Climate-Vegetation Coverage Interactions in the Hengduan Mountains Area, Southeastern Tibetan Plateau, and Their Downstream Effects

Little is known about the mechanism of climate-vegetation coverage coupled changes in the Tibetan Plateau(TP)region,which is the most climatically sensitive and ecologically fragile region with the highest terrain in the world.This study,using multisource datasets(including satellite data and meteorological observations and reanalysis data)revealed the mutual feedback mechanisms between changes in climate(temperature and precipitation)and vegetation coverage in recent decades in the Hengduan Mountains Area(HMA)of the southeastern TP and their influences on climate in the downstream region,the Sichuan Basin(SCB).There is mutual facilitation between rising air temperature and increasing vegetation coverage in the HMA,which is most significant during winter,and then during spring,but insignificant during summer and autumn.Rising temperature significantly enhances local vegetation coverage,and vegetation greening in turn heats the atmosphere via enhancing net heat flux from the surface to the atmosphere.The atmospheric heating anomaly over the HMA thickens the atmospheric column and increases upper air pressure.The high pressure anomaly disperses downstream via the westerly flow,expands across the SCB,and eventually increases the SCB temperature.This effect lasts from winter to the following spring,which may cause the maximum increasing trend of the SCB temperature and vegetation coverage in spring.These results are helpful for estimating future trends in climate and eco-environmental variations in the HMA and SCB under warming scenarios,as well as seasonal forecasting based on the connection between the HMA eco-environment and SCB climate.

Climate warming is significantly influenced by rising summer maximum temperatures: insights from tree-ring evidence of the Western Tianshan Mountains, China

As one of the regions most affected by global cli-mate warming,the Tianshan mountains has experienced sev-eral ecological crises,including retreating glaciers and water deficits.Climate warming in these mountains is considered mainly to be caused by increases in minimum temperatures and winter temperatures,while the influence of maximum temperatures is unclear.In this study,a 300-year tree-ring chronology developed from the Western Tianshan Moun-tains was used to reconstruct the summer(June-August)maximum temperature(T_(max6-8))variations from 1718 to 2017.The reconstruction explained 53.1% of the variance in the observed T_(max6-8).Over the past 300 years,the T_(max6-8)reconstruction showed clear interannual and decadal vari-abilities.There was a significant warming trend(0.18°C/decade)after the 1950s,which was close to the increasing rates of the minimum and mean temperatures.The increase in maximum temperature was also present over the whole Tianshan mountains and its impact on climate warming has increased.The T_(max6-8) variations in the Western Tianshan mountains were influenced by frequent volcanic eruptions combined with the influence of solar activity and the sum-mer North Atlantic Oscillation.This study reveals that cli-mate warming is significantly influenced by the increase in maximum temperatures and clarifies possible driving mech-anisms of temperature variations in the Western Tianshan mountains which should aid climate predictions.

Climate warming is significantly influenced by rising summer maximum temperatures:insights from tree-ring evidence of the Western Tianshan Mountains,China

As one of the regions most affected by global climate warming,the Tianshan mountains has experienced several ecological crises,including retreating glaciers and water deficits.Climate warming in these mountains is considered mainly to be caused by increases in minimum temperatures and winter temperatures,while the influence of maximum temperatures is unclear.In this study,a 300-year tree-ring chronology developed from the Western Tianshan Mountains was used to reconstruct the summer(June-August)maximum temperature(Tmax6-8) variations from 1718 to2017.The reconstruction explained 53.1% of the variance in the observed Tmax6-8.Over the past 300 years,the Tmax6-8reconstruction showed clear interannual and decadal variabilities.There was a significant warming trend(0.18 ℃/decade) after the 1950s,which was close to the increasing rates of the minimum and mean temperatures.The increase in maximum temperature was also present over the whole Tianshan mountains and its impact on climate warming has increased.The Tmax6-8variations in the Western Tianshan mountains were influenced by frequent volcanic eruptions combined with the influence of solar activity and the summer North Atlantic Oscillation.This study reveals that climate warming is significantly influenced by the increase in maximum temperatures and clarifies possible driving mechanisms of temperature variations in the Western Tianshan mountains which should aid climate predictions.

Indole-3-propionic Acid-aggravated CCl_(4)-induced Liver Fibrosis via the TGF-β1/Smads Signaling Pathway

Background and Aims:The pathogenesis of liver fibrosis involves liver damage,inflammation,oxidative stress,and intestinal dysfunction.Indole-3-propionic acid(IPA)has been demonstrated to have antioxidant,anti-inflammatory and anticancer activities,and a role in maintaining gut homeostasis.The current study aimed to investigate the role of IPA in carbon tetrachloride(CCl4)-induced liver fibrosis and explore the underlying mechanisms.Methods:The liver fibrosis model was established in male C57BL/6 mice by intraperitoneal injection of CCl4 twice weekly.IPA intervention was made orally(20 mg/kg daily).The degree of liver injury and fibrosis were assessed by serum alanine aminotransferase(ALT),aspartate aminotransferase(AST),and histopathology.Enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction(qPCR)were used to detect the inflammatory cytokines.The malondialdehyde(MDA),glutathione,glutathione peroxidase,superoxide dismutase,and catalase were determined via commercial kits.Hepatocyte apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay.The expression of mRNA and protein was assayed by qPCR,Western blotting,or immunohistochemical staining.Results:After IPA treatment,the ALT and AST,apoptotic cells,and pro-inflammatory factor levels were enhanced significantly.Moreover,IPA intervention up-regulated the expression of collagen I,α-smooth muscle actin,tissue inhibitor of matrix metalloproteinase-1,matrix metalloproteinase-2,transforming growth factor-β1(TGF-β1),Smad3,and phosphorylated-Smad2/3.Additionally,IPA intervention did not affect the MDA level.Attractively,the administration of IPA remodeled the gut flora structure.Conclusions:IPA aggravated CCl_(4)-induced liver damage and fibrosis by activating HSCs via the TGF-β1/Smads signaling pathway.