No abstract

A review of Holocene climatic variations in different parts of China shows that they were asynchronous. Proxy data from ice cores, pollen, loess, lacustrine sediments, and changes of sea and lake levels demonstrate that many warm and cold oscillations have occurred in China during the Holocene, including a most important climatic event known as the “Holocene optimum,” a milder and wetter period, and that the duration and amplitude of the optimum period, as well as its start and end times, differed in different parts of China. Uplift of the Tibetan plateau over the past millions of years led to the development of the monsoon climate and to complex atmospheric circulation over continental China during the Holocene. As a result, the Holocene optimum began and terminated earlier in high-altitude regions of western China than at lower elevations in eastern China, and the amplitude of the variations was lower in the east. This suggests that the western higher-altitude areas were more sensitive to climatic change than were the eastern lower-altitude areas. Holocene climatic records in the Dunde and Guliya ice cores do not correspond. Inverse δ18O variations between the two cores indicate that the effects of climate and atmospheric processes on the stable isotopes at the two sites differed. The correlation between the isotopic composition of carbonates in lake deposits in western China and climatic variations is similar to that in the ice cores. The climatic resolution in ice cores and lake sediments is higher than that in other media. The lack of precise correspondence of climatic records constructed on the basis of proxy data from different parts of China is a result of the different locations and elevations of the sampling sites, the different resolutions of the source material, and the varied climatic conditions within China. Further work is needed to confirm both the conclusions and the inferences presented here.

Summary1. In facilitative interactions, the beneficiary feedback effect (BFE) has been defined as the effect of beneficiary species (facilitated species) on their benefactor. BFEs have been shown to be dependent on environmental conditions and the composition of the beneficiary community. In alpine cushion systems, BFEs are more negative with more abundant, diverse and phylogenetically aggregated communities of beneficiary species. 2. We tested the hypothesis that the functional composition of the beneficiary communities correlates with the direction and strength of BFE received by alpine cushion benefactors and specifically that a more negative BFE would occur with increasing density of graminoids and a more positive BFE would occur with increasing density of forbs and legumes. Additionally, we predicted that the negative BFE of graminoids would increase with increasing summer aridity. 3. We used a data base of alpine cushion communities from 30 sites throughout the world to assess the overall relationship between the composition of beneficiary communities and the total flower density of cushion benefactors, and its variation with increasing drought. Additionally, in order to assess more precisely the role of the functional composition of the beneficiary communities on BFE in a very dry site with cushion benefactors exhibiting contrasting functional compositions of beneficiary communities, we also designed a field study in the Qilian Shan mountain range (China). At this site with a highly continental climate, we compared the number of flowers and fruits of different phenotypes of the alpine cushion species Thylacospermum caespitosum hosting numerous graminoids, numerous forbs or very few beneficiary species. 4. In the intercontinental study, we found a negative relationship between graminoids and cushion benefactor flower density but no effect of other functional groups. The negative BFE of graminoids increased with increasing summer drought. In the dry Qilian Shan range, we found both a negative effect of graminoids on total flower density and a positive effect of forbs on flower density and fruit set. 5. Our study indicates that the context dependence of BFE may be partially explained by the composition of beneficiary communities and in particular the negative effect of graminoids.

A juniper (Juniperus przewalskii Kom) tree-ring width chronology has been developed from the westernmost forest of the Qilian Mountains. Our analyses demonstrate both temperature and precipitation have significant effects on tree growth and that both should be considered in climate reconstruction. Thus a regional drought history (A.D. 1855-2001) is reconstructed by calibrating with a linear interpolation through four Palmer Drought Severity Index (PDSI) grid values nearest the sampling site. Our reconstruction extends the drought history of this area and also reveals that the most severe drought occurred in the 1920s. In the context of the drought history of western China, this extreme drought between 1925-1931 is consistent over a large surrounding region of Northwestern China. Multi-taper spectral analysis reveals the existence of significant 40-to 46-year, 29-year, and 2.1-to 3-year periods of variability. Overall, our study provides reliable information for the research of past drought variability in the Qilian Mountains, Northwestern China.

Background/ObjectiveThe prevalence of type 2 diabetes is increasing rapidly around the world. Work-related stress is thought to be a major risk factor for type 2 diabetes; however, this association has not been widely studied, and the findings that have been reported are inconsistent. Therefore, we conducted a meta-analysis of prospective cohort studies to explore the association between work-related stress and risk for type 2 diabetes.MethodsA systematic literature search and manual search limited to articles published in English were performed to select the prospective cohort studies evaluated the association between work-related stress and risk for type 2 diabetes up to September 2014 from four electronic databases including PubMed, EMBASE, the Cochrane Library and Web of Science. A random-effects model was used to estimate the overall risk.ResultsNo significant association was found between work-related stress and risk for type 2 diabetes based on meta-analysis of seven prospective cohort studies involving 214,086 participants and 5,511 cases (job demands: relative risk 0.94 [95% confidence interval 0.72–1.23]; decision latitude: relative risk 1.16 [0.85–1.58]; job strain: relative risk 1.12 [.0.95–1.32]). However, an association between work-related stress and risk for type 2 diabetes was observed in women (job strain: relative risk 1.22 [1.01–1.46]) (P = 0.04). A sensitivity analysis conducted by excluding one study in each turn yielded similar results. No publication bias was detected with a funnel plot despite the limited number of studies included in the analysis.ConclusionsThe results of this meta-analysis did not confirm a direct association between work-related stress and risk for type 2 diabetes. In subgroup analyses we found job strain was a risk factor for type 2 diabetes in women.

Linaridin is a small class of peptide natural products belonging to the ribosomally synthesized and post-translationally modified peptides (RiPPs) superfamily. By an extensive genome-wide survey of linaridin biosynthetic genes, we show that this class of natural products is widespread in nature and possesses vast structural diversity. The linaridin precursor peptides are relatively conserved in the N-termini but have diverse sequences in the core region, which appear to have coevolved with the biosynthetic enzymes. Using the prototypic linaridin cypemycin as a model, we have explored the structure-activity relationships involved in precursor peptide maturation and generated a diverse set of novel cypemycin variants, among which the T2S variant exhibits enhanced activity against Micrococcus luteus. Our results reveal valuable insights into linaridin biosynthesis and highlight the potential to explore this class of natural products by genome mining and by biosynthetic engineering studies.

Permafrost degradation may induce soil carbon (C) loss, critical for global C cycling, and be mediated by microbes. Despite larger C stored within the active layer of permafrost regions, which are more affected by warming, and the critical roles of Qinghai-Tibet Plateau in C cycling, most previous studies focused on the permafrost layer and in high-latitude areas. We demonstrate in situ that permafrost degradation alters the diversity and potentially decreases the stability of active layer microbial communities. These changes are associated with soil C loss and potentially a positive C feedback. This study provides insights into microbial-mediated mechanisms responsible for C loss within the active layer in degraded permafrost, aiding in the modeling of C emission under future scenarios.

Climatic data, ice core records, the tree ring index, and recorded glacier variations have been used to reconstruct a history of climatic and glacial changes in the monsoonal temperate glacier region of southwestern China during the last 400 years. The region's temperature has increased in a fluctuating manner during the twentieth century after two cold stages of the Little Ice Age (seventeenth to nineteenth centuries), with a corresponding retreat of most of the glaciers, against a background of global warming. Retreat rates accelerated after the 1980s. The few advancing glaciers that did exist have started to retreat in recent years. The amount, trend, and amplitude of variation of precipitation have differed in different parts of the region. The Dasuopu ice core, from the western part of the region, shows a decreasing trend in precipitation, the converse of the trend in temperature. In the eastern part of the region, however, a rising trend of rainfall has accompanied increasing temperatures as a result of the variable atmospheric circulations from different sources. The southwest monsoon, the principal controlling factor in the Chinese monsoonal temperate glacier region, can be classified into the Indian monsoon and the Bengal monsoon. The former passes across the Indian Peninsula from the Arabian Sea and transports vapor for precipitation in the western part of the monsoonal temperate glacier region. The Bengal monsoon, originating in the Bay of Bengal, is the major source of precipitation in the eastern part of the region. The eastern part is also influenced by the southeast monsoon arriving from the western Pacific, and the western part is affected in winter by the southern branch of the westerly circulation. This complex atmospheric situation results in differing patterns of precipitation in the western and eastern zones. Although it is clear that both temperature and precipitation affect the glaciers, further work is needed to confirm which of these is the major factor influencing present glacier change.