Response of tree growth to drought variability in arid areas: Local hydroclimate and large-scale precipitation.

The impact of drought on terrestrial ecosystems is increasing, and the spatiotemporal heterogeneity of drought changes exacerbates the difficulty of determining ecosystem responses, especially in arid regions far from oceans. Tree rings have been widely used to understand how forest ecosystems respond to drought. However, the link between local hydroclimate variations related to tree rings and large-scale climate changes is not clear in the Qilian Mountains. Here, we used the tree ring width index to analyze the trend of Picea crassifolia growth and its relationship with climate in the middle Qilian Mountains. The results showed that the radial growth trend of Picea crassifolia is synchronized in the middle Qilian Mountains by calculating the Gleichläufigkeit index (GLK). Our analyses indicated that tree radial growth is positively correlated with drought during the growing season. Tree growth responds stably to drought (scPDSI and SPEI) and precipitation but unstably to temperature during 1950-2019. We further traced the meteorological factors that cause regional drought changes associated with radial growth. An increased total precipitation and decreased evaporation contribute to drought alleviation, favoring an increased tree radial growth. The increased total precipitation is mainly due to increased large-scale precipitation, which is related to water vapor transport changes. This study attempts to explore the influence of large-scale meteorology on regional drought change and its related tree radial growth response, which helps us to better understand the changes in forest ecosystems under climate change.

Measuring the cross-border spillover effects and telecoupling processes of ecosystem services in Western China.

Ecosystem services provide the basic elements for global economic development. In the context of the deepening global integration process, countries and regions are increasingly connected, resulting in a series of cross-country, cross-regional, multi-scale socio-economic-environmental impacts, these new situations and changes require a multi-site, two-way, and cross-temporal and spatial scale comprehensive study of "the relationship between ecosystem services and humans". Based on this, we apply a telecoupling synthesis framework to explore the socio-economic and eco-environmental interactions of ecosystem service spillover effects. Results show that (1) the spillover effect of ecosystem services in western China is significant. More than 66% of ecosystem services spillover to eastern China provinces, and more than 40% of ecosystem services spillover to countries in Southeast Asia, South Asia, and Central Asia, resulting in a total of 679 million people benefiting from the spillover effect. (2) There are also multiple telecoupling processes between the ecosystem service spillovers in the ecologically fragile areas in western China and the rest of the world. In combination with the scenario simulation of the InVEST model, the services such as water supply, soil retention, flood mitigation, and food supply have significant impacts on sustainable development and human well-being in Asia and even the world. (3) The positive feedback effect of telecoupling is critical to the protection of the ecological environment as well as the improvement of people's livelihood and well-being in Western China's ecologically fragile areas. Therefore, we propose strengthening ecological compensation cooperation between local governments and implementing compensatory transfer payments between upstream and downstream. Simultaneously, international cooperation must be strengthened, and an ecological compensation transfer mechanism with beneficiary countries must be established, while the cross-regional flow of ecosystem services must be maintained. This study provides an example for the "ecosystem services and human relations" in multiple places, two directions and across time and space scales, and also practical reference significance for China implementation of projects such as the "the Belt and Road" initiative and transnational and cross regional resource allocation.

Increasing forest carbon sinks in cold and arid northeastern Tibetan Plateau.

Arid forest lands account for 6 % of the world's forest area, but their carbon density and carbon storage capacity have rarely been assessed. Forest inventories provide estimates of forest stock and biomass carbon density, improve our understanding of the carbon cycle, and help us develop sustainable forest management policies in the face of climate change. Here, we carried out three forest inventories at five-year intervals from 2006 to 2016 in 104 permanent sample plots covering the Qinghai spruce (Picea crassifolia) distribution in the north slope of Qilian Mountains, northeastern Tibetan Plateau. Results shows that mean biomasses for Qinghai spruce were 133.80, 144.89, and 157.01 Mg ha-1 while biomass carbon densities were 65.52, 70.92, and 76.88 Mg C ha-1, in 2006, 2011, and 2016, respectively. This shows an increase in the Qinghai spruce carbon density of 17.34 % from 2006 to 2016. Both the precipitation and temperature play crucial roles on the increase of aboveground carbon density. The average carbon densities were different among forests with different ages and were higher for older forests. Our results show that the carbon sequestration rate for Qinghai spruce in the Qilian Mountains is significantly higher than the average rates of national forest parks in China, suggesting that this spruce forest has the potential to sequester a significant amount of carbon despite the general harsh growing conditions of cold and arid ecoregions. Our findings provide important insights that are helpful for the assessment of forest carbon for cold and arid lands.

A study of the proteomic expression in patients with complicated parapneumonic pleural effusion.

Introduction: The present study aimed to investigate the differences in the proteomic expression between uncomplicated parapneumonic pleural effusion (UPPE) and complicated parapneumonic pleural effusion (CPPE). Material and methods: There were 10 patients with UPPE and 10 patients with CPPE. These patients were combined due to the complication of pleural effusion and further divided into group A and group B. An LC-MS analysis was conducted with the extraction of high-abundance proteins, and proteins with 1.5-fold or higher difference multiples were identified as differential proteins. Then, gene ontology (GO) and KEGG analyses were conducted on the differential proteins between the groups. Results: Compared with the UPPE group, there were 38 upregulated proteins and 29 downregulated proteins in the CPPE group. The GO analysis revealed that the CPPE group had enhanced expressions in monosaccharide biosynthesis, glucose catabolism, fructose-6-phosphate glycolysis, glucose-6-phosphate glycolysis, and NADH regeneration as well as reduced expressions in fibrinogen complexes, protein polymerization, and coagulation. Moreover, the KEGG analysis showed that the CPPE group had enhanced expressions in amino acid synthesis, the HIF-1 signalling pathway, and glycolysis/glycoisogenesis and decreased expressions in platelet activation and complement activation. Conclusions: In pleural effusion in patients with CPPE, there are enhanced expressions of proteins concerning glucose and amino acid metabolism, NADH regeneration, and HIF-1 signalling pathways together with decreased expressions of proteins concerning protein polymerization, blood coagulation, platelet activation, and complement activation.

Understanding ecological civilization in China: From political context to science.

China's concept of "ecological civilization" can be understood as a new system of development and governance based on the perspective of political decision-making. Environmental management, ecological restoration, and green development are its primary principles-distinctly different from industrial and agricultural-oriented civilizations. In this paper, we evaluate the evolution of political connotations of the ecological civilization concept in China over the past 15 years through a textual analysis approach. Additionally, we systematically outline an ecological civilization indicator system and analyze its evolutionary process, applicable scales, and role in guiding the implementation of the ecological civilization concept. Eco-civilization demonstration sites and experiences are also discussed, followed by a review of academic research and policy-making responses. Finally, we propose different perspectives on the outlook for the future of ecological civilization development in China.

Influence of monsoon anomalies on intra-annual density fluctuations of Chinese pine in the Loess Plateau.

In the past few decades, the East Asian summer monsoon (EASM) has experienced an unprecedented weakening, exacerbating drought in northern China, especially in the monsoon margin area. Improving our understanding of monsoon variability will benefit agricultural production, ecological construction, and disaster management. Tree-ring is widely used as proxy data for extending the monsoon history. However, in the East Asian monsoon margin, the tree-ring width were mostly formed before the rainy season, thus may have limited ability to indicate the monsoon variability. Intra-annual density fluctuations (IADFs) can provide higher resolution information on tree growth as well as evidence of short-term climate events. Here, we used Chinese pine (Pinus tabuliformis Carr.) samples from the eastern edge of the Chinese Loess Plateau (CLP), where the climate is deeply affected by monsoon, to investigate the response of tree growth and IADFs frequency to climate variation. We show that tree-ring width and IADFs record significantly different climatic signals. The former was mainly affected by moisture conditions at the end of the previous growing season and the current spring. While the latter was common in years when severe droughts occurred in June and July, especially in June. This period coincides with the onset of the EASM, so we further analyzed the relationship between IADFs frequency and the rainy season. Both correlation analysis and the GAM model suggest that the frequent occurrence of IADFs may be related to the late start of the monsoon rainy season, meaning that we have found a new indicator in tree-ring records that can capture monsoon anomalies. Our results provide further insight into drought variation in the eastern CLP, which also implicates the Asian summer monsoon dynamic.

Nutrient allocation strategies of four conifers from semiarid to extremely arid environments.

Although the contents of limiting elements in plants, such as nitrogen (N) and phosphorus (P), have been widely studied from subtropical to humid-temperate zones, the strategies used by coniferous species to allocation N and P in arid and semiarid forests remain unclear. In this study, samples of 545 leaves, 194 twigs, and 78 fine roots were collected from four coniferous species (Pinus tabuliformis, Picea wilsonii, Juniperus przewalskii, and Picea crassifolia) of three genera (Pinus, Picea, and Juniperus) in the northeastern Tibetan Plateau, and the contents of C, N, and P were analyzed. Two key parameters, namely the allometric exponent and coefficient of variation, were calculated to illustrate the relative investment of plants to N and P uptake and plasticity (variation of N and P), respectively. The contents of N and P and the N:P ratios were the highest in leaves, but their plasticity was the lowest. This confirmed the hypothesis that the leaves of coniferous species have a high content of limiting nutrients and homeostasis. At the regional level, the allometric exponent of N and P in leaves was 0.68, 0.74 in twigs, and 0.78 in fine roots, which is consistent with the results on a global scale. Thus, this invariant allometric relationship suggests the existence of an important mechanism that constrains the allocation of plant nutrients across broad environmental gradients. However, the allocation strategies for N and P shifted with the species, climate, and soil nutrients. Namely: their preferred nutrient uptake was P when the trees had a better nutritional status (semiarid environments, mean annual precipitations (MAP) > 300 mm), but the investment of N was strengthened when the habitat conditions become more severe (extremely arid environments, MAP <100 mm). Thus, our results can provide a novel perspective to understand the strategies of plant nutrient uptake in arid and semiarid forests.

Effect of bronchofiberscopic lavage with budesonide suspension on refractory mycoplasma pneumoniae pneumonia.

Objectives: To investigate the clinical efficacy of budesonide suspension through bronchofiberscopic lavage in the treatment of refractory mycoplasma pneumoniae pneumonia.(RMPP). Methods: A total of 108 children with refractory mycoplasma pneumoniae pneumonia from June 2018 to October 2020 were randomly divided into two groups: the study group and the control group, with 54 cases in each group. Children in the control group were treated with anti-infective, antitussive, antipyretic routine symptomatic treatment and nebulization of budesonide suspension, while children in the study group were treated with bronchofiberscopic lavage with Budesonide suspension along with standard treatment as in control group. The clinical efficacy, changes in blood gas analysis indexes, levels of inflammatory mediators, time for improvement of clinical symptoms and the incidence of adverse reactions were compared between the two groups. Results: The efficacy of treatment in the study group was 85.19%, which was higher than 66.67% in the control group (P<0.05). The antipyretic time, antitussive time, lung rales disappearance time and length of hospital stay in the study group were shorter than those in the control group (P<0.05). Moreover, the levels of arterial oxygen partial pressure (PaO2) in the study group were higher than those in the control group, while the levels of partial pressure of carbon dioxide (PaCO2) and arterial oxygen saturation (SaO2) in the study group were lower than those in the control group (P<0.05). The levels of inflammatory mediators interleukin-6 (IL-6), interleukin-4 (IL-4), and interferon-γ (IFN-γ) in the study group were lower than those in the control group (P<0.05), and no significant difference was found in the comparison of the incidence of adverse reactions between the two groups (P>0.05). Conclusions: Budesonide suspension combined with bronchofiberscopic lavage with Budesonide suspension is a safe treatment regimen that can significantly improve the clinical outcome in children with RMPP. With such a combined treatment regimen, the clinical symptoms of children can be ameliorated, the ventilation function can be enhanced, and the level of inflammatory mediators will be reduced.

Research on the coordinated development of ecosystem services and well-being in agricultural and pastoral areas.

Payment for Ecosystem Services (PES) has been widely accepted as a policy tool for promoting ecological and social progress. However, PES development and implementation in traditional agricultural and pastoral areas are often more challenging than in other areas. The contradiction between ecological protection and people's livelihood development in traditional agricultural and pastoral areas is related to developing country's sustainable development strategy. Based on this, we evaluate the PES (ERCCP: the Ecological Relocation and Capital Compensation Program) program in Tianzhu County, as a case study to investigated the impact of ERCCP on the local natural and social ecosystems on a 20-year scale. The results of indicated that ERCCP has achieved "win-win" gains of restoring environment and promoting socioeconomic development: in the 10 years since ERCCP was implemented, the area of forest land and grassland increased significantly, increasing by 1135.6 ha and 919.62 ha, respectively. 57.5% of farmland was converted to grassland and 30.8% to forest, respectively. In addition, 92.2% and 7.5% of bare land were replaced by grassland and forest, respectively, indicating a gradual recovery of green land during this period. We also analyzed the effects of ERCCP on social systems, and found that the change of agro-pastoralists' attitude towards ERCCP promoted the transfer of labor force from the primary industry to the tertiary industry, accelerated the development of urbanization, and made the poor population completely out of poverty by 2020. In addition, we predict that the income level of households, the PES return on investment of local governments, and the value of regional ecosystem services will increase significantly after 2025. In this context, We establish a theoretical model to explain the win-win plan for the coordinated development of ecosystem services and regional well-being to explore the sustainability of PES and provided a typical case for the similar research area in the world, especially in the areas with the ecological fragility and poverty problems.

[Data-driven study of complex socio-economic-natural ecosystems: Scales, processes and decision linkages]. / 数据驱动的社会-经济-è‡ªç„¶å¤åˆç”Ÿæ€ç³»ç»Ÿç ”ç©¶:å°ºåº¦ã€è¿‡ç¨‹åŠå ¶å†³ç­–å ³è”.

The social-economic-natural system is a complex system for human survival and development, and the data-driven system research provides a new value-added orientation to enhance the cognition of the ecosystem. Under the new data context, the social-economic-natural complex system shows new features. The research object is gradually changing from a single element to a multi-factor coupling direction, which makes the data system more diversified, data sources more extensive, data expression more visualized. The research scale shows the characteristics of gradually expanding, and the research object would be more detailed. In the process of data identification, expression and visualization, it is therefore necessary to strengthen the coupling of time, space, structure, quantity and order, as well as to focus on the integration with decision making and local services. The future research of complex ecosystems in the new era should be carried out in terms of key scientific issues and supporting technologies, the role of scale and multi-factor coupling, as well as scientific and technological support for local and global governance. Under the continuous innovation of data, strengthening the cognition of multi-source data, long-term monitoring and time series still needs to be studied in depth. Carrying out data-driven analysis of complex ecosystems not only provides technical support for ecosystem services and sustainable development and enhances the long-term data sharing mechanism, but also provides more value support for realizing decision making and information dissemination.

[Effects of warming on radial growth of Picea crassifolia in the eastern Qilian Mountains, China]. / 升温对祁连山东部青海云杉径向生长的影响.

Tree-rings of Picea crassifolia from high (3000 m), middle (2750 m) and low (2500 m) altitudes were collected from the Xiying River basin in the eastern Qilian Mountains, with the standard chronology being established using dendrochronological methods. Results of the correlation analysis between tree-ring width index and temperature and precipitation during different periods showed that radial growth of P. crassifolia at different altitudes responded differently to climate warming in the eastern Qilian Mountains. Water and heat availability were the main limiting factors for the radial growth of P. crassifolia in the eastern part of Qilian Mountains. The growth limiting factors at different altitudes were generally the same. Before the prominent warming (1961-1986), radial growth of P. crassifolia at the three sampling altitudes was significantly negatively correlated with mean maximum temperature in July-August of the previous year and August of the current year, and significantly positively correlated with the relative humidity in June of the current year. After the prominent warming period (1986-2014), tree growth at high, middle, and low altitudes remained significantly negatively correlated with air temperature, changed from non-significantly negative to significantly positive correlation with relative humidity in February of the current year, and changed from significantly positive to non-significantly negative correlation with precipitation and relative humidity in June. Warming caused a slowing growth of P. crassifolia tree-ring at all altitudes, with the highest altitude being the most sensitive. Drought stress caused by climate warming might be the main reason for the changes of radial growth of P. crassifolia.

[Stem radial growth of Picea crassifolia in response to climatic factors in the western Qilian Mountains, China]. / ç¥è¿žå±±è¥¿éƒ¨é’æµ·äº‘æ‰å¾„å‘ç”Ÿé•¿å¯¹æ°”å€™å› å­çš„å“åº”.

The radial growth of eight individuals of Picea crassifolia and environmental factors were monitored by Dendrometer and automatic meteorological station in the western Qilian Mountains. The Gompertz function fitted results showed that the radial growth of P. crassifolia started on April 19, April 17, and April 10 in 2018, 2019 and 2020, respectively, and that the radial growth started when daily mean temperature exceeded 5.5 ℃. The radial growth of P. crassifolia ended on August 17, August 21, and July 19 in the three years, respectively. The ending time of radial growth was related to precipitation at the end of growing season. The radial growth of P. crassifolia was strongly inhibited by drought, and it had the strongest correlation with daily mean temperature (negative correlation) and daily precipitation (positive correlation) in July. The correlation of radial growth with the daily precipitation in the early growing season (May) showed significant inter-annual variation.

[Research progress on cambial activity of trees and the influencing factors]. / æ ‘æœ¨å½¢æˆå±‚æ´»åŠ¨åŠå ¶å½±å“å› ç´ ç ”ç©¶è¿›å±•.

Tree growth is the main way of carbon sequestration in forest ecosystems, which is influenced by climatic and non-climatic factors. The long-term location monitoring of cambial phenology and wood formation dynamics (xylogenesis) is an important method to clarify the responses of radial growth to climate change. Here, we reviewed studies on cambial phenology and xylogenesis by microcoring method. Firstly, we reviewed the effects of climatic factors on cambial phenology. The onset and cessation of xylogenesis were determined by temperature in cold and humid conditions. Temperature and water availability collectively modulated the onset of xylogenesis under dry conditions, and the later determined the end of xylogenesis. The radial increment was regulated by rate and duration of cell production, with the maximum of growth rate occurring around the summer solstice. Short-term N addition did not affect wood formation dynamics. Secondly, we reviewed the roles of biological factors in regulating xylogenesis. The onset of xylogenesis differred among species, ages, and inter-specific competition. Seasonal dynamics of non-structural carbohydrates were coupled with wood formation. Finally, we reviewed the response mechanisms of xylogenesis to the interaction of climatic and biological factors. In conclusion, we put forward problems in current studies and prospected future development to provide reference for further scientific research.

Climatic change in southern Kazakhstan since 1850 C.E. inferred from tree rings.

Although global warming is an indisputable fact, there is still uncertainty about how climate change will occur at regional levels. Kazakhstan is the largest landlocked country in the world. To best manage this country's limited water resources, socio-economic development and environmental protection, a solid understanding of regional climate change impacts is needed. In this study, tree-ring width and δ13C chronologies were established based on 99 tree-ring samples of Schrenk spruce (Picea schrenkiana Fisch. et Mey.) collected in Almaty, Kazakhstan. Climate response analysis between the tree-ring chronologies and climate data indicates that summer mean temperature is the strongest climate signal recorded by tree-ring δ13C. We reconstructed temperature change in southern Kazakhstan since 1850 C.E. using the tree-ring δ13Ccorr chronology. The results show that the temperatures in southern Kazakhstan have risen at a rate of about 0.27 °C per decade over the past 166 years. However, the rate has increased by as much as 0.44 °C per decade over the past 30 years. Analyses of temperature and precipitation data show that the climate has alternated between warm-dry and cold-humid periods over the past 166 years. The extreme droughts of 1879, 1917 and 1945 were caused by the combination of continuously high temperatures and reduced precipitation.

Variations in leaf traits of Juniperus przewalskii from an extremely arid and cold environment.

How leaf traits vary with environmental and climatic variables in cold and arid environments is an essential issue in environmental ecology. Here, we analyzed the variations in leaf nitrogen (N) and phosphorus (P) stoichiometry and leaf dry matter content (LDMC) in Qilian juniper (Juniperus przewalskii Kom.) growing in 14 environmentally different plots on the northeastern Tibetan Plateau. The results showed that the N and P concentrations, N:P ratio and LDMC of Qilian juniper were 10.89 mg.g-1, 1.04 mg.g-1, 10.80 and 483.06 mg.g-1, respectively. The spatial coefficients of the variations in leaf N and P stoichiometry were significantly higher than the seasonal ones, and the correlations of leaf N and P concentrations with spatial variables were stronger than their correlations with the season. During the growing season, only the leaf N concentration and N:P ratio significantly increased. Soil nutrients were highly positively significantly correlated with leaf P concentrations but negatively correlated with the N:P ratio and LDMC. However, leaf N concentrations showed no significant correlations with soil nutrients. We suggest that the effects of temperature on the N concentration and LDMC were stronger than the effects of drought, while those on the P concentration and N:P ratio were weaker. Drought reduced leaf N and P concentrations and increased the N:P ratio and LDMC. In the arid region, with an increasing mean annual temperature (MAT), leaf N concentration significantly decreased, and LDMC significantly increased. In the semi-arid region, as MAT increased, leaf N and P concentrations significantly increased and LDMC and the N:P ratio significantly decreased. These opposite results supported the growth rate hypothesis that plant N and P concentrations increase while the N:P ratio and LDMC decrease as the growth rate increases.

A Case of Massive Cerebral Arterial Air Embolism Induced by Artificial Pneumothorax and Its Analysis.

OBJECTIVE: This study aimed to investigate the characteristics of cerebral arterial air embolism. CLINICAL PRESENTATION AND INTERVENTION: The clinical data of a patient with cerebral arterial air embolism induced during artificial pneumothorax were retrospectively analyzed. The patient needed the induction of artificial pneumothorax for medical thoracoscopy but developed hemiplegia and disturbance of consciousness during the induction. Cerebral arterial air embolism was detected by head computed tomography. CONCLUSION: Artificial pneumothorax may induce cerebral arterial air embolism.

Cambial phenology in Juniperus przewalskii along different altitudinal gradients in a cold and arid region.

Knowing more precisely the cambial phenology and wood formation dynamics of trees can lead to a better understanding on how trees react to short-term changes in environmental conditions. Such an understanding could also shed light on the physiological foundation of climate-growth interactions at a regional scale. Although it has been documented that temperature is an important factor determining the cambial phenology in cold and humid climates, there is less agreement on the driver(s) that trigger the onset and end of wood formation in cold and arid climates. Here, the phenological traits of cambial activity and xylem formation were analyzed biweekly along an altitudinal transect ranging from 3580 to 3980 m above sea level, a transect that covers the distribution of Qilian juniper (Juniperus przewalskii Kom.) along a slope of the Tibetan Plateau. Cambial phenology and the duration and rate of wood formation were assessed from anatomical observations during the growing season of the developing xylem obtained from microcores collected from the stem of 10 trees total in 2012 (five at two altitudes each) and 25 trees (five at five altitudes each) in 2013. We found that the onset of wood formation was significantly correlated with altitude in 2013, with onset beginning 8.2 days earlier with every 100 m decrease in elevation. The change in onset with elevation corresponds to a change of 14.1 days °C-1 when adjusted for the monitored altitudinal lapse rate of -0.58 °C per 100 m. The duration of wood formation lasted from mid-May to mid-August, with the length of the 2013 growing season decreasing from 97 to 65 days from low to high elevation. Although the end of growing season appeared minimally related to altitude during both growing seasons, differences in end of wood production and wood formation between the two growing seasons were significant. It appears that summer drought conditions constricted the end of growing season across all elevations along our transect in 2013. Sensitivity analysis found xylem growth was positively correlated with rate and duration of wood production, with the former explaining most variability in growth. Our findings provide new data on the timing and duration of wood formation and help quantify the potential impacts of global warming on tree growth and productivity in cold and arid regions.

Tree growth response of Fokienia hodginsii to recent climate warming and drought in southwest China.

To date, few attempts have been made to assess the influence of climate change on forest ecosystems and on the relationship between tree growth and climate in humid areas of low latitudes. In this paper, we studied the response of tree growth and forest ecosystem to climate change by using Fokienia hodginsii tree-ring cores from the northern Yunnan-Guizhou Plateau, southwest of China. Tree growth correlates the highest (r = -0.64, p < 0.01) with mean temperature (July-September), but the coefficients were changing with time as revealed by a moving correlation analysis. Tree growth is significantly (p < 0.05) and positively correlated with January-April mean temperature from AD 1961-1987, while correlations with precipitation are insignificant. In contrast, from 1988 to 2014, tree growth correlated negatively with mean temperature of previous summer and positively with precipitation of previous August-September. This indicated that the limiting factors for tree growth have changed under different climate conditions. The meteorological data suggested that from 1961 to 1987 it was cold and wet in the study area and radial growth is limited by winter and spring temperatures. This restriction is weaker if the climate is appropriate in general. However, from 1988 to 2014, the combined effects of recent warming and decreasing precipitation have led to an increasing response of tree-ring width to drought. In addition, a large proportion of mature F. hodginsii mortality occurred from 2007 to 2013, which corresponds with a drastic reduction of radial growth (narrowest in recent 100 years). The recent drought, induced by decreasing precipitation and increasing temperature, may have passed the threshold which F. hodginsii could tolerate, causing tree growth reduction, tree growth-climate relationship change, as well as catastrophic tree mortality. All these changes may lead to further responses of the local ecosystem to climate change which should be highly regarded.

Difference in tree growth responses to climate at the upper treeline: Qilian Juniper in the Anyemaqen Mountains.

Three ring-width chronologies were developed from Qilian Juniper (Sabina przewalskii Kom.) at the upper treeline along a west-east gradient in the Anyemaqen Mountains. Most chronological statistics, except for mean sensitivity (MS), decreased from west to east. The first principal component (PC1) loadings indicated that stands in a similar climate condition were most important to the variability of radial growth. PC2 loadings decreased from west to east, suggesting the difference of tree-growth between eastern and western Anyemaqen Mountains. Correlations between standard chronologies and climatic factors revealed different climatic influences on radial growth along a west-east gradient in the study area. Temperature of warm season (July-August) was important to the radial growth at the upper treeline in the whole study area. Precipitation of current May was an important limiting factor of tree growth only in the western (drier) upper treeline, whereas precipitation of current September limited tree growth in the eastern (wetter) upper treeline. Response function analysis results showed that there were regional differences between tree growth and climatic factors in various sampling sites of the whole study area. Temperature and precipitation were the important factors influencing tree growth in western (drier) upper treeline. However, tree growth was greatly limited by temperature at the upper treeline in the middle area, and was more limited by precipitation than temperature in the eastern (wetter) upper treeline.