Global temperatures will continue to increase in the future.The∼640,000-km2 Loess Plateau(LP)is a typical arid and semi-arid region in China.Similar regions cover∼41%of the Earth,and its soils are some of the most s...Global temperatures will continue to increase in the future.The∼640,000-km2 Loess Plateau(LP)is a typical arid and semi-arid region in China.Similar regions cover∼41%of the Earth,and its soils are some of the most severely eroded anywhere in the world.It is very important to understand the vegetation change and its ecological threshold under climate change on the LP for the sustainable development in the Yellow River Basin.However,little is known about how vegetation on the LP will respond to climate change and what is the sustainable threshold level of vegetation cover on the LP.Here we show that the temperature on the LP has risen 0.27°C per decade over the past 50 years,a rate that is 30%higher than the average warming rate across China.During historical times,vegetation change was regulated by environmental factors and anthropogenic activities.Vegetation coverage was about 53%on the LP from the Xia Dynasty to the Spring and Autumn and Warring States period.Over the past 70 years,however,the environment has gradually improved and the vegetation cover had increased to∼65%by 2021.We forecast future changes of vegetation cover on the LP in 2030s,in 2050s and in 2070s using SDM(Species Distribution Model)under Low-emission scenarios,Medium-emission scenarios and High-emission scenarios.An average value of vegetation cover under the three emission scenarios will be 64.67%,62.70%and 61.47%,respectively.According to the historical record and SDM forecasts,the threshold level of vegetation cover on the LP is estimated to be 53-65%.Currently,vegetation cover on the LP has increased to the upper limit of the threshold value(∼65%).We conclude that the risk of ecosystem collapse on the LP will increase with further temperature increases once the vegetated area and density exceed the threshold value.It is urgent to adopt sustainable strategies such as stopping expanding vegetation area and scientifically optimizing the vegetation structure on the LP to improve the ecological sustainability of the Yellow River Basin.展开更多
AIM:To introduce a simple iris hook assisted phacoemulsification(PE)procedure and evaluate the safety and efficacy of it in completely vitrectomized eyes.METHODS:A single centre study which included 65 previously comp...AIM:To introduce a simple iris hook assisted phacoemulsification(PE)procedure and evaluate the safety and efficacy of it in completely vitrectomized eyes.METHODS:A single centre study which included 65 previously completely vitrectomized eyes of 62 patients who underwent cataract surgery.Patients were randomly divided into 3 groups.Patients received PE,and intraocular lens(IOL)implantation with the assistance of iris hook(SynergetiesTM)as group A(25 eyes);patients who received PE assisted with a 25 G pars plana irrigation as group B(20 eyes),and patients who received PE performed without the help of any instrument as group C(20 eyes).Main outcome measures were surgery duration,Ultrasound(U/S)total time,endothelial cell density(ECD),cumulative dissipated energy(CDE)and complications of the procedures.RESULTS:With the help of iris hook,the patients in group A had the lowest ECD loss rate(0.07±0.03,0.09±0.03,and 0.10±0.03,P<0.05),shortest CDE(12.2±4.1,15.8±6.0,and 16.0±6.0,P<0.05)and U/S total time(36.6±13.0 s,46.3±16.4 s,and 47.6±16.1 s,P<0.05),and minimal incidence of complications.The longest surgery duration was in group B(19.4±1.6 min)and maximum complications rate in group C(20%miosis,10%posterior capsular tears,5%zonular dialysis,5%cystoid macular edema).While best-corrected visual acuity(BCVA),intraocular pressure(IOP)and ECD did not show a significant difference among the three groups.CONCLUSION:Without prolonged surgery duration,the iris hook assistant method can minimize heat generation during surgery and incidence of complications,which transfer the challenged PE in vitrectomized eyes into a regular surgery.It does not need any change in the hydrodynamic parameters and in the bag PE technique,easy to operate even for junior surgeons.展开更多
Aims Grasslands are globally threatened by climate changes and unsustainable land-use,which often cause transitions among alternative stable states,and even catastrophic transition to desertification.Spatial vegetatio...Aims Grasslands are globally threatened by climate changes and unsustainable land-use,which often cause transitions among alternative stable states,and even catastrophic transition to desertification.Spatial vegetation patch configurations have been shown to signify such transitions at large spatial scale.Here,we demonstrate how small-scale patch configurations can also indicate state transitions.Methods The whole spatial series of degradation successions were chosen in alpine grasslands characterized as seven typical communities.Patch numbers,and perimeter and cover of each patch were recorded using adjacent quadrats along transects in each type of the communities.Species abundance within each patch was measured.Important Findings Across seven grazing-induced degradation stages in the world’s largest expanse of grassland,from dense ungrazed turf to bare black-soil crust,patch numbers and perimeters first increased as patch cover decreased.Numbers and perimeters then decreased rapidly beyond an intersection point at 68%of initial continuous vegetation cover.Around this point,the vegetation fluctuated back and forth between the sedge-dominated grassland breaking-up phase and the forb-dominated phase,suggesting impending shift of grassland state.This study thus demonstrates how ground-based small-scale vegetation surveys can provide a quantitative,easy-to-use signals for vegetation degradation,with promise for detecting the catastrophic transition to desertification.展开更多
基金The National Natural Science Foundation of China(42041005,U2243225)supports this research.
文摘Global temperatures will continue to increase in the future.The∼640,000-km2 Loess Plateau(LP)is a typical arid and semi-arid region in China.Similar regions cover∼41%of the Earth,and its soils are some of the most severely eroded anywhere in the world.It is very important to understand the vegetation change and its ecological threshold under climate change on the LP for the sustainable development in the Yellow River Basin.However,little is known about how vegetation on the LP will respond to climate change and what is the sustainable threshold level of vegetation cover on the LP.Here we show that the temperature on the LP has risen 0.27°C per decade over the past 50 years,a rate that is 30%higher than the average warming rate across China.During historical times,vegetation change was regulated by environmental factors and anthropogenic activities.Vegetation coverage was about 53%on the LP from the Xia Dynasty to the Spring and Autumn and Warring States period.Over the past 70 years,however,the environment has gradually improved and the vegetation cover had increased to∼65%by 2021.We forecast future changes of vegetation cover on the LP in 2030s,in 2050s and in 2070s using SDM(Species Distribution Model)under Low-emission scenarios,Medium-emission scenarios and High-emission scenarios.An average value of vegetation cover under the three emission scenarios will be 64.67%,62.70%and 61.47%,respectively.According to the historical record and SDM forecasts,the threshold level of vegetation cover on the LP is estimated to be 53-65%.Currently,vegetation cover on the LP has increased to the upper limit of the threshold value(∼65%).We conclude that the risk of ecosystem collapse on the LP will increase with further temperature increases once the vegetated area and density exceed the threshold value.It is urgent to adopt sustainable strategies such as stopping expanding vegetation area and scientifically optimizing the vegetation structure on the LP to improve the ecological sustainability of the Yellow River Basin.
基金Supported by the Research and Development Program of Shaanxi Province(No.2021SF-161)。
文摘AIM:To introduce a simple iris hook assisted phacoemulsification(PE)procedure and evaluate the safety and efficacy of it in completely vitrectomized eyes.METHODS:A single centre study which included 65 previously completely vitrectomized eyes of 62 patients who underwent cataract surgery.Patients were randomly divided into 3 groups.Patients received PE,and intraocular lens(IOL)implantation with the assistance of iris hook(SynergetiesTM)as group A(25 eyes);patients who received PE assisted with a 25 G pars plana irrigation as group B(20 eyes),and patients who received PE performed without the help of any instrument as group C(20 eyes).Main outcome measures were surgery duration,Ultrasound(U/S)total time,endothelial cell density(ECD),cumulative dissipated energy(CDE)and complications of the procedures.RESULTS:With the help of iris hook,the patients in group A had the lowest ECD loss rate(0.07±0.03,0.09±0.03,and 0.10±0.03,P<0.05),shortest CDE(12.2±4.1,15.8±6.0,and 16.0±6.0,P<0.05)and U/S total time(36.6±13.0 s,46.3±16.4 s,and 47.6±16.1 s,P<0.05),and minimal incidence of complications.The longest surgery duration was in group B(19.4±1.6 min)and maximum complications rate in group C(20%miosis,10%posterior capsular tears,5%zonular dialysis,5%cystoid macular edema).While best-corrected visual acuity(BCVA),intraocular pressure(IOP)and ECD did not show a significant difference among the three groups.CONCLUSION:Without prolonged surgery duration,the iris hook assistant method can minimize heat generation during surgery and incidence of complications,which transfer the challenged PE in vitrectomized eyes into a regular surgery.It does not need any change in the hydrodynamic parameters and in the bag PE technique,easy to operate even for junior surgeons.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)(grant no.2019QZKK0302)the National Key Research and Development Program(2016YFC0501802,2016YFC0501803)the National Natural Science Foundation of China(41671263,41730752).
文摘Aims Grasslands are globally threatened by climate changes and unsustainable land-use,which often cause transitions among alternative stable states,and even catastrophic transition to desertification.Spatial vegetation patch configurations have been shown to signify such transitions at large spatial scale.Here,we demonstrate how small-scale patch configurations can also indicate state transitions.Methods The whole spatial series of degradation successions were chosen in alpine grasslands characterized as seven typical communities.Patch numbers,and perimeter and cover of each patch were recorded using adjacent quadrats along transects in each type of the communities.Species abundance within each patch was measured.Important Findings Across seven grazing-induced degradation stages in the world’s largest expanse of grassland,from dense ungrazed turf to bare black-soil crust,patch numbers and perimeters first increased as patch cover decreased.Numbers and perimeters then decreased rapidly beyond an intersection point at 68%of initial continuous vegetation cover.Around this point,the vegetation fluctuated back and forth between the sedge-dominated grassland breaking-up phase and the forb-dominated phase,suggesting impending shift of grassland state.This study thus demonstrates how ground-based small-scale vegetation surveys can provide a quantitative,easy-to-use signals for vegetation degradation,with promise for detecting the catastrophic transition to desertification.
