Nutrient allocation patterns of Picea crassifolia on the eastern margin of the Qinghai-Tibet Plateau.

It can provide a basis for decision making for the conservation and sustainable use of forest ecosystems in mountains to understand the stoichiometric properties and nutrient allocation strategies of major tree species. However, the plant nutrient allocation strategies under different environmental gradients in forest systems of arid and semi-arid mountains are not fully understand. Therefore, three typical regions in the Qilian Mountains on the eastern edge of the Qinghai-Tibet Plateau were selected based on precipitation and temperature gradients, and the stoichiometric characteristics and nutrient allocation strategies of Qinghai spruce (Picea crassifolia) of the dominant tree species under different environmental gradients were investigated. The results showed that (1) the stoichiometric characteristics of plant tissues were different in the three regions. (2) The importance of each tissue in the plant nutrient allocation varied in different regions, showing that the plant roots are more important in the warm-wet region, while the plant leaves, branches and trunks are more important in the transition and hot-dry regions. (3) The influencing factors affecting plant nutrient allocation strategies were inconsistent across regions, which showed that plant nutrient allocation strategies in the warm-wet and transition region were mainly influenced by soil factors, while they were more influenced by climatic factors in the hot-dry region. The patterns of plant nutrient allocation strategies and drivers under different environmental gradients could help us better understand the ecological adaptation mechanism and physiological adjustment mechanism of forest ecosystem in mountains.

Wet events increase tree growth recovery after different drought intensities.

Understanding the dynamics of tree recovery after drought is critical for predicting the state of tree growth in the context of future climate change. While there has been a great deal of researches showing that drought events can cause numerous significant negative effects on tree growth, the positive effects of post-drought wetting events on tree growth remain unclear. Therefore, we analyzed the effect of wet and dry events on the radial growth of trees in Central Asia using data on the width of tree rings. The results showed that 1) Drought is the main limiting factor for radial growth of trees in Central Asia, and that as the intensity and sensitivity of drought increases, tree resistance decreases and recovery rises, and more frequent droughts reduce tree resistance. 2) Tree radial growth varied significantly with wet and dry conditions, with wet events before and after drought events significantly enhancing tree radial growth. 3) When drought is followed by a wetting event, the relationship between tree resistance and recovery is closer to the "line of full resilience", with a significant increase in recovery, and compensatory growth is more likely to occur. Thus, wetting events have a significant positive effect on tree radial growth and are a key factor in rapid tree growth recovery after drought.

[Characteristics and Identification Priority Source of Heavy Metals Pollution in Farmland Soils in the Yellow River Basin].

Assessments of the soil environmental quality of farmland and pollution source apportionment are the foundation for ensuring national food security and agricultural sustainable development, as well as an important prerequisite for the pursuit to keep our lands clean. This study evaluated the characteristics of heavy metal pollution in farmland soils in the Yellow River Basin from 2000 to 2023, based on the data of heavy metal contents including As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, using the geo-accumulation index method. Source apportionment was conducted by employing a positive matrix factorization (PMF) model. The probabilistic health risks were evaluated by coupling Monte Carlo simulation with a human health risk assessment model, and priority pollution sources and elements were identified. The results showed that:① the average content of all heavy metals in farmland soils within the study area was lower than the screening values specified in the soil environment quality risk control standard for soil contamination of agriculture land (GB 15618-2018) (pH>7.5). However, the contents of Cd, As, and Zn in the samples exceeded their screening values, with percentages of 21.69%, 5.56%, and 1.23%, respectively, with Cd having the highest rate of exceedance. ② Hg and Cd were moderately polluted, Cu and Pb were slightly polluted, and the other elements were not polluted. ③ The main sources of heavy metals in farmland soil were traffic-industrial sources, natural-agricultural sources, industrial-natural sources, and agricultural-industrial sources, with contribution rates of 37.04%, 26.69%, 21.72%, and 14.55%, respectively. ④ Heavy metals in farmland soil posed carcinogenic health risks to adults and children but did not have non-carcinogenic risks; As and Cd were priority control elements for human health risks, and industrial-natural sources and agricultural-industrial sources were priority control sources in the study area.

Pollution and source-specific risk analysis of potentially toxic metals in urban soils of an oasis-tourist city in northwest China.

Source-specific risk apportionment for soil potentially toxic metals (PTMs) is of great significance for contamination prevention and risk management in urban environments. Eighty-five urban soil samples were obtained from an oasis-tourist city, China and examined for eight PTMs (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn). The pollution levels, sources, and ecological risk of soil PTMs were quantified, and their source-specific ecological and human health effects were also estimated using the multi-proxy approaches. The results demonstrated that accumulation of Cd, Hg, Pb, Cr, Cu, and Zn in soils was observed compared to their background levels, and the soils experienced varying degrees of PTMs pollution, especially at sites with high-intensity anthropogenic activities. Natural sources, atmospheric deposition, industrial sources, vehicular emissions, and comprehensive inputs were the principal sources, with contributions of 29.28%, 25.86%, 20.13%, 16.50%, and 8.23%, respectively. The integrated ecological risks of PTMs in soils were moderate at most sites, with atmospheric deposition being the dominant contributor to ecological risks. Children exhibited pronounced non-cancer risks, but adults had no notable non-cancer risks. Moreover, there were potential carcinogenic risks for both children and adults within the study region. Non-cancer and carcinogenic risks were more significant for children than adults, and traffic emissions were the primary contributor to non-cancer risks (adults: 20.53%, children: 20.49%) and carcinogenic risks (adults: 22.95%, children: 22.08%). The industrial and traffic activities were considered as priority control sources for soil pollution control and risk management, with Hg, Cd, Zn, and Pb corresponding to the priority elements. This study highlights the source-specific ecological and human health effects of PTMs pollution in urban soils, thereby providing valuable information for targeted pollution control and priority source management.

Conservation of aged paper using reduced cellulose nanofibrils/aminopropyltriethoxysilane modified CaCO3 particles coating.

Deacidification and strengthening play pivotal roles in the enduring conservation of aged paper. In this study, we innovatively propose the use of reduced cellulose nanofibrils (rCNFs) and aminopropyltriethoxysilane modified CaCO3 (APTES-CaCO3) for preserving aged paper. The sodium borohydride-mediated reduction of cellulose nanofibrils diminished the carboxylate content and O/C mass ratio in rCNFs, which in turn amplified the swelling of rCNFs and their crosslinking potential with paper fibers. By introducing amino groups to the CaCO3 surface, the dispersion property of APTES-CaCO3 in organic solvent was enhanced, as well as the deacidification ability and the retention on the paper. The distinct structures and attributes of rCNFs and APTES-CaCO3 were characterized by various techniques. Following the conservation application to aged paper using this system, a desired internal pH value of 8.31 and an alkaline reserve of 0.8056 mol/kg were achieved, alongside a 33.6 % elevation in the tensile index. The aging resistance of the treated paper was evaluated by dry heat and hygrothermal aging tests. The findings revealed that the treatment bestowed the treated paper with outstanding anti-aging properties, notably in terms of internal pH, alkaline reserve and mechanical robustness. Additionally, the paper's brightness was amplified, while its color alteration remained negligible.

Current Global Research Trends of Tethered Cord Syndrome Surgery: A Scientometric and Visual Analysis.

BACKGROUND: Since tethered cord syndrome (TCS) may lead to neurologic and motor dysfunction, surgeries often are applied to relieve the symptoms. The aim of the research was to explore the current global research trends of TCS surgery. METHODS: In this article, articles on TCS surgery in the Web of Science Core Collection from 1980 to 2023 were searched. Research trends, countries, institutions, journals, authors, highly cited articles, and key words were analyzed using bibliometric methods. The literature co-citation network was mapped using VOSviewer, and research hotspots and trends were analyzed using CiteSpace. RESULTS: A total of 432 publications were included. The number of publications and related research interest in the field of TCS surgery has increased globally year by year. The United States is the largest contributor (154 publications). The journal Childs Nervous System has the greatest number of publications (48 publications) and the most frequently cited journal is Neurosurgery (973 citations). In network visualization, the institution with the greatest contribution is University of California System (16 publications). Lee JY and Wang KC are the authors with the greatest number of publications (8 publications), and the most frequently cited author is Klekamp J (268 citations). Neurogenic bladder and spina bifida may be the next hot spot in this field. CONCLUSIONS: This study will help researchers to identify the mainstream research directions and the latest hotspots in the field of TCS surgery and provide a reference for further research.

[Contamination Characteristics and Source Apportionment of Potentially Toxic Elements in Soil around the Coal-fired Power Plant Using APCS-MLR and PMF Models].

To investigate the characteristics and sources of potentially toxic elemental contamination in soils around the coal-fired power plant, we selected the soil around the Jingyuan power plant as the object of investigation. Thirty-six and 27 soil samples collected from the urban and farmland areas were analyzed for PTEs (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn), respectively. We employed the geoaccumulation index, single-factor pollution index, and improved Nemerow integrated pollution index to evaluate the contamination characteristics of PTEs, and combined correlation analysis with absolute principal component scores-multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) receptor models were used to quantitatively analyze the pollution sources of PTEs. The results revealed that all the average concentrations of other soil metals around Jingyuan power plant exceeded their corresponding background values of Gansu Province, except for As, in agricultural soil, and Hg exhibited significant spatial non-homogeneity, and thus it was visibly affected by anthropogenic activities. The values of the single-factor pollution and geoaccumulation indices indicated that the soils of both sites were mainly contaminated with Cd, Cr, Ni, and Pb, and Hg contamination was reflected in wide areas for both sites. Additionally, the results of the improved Nemerow index demonstrated that the investigated soil was between moderately contaminated and heavily contaminated. Further, the comprehensive pollution degree of urban soil was higher than that of agricultural soil. Moreover, source apportionment revealed that PTEs in urban soil were derived from mixed sources of traffic activities and coal combustion, mixed sources of traffic activities and industrial and mining activities, and atmospheric deposition from industrial activities, with contribution rates of APCS-MLR of 35.2%, 25.1%, and 23.4%, respectively. The PMF contribution rates were 40.2%, 12.4%, and 47.7%, respectively. PTEs in agricultural soil were from one mixture source of industrial, mining, agricultural, and traffic sources, and the other mixed source was of traffic activities and coal combustion, with a APCS-MLR contribution rate of 40.3% and 35.9% and a contribution rate of PMF of 36.2% and 18.0%, respectively. In addition, another mixed source of agricultural activities and coal combustion was obtained using the PMF model, with a contribution rate of 48.5%.

The key role of ecological resilience in radial growth processes of conifers under drought stress in the subalpine zone of marginal deserts.

Global climate change is exacerbating drought pressure on forests. However, the response patterns and physiological mechanisms of conifer species to drought, specifically in terms of radial growth, ecological resilience and soil water utilization, are not clearly understood. This study aims to quantify the effects of resilience on radial growth and identify the role of soil moisture utilization strategies in the resilience of species under drought intensities. We focus on two conifer species, Picea crassifolia (spruce) and Pinus tabuliformis (pine), located on the southern edge of the Tengger Desert in northwestern China. The dynamics of radial growth and ecological resilience were identified, and the seasonal growth rates of species based on soil water were simulated using the VS-oscilloscope model under varying drought stress. The results showed that spruce growth and recovery contributed by soil water were suppressed with frequent severe droughts, leading to a decline in growth (-0.5 cm2 year-1/10a, p < 0.05), despite its greater resistance to mild and moderate drought (-4.63 %). However, pine exhibited a stronger recovery (+40.25 %, p < 0.05) and higher variation in growth (-0.3 cm2 year-1/10a, p < 0.05) under soil moisture stress, despite its weaker resistance to drought (-23.53 %, p < 0.05). These findings provide insights into the growth, resilience, and water adaptation mechanisms of species under drought events, and theoretical support for the conservation and management of conifer diversity and forest ecosystem stability in climate-sensitive regions.

Synergistic phototherapy of NIR wavelength xanthene-quinoline salt-based heavy-atom-free photosensitizers for tumor therapy.

We propose a practical strategy to design a series of heavy-atom-free synergistic phototherapy agents (CSQs) with both photodynamic therapy (PDT) and photothermal therapy (PTT) under NIR wavelength excitation by simply replacing the indole salt of xanthene Changsha (CS) with quinoline salt.

Efficacy of ultrasound guided superior laryngeal nerve block on sedation for delayed extubation in maxillofacial surgery with free flap reconstruction.

OBJECTIVE: Superior laryngeal nerve block (SLNB) is a regional anesthesia technique for addressing airway response. However, SLNB on the efficacy of sedation in patients with delayed extubation is unknown, particularly for maxillofacial surgery (MS). The aim of the study was to assess whether ultrasound guided (UG) SLNB reduces the incidence of moderate to severe cough for delayed extubation in MS with free flap reconstruction. METHODS: 60 patients were randomly assigned to the GEA group (control group) and the SLNB group (UG-SLNB postoperatively, study group). During the initial two postoperative hours, the incidence of moderate and severe cough, agitation, and the number of patients requiring rescue propofol and flurbiprofen were recorded. Additionally, the time spent under the target level of sedation, postoperative hemodynamics, and the total does of propofol during the postoperative 24 h were recorded. RESULTS: The data showed the SLNB group had a significantly lower incidence of moderate to severe cough and agitation (p < 0.05), and a longer sedation time (p < 0.05). The number of patients required rescue propofol and flurbiprofen, as well as the hemodynamic changes, were significantly different between the two groups (p < 0.05). CONCLUSION: The use of UG-SLNB is associated with reduced incidence of postoperative cough. Moreover, SLNB can enhance the efficacy of postoperative sedation with need of fewer agents postoperatively. CLINICAL TRIAL REGISTRATION: ChiCTR2000039982.

Contamination, ecological-health risks, and sources of potentially toxic elements in road-dust sediments and soils of the largest urban riverfront scenic park in China.

Identifying the contamination and sources of potentially toxic elements (PTEs) in road-dust sediment (RDS) and the surrounding greenspace soil of urban environments and understanding their ecological-health risks are important for pollution management and public health. The contamination characteristics, ecological and probabilistic health risks, and source apportionment of eight PTEs (Cd, Pb, Cr, Cu, Ni, As, Zn, and Hg) in the Yellow River Custom Tourist Line of Lanzhou, which is the largest open urban riverfront scenic park in China, were investigated. The results showed that all the RDS PTE mean concentrations exceeded their soil background values, whereas for the surrounding greenspace soils, the concentrations of the PTEs, except for Cr and Ni, were also higher than their local background levels. Moreover, the RDS-soil system was mainly contaminated by Cd, Zn, Pb, Cu, and Hg to varying degrees, and the integrated ecological risks of PTEs in the RDS and soil were high and considerable at most sites, respectively. The probabilistic health risk assessment results demonstrated that the non-carcinogenic hazard risk for humans was negligible, but the total carcinogenic risks should be considered. Source apportionment using a positive matrix factorization model combined with multivariate statistical analyses revealed that Cr, Ni, and As in the RDS-soil system were from natural and industrial sources, Cd, Pb, Zn, Cu came from vehicle emissions and pesticide and fertilizer applications, and Hg was from natural and industrial sources and utilization of pesticides with fertilizers. This work provides scientific evidence for urban planning and human health protection in urban environments.

Supramolecular Dimer as High-Performance pH Probe: Study on the Fluorescence Properties of Halogenated Ligands in Rigid Schiff Base Complex.

The development of high-performance fluorescence probes has been an active area of research. In the present work, two new pH sensors Zn-3,5-Cl-saldmpn and Zn-3,5-Br-saldmpn based on a halogenated Schiff ligand (3,5-Cl-saldmpn = N, N'-(3,3'-dipropyhnethylamine) bis (3,5-chlorosalicylidene)) with linearity and a high signal-to-noise ratio were developed. Analyses revealed an exponential intensification in their fluorescence emission and a discernible chromatic shift upon pH increase from 5.0 to 7.0. The sensors could retain over 95% of their initial signal amplitude after 20 operational cycles, demonstrating excellent stability and reversibility. To elucidate their unique fluorescence response, a non-halogenated analog was introduced for comparison. The structural and optical characterization suggested that the introduction of halogen atoms can create additional interaction pathways between adjacent molecules and enhance the strength of the interaction, which not only improves the signal-to-noise ratio but also forms a long-range interaction process in the formation of the aggregation state, thus enhancing the response range. Meanwhile, the above proposed mechanism was also verified by theoretical calculations.

[Pollution Characteristics and Risk Assessment of Heavy Metals in Surface Dusts and Surrounding Green Land Soils from Yellow River Custom Tourist Line in Lanzhou].

In order to investigate the contamination levels of dust and its surrounding green land soil heavy metal pollution and potential ecological and health risks in the scenic areas of urban waterfront parks, the gardens, squares, and theme parks of the Yellow River Custom Tourist Line in Lanzhou were selected as the research area, using 27 dust samples and 26 soil samples from its surrounding green lands. The contamination characteristics and potential ecological risks of eight heavy metals (Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb) were evaluated using the geo-accumulation index (Igeo), single-factor pollution index (Pi), Nemerow integrated pollution index (PN), and improved potential ecological risk index (RI). The human health risk assessment was also evaluated using the exposure risk model. The results showed that the average concentrations of the other heavy metals in the surface dusts were higher than the background values of Gansu Province and Lanzhou City, except that the As mean concentrations in the surface dusts and the surrounding green land soils were slightly lower than the Gansu Province background values. For its surrounding green land soils, the mean concentrations of the other heavy metals (Cu, Zn, Cd, Hg, and Pb) exceeded the soil background values of Gansu Province and Lanzhou City, whereas the Cr and Ni mean concentrations were lower than their corresponding soil background values of Gansu Province and Lanzhou City. The geo-accumulation and single-factor pollution indices demonstrated that a slight to moderate pollution of Cr, Cu, Zn, Cd, Hg, and Pb occurred in surface dusts, and Cu, Zn, Cd, Hg, and Pb appeared in varying degrees of contamination levels in its surrounding green land soils. The Nemerow integrated pollution index analysis manifested that the overall contamination status of the study areas was between slightly and heavily polluted. The potential ecological risk index suggested that Cd and Hg were recognized as significant pollutant elements and that the RI of the other heavy metals were all below 40, presenting slight ecological risk. The health risk assessment indicated that ingestion was the dominant exposure pathway for heavy metals from the surface dusts and the surrounding green land soils, and no carcinogenic and noncarcinogenic risks posed threats to adults and children.

[Spatial Distribution Characteristics and Source Analysis of Heavy Metals in Urban River Surface Sediments from the Lanzhou Reach of the Yellow River].

In order to investigate the contamination characteristics and potential sources of heavy metals from the urban river surface sediments in the Yellow River Basin, we selected the Lanzhou reach of the Yellow River as the object of investigation. A total of 46 surface sediment samples were collected along the Lanzhou reach of the Yellow River, and the contents of eight heavy metals, Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb, were determined by using inductively coupled plasma mass spectrometry and an atomic fluorescence spectrometer. Contamination indexes including single factor pollution index (Pi) and geo-accumulation index (Igeo), together with the sediment pollution index (SPI), were used to assess heavy metal pollution characteristics and ecological risk levels in the urban river surface sediments of the Lanzhou reach of the Yellow River. Pearson's correlation analysis (CA), positive matrix factorization (PMF), and principal component analysis/absolute principal component score (PCA/APCS) were jointly employed to quantitatively analyze pollution sources of heavy metals. The results showed that the mean concentrations of the majority of heavy metals exceeded their corresponding background values of Gansu Province and Lanzhou City with the exception of As, and the spatial distribution of high concentrations of heavy metals was mainly concentrated in the corner of the river. Based on the single factor pollution and geo-accumulation indexes of the eight heavy metals, in the Lanzhou reach of the Yellow River, Cr was the dominant pollution element in the urban river surface sediments, followed by Cd and Ni. Additionally, the SPI values for the eight heavy metals in the surface sediments ranged from 0.48 to 8.56, presenting natural to low ecological risk level. Furthermore, source apportionment revealed that a mixture source of industrial and agricultural activities (77.6%) was the largest contributor of Cr, Ni, Zn, As, Cd, and Pb in the urban river surface sediments, followed by natural sources (11.4%) and a mixed source of industrial and traffic activities (11%).

Dekyphosis operation combined with limited osteotomy to treat the symptomatic adult tethered cord syndrome with complicated malformations: A case report.

RATIONALE: Tethered cord syndrome (TCS) represents a spectrum of neurological symptoms that are caused by constant or intermittent axial traction of the terminal cone of the spinal cord due to abnormal positioning. It is uncommon for abnormal structures of TCS to be accompanied by split cord malformation, thoracic spinal stenosis, and other spinal cord diseases. PATIENT CONCERNS: A 45-year-old male patient visited our hospital due to severe lower back pain, extensive left lower limb muscle weakness, and intermittent claudication. DIAGNOSES: TCS combined with stenosis of the thoracic canal, split cord malformation, and kyphosis deformity. INTERVENTIONS: The patient underwent Dekyphosis operation combined with limited osteotomy symptoms. OUTCOMES: The patient felt the right lower limb improved after surgery. At 4-month follow-up, a radiological examination showed adequate decompression of the spinal cord and a good internal fixation position. Overall, the patient's clinical symptoms significantly improved. CONCLUSION: This is a rare case of TCS combined with thoracic disc herniation and bony mediastinum. A more conservative invasive surgical approach was elected and markedly improved the patient's symptoms. Additional clinical cases are needed to confirm the stability and feasibility of this surgical approach.

Spatial characteristics of nutrient allocation for Picea crassifolia in soil and plants on the eastern margin of the Qinghai-Tibet Plateau.

BACKGROUND: Understanding the stoichiometric characteristics and nutrient allocation strategies of dominant tree species in montane forest systems can provide a basis for decision-making in relation to montane system management. Therefore, according to precipitation and temperature gradients, we selected three typical areas in the Qilian Mountains on the eastern margin of the Qinghai-Tibet Plateau to analyse the spatial relations of plant-soil stoichiometric characteristics and nutrient allocation strategies of plant tissues for Qinghai spruce (Picea crassifolia) along different environmental gradients. RESULTS: 1) The plant and soil stoichiometric characteristics had similar spatial patterns. The C content of plants and soils tended to decrease with increasing latitude, and the N and P contents and the N:P ratio tended to increase with increasing latitude. 2) The stoichiometric characteristics of the plant tissues also interacted with each other and showed synergistic trade-offs. Nutrient allocation in the eastern section of the Qilian Mountains was similar to that in the western section, while more N and P in the plant stems were allocated to maintain plant growth in the relatively arid western Sect. 3) The nutrient allocation strategies in the plant tissues were mainly regulated by soil and climate. CONCLUSIONS: Information on plant-soil stoichiometric characteristics along different gradients can help us better understand the nutrient patterns and dynamics of forest ecosystems under arid and semiarid conditions at a wide geographic scale from the perspective of plant nutrient partitioning.

Cyclic synthesis of lignin anthraquinone electrolytes for aqueous redox flow batteries.

Lignin, which is rich in phenolic hydroxyl/methoxy groups as redox active groups, is a potential electrolyte material for aqueous redox flow batteries (ARFBs). This work demonstrated to the synthesis of lignin-derived electrolytes via cyclization with 1,4-dihydroxyanthraquinone (1,4-DHAQ), in the absence of hazardous or noble metal catalysts in mild conditions (0 °C, 1 atm). The structure of lignin anthraquinone derivatives (LAQDs) cyclized in basis alkaline solution was experimentally determined. An exhaustive comparative study was conducted with respect to the electrochemical properties, charging-discharging tests and cycling performances. The initially volumetric capacitance, the capacity retention rate and coulombic efficiency of two LAQDs were determined to be 148.0 mAh.L-1, 89.3 % and 99.0 % for coniferaldehyde-anthraquinone derivative [LAQD(G)], and 132.1 mAh.L-1, 81.2 % and 99.0 % for sinusaldehyde-anthraquinone derivative [LAQD(S)], respectively. The theoretical value calculated by DFT is consistent with the actual value. Such LAQDs can be used as organic electrolyte materials, which can overcome poor chemical stability of anthraquinone, while improving the electrochemical activity of lignin-based electrolyte materials. This technology provides a pathway to prepare organic electrolyte for the development of environment friendly and better energy storage performance electrolytes for ARFBs.

Drought timing and severity affect radial growth of Picea crassifolia at different elevations in the western Qilian Mountains.

In the context of continued global climate change, the intensity and frequency of droughts have increased to varying degrees in many places. Due to the complexity of drought events, the mechanisms by which trees respond to drought are not well understood. In this study, we analyzed the growth trends of Qinghai spruce (Picea crassifolia) at different elevations in the western part of Qilian Mountains and the dynamic response to climate change. We also compared the differences in radial growth of trees at different elevations in response to drought events in the growing and non-growing seasons based on resistance (Rt), recovery (Rc), and resilience (Rs). The results showed that (1) trees at all three elevations were limited by drought stress and the lower the elevation the more sensitive the trees were to drought. (2) The response of middle- and low-elevation trees to the standardized precipitation evaporation index in June of that year was stable. (3) Growing season drought limits radial growth of trees more than non-growing season drought, and Rt is smaller and Rc is larger at low elevations. With increasing drought severity, trees at all three elevations exhibited a trend of decreasing Rt and Rs and increasing Rc. (4) There were significant differences in the growth trends of trees at the three elevations. Therefore, we should continuously pay attention to the dynamics of the forest ecosystem in the western part of Qilian Mountains and take improved measures to cope with the adverse effects of drought on Qinghai spruce.

Elevation affects the ecological stoichiometry of Qinghai spruce in the Qilian Mountains of northwest China.

Environmental heterogeneity in temperature, moisture, and soil fertility caused by elevation gradients can affect the trade-offs in the survival strategies of tree species. There is uncertainty about the allocation of resources to different tissues of trees in response to the elevation gradient with respect to carbon (C), nitrogen (N), and phosphorus (P). Here, the C, N, and P content of leaves, branches, trunks, and thick and fine roots of Picea crassifolia (Qinghai spruce) and their stoichiometric changes across three different elevations were investigated in the Qilian Mountains. We found that N:P of Qinghai spruce was <14 in all tissues at most elevations, indicating that Qinghai spruce was more susceptible to N limitation. Meanwhile, the N content and N:P of Qinghai spruce each were significantly negatively correlated with temperature (p < 0.05), and its P content was lower at high elevation. The contribution of soil-climate interactions on the elevation gradient to each tissue type was 34.02% (leaves), 16.84% (branches), 67.78% (trunks), 34.74% (thick roots), and 49.84% (fine roots), indicating that interacting climate and soil factors on the elevation gradient predominately drove the C, N, and P content and stoichiometry variation in each tissue type of Qinghai spruce trees. The results of this study clarify that the elevation gradient regulates the elemental content and resource allocation in Qinghai spruce, providing basic data and an important timely reference for future forest management in the regions where coniferous trees grows. These findings also help improve our understanding of elevational patterns of forest ecosystem stoichiometry in arid and semiarid regions.