Boehmeria nivea var. strigosa (Urticaceae), a new variety from Southwest China

Boehmeria nivea var.strigosa Zeng Y.Wu&Y.Zhao,a new variety of B.nivea(Urticaceae)from Southwest China,is here described based on evidence from morphology and molecular phylogeny.This new variety is mainly characterized by its green abaxial leaf blade,partly connate stipules,and densely patent strigose hairs on stems and potioles.The phylogenetic analysis based on rbc L,nrDNA and rbc L+nrDNA datasets,revealed that all individuals of B.nivea var.strigosa formed a monophyletic group.The conservation status of B.nivea var.strigosa is assessed as“Near Threatened”(NT)according to IUCN evaluation criteria.The discovery of this new variety is not only crucial for the taxonomy of ramie,but also provides reference for the exploration and utilization of ramie.

Deep learning-based subseasonal to seasonal precipitation prediction in southwest China:Algorithm comparison and sensitivity to input features

The prediction of precipitation at subseasonal to seasonal(S2S)timescales remains an enormous challenge because of the gap between weather and climate predictions.This study compares three deep learning algorithms,namely,the long short-term memory recurrent(LSTM),gated recurrent unit(GRU),and recurrent neural network(RNN),and selects the optimal algorithm to establish an S2S precipitation prediction model.The models were evaluated in four subregions of the Sichuan Province:the Plateau,Valley,eastern Basin,and western Basin.The results showed that the RNN model had better performance than the LSTM and GRU models.This could be because the RNN model had an advantage over the LSTM model in the transformation of climate indices with positive and negative variations.In the validation of test datasets,the RNN model successfully predicted the precipitation trend in most years during the wet season(May-October).The RNN model had a lower prediction bias(within±10%),higher sign accuracy of the precipitation trend(~88.95%),and greater accuracy of the maximum precipitation month(>0.85).For the prediction of different lead times,the RNN model was able to provide a stable trend prediction for summer precipitation,and the time correlation coefficient score was higher than that of the National Climate Center of China.Furthermore,this study proposed a method to measure the sensitivity of the RNN model to different input features,which may provide unprecedented insights into the nonlinear relationship and complicated feedback process among climate systems.The results of the sensitivity distribution are as follows.First,the Niño 4 and Niño 3.4 indices were equally important for the prediction of wet season precipitation.Second,the sensitivity of the snow cover on the Tibetan Plateau was higher than that in the Northern Hemisphere.Third,an opposite sensitivity appeared in two different patterns of the Indian Ocean and sea ice concentrations in the Arctic and the Barents Sea.

Moisture Sources and Their Contributions to Summer Precipitation in the East of Southwest China

Complex topography,special geographical location and sea-land-air interactions lead to high interannual variability of summer precipitation in the east of Southwest China(ESWC).However,the contributions,influencing factors and mechanisms of remote and local evaporation remain to be further investigated.Using clustering analysis and Hybrid Single-Particle Lagrangian Integrated Trajectory version 5 model,we analyze the contributions of remote moisture transport and local evaporation to summer precipitation in the ESWC and their causes.There are mainly five remote moisture channels in the ESWC,namely the Arabian Sea channel,Bay of Bengal channel,western Pacific channel,Northwest channel 1 and Northwest channel 2.Among the five channels,the western Pacific channel has the largest number of trajectories,while the Bay of Bengal channel has the largest contribution rate of specific humidity(33.33%)and moisture flux(33.14%).The amount of regional average precipitation is close to that of the precipitation caused by remote moisture transport,and both are considerably greater than the rainfall amount caused by local evaporation.However,on interannual time scales,precipitation recirculation rates are negatively correlated to regional average precipitation and precipitation caused by remote moisture transport but are consistent with that caused by local evaporation.An apparent"+-+"wave train can be found on the height anomaly field in East Asia,and the sea surface temperature anomalies are positive in the equatorial Middle-East Pacific,the South China Sea,the Bay of Bengal and the Arabian Sea.These phenomena cause southwest-northeast moisture transport with strong updrafts,thereby resulting in more precipitation in the ESWC.

A comparative study of seismic tomography models of Southwest China

The margin of the Tibetan Plateau of Southwest China is one of the most seismically active regions of China and is the location of the China Seismic Experimental Site(CSES).Many studies have developed seismic velocity models of Southwest China,but few have compared and evaluated these models which is important for further model improvement.Thus,we compared six published seismic shear-wave velocity models of Southwest China on absolute velocity and velocity perturbation patterns.The models are derived from different types of data(e.g.,surface waves from ambient noise and earthquakes,body-wave travel times,receiver functions) and inversion methods.We interpolated the models into a uniform horizontal grid(0.5° × 0.5°) and vertically sampled them at 5,10,20,30,40,and 60 km depths.We found significant differences between the six models.Then,we selected three of them that showed greater consistency for further comparison.Our further comparisons revealed systematic biases between models in absolute velocity that may be related to different data types.The perturbation pattern of the model is especially divergent in the shallow part,but more consistent in the deep part.We conducted synthetic and inversion tests to explore possible causes and our results imply that systematic differences between the data,differences in methods,and other factors may directly affect the model.Therefore,the Southwest China velocity model still has considerable room for improvement,and the impact of inconsistency between different data types on the model needs further research.Finally,we proposed a new reference shear-wave velocity model of Southwest China(SwCM-S1.0) based on the three selected models with high consistency.We believe that this model is a better representation of more robust features of the models that are based on different data sets.

Contribution of external forcing to summer precipitation trends over the Qinghai-Tibet Plateau and Southwest China

在过去的60年中,全球气候经历了快速变暖和短暂的变暖停滞,而中国的区域降水也经历了多样而复杂的变化.本文分析了1961年至2014年外强迫因子对青藏高原和中国西南地区夏季降水趋势的影响.观测数据显示,青藏高原的夏季降水呈增加趋势,而中国西南地区的夏季降水呈减少趋势,这两个相邻地区的夏季降水变化趋势相反.利用CMIP6数据,本文研究了不同外强迫因子对两个区域夏季降水趋势的影响.结果表明,温室气体对青藏高原夏季降水的增加具有显著影响,而气溶胶在中国西南地区夏季降水减少中起主要作用。

The Impact of Arid Climate Change on Agriculture of Dry Valley in Southwest China and Its Adaptive Countermeasures

The eco-environmental vulnerability and underdevelopment of the agriculture in Southwest China would strengthen its disadvantage conditions further on the condition of arid climate change.It is necessary to deal with the relations between resource utilization and eco-environment finely and ascertain the adaptive principles on the dry valley agriculture to the arid climate change in order to change the extensive utilization of the special agricultural resources.The paper gave some adaptive countermeasures that develop modern rangeland husbandry,strengthening the special agriculture and agricultural industrialization,emphasis on the ecological agriculture development,constructing the extension system of water-saving modern agriculture,encouraging the service industry related to ＂agriculture,peasants and the countryside＂,constructing water utilization facilities,and exploiting the renewable energies.

Assessment of Future Drought in Southwest China Based on CMIP5 Multimodel Projections

In the last decade, a series of severe and extensive droughts have swept across Southwest China, resulting in tremendous economic losses, deaths, and disruption to society. Consequently, this study is motivated by the paramount importance of as- sessing future changes in drought in Southwest China. Precipitation is likely to decrease over most parts of Southwest China around the beginning of the century, followed by widespread precipitation increases; the increase in potential evapotran- spiration （PET）, due to the joint effects of increased temperature and surface net radiation and decreased relative humidity, will overwhelm the whole region throughout the entire 21st century. In comparative terms, the enhancement of PET will outweigh that of precipitation, particularly under Representative Concentration Pathway （RCP） 8.5, resulting in intensified drought. Generally, the drying tendency will be in the southeast portion, whereas the mountainous region in the northwest will become increasingly wetter owing to abundant precipitation increases. Droughts classified as moderate/severe according to historical standards will become the norm in the 2080s under RCP4.5/RCP8.5. Future drought changes will manifest different characteristics depending on the time scale： the magnitude of change at a time scale of 48 months is nearly twice as great as that at 3 months. Furthermore, we will see that not only will incidences of severe and extreme drought increase dramatically in the future, but extremely wet events will also become more probable.

Late Silurian to Early Devonian Palynomorphs from Qujing,Yunnan,Southwest China

Well-preserved and diversified spores,cryptospores,and acritarchs have been recorded from a relatively continuous sequence that encompasses the Silurian-Devonian boundary in Qujing, Yunnan,southwest China.Four spore assemblage zones from Late Silurian to Early Devonian in age are proposed based on the first appearance datum（FAD）of characteristic spore species.In ascending stratigraphic order,they are Ambitisporites dilutus-Apiculiretusispora synorea（DS;Late Ludfordian to Early Pridoli）,Synorisporites verrucatus-Apiculiretusispora plicata（VP;Pridoli）,Apiculiretusispora minuta-Leiotriletes ornatus（MO;Lochkovian）,and Verrucosisporites polygonalis-Dibolisporites wetteldorfensis（PW;Pragian）.The acritarch assemblage from the upper part of the Yulongsi Formation,the Xiaxishancun Formation,and the lower-middle parts of the Xitun Formation indicates an age of Late Silurian.Based on palynological evidence,the upper part of the Yulongsi Formation is considered Late Ludfordian to Early Pridoli in age;the Xiaxishancun Formation is believed to be Pridoli in age;the Xitun Formation is considered Late Pridoli to Early Lochkovian in age;the Guijiatun Formation is considered Lochkovian in age;and the Xujiachong Formation is Late Lochkovian to Pragian in age.The Silurian-Devonian boundary is recognized between the VP and the MO spore biozones,and occurs within the middle part of the Xitun Formation.

Rocky Land Desertification and its Driving Forces in the Karst Areas of Rural Guangxi,Southwest China

With a subtropical climate,Guangxi Zhuang Autonomous Region has a typical karst landscape.Rocky desertification has become a serious environmental issue due to its high vulnerability caused by the joint effect of natural settings and human activities,because of which its eco-environment has been deteriorated in recent years,and farmland has been disappearing sharply at the same time.This,in turn,has exacerbated the poverty level in the rural areas of the region.In this study,we monitored the spatial distribution of rocky land desertification and its temporal evolution using Landsat TM/ETM images of 1985,1995,2000 and 2005.We also analyzed the driving forces of the desertification and its expansion.Through constructing regression models by using all the relevant variables and considering the lagged effects as well as fixed effects,we quantified the exact role of different factors causing rocky land desertification in the study area with some new findings.The new findings in this study are greatly helpful for preserving,restoring and reconstructing the degraded mountain environment in Guangxi and other karst areas in Southwest China,and also for alleviating poverty in the rural areas in the future.

Permian and Triassic Radiolarian Biostratigraphy in South and Southwest China

The study of Permian radiolarias in South and Southwest China has been advanced in recent years . A well-preserved radiolarian fauna of Triassic is recently found in Southwest China . Eight radiolarian assemblage zones are recognized as follows in ascending order: Pseudoalbaillella rhombothoracata assemblage zone (Qixian ), Pseudoalbaillella fusiformis assemblage zone (early-middle Maokouan ), Follicucullus assemblage zone (late Maokouan-Wujiapingian ), Cangyuanella assemblage zone (early-middle Changxingian ), Clavata assemblage zone (latest Permian), Triassocampe yini assemblage zone (early Early Triassic ), Pseudoeucyrtis liui assemblage zone (late Early Triassic )and Triassocampe dew even assemblage zone (Middle Triassic ). The Permo -Triassic boundary in chert mono -facial sequence of the Muyinhe Formation is discussed .

Simulation of Morphological Development of Soil Cracks in Yuanmou Dry-hot Valley Region, Southwest China

Soil cracking is an important process influencing water and solutes transport in the Yuanmou Dry-hot Valley region of Southwest China. Studying the morphological development of soil cracks helps to further reveal the close relationship between the soil cracking process and water movement in such semi-arid regions. Here we report regular changes on surface morphology of soil cracks with decreasing water in four different soils (Typ-Ustic Ferrisols,Ver-Ustic Ferrisols,Tru-Ustic Vertisols and Typ-Ustic Vertisols) through simulation experiments. Our results indicate the following: 1) Different soils ultimately have different development degrees of soil cracks,according to their various values of crack area density. Soil cracks in Typ-Ustic Ferrisols can only develop to the feeble degree,while those in the other three soils are capable of developing into the intensive degree,and even into the extremely intensive degree. 2) Soil crack complexity,as expressed by the value of the area-weighted mean of crack fractal dimension (AWMFRAC),is found to continuously decrease as a whole through the whole cracking process in all the studied soils. 3) Soil crack connectivity shows a uniform trend in the studied soils,that is to say,connectivity gradually increases with soil crack development.

Preliminary research to determine stressdistricts form focal mechanism solutions in Southwest China and its adjacent area

The method of sliding direction fitting is used to determine stress districts, taking the shear stress directions andratios of shear stress to stress on fault planes given by focal mechanism solutions as the criteria to select focalmechanism solutions of one region and sorting out the ear'thquakcs controlled by different tectonic stfess fields,and then determining the stress districts from epicenter distribution of eanhquakes. We call this method as step bystep convergence method. By inversion analyzing of 297 focal mechanism solutions, we consider that SouthwestChina and its adjacent area can be divided into 5 stress districts, and we worked out directions of the three principal stresses and values of shape factor gi in 5 stress districts.

Stable Isotopic Variations in Precipitation in Southwest China

This study analyzes .the relationships of stable isotopes in precipitation with temperature, air pressure and humidity at different altitudes, and the potential influencing mechanisms of control factors on the stable isotopes in precipitation in Southwest China. There appear marked negative correlations of the δ^18 in precipitation with precipitation amount, vapor pressure and atmospheric precipitable water （PW） at the Mengzi, Simao and Tengchong stations on the synoptic timescale; the marked negative correlations between the δ^18 in precipitation and the diurnal mean temperature at 400 hPa, 500 hPa, 700 hPa and 850 hPa are different from the temperature effect in middle-high-latitude inland areas. In addition, the notable positive correlation between the δ^18 in precipitation and the dew-point deficit ATd at different altitudes is found at the three stations. Precipitation is not the only factor generating an amount effect. Probably, the amount effect is related to the variations of atmospheric circulation, and vapor origins. On the annual timescale, the annual precipitation amount weighted-mean δ^18 displays negative correlations not only with annual precipitation but also with annual mean temperature at 500 hPa. It can be deduced that, in the years with an abnormally strong summer monsoon, more warm and wet air from low-latitude oceans is transported northward along the vapor channel located in Southwest China and generates abnormally strong rainfall on the way. Meanwhile, the abnormally strong condensation process will release more condensed latent heat in the atmosphere, and this will lead to a rise of atmospheric temperature during rainfall but a decline of δ^18 in the precipitation. On the other hand, in the years with an abnormally weak summer monsoon, the precipitation and the atmospheric temperature during rainfalls decrease abnormally but the δ^18 in precipitation increases.

ECOLOGICAL AND SOCIO-ECONOMIC REHABILITATION IN THE KARST OF SOUTHWEST CHINA

The Karst of Southwest China is a typical representative of poverty stricken region with impoverishment-degradation spiral. To essentially break away from this vicious circle, the local ecology, economy and society should be rehabilitated, and hence to strengthen the self-development capacity building of the localities. Two considerations are stressed in this article: (1) Poverty alleviation is a system project with great complexities. Any single approach is difficult to success and integrated measures should be taken. (2) Some typical and feasible areas should be selected to demonstrate the project of poverty alleviation and ecological, socio-economic reconstruction. Then, they can be used as a model to promote the sustainable development of the whole region. Based upon these ideals, a project entitled “Reversal of Impoverishment-Degradation Spiral in the Karst of Southwest China' was proposed and has been listed in 《Priority Programme for China's Agenda 21》.

PV Perspective of Impacts on Downstream Extreme Rainfall Event of a Tibetan Plateau Vortex Collaborating with a Southwest China Vortex

An extreme rainfall event occurred over the middle and lower reaches of the Yangtze Basin(MLY)during the end of June 2016,which was attributable to a Tibetan Plateau(TP)Vortex(TPV)in conjunction with a Southwest China Vortex(SWCV).The physical mechanism for this event was investigated from Potential Vorticity(PV)and omega perspectives based on MERRA-2 reanalysis data.The cyclogenesis of the TPV over the northwestern TP along with the lower-tropospheric SWCV was found to involve a midtropospheric large-scale flow reconfiguration across western and eastern China with the formation of a high-amplitude Rossby wave.Subsequently,the eastward-moving TPV coalesced vertically with the SWCV over the eastern Sichuan Basin due to the positive vertical gradient of the TPV-related PV advection,leading the lower-tropospheric jet associated with moisture transport to intensify greatly and converge over the downstream MLY.The merged TPV−SWCV specially facilitated the upper-tropospheric isentropic-gliding ascending motion over the MLY.With the TPV-embedded mid-tropospheric trough migrating continuously eastward,the almost stagnant SWCV was re-separated from the overlying TPV,forming a more eastward-tilted high-PV configuration to trigger stronger ascending motion including isentropic-gliding,isentropic-displacement,and diabatic heating-related ascending components over the MLY.This led to more intense rainfall.Quantitative PV diagnoses demonstrate that both the coalescence and subsequent re-separation processes of the TPV with the SWCV were largely dominated by horizontal PV advection and PV generation due to vertically nonuniform diabatic heating,as well as the feedback of condensation latent heating on the isentropic-displacement vertical velocity.

Surface Morphology of Soil Cracks in Yuanmou Dry-hot Valley Region,Southwest China

Surface morphology of soil cracks is one of the important factors influencing the water evaporation rate in cracked soil in Yuanmou Dry-hot Valley Region,Southwest China. Quantitative study of the complicated surface morphology of soil cracks is a prerequisite for further studies of soil-cracking mechanisms. The present paper establishes a quantitative indicator system by application of concepts and methods originating from Fractal Geometry and Network Analysis. These indicators can effectively express the complicated features of soil-crack network structure. Furthermore,a series of values related to soil-crack morphology was obtained by image processing on field photos of soil-crack quads,and gradation criteria for the degree of development of soil cracks were determined. Finally,the changes in values of the morphological indicators under different degrees of development were analyzed in detail. Our results indicate that (1) the degree of development of soil cracks can be divided into five grades,i.e.,feeble development,slight development,medium development,intensive development and extremely intensive development; (2) the values of the indicators change predictably with increasing degree of development of soil cracks. The area density (Dc) increases,and both the area-weighted mean ratio of crack area to perimeter (AWMARP),which reflects the intensity of cracking,and the index r,which is related to the connectivity of a soil crack,grow uniformly (albeit with different forms). AWMRAP increases at a geometric rate while r shows logarithm-mic growth,indicating a gradual increase in theconnectivity of a soil crack. Nevertheless,the area-weighted mean of soil-crack fractal dimension (AWMFRAC) shows a decreasing trend,indicating a gradual decline in the complexity of cracks as area density increases.

Natural resources deterioration,environmental degradation and sustainable resetlement in Southwest China

As a consequence of increased population growth and environmental degradation, a particular type of population mobility-environmental migration-has emerged in the Third World. In this paper environmental migration is defined and previous practices in some developing countries are reviewed. A case study of the Karst Region of Southwest China is used to illustrate the phenomenon, including root causes, restrictive factors, nature of the migration, desires of migrants, strategies of response and optional policies. It is argued that a comprehensive approach to the prevention of environmentally caused displacement should be developed.

Geology and Isotope Geochemistry of the Yinchanggou-Qiluogou Pb-Zn Deposit,Sichuan Province,Southwest China

The Yinchanggou-Qiluogou Pb-Zn deposit,located in the western Yangtze Block,southwest China,is hosted by the Upper Sinian Dengying Formation dolostone.Ore bodies occur in the Qiluogou anticline and the NS-and NNW-trending faults.Sulfide ores mainly consist of sphalerite,pyrite,galena and calcite,with subordinate dolomite and quartz.Seventeen ore bodies have been discovered to date and they have a combined 1.0 million tons of sulfide ores with average grades of 2.27wt%Zn and 6.89wt%Pb.The δD（H2O-SMOW） and δ18O（H2O-SMOW） values of fluid inclusions in quartz and calcite samples range from-68.9‰ to-48.7‰ and 7.3‰ to 15.9‰,respectively,suggesting that H2O in the hydrothermal fluids sourced from metamorphic water.Calcite samples have δ13C（PDB） values ranging from-6.2‰ to-4.1‰ and δ18O（SMOW） values ranging from 15.1‰ to 17.4‰,indicating C and O in the hydrothermal fluids likely derived from a mixed source of metamorphic fluids and the host carbonates.The δ34S（CDT） values of sulfide minerals range from 5.5‰ to 20.3‰,suggesting that thermal chemical reduction of sulfate minerals in evaporates were the most probable source of S in the hydrothermal fluids.The 206Pb/204Pb,207Pb/204Pb and 208Pb/204Pb ratios of sulfide minerals fall in the range of 18.11 to 18.40,15.66 to 15.76 and 38.25 to 38.88,respectively.The Pb isotopic data of the studied deposit plot near the upper crust Pb evolution curve and overlap with the age-corrected Proterozoic basement rocks and the Upper Sinian Dengying Formation hosting dolostone.This indicates that the Pb originated from a mixed source of the basement metamorphic rocks and the ore-hosting carbonate rocks.The ore geology and C-H-O-S-Pb isotopic data suggest that the YinchanggouQiluogou deposit is an unusual carbonate-hosted,strata-bound and epigenetic deposit that derived ore-forming materials from a mixed source of the underlying Porterozoic basements and the Sinian hosting carbonates.

Spatiotemporal evolution of land transportation networks and accessibility in inland mountainous areas 1917-2017:A case study of Southwest China

Located in the western hinterland,Southwest China is a typical mountainous area covered by plateaus,mountains and hills.Its ruggedness hinders regional internal and external connections,and its poor transportation infrastructure has long constrained the socioeconomic development of Southwest China.Based on the GIS transportation database,this paper explored the spatiotemporal evolution and characteristics of the land transportation networks and the accessibility of Southwest China from 1917 to 2017.Regional accessibility in Southwest China has significantly improved,and transportation infrastructure has gradually integrated the transportation circles of the52 central cities.The transportation network has followed an evolutionary process from a"hub-spoke pattern"to a"network pattern",while the construction of a high-speed railway(HSR)has brought about significant spatial polarization.We argue that innovation in transportation technology is one of the most effective factors for promoting a significant change in regional accessibility.In addition,the spatial distribution and evolution of accessibility in Southwest China presents a verticalcharacteristic that distinguishes it from the plains,as the spillover effects of new transportation infrastructure on accessibility improvement are partly offset by the mountainous terrain.Additionally,in Southwest China,there is significant"path dependence"in the evolution of the transportation network,since a large portion of the population is concentrated along transportation corridors in mountainous areas.

Assessing the impacts of climate change and anthropogenic activities on vegetation in southwest China

The topography and geomorphology of southwest China are complex,and the intensity of human activities not balanced.The impact of climate change and anthropogenic activities on vegetation shows temporal and spatial differences.Therefore,we used normalized difference vegetation index(NDVI)to analyze the impact of climate change and anthropogenic activities on vegetation in four provinces and municipality in the southwest China from 2000 to 2015.The results showed that(1)NDVI increased 0.004–0.005/yr during this period.About 57.74%–69.09%of the area with significant changes was found to be primarily affected by anthropogenic activities during all four seasons and the growing season,while 6.05%–10.74%and 5.09%–9.77%of the area was affected by temperature and precipitation,respectively.(2)The impact of temperature and precipitation changes were spatially heterogeneous.Temperature had a positive impact during spring and summer in the northwestern region.Furthermore,NDVI was positively affected in the southwestern and eastern regions,while the western region was negatively affected by precipitation.Summer temperatures and precipitation had the greatest impact throughout the year.(3)Returning farmland to forests and improving agricultural management demonstrated positive impacts of anthropogenic activities on the vegetation,while areas with significant negative impacts due to anthropogenic activities were located near the provincial capitals of the four provinces and municipality.This study can provide a scientific basis for accurately identifying key ecological protection areas in Southwest China.