co2 C was in-situ formed by carburization of the extracted Co0 during CO_(2) methanation for the PdO@LaCoO_(3) sample. Whereas, the LaCoO_(3) with surface supported PdO(PdO/LaCoO_(3)) showed a weak interaction and remained a perovskite structure with few Co_(2)C active centers after the catalytic reaction, which was similar to the parent LaCoO_(3). Accordingly, the PdO/LaCoO_(3) showed an inferior catalytic performance with 31.8% CO_(2) conversion and 87.4% CH_(4) selectivity. Therefore, the designed encapsulation structure of PdO within perovskite is critical to extract metallic NPs from perovskite-type oxides, which has the potential to prepare other integrated nanocatalysts based on perovskite-type oxides.

3D hierarchical architecture collaborating with 2D/2D interface interaction in Ni Al-LDH/Ti_(3)C_(2) nanocomposite for efficient and selective photoconversion of CO_(2)

Photocatalytic conversion of CO_(2)into a special chemical fuel with high yield and selectivity is still a major challenge.Herein,a 3 D hierarchical Ni Al-LDH/Ti_(3)C_(2)MXene(LDH/TC)nanocomposite is constructed through in situ loading of Ti_(3)C_(2)nanosheets on the Ni Al-LDH scaffold during the hydrothermal process.The formation of a uniform and well-defined 2 D/2 D heterogeneous interface can be realized by optimizing the ratio of Ti_(3)C_(2)and the precursors for Ni Al-LDH.The 3 D hierarchical scaffold with high specific surface area contributes to the favourable photon adsorption and utilization.The intimate contact between Ti_(3)C_(2)and Ni Al-LDH with numerous interfaces effectively promotes the separation of the photoinduced electron-hole pairs in Ni Al-LDH.Together with the highly exposed oxidation-reduction active sites and the enhanced CO_(2)capture and activation.The maximum photocatalytic CO production rate on Ni AlLDH/Ti_(3)C_(2)reaches 11.82 lmol g^(-1)h^(-1)with 92%selectivity and superior stability.This work provides an effective approach for the development of an ideal photocatalyst by collaborative utilization of materials with different dimensionalities.

Anti-Icing Method Based on Reducing Voltage of Transmission Lines

The icing of transmission lines threatens the security of power system. This paper proposes a novel anti-icing method based on reducing voltage of the transmission lines. The line voltage can be reduced by regulating the ratio of the transformers which install the both ends of the transmission lines. The line current can be increased and the power loss of the transmission lines can also be increased, which means the heat generated by power loss increases and the icing process of the transmission lines can be restrained. When the icing may occur in the atrocious weather, the anti-icing transformers installed the both ends of transmission line are put into operation. The ratios of transformers are regulated to the appropriate value. The current of transmission line can be increased to the value that is a little greater than the critical current, which can realize the purpose of anti-icing. At the same time, the conditions of normal running in the load side are kept invariably, which can ensure the security of power system. This method can be applicable to a wide range. It's an effective measure to prevent the icing of the transmission lines.

Polyurethane grouting materials with different compositions for the treatment of mud pumping in ballastless track subgrade beds:properties and application effect

Mud pumping in subgrade beds under ballastless tracks will deteriorate the dynamic performance of infrastructure under railway lines,reduce the smoothness of the railway lines,and seriously affect the comfort and safety of the trains.Due to their good mechanical properties,twocomponent polyurethane materials can be used for grouting to treat the fouling problems caused by ballastless track mud pumping.To develop a polyurethane formula suitable for the treatment of ballastless track mud pumping,we first performed indoor experiments to investigate the mechanical properties and gelation time of polyurethane elastomers synthesized with different raw material composition ratios,to determine an optimal composition ratio of the raw materials.Then,we conducted a dynamic field test to verify the remediation effect of the polyurethane material fabricated according to the design ratio.The results showed that polyurethane grouting material with the selected design ratios improved the contact characteristics between the surface layer of the subgrade bed and the base plate in the area,coordinating the dynamic response between the track structure and the subgrade bed.Thus,the obtained polyurethane grouting material could be used to renovate mud pumping areas of ballastless tracks with a good treatment effect.

Effects of basic fibroblast growth factor on superoxide dismutase activity and malondialdehyde content in the rat brain following intracerebral hemorrhage

BACKGROUND： Studies have confirmed that basic fibroblast growth factor （bFGF） promotes neuronal survival and neurite outgrowth. OBJECTIVE： To compare and verify the effects of bFGF on superoxide dismutase activity and malondialdehyde content in rat brain tissues surrounding a hemorrhagic lesion, as well as the hippocampus at the hemorrhagic side. DESIGN, TIME AND SETTING： The randomized, controlled, neurobiological study was performed at the Science Experimental Center and Research Laboratory, Guangxi Medical University, China, from September to December 2006. MATERIALS： Ninety-two adult, healthy, Wistar rats of equal gender were used to establish intracerebral hemorrhage by infusing type VII collagenase into the left internal capsule. Type Ⅶ collagenase （Sigma, USA）, superoxide dismutase and malondialdehyde kits （Jiancheng, China）, and bFGF （Institute of Bioengineering, Ji＇nan University, China） were used for this study. METHODS： Ninety successfully lesioned rats were equally and randomly divided into three groups. Rats in the bFGF group were intramuscularly injected daily with bFGF （8 ug/kg）. Rats in the saline control group received an equal volume of saline. The rats in the model group did not receive other interventions. Superoxide dismutase activity was measured using the xanthine oxidase method. Malondialdehyde contents were detected using the thiobarbituric acid method. MAIN OUTCOME MEASURES： At 1, 3, and 7 days following intracerebral hemorrhage, superoxide dismutase and malondialdehyde were determined in the brain tissue surrounding the hematoma and in the hippocampus in the affected hemisphere. RESULTS： In brain tissue surrounding the hematoma, superoxide dismutase activity was significantly increased in the bFGF group at 3 and 7 days after intracerebral hemorrhage compared with the saline control group, whereas malondialdehyde content was significantly decreased （P 〈 0.05）. In the hippocampus, superoxide dismutase activity was significantly increased in the bFGF group at 7 days following intracerebral hemorrhage compared with the saline control group, whereas malondialdehyde content was significantly decreased （P 〈 0.05）. At 1, 3, and 7 days after intracerebral hemorrhage, there was no significant difference between the saline control group and the model group with regards to parameter or brain region （P 〉 0.05）. CONCLUSION： Increased superoxide dismutase activity and decreased malondialdehyde content were detected in tissue surrounding the hematoma, as well as the ipsilateral hippocampus, of intracerebral hemorrhage rats treated with bFGF. Changes in these parameters were detected earlier in tissue adjacent to the lesion, compared with the ipsilateral hippocampus.

Component fault diagnosis for nonlinear systems

In the field of fault diagnosis, the state equation of nonlinear system, including the actuator and the component, has been established. When the faults in the system appear, it is difficult to observe the fault isolation between the actuator and the component. In order to diagnose the component fault in the nonlinear systems, a novel strategy is proposed. The nonlinear state equation with only the component system is built on mathematical equations. The nonlinearity of the component equation is expanded and estimated with Taylor series. If the actuator is perfect, the anomaly of the state equations reflects the component fault. The fault feature index is defined to detect the component fault and the initial fault. The numerical examples of the component faults are simulated for multiple-input multiple-output(MIMO)nonlinear systems. The results show that the component faults,as well as the incipient faults, can be detected. Furthermore, the effectiveness of the proposed strategy is verified. This method can also provide a foundation for the component fault reconfiguration control.

Effect of graphene grain boundaries on MoS2/graphene heterostructures

The grain boundaries of graphene are disordered topological defects,which would strongly affect the physical and chemical properties of graphene.In this paper,the spectral characteristics and photoresponse of MoS2/graphene heterostructures are studied.It is found that the blueshift of the G and 2D peaks of graphene in Raman spectrum is due to doping.The lattice mismatch at the graphene boundaries results in a blueshift of MoS2 features in the photoluminescence spectra,comparing to the MoS2 grown on SiO2.In addition,the photocurrent signal in MoS2/hexagonal single-crystal graphene heterostructures is successfully captured without bias,but not in MoS2/polycrystalline graphene heterostructures.The electron scattering at graphene grain boundaries affects the optical response of MoS2/graphene heterostructures.The photoresponse of the device is attributed to the optical absorption and response of MoS2 and the high carrier mobility of graphene.These findings offer a new approach to develop optoelectronic devices based on two-dimensional material heterostructures.

Mesoscopic characterization and modeling of microcracking in cementitious materials by the extended finite element method

This study develops a mesoscopic framework and methodology for the modeling of microcracks in concrete. A new algorithm is first proposed for the generation of random concrete meso-structure including microcracks and then coupled with the extended finite element method to simulate the heterogeneities and discontinuities present in the meso-structure of concrete. The proposed procedure is verified and exemplified by a series of numerical simulations. The simulation results show that microcracks can exert considerable impact on the fracture performance of concrete. More broadly, this work provides valuable insight into the initiation and propagation mechanism of microcracks in concrete and helps to foster a better understanding of the micro-mechanical behavior of cementitious materials.

Mo-doped one-dimensional needle-like Ni_(3)S_(2) as bifunctional electrocatalyst for efficient alkaline hydrogen evolution and overall-water-splitting

Hydrogen energy plays an important role in clean energy system and is considered the core energy source for future technological development owing to its lightweight nature,high calorific value,and clean combustion products.The electrocatalytic conversion of water into hydrogen is considered a highly promising method.An electrocatalyst is indispensable in the electrocatalytic process,and finding an efficient electrocatalyst is essential.However,the current commercial electrocatalysts(such as Pt/C and Ru)are expensive;therefore,there is a need to find an inexpensive and efficient electrocatalyst with high stability,corrosion resistance,and high electrocatalytic efficiency.In this study,we developed a cost-effective bifunctional electrocatalyst by incorporating molybdenum into nickel sulfide(Ni_(3)S_(2))and subsequently tailoring its structure to achieve a one-dimensional(1D)needle-like configuration.The hydrogen production efficiency of nickel sulfide was improved by changing the ratio of Mo doping.By analyzing the electrochemical performance of different Mo-doped catalysts,we found that the Ni_(3)S_(2)-Mo-0.1 electrocatalyst exhibited the best electrocatalytic effect in 1 M KOH;at a current density of 10 mA cm^(-2),it exhibited overpotentials of 120 and 279 mV for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),respectively;at a higher current density of 100 mA cm^(-2),the HER and OER overpotentials were 396 and 495 mV,respectively.Furthermore,this electrocatalyst can be used in a two-electrode water-splitting system.Finally,we thoroughly investigated the mechanism of the overall water splitting of this electrocatalyst,providing valuable insights for future hydrogen production via overall-water-splitting.

Pathological Mechanism of “Phlegm, Blood stasis, Toxin ”in a Rabbit Model of Carotid Atherosclerosis Based on Gut Microbiota-host Metabolism Interactions

Background:In Traditional Chinese Medicine(TCM)theory,"phlegm,blood stasis and toxin"are the pathogenesis of carotid atherosclerosis(CAS).The rabbit carotid atherosclerosis(CAS),which is induced by high-cholesterol diet combined with carotid artery balloon injury,is a classic model for studying CAS.Many studies indicate that gut microbiota and host metabolic disorders are involved in the pathogenesis of rabbit CAS.However,the TCM pathological features and syndromes of this classic rabbit CAS model have not been reported.Objective:To explore the pathogenesis of the rabbit CAS model and its TCM syndrome types from the perspective of"phlegm,blood stasis,and toxin".Methods:Twelve male New Zealand white rabbits were randomly divided into NC group and CAS group according to their body weight,followed by feeding of basic feed and a 1%high cholesterol diet,respectively.After two weeks,the rabbits in the CAS group underwent common carotid artery(CCA)balloon injury,while the rabbits in the NC group underwent only CCA separation without balloon injury.The two groups received differential feed postoperatively for six more weeks,after which,changes in lipids,hemorheology,inflammation,oxidative stress,and CAS phenotypes were analyzed.In addition,the colon contents and serum were collected for 16S rRNA sequencing and ^(1)H-NMR metabonomic analysis.Results:The CAS rabbits were observed to form noticeable abnormalities in lipid metabolism and blood rhe-ology,a sharp increase in oxidative stress levels,excessive release of inflammatory factors and apparent CAS plaque formation.Furthermore,10 specific gut microbiota(such as Akkermansia muciniphila,Barnesiellaceae and Faecalibacterium)and 14 characteristic metabolites(such as trimethylamine oxide,acetic acid and L-carnitine)were identified in the CAS rabbits,which were significantly related to the CAS phenotypes.The pathway func-tion analysis showed that the gut microbiota and its metabolites mainly affected cholesterol metabolism,energy metabolism,inflammation and oxidative stress.Conclusion:The rabbit CAS model conforms to the“phlegm,blood stasis and toxin damage”theory.The gut microbiota and host metabolic disorders of the CAS rabbits interact and promote internal and external toxins,aggravating the progression of CAS.Our study provided experimental evidence for the application of this model in the TCM-based research of CAS.

SUMOylation facilitates the assembly of a Nuclear Factor-Y complex to enhance thermotolerance in Arabidopsis

Heat stress(HS) has serious negative effects on plant development and has become a major threat to agriculture. A rapid transcriptional regulatory cascade has evolved in plants in response to HS. Nuclear Factor-Y(NF-Y) complexes are critical for this mechanism, but how NF-Y complexes are regulated remains unclear.In this study, we identified NF-YC10(NF-Y subunit C10), a central regulator of the HS response in Arabidopsis thaliana, as a substrate of SUMOylation, an important post-translational modification. Biochemical analysis showed that the SUMO ligase SIZ1(SAP AND MIZ1 DOMAINCONTAINING LIGASE1) interacts with NF-YC10and enhances its SUMOylation during HS. The SUMOylation of NF-YC10 facilitates its interaction with and the nuclear translocation of NF-YB3, in which the SUMO interaction motif(SIM)is essential for its efficient association with NF-YC10. Further functional analysis indicated that the SUMOylation of NF-YC10 and the SIM of NF-YB3 are critical for HS-responsive gene expression and plant thermotolerance. These findings uncover a role for the SIZ1-mediated SUMOylation of NF-YC10 in NF-Y complex assembly under HS, providing new insights into the role of a post-translational modification in regulating transcription during abiotic stress responses in plants.

IQ67 DOMAIN protein 21 is critical for indentation formation in pavement cell morphogenesis

In plants, cortical microtubules anchor to the plasma membrane in arrays and play important roles in cell shape. However, the molecular mechanism of microtubule binding proteins, which connect the plasma membrane and cortical microtubules in cell morphology remains largely unknown. Here, we report that a plasma membrane and microtubule duallocalized IQ67 domain protein, IQD21, is critical for cotyledon pavement cell(PC) morphogenesis in Arabidopsis. iqd21 mutation caused increased indentation width, decreased lobe length, and similar lobe number of PCs, whereas IQD21 overexpression had a different effect on cotyledon PC shape. Weak overexpression led to increased lobe number, decreased indentation width, and similar lobe length, while moderate or great overexpression resulted in decreased lobe number, indentation width, and lobe length of PCs. Live-cell observations revealed that IQD21 accumulation at indentation regions correlates with lobe initiation and outgrowth during PC development. Cell biological and genetic approaches revealed that IQD21 promotes transfacial microtubules anchoring to the plasma membrane via its polybasic sites and bundling at the indentation regions in both periclinal and anticlinal walls. IQD21 controls cortical microtubule organization mainly through promoting Katanin 1-mediated microtubule severing during PC interdigitation. These findings provide the genetic evidence that transfacial microtubule arrays play a determinant role in lobe formation, and the insight into the molecular mechanism of IQD21 in transfacial microtubule organization at indentations and puzzle-shaped PC development.

高寒小嵩草草甸可能成为青藏高原相同地理和气候单元下多种类型草地的偏途演替状态

高寒嵩草(Kobresia)草甸是青藏高原冬春放牧草场的主体,在放牧强度分异的条件下可以形成特征迥异的稳态。然而,目前还不清楚在不同放牧强度下其他类型草地是否可以演替成为这些稳态。本研究通过土壤剖面特征推断其历史植物群落特征,以植物群落现场调查确定其现实植物群落特征,以非结构式问卷调查确定草地放牧强度,采用多元回归树模型分析导致草地稳态转化的节点。研究结果表明,高寒灌丛草甸和旱化沼泽草甸在过度放牧条件下均可转化成为高寒矮嵩草(K.humilis)草甸和高寒小嵩草(K.pygmaea)草甸,从而使高寒灌丛草甸和旱化沼泽化草甸进入高寒矮嵩草草甸退化演替序列,最终转化成为黑土滩-杂类草次生裸地。以放牧强度为分节点,最多可以将这些植物群落划分为4类稳态,各稳态转化的节点依次为11.0、8.0、5.5羊/ha。所有研究草地总体表现为随放牧强度的增高地上总生物量呈下降趋势。其中,11.0羊/ha是草地转化成为黑土滩杂类草次生裸地的节点。放牧强度改变可以影响植物群落特征及其演替方向,进而改变草地的畜牧生产服务能力,因此放牧强度可以作为反映牧场畜牧生产服务能力的表观指标。未来牧场的可持续发展策略应以草畜平衡为主,合理控制放牧强度,增加草地生产附加值和延伸畜牧业产业链以实现区域草场生态和生产效益的双赢。

Self-stabilizing maintenance process in plant communities of alpine meadows under different grazing intensities

Backgrounds:Grazing prohibition and reduced grazing intensity,as two important“vegetation close-to-nature recovery”methods,have been suggested as economical and effective technologies for enhancing forage production.However,numerous studies have found that the yield of forage could be increased by removing or reducing grazing in a short time in some steady stage of alpine Kobresia meadows,but not in others.To reveal the mechanism behind this phenomenon,we proposed a series of experiments.Methods:We monitored the plant and soil characteristics in the key steady stages of Kobresia meadows under reduced and prohibited grazing conditions in the same geographic and climatic environments in the northeastern Qinghai-Tibet Plateau for 6 years.We estimated the relationships between the plant community and soil nutrients and obtained the following results.Results:All measured variables were positively correlated with each other.The plant community structure had higher path coefficients to aboveground biomass,soil organic matter,total nitrogen,and nitrate nitrogen than to other factors.The plant community structure played an important role in response to grazing intensity.Different plant functional groups(PFGs)had different responses to grazing intensity,which led to plant community re-establishment or re-organization under different grazing intensities.Poaceae and Kobresia were more sensitive to grazing intensity than other PFGs,and the ratio of Kobresia biomass(including Kobresia humilis and Kobresia pygmaea)to the total biomass of Poaceae and Kobresia could be used as an indicator of regime shifts within plant communities.With Kobresia pygmaea as the dominant species,the prohibition of grazing was not an efficient approach to increase the yield in the steady stages because this treatment needed more time to recover aboveground biomass.If Poaceae is the dominant PFG,grazing should only be prohibited for 3 years in the steady stages because the aboveground biomass will decrease if grazing is prohibited for more than 3 years.Conclusions:Therefore,the different steady stages of alpine meadows require different recovery methods to increase recovery efficiency and speed.

Synergies between microsites of plant communities and steady-stage alpine meadows on the Qinghai-Tibetan Plateau

Background:Due to the effects of climate change and overgrazing in recent decades,alternative stable states in the alpine Kobresia meadow degradation process have coexisted in the same geographical and climatic environment,with variations occurring among microsites.Methods:We used a space-for-time substitution approach to explore the synergies of microsite variation according to its numerical characteristics and the proportion of each stable state at various stages of succession in alpine Kobresia meadows on the Qinghai-Tibetan Plateau.Results:(1)The highest average aboveground biomass in summer was 196.2±20.3 gm^(-2),with significantly higher levels of biomass in≤3.65 sheep unit ha^(-1) than in other levels of grazing intensity,while the parameters showed no significant differences among grazing intensity levels in>3.65 sheep unit ha^(-1).(2)The importance of plant functional groups,aboveground biomass,and niche breadth of Poaceae and Cyperaceae significantly decreased as the grazing intensity increased.(3)The effects of≥0°C accumulated temperature,total precipitation,altitude,longitude,and latitude cumulatively contributed less than 20%of the variation in the distribution of functional group characteristics across microsites.Conclusions:(1)Overgrazing decreases primary production in alpine Kobresia meadows,but ecosystem responses regulate plant community structure and botanical components so as to partially counteract grazing disturbance.(2)Overgrazing changed the proportion of microsites,which in turn led to regime shift in the plant community and subsequent synergies between the microsites of plant communities and their stable states.