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Grassland caterpillars (Lepidoptera: Lymantriinae: Gynaephora) are the most damaging pests to alpine meadows in the Qinghai–Tibetan Plateau (QTP). Here, we conducted extensive sampling from 39 geographic populations covering almost the entire distribution of the eight QTP Gynaephora (Hübner) species to investigate phylogeographic patterns and speciation based on two mitochondrial genes (COI and ND5). A total of 40 haplotypes were detected in the 39 populations, with >70% of all haplotypes not shared between populations. The monophyletic QTP Gynaephora migrated from non‐QTP regions during the Pliocene, corresponding to the uplift of the QTP, suggesting a mode of transport into the QTP. Among the eight QTP Gynaephora species described by morphological characteristics, two species (G. alpherakii and G. menyuanensis) were recovered as monophyletic groups (Clades B and C), while the remaining six formed two monophyletic clades: Clade A (G. qinghaiensis, G. jiuzhiensis, and G. qumalaiensis) and Clade D (G. aureata, G. ruoergensis, and G. minora). These results suggested that the number of the QTP Gynaephora species may be overestimated and further studies based on both morphological and nuclear gene data are needed. Genetic differentiation and speciation of the QTP Gynaephora were likely driven by the QTP uplifts and associated climate fluctuations during the Pleistocene, indicated by divergence time estimation, suggesting that isolation and subsequent divergence was the dominant mode of speciation. The Sanjiangyuan region (i.e., Clade A, characterized by high genetic diversity) may have been a glacial refugium of the QTP Gynaephora, as supported by analyses of gene flow and biogeography. High levels of genetic diversity were found in QTP Gynaephora, without population expansion, which may explain the high‐altitude adaptation and outbreaks of grassland caterpillars in alpine meadows of the QTP. This study provides the largest phylogeographic analysis of QTP Gynaephora and improves our understanding of the diversity and speciation of QTP insects. [ABSTRACT FROM AUTHOR]

Atmospheric aerosol in the Tibetan Plateau (TP) and its surroundings has attracted significant scientific interest in recent decades due to its notable impacts on regional climatic and cryospheric changes, ecological and environmental security, and the hydrological cycle. However, our understanding of the atmospheric aerosol in this remote region is highly limited by the scarcity of available datasets owing to the extremely harsh natural conditions. This challenge has been mitigated in recent decades by establishing field observatories at typical sites within the TP and its surroundings. A continuous project initiated in 2015 aims to explore the properties and sources of atmospheric aerosols, as well as their regional differences, through multiple short-term intensive observations obtained across this vast region utilizing a suite of high-time-resolution online instruments. This paper presents a systematic and hourly scale dataset of aerosol physicochemical and optical properties at eight sites across the TP and its surroundings that is derived from the project. It includes size-resolved chemical compositions of submicron aerosols, high-resolution mass spectra and sources of organic aerosols, size distributions of particle number concentrations, particle light-scattering and light-absorption coefficients, particle light absorptions attributed to different carbonaceous substances including black carbon and brown carbon, and number concentrations of cloud condensation nuclei. In brief, atmospheric aerosols in these remote sites were all well mixed and highly aged, reflecting their dominant regional transport sources. However, the southern TP region exhibited high contributions of carbonaceous organic aerosols, neutralized bulk submicron aerosols, and a relatively high light-absorption capacity, whereas in the northern TP region, secondary inorganic species were the main contributors to the overall acidic submicron aerosols. Beyond providing insights into the regional differences in aerosol sources and properties across the TP and its surroundings, the datasets will also benefit simulations of aerosol radiative forcing and evaluations of interactions among different Earth system components in numerical models for this region. The datasets are accessible through the National Cryosphere Desert Data Center, Chinese Academy of Sciences (10.12072/ncdc.NIEER.db2200.2022; Xu, 2022). [ABSTRACT FROM AUTHOR]

This study investigated the relationship between residence altitude and serum folate levels in healthy Tibetans living on the Tibetan Plateau. Participants were selected from those who underwent physical examinations at our health center between November 2019 and February 2020. Demographic characteristics and medical histories were collected, and fasting blood was tested for serum folate and other hematological indicators. The relationship between altitude and serum folate levels was analyzed using a multivariable linear regression model. Serum folate levels were associated with altitude (β = − 0.44; 95% confidence interval [CI] − 0.71; − 0.16), hemoglobin (β = − 0.01; 95% CI − 0.03; − 0.00), red blood cells (β = − 0.72; 95% CI − 1.18; − 0.27), hematocrit (β = − 0.07; 95% CI − 0.12; − 0.02), high-density lipoprotein cholesterol (β = 2.67; 95% CI 1.35; 3.98), and sex (β = 0.68; 95% CI 0.12; 1.23). Multivariate linear regression analysis revealed that altitude was negatively associated with serum folate levels. After adjusting for confounding factors, serum folate levels decreased by 0.33 ng/mL per each 500-m increase in altitude (β = − 0.33; 95% CI − 0.6; − 0.05; P = 0.022). Altitude was negatively associated with serum folate levels in Tibetan adults. The relationship between altitude and folate levels should be further explored in populations of different races and disease states. Further large-scale prospective studies should illustrate the causality of this relationship. [ABSTRACT FROM AUTHOR]

Rock engineering in the Tibetan Plateau is usually suffered severe freeze-thaw (F-T) deterioration, triggering numerous geotechnical engineering disasters. As the essential triggering factor of F-T damage, the frost heave pressure (FHP) in rocks should be quantitatively described and predicted. In this study, a novel theoretical model is established and validated to estimate the critical entire evolution process of FHP in fractured rocks subjected to repeated F-T deterioration, in which the influence of fracture geometric configuration, rock mechanical properties and F-T conditions are comprehensively considered. Besides, given the obvious five-stage manner of FHP evolution, the combination effect of different dominant mechanisms in different stages is theoretically addressed. During freezing, after a silence stage induced by temperature above freezing point of water, volumetric expansion and frost-heave cracking separately controls the generation and reduction stages of FHP, and the solutions are obtained based on elastic mechanics and Griffith energy balance theory, respectively. During thawing, ice segregation dominates the second-arising stage of FHP that is quantitatively described via segregation potential and water migration velocity, and then the FHP enters the dissipation stage owing to complete melting of fracture ice. In addition, a decay coefficient is introduced to estimate the influence of F-T cycle number on FHP, and a piecewise FHP model is finally constructed for fractured rocks subjected to repeated F-T deterioration. To validate our new model, a total of 12 F-T cycle tests with real-time FHP monitoring are conducted on granite and sandstone specimens considering three typical influencing factors, i.e., fracture width, rock types and freezing temperatures. A rational consistency is identified between the theoretical and testing results in terms of the FHP evolution curves and the peak FHPs in rock fracture, demonstrating the generalizability and robustness of our proposed model. • Established a theoretical model to predict entire evolution of FHP in fractured rocks. • Considered different dominant mechanisms in different evolution stages of FHP. • Reflected influences of fracture geometry, rock mechanical properties and F-T conditions. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) has received wide scientific concern in recent decades owing to its important impacts on regional climatic and cryospheric changes, hydrological cycles, and environments. However, our understanding of the spatial distribution of the chemical and optical properties of aerosols is still limited based on prior single‐site observations. In this study, aerosol light absorptions from black carbon (BC) and brown carbon (BrC) were explored and compared among three remote TP sites, including Qomolangma Station (QOMS) on the southern TP, Nam Co Station (NamCo) on the central TP, and Waliguan Observatory on the northeastern TP. Although the aerosol mass concentration at QOMS was less than half of that at Waliguan, the light absorption coefficient of aerosols at QOMS was nearly 5 times higher than that at Waliguan, mainly as a result of more light‐absorbing carbonaceous aerosols on the southern TP due to long‐range transported biomass burning emissions. Specifically, BC dominated aerosol light absorption at all wavelengths, whereas BrC contributed ∼30% of the light absorption at 370 nm at QOMS and ∼20% at Waliguan and NamCo. A major contributor to BrC light absorption at QOMS was biomass burning‐related organic aerosols apportioned from aerosol mass spectrometry measurements. Understanding the significant regional differences in aerosol light absorption properties on the TP is useful for evaluating the regional climatic and environmental effects and validating the model results on aerosol radiative forcing. Plain Language Summary: Brown carbon (BrC) is a group of organic compounds that preferentially absorbs solar light at short wavelengths and has raised wide scientific concerns. However, understanding the physicochemical and optical properties of BrC is still limited, especially in remote regions. Combining two online instruments and adopting a novel approach, our study focuses on the absorption properties of BrC on the Tibetan Plateau (TP), which should be considered carefully in future climate models for evaluating the radiant energy budget and potential impacts on climatic and cryospheric changes over the TP. Key Points: The aerosol light absorption coefficient in the southern region of the Tibetan Plateau (TP) was much higher than that in the northeastern TPBrown carbon contributed significantly to light absorption in the southern TP and was mainly related to biomass burning emissions [ABSTRACT FROM AUTHOR]

The decreasing trend in diurnal temperature range (DTR) since the 1950s has been widely observed in many regions of the world, including the Tibetan Plateau (TP). However, scarce instrumental records on the TP before the 1950s limit the understanding of DTR variation on a longer timescale, and its internal forcing mechanisms remain unclear. Here, we present two regional records of May–June DTR since 1753 reconstructed from tree rings on the northeastern TP (NETP) and southeastern TP (SETP), respectively. The decreasing trend in DTR in the second half of the twentieth century also occurred in the time earlier than the 1950s, indicating that the reduction in DTR is not unique to global warming. Spatially, both the instrumental and reconstructed DTR show different modes on the NETP and SETP. Composite analysis and superposed epoch analysis reveal the linkage between El Niño‐Southern Oscillation (ENSO) and the DTR on the SETP. La Niña (El Niño) winters are generally followed by the stronger (weaker) early Indian summer monsoon so that may lead to the decrease (increase) in May–June DTR. The positive correlation between Niño 3.4 index and the DTR on the SETP over the past two and a half centuries is accompanied by a stable response of the decreased DTR to La Niña events. These results suggest that ENSO is a crucial driver for the DTR variation on the SETP through oceanic‐atmospheric modulation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The faults in the Anninghe-Zemuhe-Daliangshan fault system are mechanically coupled and interact with each other over various timescales. • The fault interactions and mechanical coupling between faults can cause regional earthquake clusters. • The model seismicity, seismic moment release rates, and slip rates on the Anninghe-Zemuhe fault and Daliangshan fault are interdependent and complementary. • The change in mechanical strength of the Daliangshan fault can influence seismicity and slip rates on itself and other faults in this region. The mechanical coupling and interactions between faults over various timescales, and their relationships with regional seismicity have not been clarified. In order to study these problems, we built a three-dimensional viscoelastoplastic finite element model to simulate stress evolution, long-term fault slip rates, and regional seismicity in the Anninghe-Zemuhe-Daliangshan fault system. The fault system consists of two parallel faults, the Anninghe-Zemuhe fault and Daliangshan fault, and is a main boundary between Sichuan-Yunnan block and South China block in southeastern Tibetan Plateau. By analyzing the model results, we investigated mechanical coupling and fault interactions in the fault system, the characteristics of seismicity, and the relationship between them over timescales of earthquake cycles. The results showed that mechanical coupling or fault interaction in a fault system is an important factor to cause earthquake clusters. The model results and observation data showed that seismicity and seismic moment release rates on the Anninghe-Zemuhe fault and Daliangshan fault are interdependent: active seismicity or high seismic moment release rate on one fault is usually accompanied by relatively quiescent seismicity or low seismic moment release rate on the other fault. We observed that the two faults collectively accommodate crustal relative motion and their slip rates are complementary. We also found that the development and maturity of Daliangshan fault in the future can increase its own seismicity and slip rate, but decrease those on the Anninghe-Zemuhe fault. This study reveals mechanical coupling and fault interactions over various timescales and their impact on regional seismicity in the Anninghe-Zemuhe-Daliangshan fault system. [ABSTRACT FROM AUTHOR]

Grassland caterpillars (Lepidoptera: Lymantriinae: Gynaephora ) are the most important pests in alpine meadows of the Tibetan Plateau (TP) and have well adapted to high-altitude environments. To further understand the evolutionary history and their adaptation to the TP, we newly determined seven complete TP Gynaephora mitogenomes. Compared to single genes, whole mitogenomes provided the best phylogenetic signals and obtained robust results, supporting the monophyly of the TP Gynaephora species and a phylogeny of Arctiinae + (Aganainae + Lymantriinae). Incongruent phylogenetic signals were found among single mitochondrial genes, none of which recovered the same phylogeny as the whole mitogenome. We identified six best-performing single genes using Shimodaira-Hasegawa tests and found that the combinations of rrnS and either cox1 or cox3 generated the same phylogeny as the whole mitogenome, indicating the phylogenetic potential of these three genes for future evolutionary studies of Gynaephora . The TP Gynaephora species were estimated to radiate on the TP during the Pliocene and Quaternary, supporting an association of the diversification and speciation of the TP Gynaephora species with the TP uplifts and associated climate changes during this time. Selection analyses revealed accelerated evolutionary rates of the mitochondrial protein-coding genes in the TP Gynaephora species, suggesting that they accumulated more nonsynonymous substitutions that may benefit their adaptation to high altitudes. Furthermore, signals of positive selection were detected in nad5 of two Gynaephora species with the highest altitude-distributions, indicating that this gene may contribute to Gynaephora ’s adaptation to divergent altitudes. This study adds to the understanding of the TP Gynaephora evolutionary relationships and suggests a link between mitogenome evolution and ecological adaptation to high-altitude environments in grassland caterpillars. [ABSTRACT FROM AUTHOR]

Recent studies have revealed a significant influx of anthropogenic aerosol from South Asia to the Himalayas and Tibetan Plateau (TP) during pre-monsoon period. In order to characterize the chemical composition, sources, and transport processes of aerosol in this area, we carried out a field study during June 2015 by deploying a suite of online instruments including an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-AMS) and a multi-angle absorption photometer (MAAP) at Nam Co station (90°57' E, 30°46' N; 4730ma.s.l.) at the central of the TP. The measurements were made at a period when the transition from premonsoon to monsoon occurred. The average ambient mass concentration of submicron particulate matter (PM1/ over the whole campaign was ~2.0 μgm-3, with organics accounting for 68 %, followed by sulfate (15 %), black carbon (8 %), ammonium (7 %), and nitrate (2 %). Relatively higher aerosol mass concentration episodes were observed during the pre-monsoon period, whereas persistently low aerosol concentrations were observed during the monsoon period. However, the chemical composition of aerosol during the higher aerosol concentration episodes in the pre-monsoon season was on a case-by-case basis, depending on the prevailing meteorological conditions and air mass transport routes. Most of the chemical species exhibited significant diurnal variations with higher values occurring during afternoon and lower values during early morning, whereas nitrate peaked during early morning in association with higher relative humidity and lower air temperature. Organic aerosol (OA), with an oxygen-to-carbon ratio (O / C) of 0.94, was more oxidized during the pre-monsoon period than during monsoon (average O/C ratio of 0.72), and an average O/C was 0.88 over the entire campaign period, suggesting overall highly oxygenated aerosol in the central TP. Positive matrix factorization of the high-resolution mass spectra of OA identified two oxygenated organic aerosol (OOA) factors: a less oxidized OOA (LO-OOA) and a more oxidized OOA (MO-OOA). The MO-OOA dominated during the pre-monsoon period, whereas LO-OOA dominated during monsoon. The sensitivity of air mass transport during pre-monsoon with synoptic process was also evaluated with a 3-D chemical transport model. [ABSTRACT FROM AUTHOR]

Brown carbon (BrC) has recently received much attention because of its light absorption features. The chemical compositions, optical properties, and sources of fine aerosol at a high-elevation mountain observatory (4730 m a.s.l.) in the central Tibetan Plateau were measured between 31 May and 1 July 2015. A low flow-rate sampler was used to collect 24-h average fine particulate matter (PM) filter samples. Water-soluble ions, organic carbon (OC), elemental carbon, water-soluble organic carbon (WSOC), and light absorption by water-soluble BrC were determined for 26 filter samples. The mean (± 1σ) OC and WSOC concentrations were 0.76 ± 0.43 and 0.39 ± 0.15 μgC/m, respectively, and the mean WSOC/OC mass ratio was 0.59 ± 0.22. The OC and WSOC concentrations were relatively higher (0.59-1.80 and 0.33-0.83 μgC/m, respectively) during the pre-monsoon period (2-13 June) and were relatively lower (0.27-0.77 and 0.12-0.50 μgC/m, respectively) during the monsoon period (14 June to 1 July), probably because of wet scavenging of aerosols during long-range transport and the presence of cleaner marine air masses during the monsoon period. The absorption spectra of PM water extracts smoothly increase from visible range to ultraviolet range. The absorption Ångström exponent, which describes the wavelength dependence of water-soluble BrC, was 2.74-10.61 (mean 6.19 ± 1.70), and its value was similar in the pre-monsoon period (6.57 ± 0.56) to that in the monsoon period (5.91 ± 2.14). The water-soluble BrC mass absorption efficiency, 0.38 ± 0.16 m/(g C), was much lower than those observed in most urban areas but similar to those in other remote sites. Absorption coefficient at 365 nm, typically used as a proxy for water-soluble BrC, correlated well with the WSOC concentration ( R = 0.57), K concentration ( R = 0.75), and organic aerosol biomass burning markers characterized by an Aerodyne aerosol mass spectrometer (CHO + CHO , R = 0.60). It can be inferred that biomass burning was an important source of water-soluble BrC in the study area combined with air mass back trajectory analysis using the NOAA HYSPLIT as well as MODIS data of fire dots and aerosol optical depths. The water-soluble BrC to BC light absorption (at 365 nm) coefficient ratios were 9-27%. [ABSTRACT FROM AUTHOR]

It is generally expected that inter-annual changes in radial growth among trees would be similar to the increase in altitude due to the limitation of increasingly harsher climatic factors. Here, we examine whether this pattern exists in alpine forests on the southeastern Tibetan Plateau. Increment cores were collected from mature trees at the lower, middle and upper limits of balfour spruce (Picea likiangensis var. balfouriana (Rehd. et Wils.) Hillier ex Slsvin) forests at the Buze and Yela Mountains in Basu County, Changdu Prefecture of Tibet, China. The treeline elevations are 4320 m and 4510 m a.s.l. for Buze and Yela, respectively. Tree-ring widths were measured, crossdated, and detrended to obtain a sequence of ring-width indices for each individual sample. Annual growth rate, climate sensitivity, growth-climate relationships, and growth synchrony among trees were calculated and compared across altitudes. In Buze Mountain, the annual growth rate of trees has no significant difference across altitudes. The mean sensitivity of trees is lower at the treelines than at lower elevations. Tree growth has stronger correlation with winter temperature at upper elevations than at lower elevations, has significant correlation with moisture, not temperature, in the growing season, and the growth response to moisture is lower at the treeline than at lower elevations. The correlation among individual tree-ring sequences is lower at the treeline than at sites at lower elevation. In Yela Mountain, the characterisitics of annual growth rate, mean sensitivity, tree growth-climate relationships, and inter-serial correlation are similar to those in Buze, but their differences along altitudinal gradients are less significant as those in Buze. Our data do not support the general expectation of growth convergence among individuals with increasing altitude. We conclude that individual heterogeneity and microhabitat diversity are important features for treeline trees that may dampen the growth synchrony in trees. The results obtained in this study expand our knowledge about the pattern of forest growth along altitudinal gradients in high-elevation regions and demonstrate the importance of checking the growth of tree individuals before analyzing the average signal. [ABSTRACT FROM AUTHOR]

Above-average climate warming occurred during the 20th century in high altitude regions, and alpine treelines are believed to be an early indicator to respond to these warming-related changes. However, empirical investigations on treeline dynamics showed diverse results. The main objectives of this study are: (1) to investigate if treeline position shifted and if tree recruitment changed along with climate warming, and (2) to test if adult trees have “nursing effect” on tree establishment at treelines. We investigated two Balfour spruce ( Picea balfouriana Rehd. et Wils.) treelines in Chang Niang (CNT) and Dang Dui (DDT), Dingqing county, Changdu prefecture, eastern Tibet. At each treeline site, three replicate plots with a size 30 m × 50 m were established. The coordinates of each tree within the plots were recorded and the age of each tree was identified by dendrochronological method. The changes in treeline position and tree recruitment were examined from spatially fine-scale distribution of trees and their age structure. The spatial patterns of individual trees were analyzed to infer the neighborhood effects. Results indicate that plots CNT2, CNT3, DDT1 and DDT2 showed stable treeline position during the last century, whereas plots CNT1 and DDT3 showed treeline advancing movement. Tree recruitments in all the six plots were enhanced during the 20th century, with two peaks occurring in the 1890–1910s and the 1950–1990s. Seedlings and saplings showed a general clustered distribution in all the six plots. The diverse pattern of treeline movement and episodic regeneration suggest that the treeline activity is not merely a result of climate change. “Nursing effects” from adult trees may play an important role in shaping the treeline activities on the eastern Tibetan Plateau. Our findings reveal diverse patterns in treeline dynamics at a local scale and highlight the importance of incorporating biotic interactions into species distribution modeling approaches. [ABSTRACT FROM AUTHOR]

Understanding the processes that influence the structure of biotic communities is one of the major ecological topics, and both stochastic and deterministic processes are expected to be at work simultaneously in most communities. Here, we investigated the vertical distribution patterns of bacterial communities in a 10-m-long soil core taken within permafrost of the Qinghai-Tibet Plateau. To get a better understanding of the forces that govern these patterns, we examined the diversity and structure of bacterial communities, and the change in community composition along the vertical distance (spatial turnover) from both taxonomic and phylogenetic perspectives. Measures of taxonomic and phylogenetic beta diversity revealed that bacterial community composition changed continuously along the soil core, and showed a vertical distance-decay relationship. Multiple stepwise regression analysis suggested that bacterial alpha diversity and phylogenetic structure were strongly correlated with soil conductivity and pH but weakly correlated with depth. There was evidence that deterministic and stochastic processes collectively drived bacterial vertically-structured pattern. Bacterial communities in five soil horizons (two originated from the active layer and three from permafrost) of the permafrost core were phylogenetically random, indicator of stochastic processes. However, we found a stronger effect of deterministic processes related to soil pH, conductivity, and organic carbon content that were structuring the bacterial communities. We therefore conclude that the vertical distribution of bacterial communities was governed primarily by deterministic ecological selection, although stochastic processes were also at work. Furthermore, the strong impact of environmental conditions (for example, soil physicochemical parameters and seasonal freeze-thaw cycles) on these communities underlines the sensitivity of permafrost microorganisms to climate change and potentially subsequent permafrost thaw. [ABSTRACT FROM AUTHOR]

The coupling problem of freeze-thaw (F-T) treatment and cyclic loading is extremely prominent for rock engineering in Tibetan Plateau, which has triggered many serious geotechnical engineering disasters. It is thus essential to systematically characterize the fatigue mechanism of rocks exposed to F-T treatment and cyclic loading. In this study, a series of cyclic uniaxial compression tests are conducted on sandstone subjected to 0, 10, 20, 30, 40 and 50 artificial F-T cycles to investigate the influence of F-T treatment on the fatigue mechanical properties of sandstone, regarding the fatigue deformation characteristics, energy evolution and coupled F-T-fatigue damage. Our testing results indicate that sandstone specimens exposed to higher F-T cycles are featured by larger irreversible strain and faster damage accumulation, leading to higher fatigue damage variable and lower fatigue life. By virtue of the digital image correlation (DIC) technique and scanning electron microscope (SEM), the progressive fatigue fracture process and the microscopic morphologies of fracture surfaces of the F-T treated sandstone specimens are revealed. During the cyclic loading process, the strain field in specimens uniformly distributes initially, and then it localizes continually with increasing cyclic number, triggering the eventual fatigue fracture. With increasing F-T cycles, the fatigue fracture of sandstone is more ductile and progressive. Moreover, the hidden linkage between microscopic fracture mechanism and macroscopic mechanical properties is further analyzed based on the test results. In addition, the microscopic fracture mechanism of F-T treated sandstone under cyclic loading and monotonic loading is also compared and discussed: the primary micro-mechanism causing the fatigue fracture of sandstone is the inter-granular (IG) fracture, while the micro-mechanism triggering the monotonic failure is the trans-granular (TG) fracture. • Investigated the influence of F-T treatment on fatigue mechanical properties of sandstone under cyclic uniaxial compression. • Revealed the progressive fracture process and microscopic morphologies of F-T treated sandstone under cyclic loading. • Analyzed the hidden linkage between micro-fracture mechanism and macro-mechanical properties of F-T treated sandstone. [ABSTRACT FROM AUTHOR]

Climate on the Tibetan Plateau is often considered sensitive to global changes, yet the degree of sensitivity in different spaces and seasons prior to instrumental records is not clear. In this paper, we studied tree-ring maximum latewood density (MXD) to examine the late-summer (August–September) temperature variation over the past two and half centuries on the eastern Tibetan Plateau. The MXD regional chronology was established from 109 tree-ring samples of Balfour spruce [ Picea likiangensis var. balfouriana (Rehd. et Wils.)] at four high elevation sites. The chronology exhibited a high correlation ( r = 0.82, n = 56, p < 0.001) with the mean August–September temperature. Using the tree-ring data, we reconstructed the late-summer temperature for the period A.D. 1765–2009. The reconstruction accounted for 71.4% of the variance in instrumental temperature in the period 1954–2009. The reconstructed temperature did not show a warming trend in the past 250 years, suggesting a unique characteristic of late-summer temperature variability in the study region of the Tibetan Plateau. Our tree-ring data are useful for further understanding of the plateau's thermal condition in late summer and its role in regulating southward retreat of the Southwest Asian monsoon. [ABSTRACT FROM AUTHOR]

While a vast number of studies have addressed the prokaryotic diversity in permafrost, characterized by subzero temperatures, low water activity, and extremely low rates of nutrient and metabolite transfer, fungal patterns have received surprisingly limited attention. Here, the fungal diversity and community structure were investigated by culture-dependent technique combined with cloning-restriction fragment length polymorphism (RFLP) analysis of sediments in a 10-m-long permafrost core from the Qinghai-Tibet Plateau of China. A total of 62 fungal phylotypes related to 10 distinct classes representing three phyla were recovered from 5031 clones generated in 13 environmental gene libraries. A large proportion of the phylotypes (25/62) that were distantly related to described fungal species appeared to be novel diversity. Ascomycota was the predominant group of fungi, with respect to both clone and phylotype number. Our results suggested there was the existence of cosmopolitan psychrophilic or psychrotolerant fungi in permafrost sediments, the community composition of fungi varied with increasing depth, while these communities largely distributed according to core layers. [ABSTRACT FROM AUTHOR]

Abstract: Solar activity is one of the most important driving forces of the global climate and environment change. However, little is known about how this force is influencing the earth''s climate system due to short solar activity records. A tree-ring chronology of Abies georgei var. smithii at Sygera Mountain in southeast Tibet was developed and used to investigate solar activity signals by spectral, wavelet and cross-wavelet analyses. The results showed that fluctuations in tree-ring data coincided well with variations in sunspot numbers. Periodicities of 5.3–5.1, 11.2–11.1, 20.5, 73, and 204.1 years may be related to solar activity of the second harmonic of the Schwabe, Schwabe, Hale, Gleissberg, and Suess cycles. The cross-wavelet analysis between tree-ring data and sunspot numbers indicated that the cross power around the 11-year solar cycle is more significant during periods of high solar activity than low solar activity, and the significant 22-year solar cycle is also found. Cross-correlation analysis between these two series showed a significant relationship with a time lag of about 13 years and a non-stationary phase relationship. We therefore propose that solar activity modulated climatic conditions and tree growth by influencing surface temperature through variations in radiation energy and monsoonal precipitation on the Tibetan Plateau. [Copyright &y& Elsevier]

Abstract: Two new Juniper tree-ring-width (TRW) chronologies spanning more than 500 years were developed in the Yellow River source area, North Eastern Qinghai-Tibetan Plateau (NE-QTP). For the two studied sites, located approximately 50km apart, split correlation and coherence analysis reveal unstable tree-growth responses to local moisture availability. While significant correlations are obtained with April–June local precipitation, Palmer Drought Severity Index (PDSI) and river flow from 1948/1954 to 1998 and from 1948/1954 to 1970s, these correlations vanish for the time period 1970s-1998. The local instrumental climate data (precipitation, PDSI and river flow) exhibit opposite correlations with large scale modes of variability (El Niño Southern Oscillation, ENSO, and Pacific Decadal Oscillation, PDO) before and after the 1977 PDO shift. One tree-ring chronology is coherent and anti-phased with instrumental ENSO/PDO indices at 5.2-year frequency. On the longer time span, this TRW chronology is compared with PDO reconstructed from historical Chinese data. This comparison also exhibits unstable multi-decadal relationships, notably in the mid 19th century. Altogether, the comparison between our two chronologies, local instrumental climate records, and ENSO/PDO indices suggest a cautious use of local TRW records for paleoclimate reconstructions. Further studies are needed to explore both the spatial coherency of tree-ring records and the temporal stability of their response to local and large scale climate variability. [ABSTRACT FROM AUTHOR]

• Juniper trees recover faster in dry than in wet conditions on the Tibetan Plateau. • Growth differences in individual trees are crucial for assessment of recovery time. • Long-term adaption of trees to dry conditions may improve the capacity of recovery. The recovery time of trees after extreme events may vary over space and among individuals, affecting the accuracy of predicting forest vulnerability to climate change. However, it remains unclear how different regional moisture conditions modulate the recovery time of trees in the long term. Here, we address this problem by examining 747 juniper trees at 24 sites on the Tibetan Plateau (TP). Tree-growth recovery time after extreme events was defined when reduced tree-ring indices returned to one, and site-level recovery time was assessed by calculating the time required to reach two levels of recovery, that is, 50% and 90% of trees recovered. We found that, in general, 50% of trees have recovered within three years following extreme events in the past two centuries; it took approximately 16 years for 90% of trees to recover. The recovery time for juniper trees increased from the northeastern TP to the southern TP and showed a significant positive correlation with the local latitudinal gradient of moisture conditions, particularly for the timespan at which 90% of trees recovered. Our study demonstrates that within certain moisture conditions, juniper trees on the TP recover faster after extreme events in dryer rather than wetter conditions, suggesting that juniper trees long established in dry conditions may have developed a greater ability to adapt to extremes than those in wet conditions. These findings highlight the importance of considering different performances of individuals in evaluating recovery time. In addition, the long-term influence of moisture conditions on tree recovery should be considered in the future when assessing the vulnerability of this high-elevation forest ecosystem. [ABSTRACT FROM AUTHOR]

• Trees at mid-latitudes of their distribution show greater sensitivity to drought. • Water deficit mainly controls tree resistance and spatial sensitivity to drought. • At wetter sites, higher drought frequency trains tree memory response to drought. • At drier sites, higher drought frequency causes substantial damage to junipers. The resistance of forests to extreme climatic events such as drought shapes their sensitivity to future extreme events in space and time. To a large extent, the ability of trees to learn from prior droughts explains how trees adjust their sensitivity to water deficit. We use tree-ring width data collected from 1565 juniper trees (Juniperus prezwalskii and Juniperus tibetica) across 57 sites on the Tibetan Plateau to model tree resistance to water deficit and to map drought sensitivity across the species' distribution. We test the effect of both the frequency and severity of drought on the drought memory of trees. We find that trees at mid-latitudes and in the northwestern part of the juniper distribution range exhibit higher drought sensitivity. Water deficit is the main factor controlling tree resistance and thus affects spatial sensitivity to drought. At wetter sites, higher drought frequency enhances tree adaptability through ecological memory, thereby promoting tree resistance and decreasing tree sensitivity to extreme drought events. At drier sites, higher drought frequency causes junipers' growth decline that is not beneficial for tolerance to extreme drought events. Regional drought conditions and the frequency of pre-droughts affect tree resistance and sensitivity to extreme drought events. This explains the spatial pattern of drought risk for juniper forests on the Tibetan Plateau, and helps us to better understand the vulnerability of this high-elevation forest ecosystem. Such information is important for maintaining forest health and informing the sustainable development of the Tibetan Plateau under a changing climate. [ABSTRACT FROM AUTHOR]

We sequenced and annotated the complete mitochondrial genome (mitogenome) of Gynaephora menyuanensis (Lepidoptera: Lymantriidae), which is a major pest in alpine meadows and endemic to the Qinghai-Tibetan Plateau. This mitogenome is 15,770 bp in length with an A+T content of 81.48%, and contains 37 typical animal mitochondrial genes that are arranged in the same order as that of other lepidopteran species. All protein-coding genes (PCGs) start with a typical ATN codon, with the exception of cox1, which begins with CGA. Eleven PCGs stop with termination codon TAA, whereas cox2 and nad4 have single T as the incomplete stop codon. All of the 22 transfer RNA genes present the typical clover leaf secondary structure. The A+T-rich region is located between rrnS and trnM with a length of 449 bp, and contains a 19 bp poly-T stretch as found in other lepidopteran mitogenomes. This is the second completely sequenced mitogenome from the family Lymantriidae of Lepidoptera, providing important molecular information to phylogenetic and population genetic researches. [ABSTRACT FROM AUTHOR]

Abstract: We explore the potential of tree-ring cellulose δ 18O and δ 13C records for reconstructing climate variability in the southeast Tibetan Plateau. Our sampling strategy was designed to investigate intra and inter-tree variability, and the effects of the age of tree on δ 18O variation. We show that intra-tree δ 13C and δ 18O variability is negligible, and inter-tree coherence is sufficient to build robust tree-ring δ 18O or δ 13C chronologies based on only four trees. There is no evidence of an age effect regarding δ 18O, in contrast with tree-ring width. In our warm and moist sampling site, young tree δ 13C is not clearly correlated with monthly mean meteorological data. Tree-ring δ 18O appears significantly anti-correlated with summer precipitation amount, regional cloud cover, and relative humidity. Simulations conducted with the ORCHIDEE land surface model confirm the observed contribution of relative humidity to tree cellulose δ 18O, and explain the weak correlation of δ 13C with climate by the non-linear integration linked with photosynthesis. Altogether, the tree-ring cellulose δ 18O is shown to be a promising proxy to reconstruct regional summer moisture variability prior to the instrumental period. [Copyright &y& Elsevier]