Grazing during the grassland greenup period promotes plant species richness in alpine grassland in winter pastures

Although grazing is the most common use of grassland, the ecological function of grassland far exceeds its productivity. Therefore, the protection of plant diversity is of the utmost importance and cannot be ignored. Existing research on the effect of grazing on grassland mainly focuses on grazing intensity and the type of livestock, but the consequences of the timing of the grazing on the vegetation community remains unclear. We investigated plant community characteristics of winter pastures in alpine meadow with different grazing termination times (grazing before and during the grassland greenup periods) in Maqu County, eastern QTP. The results showed that vegetation height, coverage, aboveground biomass and Graminoid biomass were lower in grassland when grazing happened during the greenup period compared to grassland where grazing was terminated before the greenup period. However, the total plant species richness and forbs richness were higher in grassland with grazing during the greenup period compared to grassland without grazing during the greenup period. Our structural equation modeling reveals a potential indirect implication for the total plant species richness and forbs richness of winter pastures mainly through a decrease in the vegetation coverage and grass biomass abundance. Our findings imply that grazing during the grassland greenup period may facilitate the maintenance of plant diversity in winter pastures. These findings have important implications for grassland ecosystem functioning and for the conservation of plant diversity.https://www.frontiersin.org/journals/plant-sciencedm2022Mammal Research InstituteZoology and Entomolog

Experimental duration determines the effect of arbuscular mycorrhizal fungi on plant biomass in pot experiments

DATA AVAILABILITY STATEMENT : The original contributions presented in the study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding author.Arbuscular mycorrhizal fungi (AMF) play various important roles in promoting plant growth. Numerous environmental and evolutionary factors influence the response of plants to AMF. However, the importance of the individual factors on the effects of AMF on plant biomass is not clearly understood. In this study, a meta-analysis using 1,640 observations from 639 published articles related to the influence of AMF on the plant shoot, root, and total biomass was performed; 13 different experimental setting factors that had an impact on the influence of AMF and their importance were quantitatively synthesized. The meta-analysis showed that AMF had positive effects on the plant shoot, root, and total biomass; moreover, the experimental duration, plant root-to-shoot ratio (R/S), AMF root length colonization, plant family, pot size, soil texture, and the soil pH all influenced the effects of AMF on the shoot, root, and total biomass. In addition, the plant root system and plant functional type had impacts on the effect of AMF on shoot biomass; AMF guild also impacted the effect of AMF on root biomass. Of these factors, the experimental duration, plant R/S, and pot size were the three most important predicting the effects of AMF on the plant shoot, root, and total biomass. This study comprehensively assessed the importance of the different factors that influenced the response of plants to AMF, highlighting that the experimental duration, plant R/S, and pot size should be taken into consideration in pot experiments in studies of the functions of AMF. Multiple unfavorable factors that may obscure or confound the observed functions of AMF should be excluded.The Second Tibetan Plateau Scientific Expedition and Research Program; the Fundamental Research Funds of China West Normal University; the National Natural Science Foundation of China; and the Applied Basic Research Program of Sichuan Province.https://www.frontiersin.org/journals/plant-scienceam2023Mammal Research Institut

Suitable grazing during the regrowth period promotes plant diversity in winter pastures in the Qinghai-Tibetan plateau

DATA AVAILABILITY STATEMENT : The original contributions presented in this study are included in the article/supplementary material, further inquiries can be directed to the corresponding authors.Vegetation is a crucial component of any ecosystem and to preserve the health and stability of grassland ecosystems, species diversity is important. The primary form of grassland use globally is livestock grazing, hence many studies focus on how plant diversity is affected by the grazing intensity, differential use of grazing time and livestock species. Nevertheless, the impact of the grazing time on plant diversity remains largely unexplored. We performed a field survey on the winter pastures in alpine meadows of the Qinghai- Tibetan Plateau (QTP) to examine the effects of grazing time on the vegetation traits. Livestock species, grazing stocking rates and the initiation time of the grazing were similar, but termination times of the grazing differed. The grazing termination time has a significant effect on most of the vegetation traits in the winter pastures. The vegetation height, above-ground biomass, and the Graminoids biomass was negatively related to the grazing termination time in the winter pastures. In contrast, vegetation cover and plant diversity initially increased and subsequently decreased again as the grazing termination time was extended. An extension of the grazing time did not have any effect on the biomass of forbs. Our study is the first to investigate the effects of grazing during the regrowth period on vegetation traits and imply that the plant diversity is mediated by the grazing termination time during the regrowth period in winter pastures. These findings could be used to improve the guidelines for livestock grazing management and policies of summer and winter pasture grazing of family pastures on the QTP from the perspective of plant diversity protection.The Fundamental Research Funds of China West Normal University, the Gansu Provincial Science and Technology Program and the Natural Science Foundation of Sichuan.http://frontiersin.org/Ecology_and_Evolutionam2023Mammal Research InstituteZoology and Entomolog

Study on SnO2/graphene composites with superior electrochemical performance for lithium-ion batteries

NSFC [U1305246, 21321062]; Xiamen city [3502Z20121002]; Quanzhou "Tong-Jiang Scholar" program; Fujian "Min-Jiang Scholar" program; program for New Century Excellent Talents in University [NCET-13-0879]; Education and Scientific Research Foundation (Class A) for Young Teachers of Education Bureau of Fujian Province, China [JA13263]; National Natural Science Foundation of China [21353001]In this study, the in situ growth of tin dioxide (SnO2) nanoparticles on reduced graphene oxide (rGO) has been realized using a hydrothermal method. The size of the SnO2 nanoparticles in the SnO2/rGO composites prepared by three different procedures is about 5 nm, and they are well dispersed on rGO. When applied as anode materials for lithium-ion batteries, we found that the composites synthesized from the stannous oxalate precursor showed the best rate performance and highest cyclic stability. The surface status of the composites, including interactions between SnO2 and rGO and surface chemical components, was investigated in detail in order to understand why the composites prepared using different procedures displayed vastly different electrochemical performances. The results presented here describe a new approach for the synthesis of uniform and nanosized metal-oxide/rGO composites with excellent electrochemical performance

Measurement of Slips at Contact Interfaces Using a Self-Powered Sensor Based on Triboelectric Nanogenerators

The accumulation of tangential small slips at contact interfaces may occur in mechanical assemblies when subjected to cyclic loadings, and cause failure of parts. However, the slip is difficult to measure directly. In this paper, a self-powered displacement sensor based on triboelectric nanogenerator (TENG) is fabricated, which is used to measure the microslip of the specimen in the designed test bench. When the specimen slips under the cyclic tangential load with a frequency of 10 Hz, the resulted average slip displacement of the specimen under a single load cycle is 9.01 μm, which is measured by the Keithley DAQ 6510 multimeter (Tektronix, Shanghai, China). This value is close to that measured by the Keithley 6514 electrometer. In addition, adding a BaTiO3 thin film with a thickness of 100 nm between the Kapton triboelectric layer and the Cu electrode, the output voltage of the sensor is increased by 51.5%. Thus, the sensitivity of the self-powered sensor is improved effectively

Freeze–Thaw Cycles Have More of an Effect on Greenhouse Gas Fluxes than Soil Water Content on the Eastern Edge of the Qinghai–Tibet Plateau

The Qinghai-Tibetan Plateau (QTP) is sensitive to global climate change. This is because it is characterized by irregular rainfall and freeze–thaw cycles resulting from its high elevation and low temperature. Greenhouse gases (GHGs) mainly contribute to the warming of the QTP, but few studies have investigated and compared the effects of irregular rainfall and freeze–thaw cycles on GHGs. In this study, we conducted a laboratory experiment under four types of freeze–thaw treatments with three soil water content levels to simulate the irregular freeze–thaw and rainfall conditions. The results showed that both the soil water content and freeze–thaw treatment influenced the soil properties, soil enzyme activities, and the microbial biomass; however, the freeze–thaw treatment had significantly higher influences on GHG fluxes than soil water content. In order to explore other biotic and abiotic factors in an attempt to establish the main factor in determining GHG fluxes, a variation partition analysis was conducted. The results revealed that freeze–thaw treatments were the strongest individual factors in predicting the variance in N2O and CO2 fluxes, and the pH, which was only significantly affected by freeze–thaw treatment, was the strongest individual factor in predicting CH4 flux. Across the water content levels, all the freeze–thaw treatments increased the N2O flux and reduced the CH4 flux as compared to the CK treatment. In addition, long-term freezing reduced the CO2 flux, but the treatment of slowly freezing and quickly thawing increased the CO2 flux. In summary, these results suggest that the freeze–thaw treatments had quite different effects on N2O, CH4, and CO2 fluxes, and their effects on GHG fluxes are more significant than those of soil water content on the eastern edge of the QTP

Reduced-Dynamic Precise Orbit Determination of Haiyang-2B Altimetry Satellite Using a Refined Empirical Acceleration Model

The Haiyang 2B (HY-2B) satellite requires precise orbit determination (POD) products for geodetic remote sensing techniques. An improved set of reduced-dynamic (RD) orbit solutions was generated from the onboard Global Positioning System (GPS) measurements over a 14-month period using refined strategies and processing techniques. The key POD strategies include a refined empirical acceleration model, in-flight calibration of the GPS antenna, and the resolution of single-receiver carrier-phase ambiguities. In this study, the potential periodicity of empirical acceleration in the HY-2B POD was identified by spectral analysis. In the along-track direction, a noticeable signal with four cycles per revolution (CPR) was significant. A mixed spectrum was observed for the cross-track direction. To better understand the real in-flight environment, a refined empirical acceleration model was used to cope with the time variability of empirical accelerations in HY-2B POD. Three POD strategies were used for the reprocessing for superior orbit quality. Validation using over one year of satellite laser ranging (SLR) measurements demonstrated a 5.2% improvement in the orbit solution of the refined model. Reliable correction for the GPS antenna phase center was obtained from an over-420-day dataset, and a trend in radial offset change was observed. After application of the in-flight calibration of the GPS antenna, a 26% reduction in the RMS SLR residuals was achieved for the RD orbit solution, and the carrier phase residuals were clearly reduced. The integer ambiguity resolution of HY-2B led to strong geometric constraints for the estimated parameters, and a 15% improvement in the SLR residuals could be inferred compared with the float solution

Response of microbial functional groups involved in soil N cycle to N, P and NP fertilization in Tibetan alpine meadows

The nitrogen (N) cycle is an important part of earth's biogeochemical cycles and N is a critical element for all life. Whereas the response to N - and more rarely phosphorus, P - fertilization of some microbial groups involved in soil N cycling has been studied, a comprehensive view of how the major microbial groups involved in soil N dynamics respond to combined N and P fertilization is lacking, which restricts our understanding of ecosystem responses to fertilization. Here we investigated the effects of different N, P and NP fertilizer levels (4 N levels without P; 4 P levels without N; and 4 P levels with constant N addition) on the abundances of 9 microbial groups involved in N dynamics. Real time PCR was used to target free N-2 fixers, nitrifiers (bacterial and archaea ammonia oxidizers, AOB and AOA, respectively; and the nitrite oxidizers Nitrobacter and Nitrospira), nitrate reducers, nirK- and nirS-nitrite reducers, and nitrous oxide reducers. Soil physical-chemical characteristics and potential nitrification, PNR, were also measured. N fertilization increased the abundances of AOB and Nitrobacter but did not, affect the abundances of the other groups. P fertilization decreased the abundances of N2 fixers, nitrate reducers and AOA, and increased the abundances of Nitrobacter and nitrous oxide reducers. NP fertilization decreased the abundances of AOA and nirK-nitrite reducers. Using a correlation network analysis, we demonstrate the strong coupling generally observed in these grasslands between N2 fixers, AOA, Nitrospira, narG-nitrate reducers and nirK-denitrifiers (most of them responding to N/P availability, and being known to be favored by low oxygen availability); and between AOB and Nitrobacter (known to be favored by high oxygen and high N levels) that controlled changes in PNR. The observed (de)coupling between the responses of the different microbial groups may have major consequences for N cycling and N losses from fertilized Tibetan alpine meadows

Data from: How do soil microorganisms respond to N, P and NP additions? Application of the ecological framework of (co‐)limitation by multiple resources

1.Nitrogen, N, and phosphorus, P, often limit biological processes in terrestrial ecosystems. Based on previous studies mainly focusing on plants, the concept of resource limitation has evolved towards a theory of (co)limitations by multiple‐resources. However, this ecological framework has not been applied to analyse how soil microorganisms and plants concurrently respond to N and/or P addition, and whether these responses are constrained by phylogenetic relatedness. 2.Here, we applied this framework to analyse microbial and plant responses at community and taxon levels to different fertilization treatments (4 N levels without P; 4 P levels without N; and 4 NP levels) in Tibetan grasslands. 3.Total plant biomass showed serial limitation by N then P, and most plant species were limited by N only. Total archaeal abundance decreased with P addition, but diverse nutrient limitation types were observed for archaeal taxa. Closely related archaeal taxa tended to similarly respond to N, and functional similarity between distant archaeal groups was observed for response to P, possibly due to functional convergence. In contrast, total bacteria slightly increased with P addition only when plants remained N‐limited, whereas without N limitation plants rather than bacteria benefited from P addition. Most bacterial taxa were limited by other resources than N and P, and no clear phylogenetic signals were observed regarding bacterial responses to N/P additions. 4.Synthesis: We propose a novel approach for characterizing microbial response types to nutrient addition. It demonstrates that in Tibetan meadows, most dominant plant species, archaea and bacteria respectively depend on N, both N and P, and other resources

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Including soil archaeal and bacterial communities, plant community and soil properties