CO2 fertilization contributed more than half of the observed forest biomass increase in northern extra-tropical land.

The existence of a large-biomass carbon (C) sink in Northern Hemisphere extra-tropical ecosystems (NHee) is well-established, but the relative contribution of different potential drivers remains highly uncertain. Here we isolated the historical role of carbon dioxide (CO2 ) fertilization by integrating estimates from 24 CO2 -enrichment experiments, an ensemble of 10 dynamic global vegetation models (DGVMs) and two observation-based biomass datasets. Application of the emergent constraint technique revealed that DGVMs underestimated the historical response of plant biomass to increasing [CO2 ] in forests ( ß Forest Mod ) but overestimated the response in grasslands ( ß Grass Mod ) since the 1850s. Combining the constrained ß Forest Mod (0.86 ± 0.28 kg C m-2 [100 ppm]-1 ) with observed forest biomass changes derived from inventories and satellites, we identified that CO2 fertilization alone accounted for more than half (54 ± 18% and 64 ± 21%, respectively) of the increase in biomass C storage since the 1990s. Our results indicate that CO2 fertilization dominated the forest biomass C sink over the past decades, and provide an essential step toward better understanding the key role of forests in land-based policies for mitigating climate change.

Global vegetation biomass production efficiency constrained by models and observations.

Plants use only a fraction of their photosynthetically derived carbon for biomass production (BP). The biomass production efficiency (BPE), defined as the ratio of BP to photosynthesis, and its variation across and within vegetation types is poorly understood, which hinders our capacity to accurately estimate carbon turnover times and carbon sinks. Here, we present a new global estimation of BPE obtained by combining field measurements from 113 sites with 14 carbon cycle models. Our best estimate of global BPE is 0.41 ± 0.05, excluding cropland. The largest BPE is found in boreal forests (0.48 ± 0.06) and the lowest in tropical forests (0.40 ± 0.04). Carbon cycle models overestimate BPE, although models with carbon-nitrogen interactions tend to be more realistic. Using observation-based estimates of global photosynthesis, we quantify the global BP of non-cropland ecosystems of 41 ± 6 Pg C/year. This flux is less than net primary production as it does not contain carbon allocated to symbionts, used for exudates or volatile carbon compound emissions to the atmosphere. Our study reveals a positive bias of 24 ± 11% in the model-estimated BP (10 of 14 models). When correcting models for this bias while leaving modeled carbon turnover times unchanged, we found that the global ecosystem carbon storage change during the last century is decreased by 67% (or 58 Pg C).

Elevated CO2 does not stimulate carbon sink in a semi-arid grassland.

Elevated CO2 is widely accepted to enhance terrestrial carbon sink, especially in arid and semi-arid regions. However, great uncertainties exist for the CO2 fertilisation effects, particularly when its interactions with other global change factors are considered. A four-factor (CO2 , temperature, precipitation and nitrogen) experiment revealed that elevated CO2 did not affect either gross ecosystem productivity or ecosystem respiration, and consequently resulted in no changes of net ecosystem productivity in a semi-arid grassland despite whether temperature, precipitation and nitrogen were elevated or not. The observations could be primarily attributable to the offset of ecosystem carbon uptake by enhanced soil carbon release under CO2 enrichment. Our findings indicate that arid and semi-arid ecosystems may not be sensitive to CO2 enrichment as previously expected and highlight the urgent need to incorporate this mechanism into most IPCC carbon-cycle models for convincing projection of terrestrial carbon sink and its feedback to climate change.

Fetuin-B Links Nonalcoholic Fatty Liver Disease to Chronic Kidney Disease in Obese Chinese Adults: A Cross-Sectional Study.

BACKGROUND: There is no evidence available on the association of Fetuin-B with chronic kidney disease (CKD), and mechanisms linking nonalcoholic fatty liver disease (NAFLD) to CKD are not fully understood. We aimed to explore the independent associations and potential mechanisms of Fetuin-B and NAFLD with CKD. METHODS: A cross-sectional study of 1,072 Chinese adults who underwent serum Fetuin-B test and hepatic ultrasonography scanning was conducted in Xiamen, China. CKD was defined as estimated glomerular filtration rate < 60 mL/min/1.73 m2 and/or the presence of albuminuria. RESULTS: Subjects with CKD showed significantly higher prevalence of NAFLD (69.5 vs. 57.2%, p < 0.001) and serum Fetuin-B levels (4.32 ± 1.45 vs. 4.05 ± 1.36 µg/mL, p = 0.007) than their controls. Increased serum Fetuin-B was also significantly associated with increased levels of fasting insulin and homeostasis model assessment - insulin resistance (both p values < 0.05). NAFLD and higher serum Fetuin-B were significantly associated with increased risk of CKD, and the unadjusted ORs (95% CIs) were 1.701 (1.256-2.303, p = 0.001) and 1.213 (1.053-1.399, p = 0.008, per SD increase of Fetuin-B), respectively. With adjustment for potential confounding factors, including metabolic/insulin resistance syndrome, NAFLD but not serum Fetuin-B was still significantly associated with increased risk of CKD, and the adjusted ORs (95% CIs) were 1.820 (1.327-2.496, p < 0.001) and 1.116 (0.959-1.298, p = 0.153, per SD increase of Fetuin-B), respectively. CONCLUSIONS: Fetuin-B might link NAFLD to CKD via inducing insulin resistance, and NAFLD contributes independently to the pathogenesis of CKD via multiple mechanisms besides of metabolic/insulin resistance syndrome.

Fetuin-B links nonalcoholic fatty liver disease to type 2 diabetes via inducing insulin resistance: Association and path analyses.

OBJECTIVE: Laboratory models suggested that Fetuin-B impaired insulin action in myotubes and hepatocytes and caused glucose intolerance in mice. We aimed to explore the independent associations and pathways among serum Fetuin-B, nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2D). METHODS: A cross-sectional study of 1318 obese adults who underwent serum Fetuin-B test and hepatic ultrasonography scanning was conducted in Xiamen, China. Multivariable logistic regression was used to calculate adjusted odds ratio (OR) and 95% confidence intervals (CI) of serum Fetuin-B level and NAFLD for T2D in different models with adjustment for potential confounders. Structural equation modeling (SEM) was used to examine the paths among NAFLD, serum Fetuin-B, metabolic/insulin resistance syndrome and T2D. RESULTS: Subjects with T2D or NAFLD showed significantly increased serum Fetuin-B levels compared to their controls (4.25 ±â€¯1.35 vs. 4.08 ±â€¯1.38 µg/ml for diabetes; and 4.26 ±â€¯1.41 vs. 4.07 ±â€¯1.33 µg/ml for NAFLD; both p-values < 0.05). NAFLD and higher serum Fetuin-B were significantly associated with higher risk of T2D with adjustment for sociodemographic and lifestyle habits; and the adjusted ORs (95%CIs) were 2.90 (2.17-3.87, p < 0.001) and 1.16 (1.01-1.32, p = 0.032), respectively. With further adjustment for metabolic/insulin resistance syndrome (BMI, systolic and diastolic BP, triglyceride, total cholesterol, HDL- and LDL-cholesterol, HOMA-IR and serum uric acid), NAFLD but not serum Fetuin-B was significantly associated with increased risk of T2D (ORs (95%CIs): 1.58 (1.12-2.21, p = 0.009) and 1.07 (0.92-1.23, p = 0.384), respectively). A one pathway model by using SEM fitted well (χ2 = 497.92, p < 0.001; CFI = 0.965; TLI = 0.926; and RMSEA = 0.097) and showed that NAFLD increased serum Fetuin-B and elevated Fetuin-B increased fasting insulin level, which in turn induced insulin resistance and T2D. Besides, NAFLD increased the risk of T2D directly in addition to its indirect effects of inducing metabolic/insulin resistance syndrome which in turn increased the risk of T2D. CONCLUSIONS: Fetuin-B links NAFLD to T2D via inducing insulin resistance, and NAFLD contributes to the pathogenesis of T2D via multiple mechanisms.

Simulating the onset of spring vegetation growth across the Northern Hemisphere.

Changes in the spring onset of vegetation growth in response to climate change can profoundly impact climate-biosphere interactions. Thus, robust simulation of spring onset is essential to accurately predict ecosystem responses and feedback to ongoing climate change. To date, the ability of vegetation phenology models to reproduce spatiotemporal patterns of spring onset at larger scales has not been thoroughly investigated. In this study, we took advantage of phenology observations via remote sensing to calibrate and evaluated six models, including both one-phase (considering only forcing temperatures) and two-phase (involving forcing, chilling, and photoperiod) models across the Northern Hemisphere between 1982 and 2012. Overall, we found that the model that integrated the photoperiod effect performed best at capturing spatiotemporal patterns of spring phenology in boreal and temperate forests. By contrast, all of the models performed poorly in simulating the onset of growth in grasslands. These results suggest that the photoperiod plays a role in controlling the onset of growth in most Northern Hemisphere forests, whereas other environmental factors (e.g., precipitation) should be considered when simulating the onset of growth in grasslands. We also found that the one-phase model performed as well as the two-phase models in boreal forests, which implies that the chilling requirement is probably fulfilled across most of the boreal zone. Conversely, two-phase models performed better in temperate forests than the one-phase model, suggesting that photoperiod and chilling play important roles in these temperate forests. Our results highlight the significance of including chilling and photoperiod effects in models of the spring onset of forest growth at large scales, and indicate that the consideration of additional drivers may be required for grasslands.

Delayed autumn phenology in the Northern Hemisphere is related to change in both climate and spring phenology.

The timing of the end of the vegetation growing season (EOS) plays a key role in terrestrial ecosystem carbon and nutrient cycles. Autumn phenology is, however, still poorly understood, and previous studies generally focused on few species or were very limited in scale. In this study, we applied four methods to extract EOS dates from NDVI records between 1982 and 2011 for the Northern Hemisphere, and determined the temporal correlations between EOS and environmental factors (i.e., temperature, precipitation and insolation), as well as the correlation between spring and autumn phenology, using partial correlation analyses. Overall, we observed a trend toward later EOS in ~70% of the pixels in Northern Hemisphere, with a mean rate of 0.18 ± 0.38 days yr-1 . Warming preseason temperature was positively associated with the rate of EOS in most of our study area, except for arid/semi-arid regions, where the precipitation sum played a dominant positive role. Interestingly, increased preseason insolation sum might also lead to a later date of EOS. In addition to the climatic effects on EOS, we found an influence of spring vegetation green-up dates on EOS, albeit biome dependent. Our study, therefore, suggests that both environmental factors and spring phenology should be included in the modeling of EOS to improve the predictions of autumn phenology as well as our understanding of the global carbon and nutrient balances.

Elevated circulating irisin is associated with lower risk of insulin resistance: association and path analyses of obese Chinese adults.

BACKGROUND: Evidence on the role of irisin in insulin resistance is limited and controversial, and pathways between them remain unknown. We aimed to examine the independent effects of circulating irisin and different adiposity measurements, as well as their potential interactions, on insulin resistance. We also aimed to explore possible pathways among circulating irisin, adiposity, glucose and insulin levels and insulin resistance. METHODS: A cross-sectional study of 1,115 community- living obese Chinese adults, with data collection on clinical characteristics, glucose and lipid metabolic parameters and circulating irisin levels. RESULTS: Among the 1,115 subjects, 667 (59.8 %) were identified as insulin-resistance, and showed significantly decreased serum irisin than their controls (log-transformed irisin: 1.19 ± 2.34 v.s. 1.46 ± 2.05 ng/ml, p = 0.042). With adjustment for potential confounders, elevated circulating irisin was significantly associated with reduced risk of insulin resistance, with adjusted odds ratio per standard deviation increase of irisin of 0.871 (0.765-0.991, p = 0.036). As for different adiposity measurements, body fat percentage, but neither BMI nor waist, was significantly associated with increased risk of insulin resistance (OR: 1.152 (1.041-1.275), p = 0.006). No significant interaction effect between serum irisin and adiposity on insulin resistance was found. A one pathway model about the relationship between serum irisin and insulin resistance fits well (χ (2) = 44.09, p < 0.001; CFI-0.994; TLI =0.986; and RMSEA = 0.067), and shows that elevated circulating irisin might improve insulin resistance indirectly through lowering fasting insulin levels (standardized path coefficient = -0.046, p = 0.032). CONCLUSIONS: Elevated circulating irisin is associated with lower risk of insulin resistance indirectly through lowering fasting insulin.

Association of serum irisin and body composition with chronic kidney disease in obese Chinese adults: a cross-sectional study.

BACKGROUND: Irisin, an exercise induced myokine, has broad implications for metabolism and energy homeostasis. Available evidence about the association of serum irisin with chronic kidney disease (CKD) is limited. METHODS: Cross-sectional data on socio-demographic, lifestyle, clinical characteristics and serum irisin were collected for 1,115 community-living obese Chinese adults (waist circumference ≥ 90 cm for men and ≥ 80 cm for women). CKD was defined as estimated glomerular filtration rate less than 60 ml/min per 1.73 m(2) and/or the presence of albuminuria. Associations of serum irisin and body composition measurements with CKD were analyzed using multivariable logistic regression. RESULTS: The overall prevalence of CKD were 23.1% (26.6% in females and 15.5% in males, p < 0.001). Subjects within quartile 4 group of serum irisin had significantly the lowest prevalence of CKD (22.9%, 22.2%, 28.7% and 18.7% for quartile 1-4 groups, respectively, p = 0.046). With adjustment for potential confounders, compared with those within quartile 1 group of serum irisin, subjects within quartile 4 group showed significantly decreased risk of CKD and marginally decreased risk of albuminuria, with the adjusted odds ratios (ORs, 95% CI) of 0.572 (0.353-0.927, p = 0.023) and 0.611 (0.373-1.000, p = 0.050), respectively. As for body composition measurements, only body fat percentage was significantly associated with both albuminuira and CKD, with ORs (95% CI) of 1.046 (1.002-1.092, p = 0.039) and 1.049 (1.006-1.093, p = 0.025), respectively. No statistically significant interaction effect between serum irisin and body composition measurements on CKD was found. CONCLUSIONS: Our results imply that high serum irisin level was associated with reduced risk of CKD, and should be confirmed in future studies. Furthermore, adiposity per se, rather than body weight or body shape, is independently associated with increased risk of CKD. Future studies should examine whether decreasing body fat percentage may prevent or slow CKD.

Exact solution of three dimensional schrödinger equation with power function superposition potential.

Finding an analytical solution to the Schrödinger equation with power function superposition potential is essential for the development of quantum theory. For example, the harmonic oscillator potential, Coulomb potential, and Klazer potential are all classed as power function superposition potentials. In this study, the general form of the power function superposition potential was used to decompose the second-order radial Schrödinger equation with this potential into the first-order Ricatti equation. Furthermore, two forms of the power function superposition potential are constructed with an exact analytical solution, and the exact bound-state energy level formula is obtained for these two potentials. Finally, the energy levels of some of the diatomic molecules were determined through calculation. And our results are actually consistent with those obtained by other methods.

Estimates of the global, regional, and national burden of atrial fibrillation in older adults from 1990 to 2019: insights from the Global Burden of Disease study 2019.

Background: Atrial fibrill ation (AF) is a predominant public health concern in older adults. Therefore, this study aimed to explore the global, regional, and national burden of AF in older adults aged 60-89 between 1990 and 2019. Methods: The morbidity, mortality, disability-adjusted life years (DALYs), and age-standardized rates of AF were refined from the Global Burden of Diseases study 2019. The epidemiological characteristics were assessed based on numerical values, age-standardized rates per 100,000 person-years, and estimated annual percentage changes (EAPC). Results: Globally, a total of 33.31 million AF cases, 219.4 thousand deaths, and 65.80 million DALYs were documented in 2019. There were no appreciable changes in EAPC from 1990 to 2019. The disease burden of AF differed significantly across different territories and countries. At the national level, China exhibited the highest number of incident cases [818,493 (562,871-1,128,695)], deaths [39,970 (33,722-46,387)], and DALYs [1,383,674 (1,047,540-1,802,516)]. At the global level, high body mass index (BMI) and high systolic blood pressure (SBP) were two predominant risk factors contributing to the proportion of AF-related deaths. Conclusion: AF in older adults remains a major public health concern worldwide. The burden of AF varies widely at both national and regional levels. From 1990 to 2019, the cases of incidences, deaths, and DALYs have shown a global increase. The ASIR, ASMR, and ASDR have declined in the high-moderate and high SDI regions; however, the burden of AF increased promptly in the lower SDI regions. Special attention should be paid to the main risk factors for high-risk individuals with AF, which can help control systolic blood pressure and body mass index within normal limits. Over all, it is necessary to illustrate the features of the global AF burden and develop more effective and targeted prevention and treatment strategies.

Gender difference in the association of hyperuricemia with chronic kidney disease in southern China.

BACKGROUND: The effect of hyperuricemia on chronic kidney disease (CKD) is controversial, and little is known about gender as it relates to hyperuricemia and CKD. METHODS: This was a cross-sectional study of 7,053 adults in the general Chinese population in Southern China using a multi-stage stratified sampling method. In which associations between hyperuricemia and indicators of CKD (defined by albuminuria (urinary albumin-to -creatinine ratio ≥ 30 mg/g) or decreased modified MDRD equation estimated GFR (<60 ml/min per 1.73 m2) were tested using multivariate logistic regression. RESULTS: After adjustment for potential confounders, hyperuricemia was associated with increased risk of reduced renal function and CKD but not albuminuria, with odds ratios (ORs) (95% CI) of 4.39 (3.38-5.70, P < 0.001), 1.54 (1.31-1.82, P <0.001) and 0.96 (0.78-1.17, P =0.671), respectively. The interaction between gender and hyperuricemia with CKD was significant (P =0.010); and stratified analysis showed a stronger association of hyperuricemia with CKD in males (OR (95% CI): 2.04 (1.56-2.67), P < 0.001) than in females (1.45 (1.17-1.80), P = 0.001). CONCLUSIONS: We observed an independent association of hyperuricemia with CKD that was stronger in males, and this independent association in male might imply some gender specific mechanisms. These results should be confirmed in future prospective studies.

Association between intrahepatic triglyceride content in subjects with metabolically healthy abdominal obesity and risks of pre-diabetes plus diabetes: an observational study.

OBJECTIVE: We aimed to evaluate the association of intrahepatic triglyceride (IHTG) content in subjects with metabolically healthy abdominal obesity (MHAO) on risks of pre-diabetes plus diabetes. DESIGN: Cross-sectional survey. SETTING: Lianqian community, the First Affiliated Hospital of Xiamen University, Xiamen, China. PARTICIPANTS: Among 1523 community-living healthy adults aged 40 years or older with abdominal obesity recruited at baseline, 428 subjects who underwent IHTG content measurement were selected. OUTCOME MEASURES: Risk of pre-diabetes plus diabetes. RESULTS: Non-alcoholic fatty liver disease (NAFLD) was diagnosed as 203 (69.1%) in MHAO and 121 (90.3%) in metabolically unhealthy abdominal obesity (MUAO) (p<0.001). The prevalence rates of pre-diabetes plus diabetes were 81.1%, 88.8% and 90.9% across the tertiles of IHTG content (p=0.037). Both MUAO (vs MHAO) and NAFLD (vs non-NAFLD) were independently associated with increased risks of pre-diabetes plus diabetes, the adjusted ORs (95% CIs) were 10.90 (3.15 to 37.69, p<0.001) and 3.02 (1.47 to 6.20, p=0.003), respectively. Higher IHTG content was significantly associated with increased risk of pre-diabetes plus diabetes with the adjusted OR (95% CI) of per SD increase of IHTG content of 1.62 (1.07 to 2.46, p=0.024). And there was a significantly positive trend between increasing categories of IHTG content tertiles and excessive risks of pre-diabetes plus diabetes (trend test p value=0.011). Stratified analyses showed similar results on the associations of NAFLD and IHTG content with risks of pre-diabetes plus diabetes for subjects with MHAO but not for those with MUAO. CONCLUSIONS: NAFLD and higher IHTG content were independently associated with increased risks of pre-diabetes plus diabetes in MHAO subjects. NAFLD or quantity of liver fat should be considered as additional criterion when defining and diagnosing MHO. Screening of NAFLD and intervention to reduce liver fat should be strengthened even for those seemly metabolically healthy obese.

Diverging models introduce large uncertainty in future climate warming impact on spring phenology of temperate deciduous trees.

Spring phenology influences terrestrial ecosystem carbon, water and energy exchanges between the biosphere and atmosphere. Accurate prediction of spring phenology is therefore a prerequisite to foresee the impacts of climate warming on terrestrial ecosystems. In the present study, we studied the model performance of four widely used process-based models of spring leaf unfolding, including both a one-phase model (not considering a chilling phase: the Thermal Time model) and three two-phase models (all accounting for a required chilling period: the Parallel model, the Sequential model, the Unified model). Models were tested on five deciduous tree species occurring across Europe. We specifically investigated the divergence of their phenology predictions under future climate warming scenarios and studied the differences in the chilling periods. We found that, in general, the two-phase models performed slightly better than the one-phase model when fitting to the observed data, with all two-phase models performing similarly. However, leaf unfolding projections diverged substantially among the two-phase models over the period 2070-2100. Furthermore, we found that the modeled end dates of the chilling periods in these models also diverged, with advances for both the Sequential and Parallel models during the period 2070-2100 (compared to the period 1980-2010), and delays in the Unified model. These findings thus highlight large uncertainty in the two-phase phenology models and confirm that the mechanism underlying the leaf unfolding process is not yet understood. We therefore urgently need an improved understanding of the leaf unfolding process in order to improve the representation of phenology in terrestrial ecosystem models.

Joint associations of metabolically healthy abdominal obesity and non-alcoholic fatty liver disease with prediabetes and diabetes in Chinese adults.

INTRODUCTION: We aimed to evaluate the joint associations of metabolically healthy abdominal obesity (MHAO) with non-alcoholic fatty liver disease (NAFLD) on risks of diabetes and prediabetes. RESEARCH DESIGN AND METHODS: Baseline information of 1318 adults with abdominal obesity (waist circumference ≥90 cm for men and 80 cm for women) from an ongoing cohort study in Xiamen, China were analyzed. Metabolic health was identified as none of the criteria of metabolism syndrome, except for obesity, was met. RESULTS: MHAO and metabolically unhealthy abdominal obesity (MUAO) were identified on 173 (13.1%) and 1145 (86.9%) subjects. NAFLD was further diagnosed on 60 (34.7%) in MHAO and 721 (63.0%) in MUAO groups (p<0.001). Both MUAO (vs MHAO) and NAFLD (vs non-NAFLD) were independently associated with increased risks of diabetes as well as prediabetes plus diabetes, with the adjusted ORs (95% CIs) of 9.40 (3.38 to 26.14) and 2.02 (1.47 to 2.77), respectively. Compared with MHAO and non-NAFLD, MHAO and NAFLD showed significantly increased risks of prediabetes plus diabetes with the adjusted ORs (95% CIs) of 2.87 (1.32 to 6.27, p=0.008). And there were significantly positive trends between increasing categories jointly by MHAO and NAFLD (from MHAO and non-NAFLD, MHAO and NAFLD, MUAO and non-NAFLD to MUAO and NAFLD) with risks of diabetes and prediabetes plus diabetes (both trend tests: p<0.001). CONCLUSIONS: About 35% of subjects with MHAO accompanied by NAFLD showed excessive risk of prediabetes plus diabetes compared with MHAO and non-NAFLD. Thus, NAFLD should be screened and intervened even for those subjects with metabolically healthy obesity (MHO) and should be considered as one additional criterion when defining and diagnosing MHO.

Divergence in ecosystem carbon fluxes and soil nitrogen characteristics across alpine steppe, alpine meadow and alpine swamp ecosystems in a biome transition zone.

Alpine ecosystem carbon cycling is sensitive to climate change, particularly in the transition zones between biomes. Soil nitrogen conditions, including the ammonium to nitrate (NH4+/NO3-) ratio, regulate ecosystem carbon uptake by coupling carbon­nitrogen cycle. The largest alpine pasture on Earth is distributed on the Tibetan Plateau, where alpine biome transition zones are also widely distributed. However, it is largely unknown how the soil NH4+/NO3- ratio and net ecosystem CO2 exchange vary among vegetation types in the alpine biome transition zones due to a lack of in situ field observations. Here, we investigated soil NH4+/NO3- ratio and ecosystem carbon fluxes across alpine steppe, alpine meadow and alpine swamp ecosystems in a biome transition zone on the central Tibetan Plateau. The results showed that soil NH4+/NO3- ratio was lowest in the alpine steppe (driest environment), which had the highest soil pH, and highest in the alpine swamp (wettest environment), which had the lowest soil pH. We proposed a theoretical framework describing how soil moisture regulates soil NH4+/NO3- ratio by altering both the denitrification process and soil pH. We further found that the growing season average net ecosystem CO2 exchange for the alpine steppe, alpine meadow and alpine swamp was -1.46, -1.90 and -5.43 µmol m-2 s-1, respectively. This divergence in net ecosystem CO2 exchange across the three grasslands is primarily explained by divergence in gross ecosystem photosynthesis, rather than ecosystem respiration. The air temperature sensitivity of ecosystem respiration (Q10) for the alpine steppe, alpine meadow and alpine swamp was 1.73 ± 0.05, 1.44 ± 0.03 and 2.43 ± 0.45, respectively. Our study highlights large differences in both soil nutrient and ecosystem carbon uptake across different vegetation types in an alpine biome transition zone. More in situ investigations in various biome transition zones are urgently needed to quantitatively understand the spatial pattern of alpine ecosystem carbon­nitrogen cycling processes.

Association of Fetuin-B with Subclinical Atherosclerosis in Obese Chinese Adults.

AIM: We aimed to explore the independent associations of serum Fetuin-B and common genetic variants in FETUB locus with subclinical atherosclerosis. METHODS: A cross-sectional study of 1,140 obese adults, who underwent serum Fetuin-B testing, hepatic ultrasonography scanning, genotyping on four tagging single nucleotide polymorphisms (SNPs) in FETUB locus and atherosclerosis detection, was conducted in Xiamen, China. RESULTS: Increasing tertiles of brachial ankle pulse wave velocity (ba-PWV) were significantly associated with higher prevalence of nonalcoholic fatty liver disease (NAFLD) (48.8%, 61.5%, and 70.5% for tertiles of 1-3, respectively, p＜0.001) and serum Fetuin-B (3.85±1.39, 4.09±1.40, and 4.27±1.46 µg/ml, p=0.047). Multivariable linear regression analyses with adjustment for potential confounding factors, even NAFLD per se, showed that serum Fetuin-B were significantly and positively associated with ba-PWV, with standardized regression coefficients (ß) ranging from 0.055 to 0.075 (all p-values ＜0.05) in different models. However, the significant relationship between serum Fetuin-B and ba-PWV disappeared with further adjustment for insulin resistance. Serum Fetuin-B was not significantly associated with ankle-brachial index (ABI). All genotypes of the four tested FETUB tagging SNPs were not significantly associated with either ba-PWV or ABI with adjustment for potential confounding factors. CONCLUSION: Serum Fetuin-B was positively associated with ba-PWV and may link liver fat accumulation to subclinical atherosclerosis via insulin resistance.

Deciphering impacts of climate extremes on Tibetan grasslands in the last fifteen years.

Climate extremes have emerged as a crucial driver of changes in terrestrial ecosystems. The Tibetan Plateau, facing a rapid climate change, tends to favor climate extremes. But we lack a clear understanding of the impacts of such extremes on alpine grasslands. Here we show that extreme events (drought, extreme wet, extreme cold and extreme hot) occurred at a frequency of 0.67-4 months decade-1 during 2001-2015, with extreme precipitation predominantly occurring in June-to-August and extreme temperatures in May. Drought and extreme wet cause opposite and asymmetric effects on grassland growth, with drought-induced reductions greater than increases due to extreme wet. Grassland responses to extreme temperatures, which predominantly occur in May, show a dipole-like spatial pattern, with extreme hot (cold) events enhanced (reduced) growth in the eastern plateau but slightly reduced (enhanced) growth in the western plateau. These opposite responses to extreme temperatures over the eastern plateau are explained by the possibility that the occurrence of extreme cold slows the preseason temperature accumulation, delaying the triggering of spring phenology, while extreme hot hastens the accumulation. In the western plateau, in contrast, positive responses to extreme cold are induced by accompanying high precipitation. Furthermore, high extremeness of climate events generally led to a much lower extremeness in growth response, implying that the Tibetan grasslands have a relatively high resistance to climate extremes. The ecosystem models tested could not accurately simulate grassland responses to drought and extreme temperatures, and require re-parameterization before trust can be placed in their output for this region.

An alternative approach to reduce algorithm-derived biases in monitoring soil organic carbon changes.

Quantifying soil organic carbon (SOC) changes is a fundamental issue in ecology and sustainable agriculture. However, the algorithm-derived biases in comparing SOC status have not been fully addressed. Although the methods based on equivalent soil mass (ESM) and mineral-matter mass (EMMM) reduced biases of the conventional methods based on equivalent soil volume (ESV), they face challenges in ensuring both data comparability and accuracy of SOC estimation due to unequal basis for comparison and using unconserved reference systems. We introduce the basal mineral-matter reference systems (soils at time zero with natural porosity but no organic matter) and develop an approach based on equivalent mineral-matter volume (EMMV). To show the temporal bias, SOC change rates were recalculated with the ESV method and modified methods that referenced to soils at time t1 (ESM, EMMM, and EMMV-t1) or referenced to soils at time zero (EMMV-t0) using two datasets with contrasting SOC status. To show the spatial bias, the ESV- and EMMV-t0-derived SOC stocks were compared using datasets from six sites across biomes. We found that, in the relatively C-rich forests, SOC accumulation rates derived from the modified methods that referenced to t1 soils and from the EMMV-t0 method were 5.7%-13.6% and 20.6% higher than that calculated by the ESV method, respectively. Nevertheless, in the C-poor lands, no significant algorithmic biases of SOC estimation were observed. Finally, both the SOC stock discrepancies (ESV vs. EMMV-t0) and the proportions of this unaccounted SOC were large and site-dependent. These results suggest that although the modified methods that referenced to t1 soils could reduce the biases derived from soil volume changes, they may not properly quantify SOC changes due to using unconserved reference systems. The EMMV-t0 method provides an approach to address the two problems and is potentially useful since it enables SOC comparability and integrating SOC datasets.

The paleoclimatic footprint in the soil carbon stock of the Tibetan permafrost region.

Tibetan permafrost largely formed during the late Pleistocene glacial period and shrank in the Holocene Thermal Maximum period. Quantifying the impacts of paleoclimatic extremes on soil carbon stock can shed light on the vulnerability of permafrost carbon in the future. Here, we synthesize data from 1114 sites across the Tibetan permafrost region to report that paleoclimate is more important than modern climate in shaping current permafrost carbon distribution, and its importance increases with soil depth, mainly through forming the soil's physiochemical properties. We derive a new estimate of modern soil carbon stock to 3 m depth by including the paleoclimate effects, and find that the stock ([Formula: see text] PgC) is triple that predicted by ecosystem models (11.5 ± 4.2 s.e.m PgC), which use pre-industrial climate to initialize the soil carbon pool. The discrepancy highlights the urgent need to incorporate paleoclimate information into model initialization for simulating permafrost soil carbon stocks.