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Episodes of drought-induced decline in tree growth and mortality are becoming more frequent as a result of climate warming and enhanced water stress in semi-arid areas. However, the ecophysiological mechanisms underlying the impact of drought on tree growth remains unresolved. In this study, earlywood and latewood tree-ring growth, δ13C, and δ18O chronologies of Picea mongolica from 1900 to 2013 were developed to clarify the intra- and inter-annual tree-ring growth responses to increasingly frequent droughts. The results indicate that annual basal area increment residuals (BAIres), which removed tree age and size effects, have significantly decreased since 1960. However, the decreasing trend of earlywood BAIres was higher than that of latewood. Climate response analysis suggests that the dominant parameters for earlywood and latewood proxies (BAIres, δ13C and δ18O) were drought-related climate variables (Palmer drought severity index, temperature, relative humidity, and vapor pressure deficit). The most significant period of earlywood and latewood proxies’ responses to climate variables were focused on June–July and July–August, respectively. BAIres, and δ13C were significantly affected by temperature and moisture conditions, whereas δ18O was slightly affected. Decreasing stomatal conductance due to drought outweighed the influence of increasing CO2 on intrinsic water use efficiency (iWUE), and ultimately led to a decline in BAIres. Compared to latewood, the faster decreasing BAIres and smaller increasing iWUE of earlywood suggested trees were more vulnerable to water stress in the early growing season. Our study provides insights into the inter- and intra-annual mechanisms of tree-ring growth in semi-arid regions under rising CO2 and climate change. [ABSTRACT FROM AUTHOR]

Climate warming may induce growth decline in warm-temperate areas subjected to seasonal soil moisture deficit, whereas increasing atmospheric CO2 concentration (Ca) is expected to enhance tree growth. An accurate understanding of tree growth and physiological processes responding to climate warming and increasing Ca is critical. Here, we analyzed tree-ring stable carbon isotope and wood anatomical traits of Pinus tabuliformis from Qinling Mountains in China to understand how lumen diameter (LD) determining potential hydraulic conductivity and cell-wall thickness (CWT) determining carbon storage responded to climate and Ca. The effects of climate and Ca on intrinsic water-use efficiency (iWUE) were isolated, and iWUE values due to only-climate (iWUEClim) and only-CO2 effects (iWUECO2) were obtained. During a low-iWUE period, the influences of climate on earlywood (EW) LD and latewood (LW) CWT prevailed. During a high-iWUE period, CO2 fertilization promoted cell enlargement and carbon storage but this was counteracted by a negative influence of climate warming. The limiting direct effects of iWUEClim and indirect effects of climate on EW LD were greater than on LW CWT. P. tabuliformis in temperate forests will face a decline of growth and carbon fixation, but will produce embolism-resistant tracheids with narrow lumen responding to future hotter droughts. [ABSTRACT FROM AUTHOR]

In biomedical data mining, the gene dimension is often much larger than the sample size. To solve this problem, we need to use a feature selection algorithm to select feature gene subsets with a strong correlation with phenotype to ensure the accuracy of subsequent analysis. This paper presents a new three-stage hybrid feature gene selection method, that combines a variance filter, extremely randomized tree, and whale optimization algorithm. First, a variance filter is used to reduce the dimension of the feature gene space, and an extremely randomized tree is used to further reduce the feature gene set. Finally, the whale optimization algorithm is used to select the optimal feature gene subset. We evaluate the proposed method with three different classifiers in seven published gene expression profile datasets and compare it with other advanced feature selection algorithms. The results show that the proposed method has significant advantages in a variety of evaluation indicators. [ABSTRACT FROM AUTHOR]

Abundant evidence has indicated that the prognosis of cutaneous melanoma (CM) patients is highly complicated by the tumour immune microenvironment. We retrieved the clinical data and gene expression data of CM patients in The Cancer Genome Atlas (TCGA) database for modelling and validation analysis. Based on single-sample gene set enrichment analysis (ssGSEA) and consensus clustering analysis, CM patients were classified into three immune level groups, and the differences in the tumour immune microenvironment and clinical characteristics were evaluated. Seven immune-related CM prognostic molecules, including three mRNAs (SUCO, BTN3A1 and TBC1D2), three lncRNAs (HLA-DQB1-AS1, C9orf139 and C22orf34) and one miRNA (hsa-miR-17-5p), were screened by differential expression analysis, ceRNA network analysis, LASSO Cox regression analysis and univariate Cox regression analysis. Their biological functions were mainly concentrated in the phospholipid metabolic process, transcription regulator complex, protein serine/threonine kinase activity and MAPK signalling pathway. We established a novel prognostic model for CM integrating clinical variables and immune molecules that showed promising predictive performance demonstrated by receiver operating characteristic curves (AUC ≥ 0.74), providing a scientific basis for predicting the prognosis and improving the clinical outcomes of CM patients. [ABSTRACT FROM AUTHOR]

Inflammation is known to be involved in the progression of diabetic retinopathy. Follicular helper T cells (Tfh) play critical roles in the differentiation of long-live plasma cells and production of antibodies, whereas circulating CD4+CXCR5+ T cells may act as a counterpart to measure Tfh cell disorders. In this study, we investigated whether Tfh could be involved in the development of diabetic retinopathy (DR) by assessing circulating Tfh cells in peripheral blood. Data showed that serum levels of total IgG and IgA were both significantly increased in type 2 diabetes mellitus (T2DM) patients with proliferative diabetic retinopathy (PDR) than with non-PDR. Also, B cell activation and differentiation were both enhanced in T2DM patients with PDR. Little changes were detected in levels of Th1, Th2, and Th17 cells. As indicated by elevated serum levels and supernatant from cultured PBMC of IL-21, we found increased circulating Tfh cells in PDR patients with dysregulated subsets. This study suggests the involvement of circulating Tfh cells in DR and, in particular, the pathogenesis of PDR. [ABSTRACT FROM AUTHOR]

Drought-related forest growth declines are observed globally in main forest types, especially with repeatedly hot droughts. Therefore, quantifying forest resilience and identifying the factors driving resilience in response to extreme drought with the consideration of atmospheric CO2 fertilization is crucial for the accurate assessment of forest dynamics under current climate change, particularly for the widespread and climate-sensitive spruce forests in the arid Tianshan Mountains, China. Here, we explored the growth response of Schrenk spruce (Picea schrenkiana) to six extreme drought events since 1900, and investigated how tree resilience in pure stands is related to local drought intensity, cambial age (CA), and intrinsic water-use efficiency (iWUE). Specifically, we found that spruce trees had a mean resistance (Rt) value of less than 1, with iWUE contributing less to Rt variation. The results are in agreement with the drought-induced limitations on tree growth in response to increasing CO2, in spite of rising iWUE trends. However, increased iWUE has significant and positive impacts on the recovery (17%) and resilience (15%) of trees, suggesting that increased iWUE enhances the restoration of Schrenk spruce growth after extreme drought events. The growth resilience indices of Schrenk spruce showed that juvenile and adult trees exhibit different strategies to mitigate the drought influences. This study indicated that tree age, climate conditions, and variation in iWUE should be considered simultaneously in drought resilience evaluations to assess forest dynamics objectively in relation to climate change (i.e., drought) and propose appropriate forest management strategies. [ABSTRACT FROM AUTHOR]

The raspberry-like hollow SnO2-based (bare SnO2 and Pd-doped SnO2) nanostructures with different dominant crystal facets were prepared facilely using carbon nanospheres as templates via solvothermal method. Volatile organic compounds (VOCs) and ammonia (NH3) gas sensing performances of the hollow SnO2-based structures were studied systematically. The gas sensing performances were investigated in a temperature range of 150–315 °C. It was found that 285 °C was the optimum operating temperature for both the sensors. The SnO2 sensor showed excellent VOCs (1–100 ppm) sensing performances, with a fast response/recovery behavior (around 4 s/30 s) at 285 °C. While the Pd-SnO2 sensor displayed selective NH3 sensing characteristics at low concentrations of 1.5–12 ppm, interestingly, with a response/recovery time of about 4 s/80 s at 285 °C. Both the SnO2 and Pd-SnO2 sensors showed great repeatability for 8 response/recovery cycles, and very slight response recession for a long period. It was found that not only the morphology, the synergistic effect from the heterojunctions of doped Pd and SnO2, and the Pd catalysis, but also the crystal facets could modulate the sensing performance of metal oxides. [ABSTRACT FROM AUTHOR]

Studies on macrophage gene expression have historically focused on events leading to RNA polymerase II recruitment and transcription initiation, whereas the contribution of post-initiation steps to macrophage activation remains poorly understood. Here, we report that widespread promoter-proximal RNA polymerase II pausing in resting macrophages is marked by co-localization of the negative elongation factor (NELF) complex and facilitated by PU.1. Upon inflammatory stimulation, over 60% of activated transcriptome is regulated by polymerase pause-release and a transient genome-wide NELF dissociation from chromatin, unexpectedly, independent of CDK9, a presumed NELF kinase. Genetic disruption of NELF in macrophages enhanced transcription of AP-1-encoding Fos and Jun and, consequently, AP-1 targets including Il10. Augmented expression of IL-10, a critical anti-inflammatory cytokine, in turn, attenuated production of pro-inflammatory mediators and, ultimately, macrophage-mediated inflammation in vivo. Together, these findings establish a previously unappreciated role of NELF in constraining transcription of inflammation inhibitors thereby enabling inflammatory macrophage activation. Macrophage activation is integral to innate immunity and inflammation, and involves transcriptome remodeling leading to the rapid upregulation of pro- and anti-inflammatory effector genes. Here the authors show that the negative elongation factor (NELF) complex controls the transcription of anti-inflammatory genes through Pol II pause release. [ABSTRACT FROM AUTHOR]

In this study, we investigated the potential influence of central and eastern Pacific sea surface temperatures (SSTs) on the unstable relationship between earlywood δ18O and climatic factors in the southwestern China from 1902 to 2005. The results show that the strength of the climate signals recorded in the earlywood δ18O series has declined since the late 1970s. This reduction in signal strength may have been caused by the changes in the local hydroclimate, which is associated with the increasing SSTs in the central Pacific Ocean over recent decades. Alongside these increasing SSTs in the central Pacific, southwestern China has experienced more droughts, as well as more severe droughts through the late spring and early summer during the central Pacific (CP) El Niño years than during the eastern Pacific (EP) El Niño years in recent decades. This increased drought frequency may have weakened the response of earlywood δ18O to climate variables. [ABSTRACT FROM AUTHOR]

Drought occurrence and duration in central Asia are of important socioeconomic, ecological, and geophysical significance and have received increasing research attention in recent years. Understanding long-term drought trends and their driving forces require reliable records of past drought variability with broad spatial representativeness. Here, we compiled four tree-ring δ18O records from eastern central Asia (ECA) and composited them into a drought-sensitive proxy to explore regional ECA moisture variations over the past 301 years (1710-2010 CE). A robust regional standardized precipitation-evapotranspiration index (SPEI) reconstruction was established based on the tree-ring cellulose δ18O fractionation mechanism and statistically significant proxy-climate relationships. We identified prominent droughts in 1710-1770, 1810-1830, and the beginning of the twenty-first century, and a regime shift to a persistently wet period from the 1880s to 2000. Our reconstruction reveals the impact of drought and pluvial patterns on the decline of Zhungar Empire, and on historical agricultural and socio-economical activities, including increased migration into ECA during the 1770-1800 pluvial. Our findings also suggest that wet conditions in the twentieth century in ECA were related to a strengthening of the westerly circulation and thus shed light on large-scale atmospheric circulation dynamics in central Asia. [ABSTRACT FROM AUTHOR]

Precipitation changes such as more frequent drought and altered precipitation seasonality may impose substantial impacts on the structure and functioning of forest ecosystems. A better understanding of tree responses to precipitation changes can provide fundamental information for the conservation and management of forests under future climate regimes. We conducted a 2-year seasonal rainfall redistribution experiment to assess the responses of tree transpiration and growth to manipulated precipitation changes in a subtropical evergreen broad-leaved forest. Three precipitation treatments were administered including a drier dry season and wetter wet season treatment (DD), an extended dry season and wetter wet season treatment (ED), and an ambient control treatment, with the total amount of annual rainfall being kept the same among the three treatments. Our results showed that the DD and ED treatments reduced daily transpiration of Schima superba by 8-16 and 13-25%, respectively. The ED treatment also reduced the DBH increment of larger S. superba individuals. In contrast, neither treatment showed obvious effects on the transpiration and DBH increment of another dominant species Michelia macclurei. However, the transpiration of both species showed clear inter-annual differences between the 2 years with contrasting annual rainfall (2094 vs 1582 mm). S. superba had a lower transpiration-to-precipitation ratio (T/P) compared to M. macclurei and showed decreased sensitivities to total solar radiation and vapor pressure deficit under the DD and ED treatments. These results indicate the deep-rooted S. superba may be suppressed with a lower ability to obtain water and assimilate carbon compared to the shallow-rooted M. macclurei under the precipitation seasonality changes, which could potentially cause shifts in species dominance within the forest community. [ABSTRACT FROM AUTHOR]

Tree growth in the mid-latitudes of the northern hemisphere reveals significant inter-annual variation in carbon sequestration, and the variations have been widely attributed to climate change, especially to the recent rapid warming and increasing drought stress. However, the response of natural trees under the different regions that exist in the northeastern Qinghai-Tibetan Plateau remains unclear. Here, we use nine Qilian juniper ( Sabina przewalskii) tree-ring width and basal area increment (BAI) chronologies from the middle of the Qilian Mountains and the northeastern Qaidam Basin to quantify tree growth trends and their response to the recent rapid warming. The trees, growing at high and low elevations, exhibited a consistent pattern of inter-annual variations, with increasing synchronicity in their trends since 1950. Responses to several climate factors indicate that increasing temperature accelerated tree growth in the middle of the Qilian Mountains, but restricted tree growth in the northeastern Qaidam Basin. Moving-window correlation analyses demonstrate a clearly contrasting response to the temperature variations. Our findings suggest that growth of Qilian juniper in the middle of the Qilian Mountains will increase steadily in the future rapid warming, but may remain constant or even decrease in the northeastern Qaidam Basin. These contrasting responses to temperatures provide valuable information on forest dynamics in the critical mid-latitude regions that should be incorporated into predictions of future forest carbon cycling under global warming. [ABSTRACT FROM AUTHOR]

Pollution from urban centers and fossil fuel combustion can decrease forest growth and interfere with physiological processes. To evaluate whether tree growth and the carbon isotope ratio (δC) and nitrogen isotope ratio (δN) in tree rings can serve as proxies for air pollution, this study compared these indices for poplar ( Populus cathayana) growing at urban and suburban locations in Lanzhou, in northwestern China. Basal area increment values were much lower at the urban site than in the suburbs from 1985 to 2009, were negatively correlated with NO ( r = −0.56, p < 0.01) and SO ( r = −0.52, p < 0.05) emissions from 1990 to 2009, and increased abruptly after the Lanzhou urban steel factory closed. Urban tree-ring δC values were not significantly correlated with NO and SO concentrations, and did not differ significantly between the two sites, indicating that other environmental effects (such as precipitation) masked the pollution effects. Tree-ring δN values in the urban samples were much higher than the suburban values. Such differences may be attributable to uptake of N-enriched compounds caused by a higher urban N deposition rate. Tree growth is a promising tool for detecting ecophysiological responses of trees to both diffuse and point-source air pollution, but δC and δN in poplar were not sensitive to point-source air pollution in a heavily polluted environment. [ABSTRACT FROM AUTHOR]

Annual tree ring δO and δC chronologies from 1790 to 2008 were established using Tianshan spruce ( Picea schrenkiana) in the central Tianshan Mountains of northwestern China. Temperature has a positive effect on tree ring δO and δC in the study area, while precipitation and relative humidity have negative effects. The standardized precipitation-evapotranspiration index (SPEI) considered all of these effects and was significantly negatively correlated with tree ring δO and δC. We combined the tree ring δO and δC series to reconstruct the past 192 years of SPEI, which accounted for about 46 % of the total variance of SPEI from 1950 to 2006. The reconstruction showed good spatial agreement with gridded data in Palmer Drought Severity Index and precipitation and an inverse relationship with temperature. Our SPEI reconstruction reveals several wet and dry periods over the past 192 years and has good agreement with other drought records. Wavelet analysis showed quasi-periodic 10-, 20-, 30-, and 70-year fluctuations in the reconstruction. The 10-, 20-, and 30-year periodicities may reflect the potential influence of North Atlantic Oscillation (NAO). Overall, this study indicates that the SPEI is a potential drought index, and the winter NAO affects regional moisture conditions in the long term. [ABSTRACT FROM AUTHOR]

We measured the annual variation in the stable isotopes of oxygen (δO) and hydrogen (δD) in tree rings of Abies georgei on the Batang-Litang Plateau of western China. Although correlations between tree-ring δO and δD are relatively weak in semi-arid regions, we found a strong correlation between the δO and δD time series from 1755 to 2009 under the wetter environment. Tree-ring δO and δD time series are both significantly and negatively correlated with moisture conditions from June to August, including relative humidity and total precipitation, respectively, from 1960 to 2009. Considering the difference in low-frequency domain between the two isotopes, the relative humidity histories from June to August, reconstructed separately from the tree-ring δO and δD data with instrumental climate data, reveal a persistent drying trend since 1850s, especially since the early 1970s. There is an obvious offset of reconstructed relative humidity from tree-ring δO and δD in the period 1755-1820, despite the strong similarity in their 21-year moving averages. The decreased relative humidity since the 1850s may be associated with the thermal contrast between the sea surface temperature of the Indian Ocean and the Qinghai-Tibetan Plateau, which determines the strength of moisture transfer via the Indian summer monsoon. [ABSTRACT FROM AUTHOR]

Relative humidity is an important factor in water and water vapor feedback cycles. In this study, we established a 222-year annual tree-ring δO chronology for Siberian larch ( Larix sibirica Ldb.) from the Altay Mountains in northwestern China. Climate response analyses revealed that the relative humidity was the primary factor limiting tree-ring δO fractionation. Based on our analysis, tree-ring δO can be used to reconstruct the July-August relative humidity based on both a reasonable mechanism of tree-ring δO fractionation and a statistically significant regression model. We used this model to reconstruct variations in the July-August relative humidity, and the model explained 47.4 % of the total variation in the measured relative humidity data from 1961 to 2011. The relative humidity in the study area increased from 1900 to the 1990s and decreased thereafter. Two regime-shift dry periods were detected during the study period (one from 1817 to 1830 and the other from 2004 to 2011). [ABSTRACT FROM AUTHOR]

High-resolution tree-ring δ18O chronologies covering the last millennium, although scarce, are essential in understanding patterns of climatic changes in the northeastern region of the Qinghai-Tibetan Plateau. For this study, a tree-ring δ18O chronology with a temporal resolution of 3-years was developed from the long-lived Qilian juniper ( Sabina przewalskii Kom.), extending back in time to AD 991. This long δ18O chronology was significantly correlated with the yearly δ18O in tree rings during the common period from 1800 to 2006, and was an effective proxy for relative humidity during the growing season. A low-frequency moisture pattern signified the occurrence of a slight drought during the Medieval Climate Anomaly, a marked occurrence of a wet period during the Little Ice Age, and a trend in increasing moisture levels, although lower than average, alongside the Twentieth Century warming trend. Comparisons to other hydroclimatic reconstructions indicate that this tree-ring δ18O chronology serves as a reliable paleo-humidity proxy for the Qaidam Basin as well as documenting details of past humidity levels in the region. [ABSTRACT FROM AUTHOR]

We investigated the physiological responses of Tibetan juniper ( Sabina tibetica) to changes in the atmospheric CO concentration ( C) and climate on the northeastern Tibetan Plateau based on annual tree-ring δC values since 1850. Intrinsic water-use efficiency ( iWUE) increased, and the internal to ambient CO ratio ( C /C) showed no significant trend from 1895 to 1974 in the study region, indicating an active response to changing C. The long-term trends in iWUE in the naturally occurring trees were mainly caused by the anthropogenic increase in C. However, from 1975 to 2002, iWUE increased rapidly at the study site (by 12.4 % compared with the overall mean from 1850 to 2002), which is greater than the expected increase due only to an active response to C. Our analysis showed that decreased water availability caused by greater evaporation due to decreased precipitation and a warming growth environment from 1975 to 2002 may have reduced stomatal conductance, leading to a higher iWUE. The warming climate and increased C accounted for 83.6 % of the variance in iWUE of Tibetan juniper on the northeastern Tibetan Plateau from 1975 to 2002. [ABSTRACT FROM AUTHOR]