Does the Short-Term Grazing Affect Functional Group and Plant Species Diversity of Alpine Meadow in the Tibetan Plateau?

Grazing affects the physiological and ecological characteristics of the plant community, through livestock intake and trampling (Georgiadis et al. 1989). Previous studies in the Qinghai-Tibetan Plateau have shown that the composition and structure of alpine meadow plant communities respond to grazing (Niu et al. 2010). However, the changes to functional groups and species diversity caused by grazing are not well documented, especially with regards to short term effects (McLaren 2008). In this study, different grazing rates were used to determine the relationship between functional groups, community diversity and yak stocking rates. The objective of this study was to reveal plant functional group responses to grazing and to predict the evolutionary trend of alpine meadow plant functional groups and community diversity under different grazing conditions, thereby providing a theoretical basis for the management of degraded grassland and the conservation of grassland diversity

Leaf Nitrogen and Phosphorus Stoichiometry of Natural Plant Community and Restorable Plant Community in the Northern Qinghai-Tibet Plateau, China

The human engineering activities (highway, railway, cable, gas line and high line construction) has a negative impact on the alpine grassland ecosystem in the Qinghai-Tibet Plateau (QTP), and the natural restoration of plant community in land used for engineering construction is an important part of the rehabilitation of the degraded alpine grassland ecosystem. Previous studies have shown that the plant species and community diversity relationship in natural plant community and restorable plant community vary with the elevation (Guo et al. 2007) and restoration duration of land for engineering construction is more than 20 years at present (Ma et al. 2004). Understanding the mechanisms of plant species replacement in the process of plant restoration is important to restore the land used for engineering construction. The ecological stoichiometry is considered as an effective tool to disclose the inter-specific competition process and determine the succession trend (Güsewell 2004; Güsewell 2005; Yin et al. 2010). However, the stoichiometry relationship between natural plant community and restorable plant community is not well known yet. The objective of this study is to investigate the nitrogen (N) and phosphorus (P) stoichiometry of natural plant community and restorable plant community and its changes with elevation

Effect of Plateau Pika (\u3cem\u3eOchotonacurzionae\u3c/em\u3e) Disturbance on Soil Microelements Content in Alpine Meadow

The plateau pika (Ochotonacurzoniae) creates the extensive disturbance on alpine meadow ecosystem in the QinghaiTibetan Plateau (Smith and Foggin, 1999, Delibes-Mateos et al., 2011), especially on soil nutrient (Davidson et al., 2012). Previous studies show that intermediate active burrows of plateau pika improved soil macro-element (organic matter, total nitrogen and total phosphorus) in alpine meadow (Guo et al., 2012). However, there is little knowledge about the underlying contribution of plateau pika disturbance in determining soil microelement in alpine meadow. The density of active burrow entrances is used to divide the disturbances levels of plateau pika to determine the effect of various disturbance levels of plateau pika on soil microelement content of alpine meadow in the Qinghai-Tibetan Plateau in this study

Effect of Grazing on Soil Carbon and Nitrogen in Alpine Madow, Eastern of Tibetan Plateau

As the grassland ecosystem in the Tibetan Plateau is very fragile, overgrazing likely leads to more serious damages to it than other ecosystems. In the past 30 years, 37% of the alpine meadows have been heavily damaged by grazing causing degradation of native vegetation, a decline in species richness and feed value, and more seriously soil erosion (Six et al. 2004). The impact of grazing on alpine grasslands appears to be hysteresis, as the soil needs more time to recover than the vegetation. So analysing the effect of grazing intensity on soil characteristics is an important way to reveal how grazing influenced grassland ecosystem. Although much research about grazing effects on nutrients, immobilization of carbon (C) and nitrogen (N) in soils and soil microbes have been done in different terrestrial environments, similar effort has rarely focused on the Tibetan Plateau. In this study, soil organic carbon (SOC) and total nitrogen (STN) in 0-30 cm soil depth were measured in the alpine meadow at the northeastern margin of the Tibetan Plateau, to determine suitable grazing intensity from the viewpoints of soil health and fertility, and providing a scientific basis for guiding the reasonable use of the alpine meadow

An artificial bee colony-based hybrid approach for waste collection problem with midway disposal pattern

This paper investigates a waste collection problem with the consideration of midway disposal pattern. An artificial bee colony (ABC)-based hybrid approach is developed to handle this problem, in which the hybrid ABC algorithm is proposed to generate the better optimum-seeking performance while a heuristic procedure is proposed to select the disposal trip dynamically and calculate the carbon emissions in waste collection process. The effectiveness of the proposed approach is validated by numerical experiments. Experimental results show that the proposed hybrid approach can solve the investigated problem effectively. The proposed hybrid ABC algorithm exhibits a better optimum-seeking performance than four popular metaheuristics, namely a genetic algorithm, a particle swarm optimization algorithm, an enhanced ABC algorithm and a hybrid particle swarm optimization algorithm. It is also found that the midway disposal pattern should be used in practice because it reduces the carbon emission at most 7.16% for the investigated instances

Internet-Based Vehicle-Cargo Matching Platform Enterprises in China

This paper examines vehicle-cargo matching platform enterprises in China, which play the role of non-truck operating common carriers that are the freight operator by entrusting transportation duties to the actual carrier. We summarize several kinds of operation modes for vehicle-cargo matching: simple vehicle-cargo matching; whole- vehicle system with single loading and multiple unloading; virtual fleet; and integration of whole-vehicle service and carpooling. We selected representative enterprises and analyzed such features as their operation, advantages and disadvantages, profit model, and applications. We compare and analyze those systems

Coal Rock Breaking Simulation and Cutting Performance Analysis of Disc Cutters

The coal rock breaking ability of disc cutters directly affects the construction efficiency and safety of rescue tunnels in collapsed coal rock formations. This paper establishes the plastic constitutive relationship under the Drucker-Prager (D-P) plasticity criterion, builds up a finite-element analysis (FEA) model for the coal rock breaking with a single cutter on Abaqus FEA, and explores the influence laws of different penetrations and cutting velocities on the rock breaking performance of the cutter. The results show that: as the penetration increased from 3.0 mm to 7.0 mm, the mean vertical force of the cutter grew from 16.97 kN to 23.36 kN, and the mean rolling force rose from 1.79 kN to 3.95 kN. The increase of the cutter\u27s vertical force improves the cutting efficiency, but intensifies the vertical impact, which undermines construction safety. As the cutting velocity increased from 0.6 rad/s to 1.5 rad/s, the mean vertical force grew from 15.64 kN to 22.94 kN, and the mean rolling force rose from 1.46 kN to 4.23 kN. With the increase of cutting velocity, the cutting force grew at an increasing speed. The increase of cutting velocity can improve cutting efficiency, but an excessively fast cutting velocity will weaken the stability of the cutting operation, and add to the wear of the tool. The research method provides theoretical supports to the cutterhead design of tunnel boring machine (TBM) and tunnelling control in broken coal rock formation

Ab initio insight into ultrafast nonadiabatic decay of hypoxanthine: keto-N7H and keto-N9H tautomers

National Science Foundation of China (NSFC) [21133007, 21103213, 91233106]; Ministry of Science and Technology [2011CB808504, 2012CB214900]; CAS; Director Innovation Foundation of CAS-QIBEBTNonadiabatic dynamics simulations at the SA-CASSCF level were performed for the two most stable keto-N7H and keto-N9H tautomers of hypoxanthine in order to obtain deep insight into the lifetime of the optically bright S-1((1)pi pi*) excited state and the relevant decay mechanisms. Supporting calculations on the ground-state (S-0) equilibrium structures and minima on the crossing seams of both tautomers were carried out at the MR-CIS and CASSCF levels. These studies indicate that there are four slightly different kinds of conical intersections in each tautomer, exhibiting a chiral character, each of which dominates a barrierless reaction pathway. Moreover, both tautomers reveal the ultrafast S-1 -> S-0 decay, in which the S1 state of keto-N9H in the gas phase has a lifetime of 85.5 fs, whereas that of keto-N7H has a longer lifetime of 137.7 fs. An excellent agreement is found between the present results and the experimental value of 130 +/- 20 fs in aqueous solution

Geographic Variation Did Not Affect the Predictive Power of Salivary Microbiota for Caries in Children With Mixed Dentition

Dental caries is one of the most prevalent chronic oral diseases, affecting approximately half of children worldwide. The microbial composition of dental caries may depend on age, oral health, diet, and geography, yet the effect of geography on these microbiomes is largely underexplored. Here, we profiled and compared saliva microbiota from 130 individuals aged 6 to 8 years old, representing both healthy children (H group) and children with caries-affected (C group) from two geographical regions of China: a northern city (Qingdao group) and a southern city (Guangzhou group). First, the saliva microbiota exhibited profound differences in diversity and composition between the C and H groups. The caries microbiota featured a lower alpha diversity and more variable community structure than the healthy microbiota. Furthermore, the relative abundance of several genera (e.g., Lactobacillus, Gemella, Cryptobacterium and Mitsuokella) was significantly higher in the C group than in the H group (p<0.05). Next, geography dominated over disease status in shaping salivary microbiota, and a wide array of salivary bacteria was highly predictive of the individuals’ city of origin. Finally, we built a universal diagnostic model based on 14 bacterial species, which can diagnose caries with 87% (AUC=86.00%) and 85% (AUC=91.02%) accuracy within each city and 83% accuracy across cities (AUC=92.17%). Although the detection rate of Streptococcus mutans in populations is not very high, it could be regarded as a single biomarker to diagnose caries with decent accuracy. These findings demonstrated that despite the large effect size of geography, a universal model based on salivary microbiota has the potential to diagnose caries across the Chinese child population