Phylogenetic pattern of alpine plants along latitude and longitude in Hengduan Mountains Region

To detect the horizontal pattern of phylogenetic structure shown by alpine plants, we measured phylogenetic structure using net related index(NRI) and net nearest taxon index(NTI), and analyzed the phylogenetic structure patterns of alpine plants along longitude, latitude and environmental gradients in the Hengduan Mountains Region(HDMR). Our results show that: 1) the phylogenetic structure tended to cluster with increasing latitude and longitude; 2) for NRI, latitude was closer related than longitude,while for NTI, longitude was closer related than latitude, though they both not significantly relate to NTI.The phylogenetic structure tended towards overdispersion in the southern HDMR, with good climate conditions of higher mean annual temperature and more mean annual precipitation. In contrast, with harsh climate conditions of lower mean annual temperature and less mean annual precipitation, the increasing environmental stress led to phylogenetic clustering in the northern HDMR. The results highlighted that in the alpine region of HDMR, environmental filters and geographical isolation had a great effect on the latitudinal and longitudinal alpine species distribution, respectively.

Forest disturbances and the attribution derived from yearly Landsat time series over 1990–2020 in the Hengduan Mountains Region of Southwest China

Background:Natural forests in the Hengduan Mountains Region(HDMR)have pivotal ecological functions and provide diverse ecosystem services.Capturing long-term forest disturbance and drivers at a regional scale is crucial for sustainable forest management and biodiversity conservation.Methods:We used 30-m resolution Landsat time series images and the LandTrendr algorithm on the Google Earth Engine cloud platform to map forest disturbances at an annual time scale between 1990 and 2020 and attributed causal agents of forest disturbance,including fire,logging,road construction and insects,using disturbance properties and spectral and topographic variables in the random forest model.Results:The conventional and area-adjusted overall accuracies(OAs)of the forest disturbance map were 92.3% and 97.70%±0.06%,respectively,and the OA of mapping disturbance agents was 85.80%.The estimated disturbed forest area totalled 3313.13 km^(2)(approximately 2.31% of the total forest area in 1990)from 1990 to 2020,with considerable interannual fluctuations and significant regional differences.The predominant disturbance agent was fire,which comprised approximately 83.33% of the forest area disturbance,followed by logging(12.2%),insects(2.4%)and road construction(2.0%).Massive forest disturbances occurred mainly before 2000,and the post-2000 annual disturbance area significantly dropped by 55% compared with the pre-2000 value.Conclusions:This study provided spatially explicit and retrospective information on annual forest disturbance and associated agents in the HDMR.The findings suggest that China’s logging bans in natural forests combined with other forest sustainability programmes have effectively curbed forest disturbances in the HDMR,which has implications for enhancing future forest management and biodiversity conservation.

A new scheme of climate-vegetation regionalization in the Hengduan Mountains Region

The Hengduan Mountains Region(HMR) is essential for the future ecological protection, clean energy production,Sichuan-Xizang and Yunnan-Xizang railways, and other major infrastructure projects in China. The distributions of climate and vegetation exhibit significant regional differentiation and vertical zonality due to the rugged longitudinal ranges and gorges and the complex disaster-prone environments in HMR. Therefore, it is urgent to develop the climate-vegetation regionalization in HMR to effectively satisfy the national requirements such as agricultural production and ecological protection, mountain disaster risk prevention, and major project construction. We here develop a new scheme of climate-vegetation regionalization with the latest demarcation outcome of HMR, the ground observation from 122 meteorological stations in HMR and its surrounding areas during 1990–2019, and the high-precision remote sensing data of land cover types. The new scheme first constructs the regionalization index system, fully considering the extraordinarily complicated geomorphic pattern of mountains and valleys, the scarcity of meteorological observations, and the remarkable differentiation of climate and vegetation in HMR. The system consists of three primary regionalization indices(i.e., days with daily average temperature steady above 10°C, aridity index, and main vegetation types, dividing the temperature zones, moisture regions, and vegetation subregions, respectively) and three auxiliary indices of the accumulated temperature above 10°C, and the temperatures in January and July. Then, the HMR is divided into five temperature zones, 20 moisture regions, and 55 vegetation subregions. Compared with previous regionalization schemes, the new scheme optimizes the climate spatial interpolation model of thin plate smoothing spline suitable for the unique terrain in HMR. Moreover, the disputed division index threshold between different climatic zones(regions) is scientifically clarified using geographical detectors. Specifically, the stepwise downscaling pane division method is initially proposed to determine the zoning boundary, alleviating the excessive dependence of the traditional zoning method on subjective experience.Besides, the scheme considers the typical regional characteristics of the complex underlying surface and the high gradient zone of climate-vegetation distribution types in HMR. Consequently, the transition zone with quick climate changes between the plateau temperate and mid-subtropical zones is divided into mountainous subtropics, taking into account the spatial distribution characteristics of climate-vegetation regionalization indices. The regionalization scheme will provide practically theoretical support for agricultural production, ecological protection, major project construction, disaster prevention and relief efforts, and other socioeconomic activities in HMR, serving as a classic case of climate-vegetation regionalization for the alpine and canyon regions with intricate underlying surface, striking regional differences, and lack of ground observations.

Hydrochemical characteristics of surface water in Hengduan mountain region of Eastern Tibet and its response to human activities:A case study of Duoqu Basin,Jinsha River

The analysis of hydrochemical characteristics and influencing factors of surface river on plateau is helpful to study water hydrological cycle and environmental evolution,which can scientifically guide rational development and utilization of water resources and planning of ecological environment protection.With the expansion and diversification of human activities,the quality of surface rivers will be more directly affected.Therefore,it is of great significance to pay attention to the hydrochemical characteristics of plateau surface rivers and the influence of human activities on their circulation and evolution.In this study,surface water in the Duoqu basin of Jinsha River located in Hengduan mountain region of Eastern Tibet was selected as the representative case.Twenty-three groups of surface water samples were collected to analyze the hydrochemical characteristics and ion sources based on correlation analysis,piper trigram,gibbs model,hydrogen and oxygen isotopic techniques.The results suggest the following:(1)The pH showed slight alkalinity with the value ranged from 7.25 to 8.62.Ca^(2+),Mg^(2+)and HCO_(3)^(–)were the main cations and anions.HCO_(3)^(-)Ca and HCO_(3)^(-)Ca·Mg were the primary hydrochemical types for the surface water of Duoqu River.The correlation analysis showed that TDS had the most significant correlation with Ca^(2+),Mg^(2+)and HCO_(3)^(–).Analysis on hydrogen and oxygen isotopes indicated that the surface rivers were mainly recharged by atmospheric precipitation and glacial melt water in this study area.(2)The surface water had a certain reverse cation alternating adsorption,and surface water ions were mainly derived from rock weathering,mainly controlled by weathering and dissolution of carbonates,and secondly by silicates and sodium rocks.(3)The influence of human activities was weak,while the development of cinnabar minerals had a certain impact on the hydrochemistry characteristics,which was the main factor for causing the increase of SO_(4)^(2–).The densely populated county towns and temples with frequent incense burning activities may cause some anomalies of surface water quality.At present,the Duoqu River watershed had gone through a certain influence of mineral exploitation,so the hydrological cycle and river eco-environment at watershed scale will still bound to be change.The results could provide basic support for better understanding water balance evolution as well as the ecological protection of Duoqu River watershed.

A New Species of the Genus Scincella Mittleman, 1950 (Squamata: Scincidae)from Sichuan Province, Southwest China, with a Diagnostic Key of Scincella Species in China

The genus Scincella Mittleman,1950 of the family Scincidae currently includes 38 species."To date,however,taxonomic assessment remains challenging.Here,phylogenetic analyses based on DNA sequences of four mitochondrial genes supported a putative new species from Sichuan Province,Southwest China,as an independent lineage.Uncorrected genetic distance of 16S rRNA between the new species and closest congener was 8%,and the population was morphologically distinguishable from all other known congeners.We herein describe the Scincella population as anew species based on both phylogeny and comparative morphology.The new species can be distinguished from its congeners by a combination of the following morphological characters:(1)body slender,mediumsized,snout-vent length 35.0-62.1 mm;(2)infralabials seven,rarely eight;(3)supraciliaries 5-7;(4)tympanum deeply sunk without lobules;(5)midbody scale-row counts 27-30;(6)dorsal scales smooth and enlarged,paravertebral scale-row counts 60-75,ventral scalerow counts 46-59,gulars 25-30;(7)upper edge of lateral longitudinal stripes relatively straight with six rows of dorsal scales in middle;(8)number of enlarged,undivided lamellae beneath fingerⅣ9-11,number of enlarged,undivided lamellae beneath toeⅣ13-16;(9)ventral side of tail densely ornamented with dark brown or black spots;and(10)grayish-brown discontinuous regular dorsal stripes 5-7,distinct black dorsolateral stripes,starting from posterior corner of eye and continuing to lateral side of tail.A diagnostic key to all Scincella members from China is also provided The new species is currently only known from Wenchuan and Lixian counties,Sichuan Province,China,and brings the number of Scincella species in China to 12.This study emphasizes the incompleteness of knowledge on herpetodiversity in China.

Attribution analysis for water yield service based on the geographical detector method:A case study of the Hengduan Mountain region

Ecosystem services,which include water yield services,have been incorporated into decision processes of regional land use planning and sustainable development.Spatial pattern characteristics and identification of factors that influence water yield are the basis for decision making.However,there are limited studies on the driving mechanisms that affect the spatial heterogeneity of ecosystem services.In this study,we used the Hengduan Mountain region in southwest China,with obvious spatial heterogeneity,as the research site.The water yield module in the InVEST software was used to simulate the spatial distribution of water yield.Also,quantitative attribution analysis was conducted for various geomorphological and climatic zones in the Hengduan Mountain region by using the geographical detector method.Influencing factors,such as climate,topography,soil,vegetation type,and land use type and pattern,were taken into consideration for this analysis.Four key findings were obtained.First,water yield spatial heterogeneity is influenced most by climate-related factors,where precipitation and evapotranspiration are the dominant factors.Second,the relative importance of each impact factor to the water yield heterogeneity differs significantly by geomorphological and climatic zones.In flat areas,the influence of evapotranspiration is higher than that of precipitation.As relief increases,the importance of precipitation increases and eventually,it becomes the most influential factor.Evapotranspiration is the most influential factor in a plateau climate zone,while in the mid-subtropical zone,precipitation is the main controlling factor.Third,land use type is also an important driving force in flat areas.Thus,more attention should be paid to urbanization and land use planning,which involves land use changes,to mitigate the impact on water yield spatial pattern.The fourth finding was that a risk detector showed that Primarosol and Anthropogenic soil areas,shrub areas,and areas with slope<5°and 250-350 should be recognized as water yield important zones,while the corresponding elevation values are different among different geomorphological and climatic zones.Therefore,the spatial heterogeneity and influencing factors in different zones should be fully con-sidered while planning the maintenance and protection of water yield services in the Hengduan Mountain region.

The new species and the third Chinese member of Colubrina(C.zhaoguangii,Rhamnaceae)

A novel species of Rhamnaceae,Colubrina zhaoguangii,is discovered in Sichuan,China,during the biodiversity investigations of the Second Tibetan Plateau Scientific Expedition and Research.Detailed descriptions and illustrations of the new species are presented herein.To date,the new species is only found in dry-warm river valleys of the Jinsha River basin in the Hengduan Mountains region(HDM).Compared with the other two known Chinese Colubrina species,C.zhaoguangii features by the habit of twisted shrub and tiny leaves with emarginate apex.In morphology,the new species highly resembles C.alluaudii endemic in Madagascar and C.viridis in northwestern Mexico,whereas it is distinguished from these two relatives by its minutely white scales on the leaf blades.The discovery of C.zhaoguangii reminds us again that the bottom region is also important for biodiversity conservation in HDM and should be a flora survey priority.