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Uncrewed Wave Gliders (UWGs) are capable of harnessing energy from ocean waves and photovoltaic sources to enable long-duration voyages. Since the float’s yaw motion relies on the rudder of the submersible for control, this introduces many unknown nonlinear and time-delay factors into the control system. Moreover, the susceptibility of UWGs to waves influences results in limited maneuverability and necessitates energy efficiency considerations, complicating the task of following a designated path to a specific point for observations. To address these challenges, this paper first introduces a differential model-free adaptive control (DMFAC) approach for managing the float’s heading control, along with a proof of its stability. Furthermore, an improved attractive force line-of-sight (IAFLOS) guidance strategy for overall mooring control is proposed. The integration of the DMFAC heading controller and the IAFLOS strategy forms a comprehensive mooring control system, which is validated through simulation studies in typical maritime conditions. This control system ensures that, while considering energy conservation strategies, the distance between the wave glider and the mooring point remains within 20 m during mooring.

Previous studies have primarily focused on the extraction of highland barley crops using single phenological images, which ignored the selection of the optimal phenological period for classification. Utilizing the multiple phenological images from Sentinel-2 to construct 25 features, including spectral, red edge, vegetation, and texture features, the recursive feature elimination algorithm and the random forest algorithm (RF) were employed to optimize feature datasets for different phenological stages, which were then used for the identification and classification of high-land barley by RF. The main results were as follows: (1) Information extraction based on feature optimization combinations yielded good overall classification accuracy, with classification accuracies for highland barley being 92.56% (jointing stage), 90.90% (heading stage), 90.74% (flowering stage), 91.55% (milk ripening stage), and 90.51% (maturity stage), respectively. (2) NDVIre1 had the highest importance score (0.1792) in the feature selection combination, indicating that the red edge index contributed significantly to crop information extraction and classification. (3) The five feature variables—GLCM_Mean, RVI, homogeneity, MAX, and GLCM_Correlation—showed stability and universality in the extraction of highland barley. These results demonstrated that the images that derived from the jointing and milk ripening phenological stages had the best applicability for highland barley extraction, and the optimized feature datasets that composed of NDVIre1 were conductive to detect and monitor of highland barley crops in the mountainous regions of northwest China.

Plants possess intricate defense mechanisms to resist cadmium (Cd) stress, including strategies like metal exclusion, chelation, osmoprotection, and the regulation of photosynthesis, with antioxidants playing a pivotal role. The application of nitrogen (N) and phosphorus (P) fertilizers are reported to bolster these defenses against Cd stress. Several studies investigated the effects of N or P on Cd stress in non-woody plants and crops. However, the relationship between N, P application, and Cd stress resistance in valuable timber trees remains largely unexplored. This study delves into the Cd tolerance mechanisms of Phoebe zhennan, a forest tree species, under various treatments: Cd exposure alone, combined Cd stress with either N or P and Cd stress with both N and P application. Our results revealed that the P application enhanced root biomass and facilitated the translocation of essential nutrients like K, Mn, and Zn. Conversely, N application, especially under Cd stress, significantly inhibited plant growth, with marked reductions in leaf and stem biomass. Additionally, while the application of P resulted in reduced antioxidant enzyme levels, the combined application of N and P markedly amplified the activities of peroxidase by 266.36%, superoxide dismutase by 168.44%, and ascorbate peroxidase by 26.58% under Cd stress. This indicates an amplified capacity of the plant to neutralize reactive oxygen species. The combined treatment also led to effective regulation of nutrient and Cd distribution in roots, shoots, and leaves, illustrating a synergistic effect in mitigating toxic impact of N. The study also highlights a significant alteration in photosynthetic activities under different treatments. The N addition generally reduced chlorophyll content by over 50%, while P and NP treatments enhanced transpiration rates by up to 58.02%. Our findings suggest P and NP fertilization can manage Cd toxicity by facilitating antioxidant production, osmoprotectant, and root development, thus enhancing Cd tolerance processes, and providing novel strategies for managing Cd contamination in the environment.

Abstract A fundamental goal of ecologists is to determine the large-scale gradients in species richness. The threatened plants are the priority of such studies because of their narrow distribution and confinement to a specific habitat. Studying the distribution patterns of threatened plants is crucial for identifying global conservation prioritization. In this study, the richness pattern of threatened plant species along spatial and elevation gradients in Sichuan Province of China was investigated, considering climatic, habitat-heterogeneity (HHET), geometric constraint and human-induced factors. The species richness pattern was analyzed, and the predictor variables, including mean annual temperature (MAT), mean annual precipitation (MAP), potential evapotranspiration (PET), HHET, and disturbance (DIST), to species richness were linked using the geographical distribution data of threatened species compiled at a spatial resolution of 20 km × 20 km. Generalized linear models and structural equation modelling were used to determine the individual and combined effects of each variable on species richness patterns. Results showed a total of 137 threatened plant species were distributed between 200 and 4800 m.a.s.l. The central region of the province harbors the highest species diversity. MAP and PET profoundly explained the richness pattern. Moreover, the significant role of DIST in the richness patterns of threatened plants was elucidated. These findings could help determine the richness pattern of threatened plant species in other mountainous regions of the world, with consideration of the impact of climate change.

In the presence of limited phosphorus (P) in terrestrial ecosystems, exploring how land use change (LUC) affects phosphatase enzyme activity and microbial communities is important for managing soil P, because microorganisms carry out the majority of P cycling in the soil through producing phosphatase enzymes. In this study, we explored the impact of LUC on P availability, phosphatase enzyme, the abundance of phosphatase-encoding genes, and microorganisms. We collected 168 soil samples at soil depths of 0–20 cm and 20–40 cm from seven sampling sites, each of which represented by four different land uses: artificial forests (AF), farmlands (FL), natural forests (NF), and shrubland (SL). We analyzed phosphatase-encoding genes and microbes from metagenome datasets. Results indicated that P availability substantially increased following NF to FL conversion. In contrast, phosphatase enzyme activity significantly decreases when NF is converted to different land uses, due to the decline of soil organic carbon (SOC), moisture content (MC) and total nitrogen (TN). We have also detected 13 P solubilizing and mineralizing genes. The phoD and gcd were the dominant mineralizing and solubilizing genes, respectively. Farmland had higher gcd gene abundance, while NF had significantly higher phoD gene abundance. The gcd gene abundance were mainly governed by pH and total P, whereas pH and available P were the primary factors controlling phoD gene. MC, SOC and TN regulated other genes detected in this study. With regard to the dominant gcd-harboring phyla, Acidobacteria, Proteobacteria, Bacteroidetes and Gemmatimonadetes were the dominant, while Proteobacteria, Acidobacteria, Actinobacteria, and Candidatus_Rokubacteria were the dominant phoD-harboring phyla. The majority of gcd and phoD-harboring microorganisms were primarily controlled by pH, available P and total P. However, some phyla also regulated by MC, SOC, and TN. In general, our findings suggested that LUC significantly alters phosphatase enzymes and the abundance of phosphate-encoding genes and microbes. These changes have significant implications for soil P cycling.

Land use change has a significant effect on soil nutrient cycling. However, data on soil phosphorus (P) fractions following land use change are scarce, especially in the subalpine ecosystem of China. Here, we investigated the influence of land use change on soil P fractions in the subalpine ecosystem of the Southeast margin of Qinghai-Tibet Plateau, Southwest China. In total, we took 168 soil samples from four land use types, including natural forest (NF), artificial forest (AF), farmland (FL), and shrubland (SL), at a depth of 0–20 and 20–40 cm. Phosphorus fractions were determined using Hedley fractionation procedures. The results showed that land use change and soil depths had a significant impact on the status of P fractions (p≤0.05). Organic P (Po) fraction significantly decreased following land use change but varied among land use types. Farmland soils showed the highest losses of Po fractions ranging from 23 to 54%, due to organic material reduction. Total P also decreased by 9.63% after the conversion of NF to AF (p≤0.05). Conversely, total P and inorganic P (Pi) fractions were significantly higher in FL soil than in other land uses (p≤0.05), likely due to the application of chemical fertilizers. Organic P extracted by NaOH was the dominant total Po fraction in all land uses, accounting for 63.3 to 73.14% of total Po, while Pi extracted by HCl was the dominant Pi fraction in FL soil, accounting for 42.74% of total P. Soil moisture content, pH, soil organic carbon (SOC), total nitrogen (total N), and calcium were key soil properties governing soil P fractions. Organic P fractions were strongly positively correlated with SOC and total N, implying that soil organic matter (SOM) plays a vital role in maintaining the soil P reserves. Generally, our findings shed light on how land use changes significantly affected P fractions. This result may have substantial implications for soil P management to maintain soil P reserves by reducing SOM losses.

Eco-environmental quality assessment is an important process for ensuring sustainable regional development because it encourages the construction of an ecological civilization. This assessment also lays a foundation for informing digital management and decision-making for the ecological environment in the near future. Due to the particularity of mountainous areas, its Eco-environmental quality assessment needs to be deeply specific and may require re-working. Here, the AHP-Entropy model was developed and constructed to scientifically analyze and evaluate the Eco-environmental quality in mountainous Western Sichuan in 2009 and 2019 at the township (street) unit. It is based on indicators representing Biological richness, Vegetation cover, Water network density, Land stress, and Social-economic stress. This newly developed model offers a more complete assessment, is based on more easily acquired data and has a higher accuracy than past models. The Eco-environmental quality index (EQI) representing eco-environmental quality (EEQ) has five levels of rating: Better, Good, Moderate, Bad and Worse. After applying this model to the region, the results show that: 1) The ecological environmental quality in the Western Sichuan mountains has improved over the past 10 years. 2) The eco-environment in the study area is generally Good, with small areas receiving a rating of Moderate. 3) The areas considered Better are mainly distributed on Longmen Mountain, Daliang mountain and Qionglai mountain, while the Moderate areas are mainly distributed in the western Chengdu Plain, the Panzhihua urban area, and Shaluli mountain. 4) The areas rated Better earn their rating due to high vegetation coverage, high habitat quality, and low degree of land degradation, such as land desertification and soil erosion. The areas with moderate eco-environmental quality were mainly affected by frequent human activity or serious land degradation. This comprehensive regional Eco-environmental quality assessment can also be used in other areas with mountains.

Abstract Studying the pattern of species richness is crucial in understanding the diversity and distribution of organisms in the earth. Climate and human influences are the major driving factors that directly influence the large‐scale distributions of plant species, including gymnosperms. Understanding how gymnosperms respond to climate, topography, and human‐induced changes is useful in predicting the impacts of global change. Here, we attempt to evaluate how climatic and human‐induced processes could affect the spatial richness patterns of gymnosperms in China. Initially, we divided a map of the country into grid cells of 50 × 50 km2 spatial resolution and plotted the geographical coordinate distribution occurrence of 236 native gymnosperm taxa. The gymnosperm taxa were separated into three response variables: (a) all species, (b) endemic species, and (c) nonendemic species, based on their distribution. The species richness patterns of these response variables to four predictor sets were also evaluated: (a) energy–water, (b) climatic seasonality, (c) habitat heterogeneity, and (d) human influences. We performed generalized linear models (GLMs) and variation partitioning analyses to determine the effect of predictors on spatial richness patterns. The results showed that the distribution pattern of species richness was highest in the southwestern mountainous area and Taiwan in China. We found a significant relationship between the predictor variable set and species richness pattern. Further, our findings provide evidence that climatic seasonality is the most important factor in explaining distinct fractions of variations in the species richness patterns of all studied response variables. Moreover, it was found that energy–water was the best predictor set to determine the richness pattern of all species and endemic species, while habitat heterogeneity has a better influence on nonendemic species. Therefore, we conclude that with the current climate fluctuations as a result of climate change and increasing human activities, gymnosperms might face a high risk of extinction.

Changes in global climate patterns and human activity have the potential to alter key components of terrestrial ecosystems, such as the productivity of grasslands. The Qinghai–Tibetan Plateau is one of the most sensitive regions and is affected by substantial climatic changes and intensive human activities. In this study, the spatial distribution and temporal variation in grassland productivity from 1980 to 2015 were examined using the proxy net primary productivity (NPP). Trend and redundancy analyses were used to determine the contributions of driving indicators (climate change and human interventions) to the changes in NPP. During the past 35 years, the trend in grassland productivity across the Qinghai–Tibetan Plateau was one of significant increasing trend (increase of 1.08 g C/m2/year). A trend of increase of NPP was observed for approximately 82.79% of the total grassland area, with most of this area distributed in the central region. However, a trend of degradation was observed in the northwestern region of the plateau. The primary reason for the complex spatial pattern and distribution of vegetation productivity was unsynchronized changes in temperature and precipitation. Therefore, temperature and water content (precipitation and melting water) were not good indicators for trends in NPP in this area. Moreover, although variation in rainfall and temperature explained 9.75% of the variation in grassland productivity, the effects of human interventions were greater (23.48%). According to the redundancy analysis, the positive contribution of ecological restoration projects (reducing the negative effects of humans) was the most important indicator in the entire study area, followed by temperature (conducive to vegetation growth and acceleration of melting glaciers). Most conservation policies produced significant positive effects on the restoration of grasslands and prevented or reversed the degradation of grasslands on the plateau. Under increases in temperature and moisture on the Qinghai–Tibetan Plateau, the ecological restoration policies in conservation areas demonstrate an “increasing trend in grassland productivity.”

Abstract Understanding the factors driving the Quaternary distribution of Abies in the Tibetan Plateau (TP) is crucial for biodiversity conservation and for predicting future anthropogenic impacts on ecosystems. Here, we collected Quaternary paleo‐, palynological, and phylogeographical records from across the TP and applied ecological niche models (ENMs) to obtain a profound understanding of the different adaptation strategies and distributional changes in Abies trees in this unique area. We identified environmental variables affecting the different historical biogeographies of four related endemic Abies taxa and rebuilt their distribution patterns over different time periods, starting from the late Pleistocene. In addition, modeling and phylogeographic results were used to predict suitable refugia for Abies forrestii, A. forrestii var. georgei, A. fargesii var. faxoniana, and A. recurvata. We supplemented the ENMs by investigating pollen records and diversity patterns of cpDNA for them. The overall reconstructed distributions of these Abies taxa were dramatically different when the late Pleistocene was compared with the present. All Abies taxa gradually receded from the south toward the north in the last glacial maximum (LGM). The outcomes showed two well‐differentiated distributions: A. fargesii var. faxoniana and A. recurvata occurred throughout the Longmen refuge, a temporary refuge for the LGM, while the other two Abies taxa were distributed throughout the Heqing refuge. Both the seasonality of precipitation and the mean temperature of the driest quarter played decisive roles in driving the distribution of A. fargesii var. faxoniana and A. recurvata, respectively; the annual temperature range was also a key variable that explained the distribution patterns of the other two Abies taxa. Different adaptation strategies of trees may thus explain the differing patterns of distribution over time at the TP revealed here for endemic Abies taxa.

The species richness–climate relationship is a significant concept in determining the richness patterns and predicting the cause of its distribution. The distribution range of species and climatic variables along elevation have been used in evaluating the elevational diversity gradients (EDG). However, the species richness of gymnosperms along elevation and its driving factors in large geographic areas are still unknown. Here, we aimed at evaluating the EDG of gymnosperms in the ecoregions of China. We divided the geographical region of China into 34 ecoregions and determine the richness pattern of gymnosperm taxa along elevation gradients. We demonstrated the richness patterns of the 237-gymnosperm (219 threatened, 112 endemic, 189 trees, and 48 shrubs) taxa, roughly distributed between 0 and 5,300 m (above sea level) in China. As possible determinants of richness patterns, annual mean temperature (TEMP), annual precipitation (PPT), potential evapotranspiration (PET), net primary productivity (SNPP), aridity index (AI), temperature seasonality (TS), and precipitation seasonality (PS) are the major predictor variables driving the EDG in plants. We used the species interpolation method to determine the species richness at each elevation band. To evaluate the richness pattern of gymnosperms in an ecoregion, generalized additive modeling and structural equation modeling were performed. The ecoregions in the southern part of China are rich in gymnosperm species, where three distinct richness patterns—(i) hump-shaped, (ii) monotonic increase, and (iii) monotonic decline—were noticed in China. All climatic variables have a significant effect on the richness pattern of gymnosperms; however, TEMP, SNPP, TS, and PS explained the highest deviance in diversity-rich ecoregions of China. Our results suggests that the highest number of gymnosperms species was found in the southwestern and Taiwan regions of China distributed at the 1,600- and 2,800-m elevation bands. These regions could be under severe stress in the near future due to expected changes in precipitation pattern and increase of temperature due to climate change. Thus, our study provided evidence of the species–climate relationship that can support the understanding of future conservation planning of gymnosperms.

Intercropping may improve community stability and yield under climate change. Here, we set up a field experiment to evaluate the advantages of cultivating Z anthoxylum bungeanum with Capsicum annum, and Z. bungeanum with Glycine max as intercrops, compared with cultivating Z. bungeanum in monoculture. Effects of extreme drought stress conditions on morphological, physiological, and biochemical traits of the three crop species cultivated in the three contrasting planting systems were compared. Results showed that extreme drought conditions induced negative impacts on Z. bungeanum grown in monoculture, due to reduced growth and metabolic impairment. However, limited stomatal conductance, reduced transpiration rate (Tr), and increased water use efficiency, carotenoid content, catalase activity, and accumulation of soluble sugars in Z. bungeanum indicated its adaptive strategies for tolerance of extreme drought stress conditions. Compared with cultivation in monoculture, intercropping with C. annum had positive effects on Z. bungeanum under extreme drought stress conditions, as a result of improved crown diameter, leaf relative water content (LRWC), net photosynthetic rate, and proline content, while intercropping with G. max under extreme drought stress conditions increased net CO2 assimilation rates, LRWC, Tr, and superoxide dismutase (SOD) activity. In conclusion, Z. bungeanum has an effective defense mechanism for extreme drought stress tolerance. Intercropping with G. max enhanced this tolerance potential primarily through its physio-biochemical adjustments, rather than as a result of nitrogen fixation by G. max.

More efficient use of soil resources, such as nitrogen (N) and phosphorus (P), can improve plant community resistance and resilience against drought in arid and semi-arid lands. Intercropping of legume and non-legumes can be an effective practice for enhancing P mineralization uptake, and plant nutrient status. However, it remains unclear how intercropping systems using desert plant species impact soil-plant P fractions and how they affect N and water uptake capacity. Alhagi sparsifolia (a legume) and Karelinia caspia (a non-legume) are dominant plant species in the Taklamakan Desert in Xinjiang Province, China. However, there is a lack of knowledge of whether these species, when intercropped, can trigger synergistic processes and mechanisms that drive more efficient use of soil resources. Thus, in a field experiment over two years, we investigated the impact of monoculture and intercropping of these plant species on soil-plant P fractions and soil-plant nutrients. Both plant species’ foliar nutrient (N, P, and K) concentrations were higher under monoculture than intercropping (except K in K. caspia). Nucleic acid P was higher in the monoculture plots of A. sparsifolia, consistent with higher soil labile P, while metabolic P was higher in monoculture K. caspia, associated with higher soil moderately labile Pi. However, both species had a higher residual P percentage in the intercropping system. Soils from monoculture and intercropped plots contained similar microbial biomass carbon (MBC), but lower microbial biomass N:microbial biomass phosphorus (MBN:MBP) ratio associated with reduced N-acetylglucosaminidase (NAG) activity in the intercropped soils. This, together with the high MBC:MBN ratio in intercropping and the lack of apparent general effects of intercropping on MBC:MBP, strongly suggest that intercropping improved microbe N- but not P-use efficiency. Interestingly, while EC and SWC were higher in the soil of the K. caspia monoculture plots, EC was significantly lower in the intercropped plots. Plants obtained better foliar nutrition and soil P mineralization in monocultures than in intercropping systems. The possible positive implications of intercropping for reducing soil salinization and improving soil water uptake and microbial N-use efficiency could have advantages in the long term and its utilization should be explored further in future studies.

The use of phosphorus (P) to alleviate soil nutrient deficiency alters resources in plant and microbial communities, but it remains unknown how mixed and monospecific planting of forest tree species shape soil microbial structure and functions in response to drought and its interplay with phosphorus addition. We investigated the microbial structure and chemical properties of forest soils planted with P. zhennan monoculture, A. cremastogyne monoculture, and their mixed cultures. The three planting systems were exposed to drought (30–35% water reduction) and the combination of drought with P. A well-watered treatment (80–85% water addition) of similar combinations was used as the control. Planting systems shaped the effects of drought on the soil microbial properties leading to an increase in nitrate nitrogen, urease activity, and microbial biomass carbon in the monocultures, but decrease in mixed cultures. In the monoculture of P. zhennan, addition of P to drought-treated soil increased enzyme activities, the concentration of dissolved organic nitrogen, and carbon, leading to increase in the total bacteria, G+ bacteria, and arbuscular mycorrhizal fungi. Except in the drought with P addition treatment, the impact of admixing on total phospholipid fatty acids (PLFAs), bacterial PLFA, and fungi PLFA was synergistic in all treatments. Our findings indicated that in monoculture of P. zhennan and its mixed planting with A. cremastogyne, greater biological activities could be established under drought conditions with the addition of P.

The wave-driven catamaran is a small surface vehicle driven by ocean waves. It consists of a hull and hydrofoils, and has a multi-body dynamic structure. The process of moving from static state to autonomous navigation driven by ocean waves is called “self-propulsion”, and reflects the ability of the wave-driven catamaran to absorb oceanic wave energy. Considering the importance of the design of the wave-driven catamaran, its self-propulsion performance should be comprehensively analysed. However, the wave-driven catamaran’s multi-body dynamic structure, unpredictable dynamic and kinematic responses driven by waves make it difficult to analyse its self-propulsion performance. In this paper, firstly, a multi-body dynamic model is established for wave-driven catamaran. Secondly, a two-phase numerical flow field containing water and air is established. Thirdly, a numerical simulation method for the self-propulsion process of the wave-driven catamaran is proposed by combining the multi-body dynamic model with a numerical flow field. Through numerical simulation, the hydrodynamic response, including the thrust of the hydrofoils, the resistance of the hull and the sailing velocity of the wave-driven catamaran are identified and comprehensively analysed. Lastly, the accuracy of the numerical simulation results is verified through a self-propulsion test in a towing tank. In contrast with previous research, this method combines multi-body dynamics with computational fluid dynamics (CFD) to avoid errors caused by artificially setting the motion mode of the catamaran, and calculates the real velocity of the catamaran.

Understanding the relationships between species richness patterns and environment constitutes a key issue in biogeography and conservation strategies. To our knowledge, this is the first integrative study that incorporates soil and human-influence data into species richness modelling. Our aims were to (a) estimate the richness patterns of four conifers groups (all conifers species, endemics, threatened, and endemic-threatened species) in south-west China, (b) assess the relative importance of environmental predictors (energy, water, climate, topography, and soil) and the human-influence on the conifers richness patterns and (c) identify hotspot ecoregions, nature reserves, or important plant areas as priority conservation areas. Generalized linear models and hierarchical partitioning were used by correlating 8962 distributional records of 97 conifer species with different environmental drivers. Results indicated that central Sichuan, northern Sichuan, northern Yunnan, and the southern areas of the Hengduan mountains were identified as distinct centres of conifers richness in China. Topographic heterogeneity and soil fertility were the strongest drivers of conifer richness patterns, while climate, energy, water, and human drivers were contributed to a lower degree. The identified conifers’ important areas were mostly located outside of the existing nature reserves but inside the ecoregions. Our findings emphasize that incorporating soil data into spatial modelling provides great insights for the conservation of conifers species. We recommend conservationists to use soil variables and other environmental data to generate a comprehensive understanding of the key drivers underlying the patterns of conifer diversity and distribution.

Climate change is an important driver of biodiversity loss and extinction of endemic montane species. In China, three endemic Juniperus spp. (Juniperuspingii var. pingii, J.tibetica, and J.komarovii) are threatened and subjected to the risk of extinction. This study aimed to predict the potential distribution of these three Juniperus species under climate change and dispersal scenarios, to identify critical drivers explaining their potential distributions, to assess the extinction risk by estimating the loss percentage in their area of occupancy (AOO), and to identify priority areas for their conservation in China. We used ensemble modeling to evaluate the impact of climate change and project AOO. Our results revealed that the projected AOOs followed a similar trend in the three Juniperus species, which predicted an entire loss of their suitable habitats under both climate and dispersal scenarios. Temperature annual range and isothermality were the most critical key variables explaining the potential distribution of these three Juniperus species; they contribute by 16–56.1% and 20.4–38.3%, respectively. Accounting for the use of different thresholds provides a balanced approach for species distribution models’ applications in conservation assessment when the goal is to assess potential climatic suitability in new geographical areas. Therefore, south Sichuan and north Yunnan could be considered important priority conservation areas for in situ conservation and search for unknown populations of these three Juniperus species.

Understanding the pattern of species distribution and the underlying mechanism is essential for conservation planning. Several climatic variables determine the species diversity, and the dependency of species on climate motivates ecologists and bio-geographers to explain the richness patterns along with elevation and environmental correlates. We used interpolated elevational distribution data to examine the relative importance of climatic variables in determining the species richness pattern of 26 species of gymnosperms in the longest elevation gradients in the world. Thirteen environmental variables were divided into three predictors set representing each hypothesis model (energy-water, physical-tolerance, and climatic-seasonality); to explain the species richness pattern of gymnosperms along the elevational gradient. We performed generalized linear models and variation partitioning to evaluate the relevant role of environmental variables on species richness patterns. Our findings showed that the gymnosperms’ richness formed a hump-shaped distribution pattern. The individual effect of energy-water predictor set was identified as the primary determinant of species richness. While, the joint effects of energy-water and physical-tolerance predictors have explained highest variations in gymnosperm distribution. The multiple environmental indicators are essential drivers of species distribution and have direct implications in understanding the effect of climate change on the species richness pattern.

Nitrate (NO3--N) and ammonium (NH4+-N) fertilizers are the main forms of chemical inorganic nitrogen fertilizers that are widely used in agro-ecosystem for high yield. However, the responses of soil nematode food web to different forms and rates of inorganic nitrogen fertilizers are not well understood. The objective of this study was to determine the responses of soil nematode food web to the applications of inorganic nitrogen fertilizers in a continuous cucumber (Cucumis sativus L.) cropping system. Nitrate (NaNO3) and ammonium (NH4HCO3) fertilizers were applied to cucumber plants at the nitrogen (N) rate of 0, 67.5, 135.0 and 202.5 kg N hm-2 before planting. It was conducted in a randomized complete block design with 4 replications at Huaizi village, Leshan district, Sichuan province, Southwestern China. The effects were analyzed at the stages of seedling, blooming and fruiting, respectively. The results indicated that the numbers of nematodes were significantly higher in soils with the addition of 67.5 kg N hm-2 than the control at the seedling and blooming stages. Nematode number strongly increased at the seedling stage and decreased at the blooming and fruiting stages in nitrate-treated soils compared to the ammonium-treated. The percentage of herbivores to total nematodes significantly decreased while that of bacterivores increased with a fertilizer rate less than 135 kg N hm-2 at the seedling and fruiting stages. Nitrate significantly reduced the percentage of herbivores, and increased that of bacterivores to total nematodes by comparison with ammonium at the blooming and fruiting stages. The application of nitrate significantly increased nematode diversity and evenness, and decreased dominance at the blooming stage relative to ammonium. Nitrate significantly decreased the values of channel index at the blooming stage and maturity index at the seedling stage in comparison with ammonium, respectively. Enrichment index and structural index strongly increased at the seedling stage, and decreased at the blooming and fruiting stages under the treatment of nitrate relative to ammonium. The results suggested responses of nematode food web dependent on the rates and forms of inorganic nitrogen fertilizers and stages of cucumber growth.

Phoebe zhennan (Gold Phoebe) is a threatened tree species in China and a valuable and important source of wood and bioactive compounds used in medicine. Apart from anthropogenic disturbances, several biotic constraints currently restrict its growth and development. However, little attention has been given to building adaptive strategies for its conservation by examining its morphological and physio-biochemical responses to drought stress, and the role of fertilizers on these responses. A randomized experimental design was used to investigate the effects of two levels of irrigation (well-watered and drought-stressed) and phosphorous (P) fertilization treatment (with and without P) to assess the morphological and physio-biochemical responses of P. zhennan seedlings to drought stress. In addition, we evaluated whether P application could mitigate the negative impacts of drought on plant growth and metabolism. Drought stress had a significant negative effect on the growth and metabolic processes of P. zhennan. Despite this, reduced leaf area, limited stomatal conductance, reduced transpiration rate, increased water use efficiency, enhanced antioxidant enzymes activities, and osmolytes accumulation suggested that the species has good adaptive strategies for tolerating drought stress. Application of P had a significant positive effect on root biomass, signifying its improved water extracting capacity from the soil. Moreover, P fertilization significantly increased leaf relative water content, net photosynthetic rate, and maximal quantum efficiency of PSII under drought stress conditions. This may be attributable to several factors, such as enhanced root biomass, decreased malondialdehyde content, and the up-regulation of chloroplast pigments, osmolytes, and nitrogenous compounds. However, P application had only a slight or negligible effect on the growth and metabolism of well-watered plants. In conclusion, P. zhennan has a strong capability for drought resistance, while P application facilitates and improves drought tolerance mostly through physio-biochemical adjustments, regardless of water availability. It is imperative to explore the underlying metabolic mechanisms and effects of different levels of P fertilization on P. zhennan under drought conditions in order to design appropriate conservation and management strategies for this species, which is at risk of extinction.

Environmental pollution with heavy metals is a serious issue worldwide posing threats to humans, animals and plants and to the stability of overall ecosystem. Chromium (Cr) is one of most hazardous heavy metals with a high carcinogenic and recalcitrant nature. Aim of the present study was to select low-cost biosorbent using wheat straw and Eupatorium adenophorum through simple carbonization process, capable of removing Cr (VI) efficiently from wastewater. From studied plants a low cost adsorbent was prepared for removing Cr (VI) from aqueous solution following very simple carbonization method excluding activation process. Several factors such as pH, contact time, sorbent dosage and temperature were investigated for attaining ideal condition. For analysis of adsorption equilibrium isotherm data, Langmuir, Freundlich and Temkin models were used while pseudo-first-order, pseudo-second-order, external diffusion and intra-particle diffusion models were used for the analysis of kinetic data. The obtained results revealed that 99.9% of Cr (VI) removal was observed in the solution with a pH of 1.0. Among all the tested models Langmuir model fitted more closely according to the data obtained. Increase in adsorption capacity was observed with increasing temperature revealing endothermic nature of Cr (VI). The maximum Cr (VI) adsorption potential of E. adenophorum and wheat straw was 89.22 mg per 1 gram adsorbent at 308K. Kinetic data of absorption precisely followed pseudo-second-order model. Present study revealed highest potential of E. adenophorum and wheat straw for producing low cost adsorbent and to remove Cr (VI) from contaminated water.

The capabilities of 23 global climate models (GCMs) from the Coupled Model Intercomparison Project Phase 6 were evaluated for six extreme precipitation indices from 1961 to 2010 using interannual variability and Taylor skill scores in the Yellow River Basin and its eight subregions. The temporal variations and spatial distributions of extreme precipitation indices were projected from 2021 to 2050 under the shared socioeconomic pathway scenarios (SSP2–4.5 and SSP5–8.5). The results show that most GCMs perform well in simulating extreme values (1-day maximum precipitation (RX1day) and 5-day maximum precipitation (RX5day)), duration (consecutive dry days), and intensity index (simple daily intensity index (SDII)), and perform poor in simulating the threshold indices (precipitation on very wet days (R95p) and number of heavy precipitation days (R10mm)). The projected changes in extreme precipitation indicate that under the SSP2-4.5 scenario, future extreme precipitation will increase by 15.7% (RX1day), 15.8% (RX5day), 30.3% (R95p), 1d (R10mm), and 6.6% (SDII), respectively, decrease by 2.1d (CDD). The aforementioned changes are further enhanced under the SSP5-8.5 scenario. Extreme precipitation changes widely in Hekou Town to Longmen, in the northeastern part of the region from Longmen to Sanmenxia, below Huayuankou, and in the interflow basin. HIGHLIGHTS The study evaluated the biases of 23 global climate models (GCMs) from observations and the spatial distribution of the biases.; Interannual variability score, Taylor diagram, and Taylor skill score were used to evaluate CMIP6 GCMs.; The future changes of the Yellow River Basin and its subregions extreme precipitation under SSP2-4.5 and SSP5-8.5 scenarios were projected by using six ETCCDI indices.;

The aim of this study is to evaluate the performance of the Global Climate Model (GCM) of the Coupled Model Intercomparison Project Phase 6 (CMIP6) in historical simulations of temperature and precipitation. The goal is to select the best performing GCMs for future projection of temperature and precipitation in the Second Songhua River Basin under multiple shared socioeconomic pathways (SSPs). Interannual variability skill (IVS) and Taylor diagrams are used to evaluate the spatiotemporal performance of GCMs against temperature and precipitation data published by the China Meteorological Science Commons during 1956–2016. In addition, five relatively independent models are selected to simulate the temperature and precipitation for 2021–2050 using Hierarchical Clustering. The selected models are CMCC-ESM2, EC-Earth3-Veg-LR, IPSL-CM6A-LR, MIROC-ES2L, and MPI-ESM1-2-HR. The projected results find that SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios show an increasing trend of future annual mean temperature and precipitation. However, for annual precipitation, there is a mixed state of increase and decrease among different models on the seasonal scale. In general, future temperature and precipitation changes still show a trend of growth and uneven distribution in the Second Songhua River Basin, which may be further accelerated by human activities.

This study aims to investigate the critical state of the saddle-shaped unstable region of the axial-flow pump and propose a suitable criterion for identifying this state. The bifurcation SST k–ω model considered the rotation effect is used in the present work and verified in the numerical calculation of a water jet pump. Then, it is used to simulate the critical state of the axial-flow pump. Results show that the leading-edge separation vortex generates at 0.6Qd, while the head declines only at 0.55Qd. Therefore, using the inflection point of the head-flow curve as the critical state criterion is unsuitable. In addition, the fixed monitoring point is unsuitable for identifying the critical state due to the insensitivity to the amplitude, main frequency, and periodicity changes at the critical state. Finally, to identify the critical state, it is essential to arrange a monitoring point at the leading edge of the blade suction near the shroud, which should rotate with the impeller. The critical state criterion is that the main frequency position of the pressure fluctuation signal is offset at the monitoring point, and the amplitude is increased by 10 times.

Abstract: This study aims to research the prediction performance of a bifurcated adaptive DDES (BADDES) model in different turbulent flows with rotation and curvature [...]