Quantifying the impact of earthquakes and geological factors on spatial heterogeneity of debris-flow prone areas:A case study in the Hengduan Mountains

Understanding the spatial heterogeneity of debris-flow-prone areas holds significant implications for regional risk management, particularly in seismically active regions with geological faults. Despite the significance of this knowledge, a comprehensive quantification of the influence of regional topographical and geological factors on the spatial heterogeneity of debris-flow-prone areas has been lacking. This study selected the Hengduan Mountains, an earthquake-prone region characterized by diverse surface conditions and complex landforms, as a representative study area. An improved units zoning and objective factors identification methodology was employed in earthquake and fault analysis to assess the impact of seismic activity and geological factors on spatial heterogeneity of debrisflow prone areas. Results showed that the application of GIS technology with hydrodynamic intensity and geographical units analysis can effectively analyze debris-flow prone areas. Meanwhile, earthquake and fault zones obviously increase the density of debrisflow prone catchments and make them unevenly distributed. The number of debris-flow prone areas shows a nonlinear variation with the gradual increase of geomorphic factor value. Specifically, the area with 1000 m-2500 m elevation difference, 25°-30° average slope, and 0.13-0.15 land use index is the most favorable conditions for debris-flow occurrence;The average annual rainfall from 600 to 1150 mm and landslides gradient from 16° to 35° are the main causal factors to trigger debris flow. Our study sheds light on the quantification of spatial heterogeneity in debris flow-prone areas in earthquake-prone regions, which can offer crucial support for post-debris flow risk management strategies.

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.

A New Species of the Genus Nanorana Günther,1896(Anura:Dicroglossidae)from Hengduan Mountains of China

An integrative study based on morphological data and mitochondrial molecular data of all known Nanorana(sensu stricto)species have revealed a new species from the Hengduan Mountains,N.huangi sp.nov.The new species can be distinguished from its congers by its:(1)medium body size,SVL 31.3–40.6 mm in adult males(n=12),39.2–48.1 mm in adult females(n=8);(2)absence of subarticular tubercles on fingers,with supernumerary tubercles below the base of the fingers small but distinct;(3)presence of dark dorsal patches without pale margins,generally creamy yellow ventral body basically,bright yellow ventral limbs;(4)small but prominent tympanum;(5)tibio-tarsal joint that reaches to the tympanum or the shoulder when hindlimbs adpressed forward towards body;(6)head length more than 30%of SVL.In addition,the new species can be separated from all other congeners by uncorrected genetic distances:ranging from 2.8%–7.5%of the mitochondrial 12S rRNA,1.1%–2.1%of the 16S rRNA,and 7.5%–11.5%of the COI.

Origins and evolution of plant diversity in the Hengduan Mountains, China

1.Introduction The Hengduan Mountains region(HDM)in southwest China,one of the earth's 34 biodiversity hotspots,is characterized by its unique geology,dramatic topography,a climate where snow and below freezing temperatures can occur on any day of the year,by its location at elevations averaging between(1400e)2000 and4500(e5300)meters above sea level(m a.s.l.),and by one of

Changes of Temperature and Precipitation Extremes in Hengduan Mountains,Qinghai-Tibet Plateau in 1961-2008

Variations and trends in extreme climate events are more sensitive to climate change than the mean values, and so have received much attention. In this study, twelve indices of temperature extremes and 11 indices of precipita- tion extremes at 32 meteorological stations in Hengduan Mountains were examined for the period 1961-2008. The re- suits reveal statistically significant increases in the temperature of the warmest and coldest nights and in the frequen- cies of extreme warm days and nights. Decreases of the diurnal temperature range and the numbers of frost days and ice days are statistically significant. Regional averages of growing season length also display the trends consistent and significant with warming. At a large proportion of the stations, patterns of temperature extremes are consistent with warming since 1961： warming trends in minimum temperature indices are greater than those relating to maximum temperature. As the center of the Shaluli Mountain, the warming magnitudes decrease from inner to outer. Changes in precipitation extremes is low： trends are difficult to detect against the larger inter-annual and decadal-scale variability of precipitation, and only the wet day precipitation and the regional trend in consecutive dry days are significant at the 0.05 level. It can be concluded that the variation of extreme precipitation events is not obvious in the Hengduan Mountains, however, the regional trends generally decrease from the south to the north. Overall, the spatial distribution of temporal changes of all extreme climate indices in the Hengduan Mountains illustrated here reflects the climatic complexity in mountainous regions.

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.

Spatio-temporal Pattern of Net Primary Productivity in Hengduan Mountains area, China： Impacts of Climate Change and Human Activities

Net primary productivity(NPP), a metric used to define and identify changes in plant communities, is greatly affected by climate change, human activities and other factors. Here, we used the Carnegie-Ames-Stanford Approach(CASA) model to estimate the NPP of plant communities in Hengduan Mountains area of China, and to explore the relationship between NPP and altitude in this region. We examined the mechanisms underlying vegetation growth responses to climate change and quantitatively assessed the effects of ecological protection measures by partitioning the contributions of climate change and human activities to NPP changes. The results demonstrated that: 1) the average total and annual NPP values over the years were 209.15 Tg C and 468.06 g C/(m2·yr), respectively. Their trend increasingly fluctuated, with spatial distribution strongly linked to altitude(i.e., lower and higher NPP in high altitude and low altitude areas, respectively) and 2400 m represented the marginal altitude for vegetation differentiation; 2) areas where climate was the main factor affecting NPP accounted for 18.2% of the total research area, whereas human activities were the primary factor influencing NPP in 81.8% of the total research area, which indicated that human activity was the main force driving changes in NPP. Areas where climatic factors(i.e., temperature and precipitation) were the main driving factors occupied 13.6%(temperature) and 6.0%(precipitation) of the total research area, respectively. Therefore, the effect of temperature on NPP changes was stronger than that of precipitation; and 3) the majority of NPP residuals from 2001 to 2014 were positive, with human activities playing an active role in determining regional vegetation growth, possibly due to the return of farmland back to forest and natural forest protection. However, this positive trend is decreasing. This clearly shows the periodical nature of ecological projects and a lack of long-term effectiveness.

Diversity and Geographical Pattern of Altitudinal Belts in the Hengduan Mountains in China

This paper analyses the diversity and spatial pattern of the altitudinal belts in the Hengduan Mountains in China. A total of 7 types of base belts and 26 types of altitudinal belts are identified in the study region. The main altitudinal belt lines, such as forest line, the upper limit of dark coniferous forest and snow line, have similar latitudinal and longitudinal spatial patterns, namely, arched quadratic curve model with latitudes and concave quadratic curve model along longitudinal direction. These patterns can be together ealled as ＂Hyperbolic-paraboloid model＂, revealing the complexity and speciality of the environment and ecology in the study region. This result further validates the hypnosis of a common quadratic model for spatial pattern of mountain altitudinal belts proposed by the authors. The spatial pattern of altitudinal belts is closely related with moisture-related exposure effect in the Hengduan Mountains. Different combinations （spectra） of altitudinal belts and different base belt types appear in windward and leeward flanks and even in the same flanks of different ranges. This is closely related with the parallel mountain ranges of the Hengduan Mountains, which, at nearly right angle with the moving direction of prevailing moisture-laden air masses from west and east, hold up the warm and humid monsoon wind from moving into the core region and result in different moisture conditions in windward and leeward flanks. However, how to quantitatively describe the moisture-related exposure effect needs further study. In addition, the data quality and data accuracy at present also affect to some extent the result of quantitative modeling and should be improved with RS/GIS in the future.

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.

Variation of Thornthwaite Moisture Index in Hengduan Mountains, China

The Thornthwaite moisture index, an index of the supply of water （precipitation） in an area relative to the climatic demand for water （potential evapotranspiration）, was used to examine the spatial and temporal variation of drought and to verify the influence of environmental factors on the drought in the Hengduan Mountains, China. Results indicate that the Thornthwaite moisture index in the Hengduan Mountains had been increasing since 1960 with a rate of 0.1938/yr. Annual Thomthwaite moisture index in Hengduan Mountains was between -97.47 and 67.43 and the spatial heterogeneity was obvious in different seasons. Thomthwaite moisture index was high in the north and low in the south, and the monsoon rainfall had a significant impact on its spatial distribution. The tendency rate of Thomthwaite moisture index variation varied in different seasons, and the increasing trends in spring were greater than that in summer and autumn. However, the Thomthwaite moisture index decreased in winter. Thomthwaite moisture index increased greatly in the north and there was a small growth in the south of Hengduan Mountains. The increase of precipitation and decrease of evaporation lead to the increase of Thomthwaite moisture index. Thornthwaite moisture index has strong correlation with vegetation coverage. It can be seen that the correlation between Normalized Difference Vegetation Index （NDVI） and Thomthwaite moisture index was positive in spring and summer, but negative in autumn and winter. Correlation between Thornthwaite moisture index and relative soil relative moisture content was positive in spring, summer and autumn, but negative in winter. The typical mountainous terrain affect the distribu- tion of temperature, precipitation, wind speed and other meteorological factors in this region, and then affect the spatial distribution of Thomthwaite moisture index. The unique ridge-gorge terrain caused the continuity of water-heat distribution from the north to south, and the water-heat was stronger than that from the east to west part, and thus determined the spatial distribution of Thornthwaite mois- ture index. The drought in the Hengduan Mountains area is mainly due to the unstable South Asian monsoon rainfall time.

Phylogenetic relationships of the zokor genus Eospalax(Mammalia,Rodentia,Spalacidae)inferred from whole-genome analyses,with description of a new species endemic to Hengduan Mountains

Zokors in the genus Eospalax,which are endemic to northern and western China,are subterranean rodents that inhabit various niches,including grasslands,high-altitude meadows,forests,and farmlands.Six species in Eospalax were described a century ago but their taxonomy and phylogeny remain controversial.In this study,we performed high-depth whole-genome sequencing of 47 zokor samples,comprising all six previously described species.Genomic analyses revealed a reliable and robust phylogeny of Eospalax and supported the validity of the six named species.According to the inferred phylogenetic relationships,Eospalax first divergent into two clades in the early Pliocene(ca.4.68 million years ago(Ma)),one inhabiting the highaltitude Qinghai-Xizang(Tibet)Plateau(QTP)and adjacent regions,and the another inhabiting the lowaltitude Loess Plateau and Qinling-Daba Mountains.The most recent divergences occurred between E.baileyi and E.smithii and between E.rufescens and E.rothschildi in the late Pliocene(ca.2.09 and 2.19 Ma,respectively).We also collected specimens of zokors in the southern Hengduan Mountains(Muli County,Sichuan Province),far from the known distributions of all other zokors.Morphological and molecular analyses strongly suggested that the specimens represent a new species,formally described here as Eospalax muliensis sp.nov.The new species belongs to the high-altitude clade and diverged from closely related species(ca.4.22 Ma)shortly after the first divergence in Eospalax.Interestingly,Eospalax muliensis sp.nov.possesses more supposedly plesiomorphic characters,suggesting a possible origin of the genus in the Hengduan Mountains.

Adaptive responses drive the success of polyploid yellowcresses(Rorippa,Brassicaceae)in the Hengduan Mountains,a temperate biodiversity hotspot

Polyploids contribute substantially to plant evolution and biodiversity;however,the mechanisms by which they succeed are still unclear.According to the polyploid adaptation hypothesis,successful polyploids spread by repeated adaptive responses to new environments.Here,we tested this hypothesis using two tetraploid yellowcresses(Rorippa),the endemic Rorippa elata and the widespread Rorippa palustris,in the temperate biodiversity hotspot of the Hengduan Mountains.Speciation modes were resolved by phylogenetic modeling using 12 low-copy nuclear loci.Phylogeographical patterns were then examined using haplotypes phased from four plastid and ITS markers,coupled with historical niche reconstruction by ecological niche modeling.We inferred the time of hybrid origins for both species as the mid-Pleistocene,with shared glacial refugia within the southern Hengduan Mountains.Phylogeographic and ecological niche reconstruction indicated recurrent northward colonization by both species after speciation,possibly tracking denuded habitats created by glacial retreat during interglacial periods.Common garden experiment involving perennial R.elata conducted over two years revealed significant changes in fitness-related traits across source latitudes or altitudes,including latitudinal increases in survival rate and compactness of plant architecture,suggesting gradual adaptation during range expansion.These findings support the polyploid adaptation hypothesis and suggest that the spread of polyploids was aided by adaptive responses to environmental changes during the Pleistocene.Our results thus provide insight into the evolutionary success of polyploids in high-altitude environments.

Geoscience landscape division and tourism zonation in the mid-southern section of the Hengduan Mountains, eastern Qinghai-Tibet Plateau

The mid-southern section of the Hengduan Mountains is a typical region of mountainous landscape in western China and is the core region of "Shangri-La", a world-famous ecotourism destination. The landscape classification system is an important scientific basis for landscape protection and tourism development in this region. By combining geology and geography and referring to the concepts of "system tract" and "tectonic system" in geology, this paper comes up with grading standards for the geoscience landscape system of this region. Based on the regional stratigraphic structure, tectonic fault marks and geomorphological differentiation, this paper comes up with 2 Grade Ⅰ geoscience landscape system tracts, 8 Grade Ⅱ geoscience landscape systems, 21 Grade Ⅲ geoscience landscape areas, and 165 representative Grade Ⅳ geoscience landscape attractions. According to the main classification methods for the geological heritage and tourism landscapes, the geoscience landscapes can be divided into 4 categories, 16 types and 19 subtypes. On this basis, 23 eco-tourism areas of the mid-southern section of the Hengduan Mountains can be delimited. The study provides a theoretical direction and method reference for the geoscience landscape division and tourism zonation, which has an importantsignificance on the mountain landscape protection and tourism development in the regions of complex geo-environments.

Elevational patterns of functional diversity and trait of Delphinium(Ranunculaceae)in Hengduan Mountains,China

Elevational patterns of trait occurrence and functional diversity provide an important perspective for understanding biodiversity.However,previous studies have mostly examined functional diversity at the community scale.Here,we examined large-scale patterns of trait occurrence and functional diversity in Delphinium along an elevational gradient from 1000 to 5700 m in the Hengduan Mountains,SW China.Elevational distribution and trait data of 102 Delphinium species were compiled to evaluate the patterns of interspecific traits,species richness,and functional diversity.We found that the distribution of species richness showed a unimodal curve that peaked between 3500 and 4000 m;functional diversity and traits showed different patterns along an elevational gradient The functional diversity increased at a lower rate along an elevation gradient,whereas species richness continued to increase.Species with large ranges and non-endemic species were most affected by geometric constraints.Richness of species endemic to the Hengduan Mountains peaked at higher elevations,likely due to increased speciation and restricted dispersion under alpine conditions.We conclude that the middle elevation region is not only the functionally richest but also the most functionally stable region for Delphinium,which could be insurance against environmental change.Extreme conditions and strong environmental filters in an alpine environment may cause the convergence of species traits,which could relate to reducing nutrient trait investment and increasing reproductive trait investment.We conclude that large-scale studies are consistent with previous studies at the community scale.This may indicate that the relationship between functional diversity and species richness across different scales is the same.

Distribution patterns of clonal plants in the subnival belt of the Hengduan Mountains,SW China

Clonal reproduction(i.e.,production of potentially independent offspring by vegetative growth)is thought to provide plants with reproductive assurance.Thus,studying the evolution of clonal reproduction in local floras is crucial for our understanding of the adaptive mechanisms plants deploy in stressful environments such as alpine regions.In this study,we characterized clonal plant species in the subnival belt of the Hengduan Mountains(a global biodiversity hotspot with extreme environmental conditions in southwest China),in order to determine the effects of sex system,growth form,and elevational distribution on clonality.We compiled clonality data of angiosperm species belonging to 41 families in the subnival belt of the Hengduan Mountains using published information.Of the 793 species recorded in the region,47.92%(380 species)are clonal species.Both sex system and growth form had significant effects on the occurrence of clonal reproduction:unisexual species(79.79%)were more likely to be clonal than bisexual species(43.63%),and herbaceous species(51.04%)were more likely to be clonal than woody species(16.67%).Compared with non-alpine-endemic species(44.60%),alpine-endemic species(58.33%)showed a significantly higher proportion of clonal reproduction.Further logistic regression analysis showed a positive association between incidence of clonality and elevational range,indicating that species distributed at high elevations are more likely to be clonal.Furthermore,the elevational gradients in clonality were contingent on sex system or growth form.This study reveals that plants in the subnival belt of the Hengduan Mountains might optimize their probability of reproduction through clonal reproduction,a finding that adds to our growing understanding of plant's adaptations to harsh alpine environments.

Spatial Information Research for Temperature and Precipitation Climate Data in Hengduan Mountains

[Objective] The aim was to study the spatial information of temperature and precipitation data in Hengduan mountains. [Method] Considering GIS spatial interpolation and numerical statistics theory, spatial prediction were carried out to the ten years average temperature and precipitation flux observation data in 109 sparse meteorological stations in Hengduan Mountains. Based on the spatial range of geographic position of Hengduan Mountains, and 1∶1 000 000 scale DEM as data sources, and using trend surface simulation and residual ordinary Kriging interpolation correction method, the spatial continuous surface for annual average temperature and precipitation were studied. [Result] It was scientific and reasonable to use certain unevenly distributed sparse climate observation station value, and by dint of trend simulation and residue interpolation method to get climate consecutive spatial result. This method can not only accurate the temperature and precipitation spatial distributions to grid point, but also can reflect macro and micro geography factors and topographic influence factor of variation. Furthermore, it can be predicted error term trend surface reasonable spatial distribution. Simulation results were basically in accordance with the objective law, and can be used for the region climate data spatial informatization simulation. [Conclusion] The study provided scientific spatial basic data for the further study of ecological and vegetation in Hengduan Mountains.

Spatio-temporal variation of Fraction of Photosynthetically Active Radiation absorbed by vegetation in the Hengduan Mountains, China

The Fraction of Absorbed Photosynthetically Active Radiation(FPAR) is an important indicator of the primary productivity of vegetation. FPAR is often used to estimate the assimilation of carbon dioxide in vegetation. Based on MOD15 A2 H/FPAR data product, the temporal and spatial variation characteristics and variation trend of FPAR in different vegetation types in 2001 to 2018 were analyzed in the Hengduan Mountains. The response of FPAR to climate change was investigated by using Pearson correlation analytical method and partial least squares regression analysis. Results showed that the FPAR in Hengduan Mountains presented an increasing trend with time. Spatially, it was high in the south and low in the north, and it also showed obvious vertical zonality by elevation gradient.The vegetation FPAR was found to be positively correlated with air temperature and sunshine duration but negatively correlated with precipitation. Partial least squares regression analysis showed that the influence of sunshine duration on vegetation FPAR in Hengduan Mountains was stronger than that of air temperature and precipitation.

Early Holocene High Magnitude Debris Flow Events and Environmental Change as Illustrated by the Moxi Platform, Hengduan Mountains, SW China

Thick debris flow deposits in the Hengduan Mountains of southwestern China record landscape instability at the close of the last glaciation and in the early Holocene. The deposits, ranging in thickness from 100 to 200 m, are common and in high magnitude in the valleys of this region. They are products of large debris flows induced by glacier and enabled by the presence of large amount of glacial debris on the landscape. The carbon 14 dating from Moxi Platform indicates that a period of catastrophic debris flows occurred at c. 7 kyr B.P., and was concurrent with other glacial-fluvial fans and terraces which tied to regional climatic oscillations elsewhere in the Himalaya. The comparable events suggest a strong climatic control on earth surface processes for the dynamics, magnitude, and frequency in this region.

A New Species of Japalura(Squamata, Agamidae) from the Nu River Valley in Southern Hengduan Mountains, Yunnan, China

A population of Japalura from Yunnan Province, China, previously assigned to Japalura splendida, is described as a new species. The new species has been recorded between 1 138–2 500 m in the Nu River drainage between the towns of Liuku and Binzhongluo, and on the lower western slopes of the Nushan and eastern slopes of the Goaligongshan. The new species can be distinguished from other species of Japalura, except J. dymondi, by the following combination of characters： exposed tympani, prominent dorso-lateral stripes, and small gular scales. It is very similar with but differs from J. dymondi by having smooth or feebly keeled dorsal head scales, three relatively enlarged spines on either side of the post-occiput area, strongly keeled and mucronate scales on occiput area and within the lateral stripes, back of arm and leg green, higher number of dorsal-ridge scales（DS） and fourth toe subdigital scales（T4S）. A principal component analysis of body measurements of adult male specimens of the new species and J. dymondi showed principal component 1 loading highest for upper arm length, fourth toe length and snout to eye length and principal component 2 loading highest for head width, head length and fourth toe length.

Spatial and temporal variation of drought index in a typical steep alpine terrain in Hengduan Mountains

This study describes the spatial and temporal variation of a drought index and makes inferences regarding the environmental factors that influence this variability in the Hengduan Mountains. A drought index is typically used to determine the moisture conditions and the magnitude of water deficiency in a given area. Based on data from 26 meteorological stations over the period 1960-2012, the spatial and temporal variations of the drought index were analyzed using a thin plate smoothing splines method that considered elevation as a covariate. The drought index was estimated based on the potential evapotranspiration(E0) as defined by the Penman Monteith model modified by FAO(1998). The results of the reported analysis showed that the drought index in the Hengduan Mountains has been decreasing since 1960 at a rate of-0.008/a. This represented a progressive shift from the "sub-humid" class, which typified the wider area in the Hengduan Mountains, toward the "humid" class, which appeared in the Hengduan Mountains areas. The drought index was relatively high in the north and low in the south and the variation of the drought index varied with seasons. The drought index showed increasing trends in summer and autumn and it is greater in autumn than in summer, while it showed a decreasing trend in spring and winter. Drought index is inversely proportional to the soil relative humidity and Normalized Difference Vegetation Index(NDVI).