Divergent coupling mechanism of precipitation on plant community multifunction across alpine grassland on the Tibetan Plateau

IntroductionIt is essential to understand plant adaptive strategies on plant stoichiometric traits at the species level rather than at the community level under various environmental conditions across the Tibetan Plateau (TP).MethodsHere, plant community function and edaphic and meteorological factors were collected at 111 sites along an extensive water–heat gradient during the peak growing season in 2015. Community-weighted mean trait (CWM) was introduced to illuminating dynamics of the functional trait at the community level.ResultsOur results indicated that plant functional traits, including CWM-leaf total carbon (CWM_LTC), CWM-leaf total nitrogen (CWM_LTN), and CWM-leaf total phosphorus (CWM_LTP), showed similar and comparatively marked increases from alpine meadow (AM) to alpine steppe (AS). Moreover, since the tightly coordinated variation among each plant functional trait of AM was higher than that of AS, a more stable coupling mechanism of these plant functional traits could be observed in AM under a long-term evolutionary habit. Specifically, there was higher annual mean precipitation (AMP) in AM than that in AS significantly (P < 0.01), and AMP was significantly correlated with soil moisture and soil total phosphorus in AM. Generally, our findings suggest that precipitation determines divergent coupling plant community function in both AS and AM

Synchronous modulation strategy for multi-objective optimization of traction converters under five-division frequency operation conditions

Restricted by heat dissipation conditions, the switching frequency of the traction inverters for rail transit typically remains below 1 kHz, to prevent potential shortening of their service lifetime due to excessive switching losses in power devices. Inverter operation in the middle and high-frequency ranges results in a decrease in carrier ratio, leading to amplified output harmonics. This not only lowers output performance but also elevates peak current levels, intensifying power losses within the insulated-gate bipolar transistor (IGBT) and consequently undermining driving safety. Unlike existing modulation strategies to address low carrier ratios, which mostly focus on optimizing output performance while overlooking the suppression of IGBT power losses, this paper presents a multi-objective optimization modulation strategy for traction inverters under five-division frequency. This strategy aims to maintain a low weighted total harmonic distortion (WTHD) in the inverter output while reducing total power losses. Firstly, numerical and phase relationships between the output voltage and current were established based on the inverter load model. A precise discrete calculation model for IGBT power losses was developed based on the data manual provided by the device manufacturer, leveraging the power loss generation mechanism. Subsequently, the switching angles were solved under the premise of ensuring the fundamental amplitude of inverter output voltages aligned with the reference level, to enable multi-objective optimization modulation for inverters, including both inverter output current harmonics and power losses as optimization objectives. Simulation results indicate that within the operating range, the proposed optimization modulation strategy significantly reduced IGBT power losses and remained superior output performance compared to traditional strategies

Root pH variation of herbaceous plants among plant functional groups in response to climate and soil gradients on the Tibetan alpine grasslands

Abstract Plant pH is an emerging functional trait that plays important roles in physiological processes and nutrient cycling. However, how root pH varies among plant functional groups (PFGs) and the regulatory factors on a large scale remain unclear. Therefore, we quantified root pH variation of herbaceous plants in four PFGs from 20 sites on the Tibetan Plateau along a 1600 km transect and explored the correlations between root pH and different PFGs, climate and soil conditions. The results showed that the root pH of herbaceous plants was slightly acidic (6.46 ± 0.05). Grasses had the highest root pH (6.91 ± 0.10) across all functional groups (p < .05), whereas legumes had the lowest (5.90 ± 0.08; p < .05). The root pH decreased with mean annual precipitation, aridity index, soil water content and soil stress coefficient, whereas the significant positive correlation with soil pH. PFGs, climate and soil explained 5.39, 11.15 and 24.94% of the root pH variance, respectively. This study provided a comprehensive analysis of root pH patterns in herbaceous plants over a large spatial scale. Root pH was controlled by the combined influence of PFGs, climate and soil properties, with moisture status being the main influential factor. In contrast to the leaf pH, the root pH of herbaceous plants is strongly affected by the soil pH along environmental gradients. Our findings provide new insights into root functional traits and survival strategies of herbaceous plants in alpine ecosystems

Additional file 1 of Non-obese NAFLD had no better cardio-metabolic risk profile than obese NAFLD in type 2 diabetic patients

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