Search Results (87)

Urban rail transit networks’ rapid expansions have led to increasing intersections between existing and new lines, particularly in dense urban areas where new stations must underpass existing infrastructure at zero distance. Deformation controls during construction are critical for maintaining the operational safety of existing stations, especially in soft soil conditions where construction-induced settlement poses significant risks to structural integrity. This study systematically investigates the influence mechanisms of different construction schemes on base plate deformation when an open-top UBIT (underground bundle composite pipe integrated by transverse pre-stressing) underpasses existing stations. Through precise numerical simulation using PLAXIS 3D, the research comparatively analyzed the effects of 12 pipe jacking sequences, 3 pre-stress levels (1116 MPa, 1395 MPa, 1674 MPa), and 3 soil chamber excavation schemes, revealing the mechanisms between the deformation evolution and soil unloading effects. The continuous jacking strategy of adjacent pipes forms an efficient support structure, limiting maximum settlement to 5.2 mm. Medium pre-stress level (1395 MPa) produces a balanced deformation pattern that optimizes structural performance, while excavating side chambers before the central chamber effectively utilizes soil unloading effects, achieving controlled settlement distribution with maximum values of −7.2 mm. The optimal construction combination demonstrates effective deformation control, ensuring the operational safety of existing station structures. These findings enable safer and more efficient urban underpassing construction. Full article

Regional increases in atmospheric O₃ are phytotoxic not only to major crops but also to root vegetables such as radish, and their effects can be further modulated by nitrogen (N) addition. To assess how cherry radish responds to elevated O₃ (eO₃) under N addition and to compare the dose–response relationships, we established six open-top chambers with two O₃ levels and two N treatments in Beijing, China, to examine gas exchange, growth, and biomass throughout the growing period. The results showed that: 1. eO₃ had a “priming effect” on photosynthesis rates (Pn) at the beginning of the experiment. N addition alleviated the O₃-induced Pn reduction at the end of the experiment by 6.76% but did not significantly influence the O₃-dose response to Pn; 2. stomatal conductance (gs) did not have a dose response to all treatments while evaporation rates (E) showed strong negative regression with AOT40; 3. N addition reduced the hypocotyl biomass (−47.70%), leaf biomass (−32.22%), and the whole plant biomass reduction caused by O₃ (−38.47%) at the end of the experiment, but N addition did not significantly influence O₃-dose response to biomass. In conclusion, N addition can alleviate O₃-induced reductions in Pn and biomass via non-stomatal mechanisms, but it is ineffective in altering long-term O₃ dose–response relationships. Soil N addition offers a short-term strategy to mitigate O₃ impacts on short-lived root vegetables such as cherry radish but does not influence key functional traits over the long term. This study highlights the potential of N addition to alleviate acute oxidative stress, while underscoring its limitations in mitigating the effects of prolonged O₃ exposure in root vegetables. Full article

In the era of global climate change, existing evidence indicates that dominant species play a crucial role in regulating grassland structure and function. However, what remains overlooked are the factors that regulate the growth of dominant species under climate change. Some studies have indicated that the future climate of the Inner Mongolia grasslands will specifically show a trend of warming and humidification. Hence, in 2013, we conducted a controlled warming and precipitation addition experiment in a temperate steppe in Inner Mongolia, China. Open-top chambers (OTCs) were used to simulate warming (by 1.5 °C) and rainfall (twice a month, 10% of the average precipitation between 1960 and 2011 of the same month each time) during the growing season. In 2023, the resource utilization efficiency, morphological characteristics, leaf anatomical structure, and population quantity characteristics of the dominant species (Leymus chinensis), and community species diversity were monitored under control (CK), warming (T), precipitation addition (P), and warming plus precipitation addition (TP) conditions. We found that the plant height of L. chinensis significantly increased under warming; its height was 41.97 cm under TP, 41.84 cm under T, 29.48 cm under P, and 28.88 cm under CK. We observed that L. chinensis primarily obtains more light by increasing leaf area and height under warming conditions. Environmental changes also alter the tissue structure of L. chinensis leaves, leading to a decrease in lignification after increasing the water content. In this study, warming significantly increased the L. chinensis leaf area but decreased the leaf carbon content. Warming and precipitation addition regulated the height of L. chinensis by affecting the leaf area, leaf–stem ratio, and distance of the bottom leaf from the ground. Our results provide reasonable predictions regarding the succession direction of the L. chinensis steppe under global climate change in the future. Full article

Climate change, represented by global warming, significantly affects the structure and function of alpine wetland ecosystems. Investigating the response strategies of alpine wetland plants to temperature changes is fundamental to understanding how alpine wetlands cope with global warming. This study, conducted at the typical alpine wetland Napahai, uses the latest predictions from the Intergovernmental Panel on Climate Change (IPCC) and employs open–top chamber warming experiments (OTCs) to study the responses of typical alpine wetland plants, Zizania caduciflor and Sparganium stoloniferum, to simulated warming. The results indicate that simulated warming significantly reduced the photosynthetic capacity of Z. caduciflor, and obviously decreased the biomass accumulation of both Z. caduciflor and S. stoloniferum (p < 0.05). The mean annual temperature (MAT) and annual maximum temperature (max) are the primary temperature factors affecting the photosynthetic and biomass parameters. Specifically, the net photosynthetic rate, stomatal conductance, transpiration rate, the aboveground, underground, and total biomasses, and the nitrogen contents of aboveground and underground buds of Z. caduciflor all showed significant negative correlations with MAT and max (p < 0.05). The parameters of S. stoloniferum mainly showed significant correlations with max, with its underground biomass, total biomass, and root nitrogen content all showing significant negative correlations with max, while its fibrous root carbon content and underground bud phosphorus content showed significant positive correlations with max (p < 0.05). The results are consistent with previous studies in high–altitude regions, indicating that warming reduces the photosynthetic capacity and biomass accumulation of alpine wetland plants, a trend that is widespread and will lead to a decline in the productivity of alpine wetlands and changes in vegetation composition. The study can provide a case for understanding the response strategies of alpine wetlands in the context of climate change. Full article

Laver fluffy is an indispensable link in the processing of laver products. After fluffing, the laver acquires an appealing color, which is conducive to better marketability. During the primary mechanical processing of laver, a valve capable of rapid opening and closing is required to ensure that the laver’s surface becomes fluffy and lustrous post-processing. However, valve products that can meet the specific requirements of laver fluffing are scarce. This study proposes a novel principle for a high-speed switching control valve. This valve can quickly turn on or cut off the high-pressure gas path during laver processing while also taking into account the response speed and service life. The structure and principle of the new control valve were introduced. Different flow field models in the valve were designed, and their flow characteristics and flow field performance under various schemes were compared and discussed by using Fluent. Subsequently, an optimized control valve structure model was proposed. Based on this, a strength analysis of the control valve was conducted via fluid–structure interaction, revealing the response characteristics of the valve under the working state. The results indicate that, when different cone angles and bell shapes were selected for the upper chamber inlet of the control valve, the number and intensity of vortices in the upper chamber can be reduced. The height of the upper chamber affected the formation of the throttle between the top and bottom surfaces of the upper chamber. When the height of the upper chamber was 32 mm, the energy loss in the upper chamber remains basically stable. Simultaneously changing the inlet shape and height of the upper chamber can effectively prevent the throttle formed by the height of the upper chamber, which was conducive to increasing the valve outlet flow rate. Through the analysis of the flow field with different valve chamber structures, the improved control valve adopted the bell-shaped inlet, with an upper chamber height of 32 mm and curved transition for the internal flow channel. Compared to the original fluid domain, when the opening was 100%, the outlet flow rate of the 10° conical tube and bell-shaped inlet increased by 12.77% and 12.59%, respectively. The outlet flow rate at the curved transition position rose by 15.35%, and the outlet flow of the improved control valve increased by 32.70%. When the control valve was operating under a preload pressure of 1 MPa, at 20% opening, the maximum equivalent stress of the valve body was 52.51 MPa, and the total deformation was 12.56 microns. When the preload pressure exceeded 1.5 MPa, the equivalent stress and total deformation of the control valve body and T-shaped valve stem exhibited an upward trend with further increases in the preload pressure. Full article

Global warming has intensified the changes in wetland carbon cycling processes, and the cbbL gene, which plays a key role in carbon fixation, is significantly affected by warming. Therefore, we set up open-top chamber warming and natural controls and used amplicon sequencing to investigate the response of the cbbL carbon-fixing microbial community in the alpine lakeshore wetland to warming. We found that after the warming treatment, the relative abundances of Actinobacteria and Chlorophyta increased, while the relative abundance of Cyanobacteria decreased (p < 0.05). Soil temperature and moisture were the most significant factors influencing the cbbL carbon-fixing microbial community in the lakeshore wetland. Deterministic processes dominated the community assembly of carbon-fixing microbes under warming conditions. Additionally, warming enhanced both cooperative and competitive interactions among carbon-sequestering microorganisms while reducing soil moisture availability and increasing environmental stress, leading to a decrease in the modularity of microbial communities. In summary, warming reduced the carbon sequestration potential of lakeside wetlands but favored the interactions among carbon-sequestering microorganisms. Full article

Water use efficiency (WUE) plays a pivotal role in connecting the carbon and water cycles and represents the amount of water used by plants or ecosystems to achieve carbon sequestration. The response of WUE to climate warming and its underlying mechanisms remain unclear. Here, we examined the effects of varying levels of warming on carbon fluxes, water fluxes, and WUE in an alpine peatland, with Blysmus sinocompressus and Carex secbrirostris as dominant species. Open-top chambers were utilized to simulate two levels of warming: low-level warming (TL) and high-level warming (TH). The carbon dioxide and water fluxes were monitored over a growing season (June to September). Gradient warming significantly decreased both gross primary productivity (GPP) and net ecosystem carbon exchange (NEE); GPP was 10.05% and 13.31% lower and NEE was 21.00% and 30.00% lower in the TL and TH treatments, respectively, than in the control. Warming had no significant effect on soil evaporation, and plant transpiration and evapotranspiration were 36.98% and 23.71% higher in the TL treatment than in the control, respectively; this led to decreases of 31.38% and 28.17% in canopy water use efficiency (WUEc) and ecosystem water use efficiency (WUEe), respectively. Plant transpiration was the main factor affecting both WUEe and WUEc in response to warming. The findings underscore the essential function of water fluxes in regulating WUE and enhance our understanding of carbon–water coupling mechanisms under climate change. Full article

Effects of climate warming on nutrition quality and storage of alpine grasslands are still controversial, which is not conducive to the management and utilization of alpine grasslands. A long-term warming experiment (with open-top chambers used to elevate temperature) was conducted at three elevations (relatively low, mid-, and high elevations with 4313, 4513, and 4693 m) of Northern Tibet in 2010 to compare the differences in forage nutritional quality and storage response to warming among three elevations and to explore the relationships between forage nutritional quality and production. In 2019, community surveys, observations of forage biomass and nutrition quality, and soil physicochemical properties were carried out. Forage nutrition quality included crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), ether extract (EE), crude ash (Ash), and water-soluble carbohydrate (WSC) content. Warming did not affect community aboveground biomass (AGB) at the three elevations. Warming improved community nutrition quality by increasing community CP content by 25.80% and decreasing community NDF content by 15.51% at the low elevation. In contrast, warming reduced community nutrition quality by increasing community CP, ADF, and NDF contents by 13.45%, 23.68%, and 17.43%, respectively, and decreasing Ash content by 39.50% at the high elevation. Warming did not affect community CP, ADF, NDF, EE, Ash, or WSC contents at the mid-elevation. Warming increased community nutrition storage by increasing community CP, ADF, and NDF storges by 74.69%, 88.18%, and 79.71%, respectively, at the high elevation. Warming did not affect community nutrition storages at the low or mid-elevations. Overall, forbs had higher CP, EE, Ash, and WSC contents and lower ADF and NDF contents compared with graminoids. Community EE content increased with community AGB, but community CP, ADF, NDF, EE, Ash, and WSC contents were not related to community AGB. Therefore, from the low to high elevation, the effects of warming on forage nutrition quality gradually changed from improving to inhibiting. Warming altered rangeland quality by affecting forage nutrition quality rather than forage production. There were no trade-offs between forage nutrition quality and forage production. Full article

Climate warming and high-intensity human activities threaten the stability of alpine meadow ecosystems. The stability of the soil microbial community is crucial for maintaining ecological service function. However, the effects of warming and litter removal on microbial interactions, community-building processes, and species coexistence strategies remain unclear. In this study, we used a fiberglass open-top chamber to simulate global change, and moderate grazing in winter was simulated by removing above-ground litter from all plants in the Qinghai–Tibet Plateau, China, to investigate the effects of warming, litter removal, and interactions on soil microbial communities. The treatments included (1) warming treatment (W); (2) litter removal treatment (L); (3) the combined treatment (WL); and (4) control (CK). The results show that compared with the control treatment, warming, litter removal, and the combined treatments increased bacterial Shannon diversity but reduced fungal Shannon diversity, and warming treatment significantly changed the bacterial community composition. Warming, litter removal, and the combined treatments reduced the colinear network connectivity among microorganisms but increased the modularity of the network, and the average path distance and average clustering coefficient were higher than those in the control group. Stochastic processes played a more important role in shaping the microbial community composition, and soil–available phosphorus and soil ammonium contributed more to the βNTI of the bacterial community, while total phosphorus and NAG enzyme in the soil contributed more to the βNTI of the fungal community. Notably, litter removal counteracts the effects of warming on bacterial communities. These results suggest that litter removal may enhance bacterial community stability under warming conditions, providing insights for managing alpine meadow ecosystems in the context of climate change. Full article

Global climate warming has led to the deepening of the active layer of permafrost on the Tibetan Plateau, further triggering thermal subsidence phenomena, which have profound effects on the carbon cycle of regional ecosystems. This study conducted warming (W) and thermal subsidence (RR) control experiments using an Open-Top Chamber (OTC) device in the river source wetlands of the Qinghai Lake basin. The aim was to assess the impacts of warming and thermal subsidence on soil temperature, volumetric water content, biomass, microbial diversity, and soil respiration (both autotrophic and heterotrophic respiration). The results indicate that warming significantly increased soil temperature, especially during the colder seasons, and thermal subsidence treatment further exacerbated this effect. Soil volumetric water content significantly decreased under thermal subsidence, with the RRW treatment having the most pronounced impact on moisture. Additionally, a microbial diversity analysis revealed that warming promoted bacterial richness in the surface soil, while thermal subsidence suppressed fungal community diversity. Soil respiration rates exhibited a unimodal curve during the growing season. Warming treatment significantly reduced autotrophic respiration rates, while thermal subsidence inhibited heterotrophic respiration. Further analysis indicated that under thermal subsidence treatment, soil respiration was most sensitive to temperature changes, with a Q₁₀ value reaching 7.39, reflecting a strong response to climate warming. In summary, this study provides new scientific evidence for understanding the response mechanisms of soil carbon cycling in Tibetan Plateau wetlands to climate warming. Full article

Rising CO₂ levels, as predicted by global climate models, are altering environmental factors such as the water cycle, leading to soil waterlogging and reduced oxygen availability for plant roots. These conditions result in decreased energy production, increased fermentative metabolism, impaired nutrient uptake, reduced nitrogen fixation, and altered leaf gas exchanges, ultimately reducing crop productivity. Co-inoculation techniques involving multiple plant growth-promoting bacteria or arbuscular mycorrhizal fungi have shown promise in enhancing plant resilience to stress by improving nutrient uptake, biomass production, and nitrogen fixation. This study aimed to investigate carbon and nitrogen metabolism adaptations in soybean plants co-inoculated with Bradyrhizobium elkanii, Azospirillum brasilense, and Rhizophagus intraradices under waterlogged conditions in CO₂-enriched environments. Plants were grown in pots in open-top chambers at ambient CO₂ concentration (a[CO₂]) and elevated CO₂ concentration (e[CO₂]). After reaching the V5 growth stage, the plants were subjected to waterlogging for seven days, followed by a four-day reoxygenation period. The results showed that plants’ co-inoculation under e[CO₂] mitigated the adverse effects of waterlogging. Notably, plants inoculated solely with B. elkanii under e[CO₂] displayed results similar to co-inoculated plants under a[CO₂], suggesting that co-inoculation effectively mitigates the waterlogging stress, with plant physiological traits comparable to those observed under elevated CO₂ conditions. Full article

Texas cotton production is facing challenges from increased temperatures and extended droughts. We sought to determine whether applying a multi-species grass mulch on the surface of cotton fields in a semiarid region would mitigate some of the negative effects of climate change. We used open-top chambers (OTCs) to mimic climate warming and compared whether the effects of residue addition were similar between dryland and irrigated cotton fields located in the High Plains region of Texas during the summer of 2021. The OTCs raised the average air temperature by 2 °C. Under experimental warming, residue addition increased moisture content in non-irrigated (i.e., dryland) soils (+9.2%) and reduced the daily temperature range (by −1.4 °C) relative to uncovered soils. Furthermore, when pooled across irrigation and warming treatments, the addition of residue increased microbial biomass, soil respiration (+78.2%), and cotton yield (+15.2%) relative to uncovered soils. OTCs further enhanced the residue effects on microbial biomass by 34.9%. We also observed higher soil organic matter, microbial biomass, cotton biomass, and yield in irrigated fields compared to dryland, irrespective of residue addition. Our findings suggest that residue addition in dryland agriculture can mitigate the adverse effects of warming by stabilizing soil microclimates and promoting microbial growth and biomass by providing a more labile source of carbon, which, in turn, could boost the yield of cotton plants. Full article

This study investigates the impact of elevated temperatures on arthropod communities in intensively managed pastures on the volcanic island of Terceira, Azores (Portugal), using a functional trait approach. Open Top Chambers (OTCs) were employed to simulate increased temperatures, and the functional traits of ground dwelling arthropods were analyzed along a small elevation gradient (180–400 m) during winter and summer. Key findings include lower abundances of herbivores, coprophagous organisms, detritivores, and fungivores at high elevations in summer, with predators showing a peak at middle elevations. Larger-bodied arthropods were more prevalent at higher elevations during winter, while beetles exhibited distinct ecological traits, with larger species peaking at middle elevations. The OTCs significantly affected the arthropod communities, increasing the abundance of herbivores, predators, coprophagous organisms, and fungivores during winter by alleviating environmental stressors. Notably, iridescent beetles decreased with elevation and were more common inside OTCs at lower elevations, suggesting a thermoregulatory advantage. The study underscores the importance of considering functional traits in assessing the impacts of climate change on arthropod communities and highlights the complex, species-specific nature of their responses to environmental changes. Full article

In this work, we assessed the effects of increasing ozone (O₃) on four petunia varieties with different floral pigmentation (pink, red, rose-red, and white). Plants were exposed, in open-top chambers located in China, to three O₃ concentrations, i.e., (i) ambient air (AA), (ii) AA + 60 ppb O₃ (AA + 60), and (iii) AA + 120 ppb O₃ (AA + 120), for 85 days (9 h day⁻¹). Flower diameter and duration were assessed, together with leaf chlorophyll and flavonoid contents. White petunia showed a reduced flower diameter and longevity under AA + 60 (−7 and −6%, respectively, in comparison to AA), whereas pink and red petunias only showed this under AA + 120 (−8 and −7%, on average, respectively). Chlorophyll loss occurred in all varieties under AA + 60 (−30%, on average), and at AA + 120 in white and red petunias (−54%, on average). The total flavonoid content in the pink and white varieties increased only under AA + 120 (around +85%), while it grew at both AA + 60 and AA + 120 (+92% and two-fold higher, respectively) in the red variety. Increasing O₃ concentrations did not affect particularly the red-rose variety. The white variety showed the strongest correlations among flower and leaf properties, confirming a variety-related O₃ response, as well as demonstrating that it had the highest O₃ sensitivity. Full article

Rising atmospheric CO₂ levels, a significant consequence of anthropogenic activities, profoundly impact global agriculture and food security by altering plant physiological processes. Despite extensive research, a comprehensive understanding of the specific effects of elevated CO₂ on maize (Zea mays L.)’s primary and secondary metabolism remains elusive. This study investigated the responses of maize seedlings cultivated in open-top chambers (OTCs) under three CO₂ concentrations: ambient (380 ppm), elevated (600 ppm), and high (1800 ppm). Key growth parameters, including plant height, leaf area, and aboveground biomass (leaf and stem), were assessed alongside metabolic profiles encompassing nonstructural and structural carbohydrates, syringyl (S) and guaiacyl lignin, the syringyl-to-guaiacyl (S/G)-lignin ratio, photosynthetic pigments, total soluble protein, and malondialdehyde (MDA) levels. The results demonstrated that exposure to 600 ppm CO₂ significantly enhanced plant height, leaf area, and aboveground biomass compared to ambient conditions. Concurrently, there were notable increases in the concentrations of primary metabolites. In contrast, exposure to 1800 ppm CO₂ severely inhibited these growth parameters and induced reductions in secondary metabolites, such as chlorophyll and soluble proteins, throughout the growth stages. The findings underscore the intricate responses of maize metabolism to varying CO₂ levels, highlighting adaptive strategies in primary and secondary metabolism under changing atmospheric conditions. This research contributes to a nuanced understanding of maize’s physiological adaptations to future climate scenarios characterized by elevated CO₂, with implications for sustainable agriculture and food security. Full article