PROXY RECORD OF A FIRN-CORE FROM AN ALPINE GLACIER AND ITS IMPLICATION TO RECENT GLACIO-CLIMATIC VARIATIONS ON MT. YULONG, SOUTHEASTERN PART OF TIBETAN PLATEAU

Mt. Yulong, located in the eastern part of Tibetan Plateau, is the southmost present glaciation area both in China and Europe\|Asia continent,where distributes 19 typical sub\|tropics temperate glaciers. In the summer of 1999, a firn core, 10 10m long to the glacier ice, was successfully recovered in the accumulation area at the largest glacier (No.1 Baishui) on Mt. Yulong. Annual and seasonal variations of different climatic signals above the depth of 7 8m are apparent and five\|year snow accumulation can be clearly identified by the seasonal changes of isotopic and ionic composition, some higher values of electrical conductivity and pH values. These annual boundaries can be also verified by the positions of dirty refrozen ice layers at summer surface of each year. The mean annual net accumulation between the balance years of 94/95 and 97/98 are calculated to about 900mm water equivalent. The amplitude of isotopic changes becomes smaller with the increasing depth of the core and isotopic homogenization occurred below the depth of 7 8m. Concentrations of Ca 2+ and Mg 2+ are much higher than those of Na + and K +, reflecting that the air masses for precipitation came far from their marine sources and passed over a longer continental route. Cl - and Na + show well corresponding variation patterns in the firn profile,indicating their same genesis. Concentrations of SO 2- 4 and NO - 3 are low, reflecting very slight pollution caused by human activities in this area. According to the sum of net income recovered from the firn core and the estimated ablation amount, the average annual precipitation above the equilibrium line is estimated in the scope of 2250mm and 3200mm but it needed to be verified by long\|term observation of mass balance. As indicated by the trend of local climatic changes in last 50years, climatic signals in the firn core and recent observation at the terminal of glacier No.1 Baishui, the glaciers in Mt. Yulong start to advance in 1998 after continuous retreat from early 1980’s to late 1990’s.

Altitude Effects of Climatic Variation on Tibetan Plateau and Its Vicinities

High topographies, such as the Tibetan plateau （TP） in China, have been considered as the sensitive areas in response to global climate change. By analyzing the relationship between warming structure and altitude （1 000-5 000 m） in the TP and its vicinities using the 46-year January mean observed temperature data, we found that there was a significant altitude effect of temperature warming onset time （mutation time） on the plateau and the neighboring regions： the higher the altitude, the later the climate warming happens, and vice versa. There also seems a slight altitude effect on warming magnitude： the higher the altitude, the less the warming magnitude. Therefore, the temperature warming in the high altitude area of the TP （below 5 000 m） responds to global warming less sensitively than the low-altitude neighboring areas both in onset time and magnitude, which may be mainly caused by high albedo and large thermal capacity of the ice/snow cover on the higher part of the plateau and possible heat island effect in the lower part of the plateau.

Formation and Variation of the Atmospheric Heat Source over the Tibetan Plateau and Its Climate Effects

To cherish the memory of the late Professor Duzheng YE on what would have been his 100 th birthday, and to celebrate his great accomplishment in opening a new era of Tibetan Plateau（TP） meteorology, this review paper provides an assessment of the atmospheric heat source（AHS） over the TP from different data resources, including observations from local meteorological stations, satellite remote sensing data, and various reanalysis datasets. The uncertainty and applicability of these heat source data are evaluated. Analysis regarding the formation of the AHS over the TP demonstrates that it is not only the cause of the atmospheric circulation, but is also a result of that circulation. Based on numerical experiments, the review further demonstrates that land–sea thermal contrast is only one part of the monsoon story. The thermal forcing of the Tibetan–Iranian Plateau plays a significant role in generating the Asian summer monsoon（ASM）, i.e., in addition to pumping water vapor from sea to land and from the lower to the upper troposphere, it also generates a subtropical monsoon–type meridional circulation subject to the angular momentum conservation, providing an ascending-air large-scale background for the development of the ASM.

Modeling black carbon and its potential radiative effects over the Tibetan Plateau

A regional climate model(RegCM4.3.4) coupled with an aerosol-snow/ice feedback module was used to simulate the deposition of anthropogenic light-absorbing impurities in snow/ice and the potential radiative feedback of black carbon(BC) on temperature and snow cover over the Tibetan Plateau(TP) in 1990-2009. Two experiments driven by ERA-interim reanalysis were performed, i.e., with and without aerosol-snow/ice feedback. Results indicated that the total deposition BC and organic matter(OM) in snow/ice in the monsoon season(MayeS eptember) were much more than non-monsoon season(the remainder of the year). The great BC and OM deposition were simulated along the margin of the TP in the non-monsoon season, and the higher deposition values also occurred in the western TP than the other regions during the monsoon period. BC-in-snow/ice decreased surface albedo and caused positive surface radiative forcing(SRF)(3.0-4.5 W m^(-2)) over the western TP in the monsoon season. The maximum SRF(5-6 W m^(-2)) simulated in the Himalayas and southeastern TP in the non-monsoon season. The surface temperature increased by 0.1-1.5℃ and snow water equivalent decreased by 5-25 mm over the TP, which showed similar spatial distributions with the variations of SRF in each season. This study provided a useful tool to investigate the mechanisms involved in the effect of aerosols on climate change and the water cycle in the cryospheric environment of the TP.

Temporal and Spatial Variations in the Climate Controls of Vegetation Dynamics on the Tibetan Plateau during 1982–2011

The ecosystem of the Tibetan Plateau is highly susceptible to climate change. Currently, there is little discussion on the temporal changes in the link between climatic factors and vegetation dynamics in this region under the changing climate.By employing Normalized Difference Vegetation Index data, the Climatic Research Unit temperature and precipitation data,and the in-situ meteorological observations, we report the temporal and spatial variations in the relationships between the vegetation dynamics and climatic factors on the Plateau over the past three decades. The results show that from the early 1980s to the mid-1990s, vegetation dynamics in the central and southeastern part of the Plateau appears to show a closer relationship with precipitation prior to the growing season than that of temperature. From the mid-1990s, the temperature rise seems to be the key climatic factor correlating vegetation growth in this region. The effects of increasing temperature on vegetation are spatially variable across the Plateau: it has negative impacts on vegetation activity in the southwestern and northeastern part of the Plateau, and positive impacts in the central and southeastern Plateau. In the context of global warming, the changing climate condition(increasing precipitation and significant rising temperature) might be the potential contributor to the shift in the climatic controls on vegetation dynamics in the central and southeastern Plateau.

Simulating Aerosol Optical Depth and Direct Radiative Effects over the Tibetan Plateau with a High-Resolution CAS FGOALS-f3 Model

Current global climate models cannot resolve the complex topography over the Tibetan Plateau(TP)due to their coarse resolution.This study investigates the impacts of horizontal resolution on simulating aerosol and its direct radiative effect(DRE)over the TP by applying two horizontal resolutions of about 100 km and 25 km to the Chinese Academy of Sciences Flexible Global Ocean-Atmosphere Land System(CAS FGOALS-f3)over a 10-year period.Compared to the AErosol RObotic NETwork observations,a high-resolution model(HRM)can better reproduce the spatial distribution and seasonal cycles of aerosol optical depth(AOD)compared to a low-resolution model(LRM).The HRM bias and RMSE of AOD decreased by 0.08 and 0.12,and the correlation coefficient increased by 0.22 compared to the LRM.An LRM is not sufficient to reproduce the aerosol variations associated with fine-scale topographic forcing,such as in the eastern marginal region of the TP.The difference between hydrophilic aerosols in an HRM and LRM is caused by the divergence of the simulated relative humidity(RH).More reasonable distributions and variations of RH are conducive to simulating hydrophilic aerosols.An increase of the 10-m wind speed in winter by an HRM leads to increased dust emissions.The simulated aerosol DREs at the top of the atmosphere(TOA)and at the surface by the HRM are–0.76 W m^(–2)and–8.72 W m^(–2)over the TP,respectively.Both resolution models can capture the key feature that dust TOA DRE transitions from positive in spring to negative in the other seasons.

Summertime Atmospheric Teleconnection Pattern Associated with a Warming over the Eastern Tibetan Plateau

By using a surface air temperature index （SATI） averaged over the eastern Tibetan Plateau （TP）, investigation is conducted on the short-term climate variation associated with the interannual air warming （or cooling） over the TP in each summer month. Evidence suggests that the SATI is associated with a consistent teleconnection pattern extending from the TP to central-western Asia and southeastern Europe. Associated rainfall changes include, for a warming case, a drought in northern India in May and June, and a stronger mei-yu front in June. The latter is due to an intensified upper-level northeasterly in eastern China and a wetter and warmer condition over the eastern TP. In the East Asian regions, the time-space distributions of the correlation patterns between SATI and rainfall are more complex and exhibit large differences from month to month. Some studies have revealed a close relationship between the anomalous heating over the TP and the rainfall anomaly along the Yangtze River valley appearing in the summer on a seasonal mean time-scale, whereas in the present study, this relationship only appears in June and the signal＇s significance becomes weaker after the long-term trend in the data was excluded. Close correlations between SATI and the convection activity and SST also occur in the western Pacific in July and August： A zonally-elongated warm tone in the SST in the northwestern Pacific seems to be a passive response of the associated circulation related to a warm SATI. The SATI-associated teleconnection pattern provides a scenario consistently linking the broad summer rainfall anomalies in Europe, central-western Asia, India, and East Asia.

The Indian monsoonal influence on altitude effect of δ^(18)O in surface water on southeast Tibetan Plateau

The altitude effect of δ18O is essential for the study of the paleo-elevation reconstruction and possible to be solved through modern process studies. This study presents new δ18O results from southeast Tibetan Plateau along two transects, the Zayu transect and the Lhasa-Nyang transect, with δ18O data from June to September representative of monsoon period and δ18O data during the rest of the year of non-monsoon period. Altitude effect outweighs the longitude and latitude effects in determining regional δ18O variation spatially. Relevant δ18O data from previous studies in the nearby region have also been combined to comprehensively understand the influence of different moisture sources on δ18O from local scale to regional scale. The δ18O in surface water in the southeast Tibetan Plateau and its nearby regions influenced by the Indian summer monsoon shows that single dominant moisture source or simple moisture sources lead to smaller altitudinal lapse rate, whilst growing contributions from local convection to precipitation enlarge δ18O-altitude rate. It thereupon reveals the significance of the Indian summer monsoon to the altitude effect of δ18O in surface water, and the complicated effect of local convection or westerlies evolution to the variation of altitudinal lapse rate. Paleo-monsoon evolution therefore should be considered when altitude effect is applied to paleo-elevation reconstruction for the Tibetan Plateau.

The influence of increasing temperatures on highland barley yields and on the maximum cultivation altitude on the Tibetan Plateau

Highland barley(Hordeum vulgare Linn.cv.nudum Hook.f.)is the principal cereal crop over the Tibetan Plateau(TP).The response of highland barely to climate change in the past decades,especially in terms of yields still remains uncertain.In this study,its responses to climate change were investigated using daily weather data and agriculture data during 1961–2018.The results showed that the annual mean air temperature over the TP increased at 0.33°C per decade during 1961–2018,and the rate of warming increased with altitude,reaching 0.41°C per decade at altitudes of 4500–4700 m.The growing degree days(GDDs)increased by 9.6%during 2011–2018 compared with the 1960s,whereas low temperature degree days(LDDs)decreased by 40.3%over the same period,indicating that the thermal conditions for highland barley cultivation have improved.A strong relationship was observed between the yield of highland barley and LDDs(−0.76,p<0.001)than GDDs(0.58,p<0.001)in Xizang,where sufficient irrigation water is available from the melting of snow cover or glaciers.In Sichuan,with abundant precipitation,significant correlations were noticed between county-level barley yield and GDDs and LDDs(0.60,p<0.001;−0.65,p<0.001).In Qinghai,the dry regions,county-level yields were influenced significantly by temperature and precipitation.These results indicated that climate warming was beneficial to highland barley yield in most region of the TP,mainly due to decreased LDDs.The potential altitude at which highland barley cultivation is feasible increased by approximately 280–484 m during 2016–2018,compared with 1981–1983.In Xizang,highland barley could be cultivated up to an altitude of 4507 m a.s.l.between 2016 and 2018,and it increased to 4179 m a.s.l.in Qinghai.These results could help local government to take actions to adapt to global warming and improve food security.

Indian monsoon influences altitude effect of δ^(18)O in precipitation/river water on the Tibetan Plateau

The δ 18O variation in precipitation acquired from 28 stations within the network of Tibetan Observation and Research Platform(TORP)is studied, with the focus on the altitude effect of δ 18O in river water during monsoon precipitation in an effort to understand the monsoon influence on isotopic composition in annual river water. It is found that δ 18O in precipitation on the Plateau is influenced by different moisture sources, with significant Indian monsoon influence on δ 18O composition in plateau precipitation and river water. The δ 18O of water bodies in the monsoon domain is generally more depleted than that in the westerly domain, suggesting gradual rainout of southwesterly borne marine moisture in the course of long-distance transportation and lifting over the Himalayas. The lapse rate of δ 18O in river water with altitude is the largest during monsoon precipitation, due to the increased temperature vertical gradient over the southern Plateau region controlled by monsoon circulation. The combination of δ 18O in river water in monsoon (wet) and non-monsoon (dry) seasons shows a larger lapse rate than that in non-monsoon (dry) season alone. As the altitude effect of δ 18O in precipitation and river water on the Tibetan Plateau results from the combined effect of monsoon moisture supply and westerly moisture supply, the δ 18O composition and its altitude effect on the Plateau during monsoon seasons should be considered in the reconstruction of paleoelevation of the Tibetan Plateau.

Area,lake-level and volume variations of typical lakes on the Tibetan Plateau and their response to climate change,1972-2019

Most lakes have undergone significant changes on the Tibetan Plateau in recent decades,affecting water resources on the Tibetan Plateau and its surrounding areas.In this paper,we investigated the variations of 25 lakes in five sub-regions on the Tibetan Plateau from 1972 to 2019 based on SRTM DEM data and Landsat imagery.We used a method to derive lake-levels based on DEM and lake boundaries delineated from Landsat imagery,and then calculated the changes in lake area,level,and volume in 1972 to 2019.We also analyzed the potential impacts of temperature,precipitation,glacial and permafrost melting in lake changes during this period.The results show that the lakes tended to shrink until 2010 in southern and western plateau,after which they began to expand gradually but the overall trend is still shrinking.Limited meltwater from glaciers and permafrost and low precipitation are the main reasons for their shrinkage.The lakes in the central plateau,northwest plateau and northeast plateau tend to expand overall.The reason for the expansion of the lakes is not only precipitation but also the melting of glaciers and permafrost.Overall,the lake changes have gone through 3 phases,namely a slight decrease during 1972-2000,a rapid increase during 2000-2010,and a slowdown in the last decade(2010-2019).Multiple factors such as temperature,precipitation,the state of glaciers and permafrost have contributed to the changes in the lake.

New proofs of the recent climate warming over the Tibetan Plateau as a result of the increasing greenhouse gases emissions

A striking climate warming over the Ti- betan Plateau during the last decades has been re- vealed by many studies, but evidence linking it to human activity is insufficient. By using historical ob- servations, here we show that the in situ climate warming is accompanied by a distinct decreasing trend of the diurnal range of surface air temperature. The ERA40 reanalysis further indicates that there seems to be a coherent warming trend near the tro- popause but a cooling trend in the lower stratosphere. Moreover, all these features can be reproduced in two coupled climate models forced by observed CO2 concentration of the 20th century but cannot be pro- duced by the fixed external conditions before the industrial revolution. These suggest that the recent climate warming over the Tibetan Plateau primarily results from the increasing anthropogenic green- house gases emissions, and impacts of the increased greenhouse gases emissions upon the climate change in the plateau are probably more serious than the rest of the world.

Study of altitudinal lapse rates of δ^(18)O in precipitation/river water with seasons on the southeast Tibetan Plateau

Seasonal δ 18O variation in water on the southeast Tibetan Plateau has been studied, showing the consistent variation pattern of δ 18O with altitude indicative of relevant atmospheric circulation processes. Study shows a similar variation pattern of fixed-site river water δ 18O with that of the precipitation δ 18O in southeast Tibet. δ 18O in regional rivers in southeast Tibet demonstrates a gradual depletion with increasing altitude, though the rates vary seasonally. The most depleted river 18O occurs during the monsoon period, with the lowest δ 18O/altitude lapse rate. The river 18O during the westerly period is also depleted, together with low δ 18O/altitude lapse rate. The pre-monsoon rivers witness the most enriched 18O with least significant correlation coefficient with the linear regression, whilst the postmonsoon rivers witness the largest δ 18O/altitude lapse rate. Different coherence of seasonal δ 18O variation with the altitude effect is attributed to different moisture supplies. Though sampling numbers vary with seasons, the δ 18O-H linear correlation coefficients all reach the 0.05 confidence level, thus witnessing the variation features of δ 18O in seasonal river water due to the influence of atmospheric general circulation and land surface processes revealed from the altitudinal lapse rates.

Changes in inland lakes on the Tibetan Plateau over the past 40 years

Inland lakes and alpine glaciers are important water resources on the Tibetan Plateau. Understanding their variation is crucial for accurate evaluation and prediction of changes in water supply and for retrieval and analysis of climatic information. Data from previous research on 35 alpine lakes on the Tibetan Plateau were used to investigate changes in lake water level and area. In terms of temporal changes, the area of the 35 alpine lakes could be divided into five groups: rising, falling-rising, rising-falling, fluctuating, and falling. In terms of spatial changes, the area of alpine lakes in the Himalayan Mountains, the Karakoram Mountains, and the Qaidam Basin tended to decrease; the area of lakes in the Naqu region and the Kunlun Mountains increased; and the area of lakes in the Hoh Xil region and Qilian Mountains fluctuated. Changes in lake water level and area were correlated with regional changes in climate. Reasons for changes in these lakes on the Tibetan Plateau were analyzed, including precipitation and evaporation from meteorological data, glacier meltwater from the Chinese glacier inventories. Several key problems, e.g. challenges of monitoring water balance, limitations to glacial area detection, uncertainties in detecting lake water-level variations and variable region boundaries of lake change types on the Tibetan Plateau were discussed. This research has most indicative significance to regional climate change.

Patterns of Multiscale Temperature Variability over the Eastern and Central Tibetan Plateau During 1960-2008

Climate variability is an important inherent characteristic of climate and it varies on all timescales. Through examination of temperature variability on multiple temporal scales at 63 stations over the eastern and central Tibetan Plateau （TP） during 1960-2008, we find decreasing trends in daily and intraannual temperature, especially in cold seasons （autumn and winter）. These changes are more sensitive than those in the eastern China coastal region at the same latitude and indicate an asymmetric change of temperature, with hourly, daily, and monthly trends in cold periods stronger than those in warm periods during the recent years. The variation of interannual temperature is complex, showing an increasing trend in autumn and winter and decreasing trend in spring and summer, which is similar to those in the northern polar region. The changes of multiscale variability of temperature are mainly related to changes of atmospheric water vapor, cloudiness, anthropogenic aerosols, monsoon-driven climate, and some local factors. To find the influences of local conditions on temperature variability, we analyze the effects of altitude, topography, and urbanization. The results show that elevation is strongly and positively related to diurnal temperature range （DTR） and slightly positively related to interannual temperature variability （IVT）, but intraannual temperature variability shows no clear elevation dependency. Topography and urbanization also play important roles in multiscale temperature variability. Finally, strong relationships are observed between temperature variability on each scale and different extreme indices.

盛夏亚洲大陆上空急流变化的两类模态及其与东亚大气环流异常的联系

基于NCEP/NCAR月平均再分析资料,利用EOF分解方法揭示出1960-2019年7-8月亚洲大陆上空西风急流变化的两类主要模态,并利用合成方法研究了两类模态与东亚大气环流异常的联系及其气候效应。研究结果表明,夏季亚洲大陆上空西风急流变化的第一模态为纬向风以急流轴为界南北的反位相变化,主要表现为急流整体的南北移动;第二模态为纬向风以青藏高原为界在东西方向上的反相变化,主要表现为急流轴的西南(西北)-东北(东南)向倾斜,该结论不同于以往大多数研究将第二模态定义为急流的强度变化。通过对大气环流异常的分析发现,急流的南北移动对应南亚高压同步的南北移动以及西太平洋副热带高压范围的变化,急流向南移动时,南亚高压脊线偏南,同时西太平洋副热带高压向南扩张,急流向北移动时则相反,该模态主要影响亚洲地区40°N以南的降水异常以及贝加尔湖一带、东亚和南亚的温度异常。第二模态即纬向风以青藏高原为界的反相变化主要伴随着南亚高压强度的东西振荡,急流轴呈西南(西北)-东北(东南)向倾斜时,南亚高压东侧(西侧)位势高度增强,该模态与西亚高纬度地区、中亚以及印度半岛的降水异常有关。此外,第二模态具有一定的特殊性,可影响整个欧亚大陆的气温,并呈现双偶极子型的异常分布。

1982—2015年青藏高原植被变化的主导环境因子

近几十年中随着全球气候环境变化,青藏高原处于变暖变湿过程之中,植被生长发生了显著变化。基于卫星遥感归一化植被指数(NDVI),采用增强回归树模型(BRT)定量分析了1982—2015年影响青藏高原植被生长变化的主要环境因子的相对重要性。结果表明:(1)整个青藏高原生长季(6—9月份)空间平均NDVI和降水呈上升趋势(1.265×10^(-4)a^(-1)和0.746 mm/a,P>0.05);温度和土壤湿度呈现显著增加趋势(0.048℃/a和3.954×10^(-4)a^(-1),P<0.01);向下短波辐射显著减小(-0.070 W m^(-2)a^(-1),P<0.01)。(2)青藏高原34.0%地区NDVI表现出显著增加趋势,主要分布在青藏高原北部大部分地区和西部部分区域;9.2%地区NDVI呈显著减小趋势,主要位于青藏高原东部地区。(3)土壤湿度、年均温、年降水和向下短波辐射分别解释了生长季NDVI变化的42%,19%,10%和9%。(4)土壤湿度、年均温、年降水和向下短波辐射对青藏高原植被生长动态影响的相对大小具有明显的空间差异特征。温度上升是青藏高原东北部和中部部分地区NDVI变化的首要因素(相对贡献率>40%),而土壤湿度增加是青藏高原西南部及东南部分地区NDVI变化的主要原因(相对贡献率>50%)。总体上,温度上升及由此所导致的冰冻圈消融引起的土壤含水量上升是近几十年青藏高原植被生长动态快速变化的主要原因。

青藏高原典型冰川和湖泊变化遥感研究

青藏高原冰川和湖泊变化是气候变化敏感的指示器,利用地形图、航空照片、TM卫星遥感资料和其它相关研究文献资料,分析了青藏高原典型地区的冰川和湖泊变化情况.结果表明:1960—2000年期间,在气温上升、降水增加、最大可能蒸散降低的背景下,研究区内不同地区湖泊的面积变化存在比较大的空间差异.以冰川融水为主要补给的纳木错和色林错地区的主要湖泊以扩大为主,而以降水为主要补给的黄河源地区的主要湖泊则基本上全面萎缩.研究区的冰川在1960—2000年期间以退缩为主,但各地退缩的幅度有较大的差异.

藏北高原典型植被样区物候变化及其对气候变化的响应

植被物候作为陆地生态系统对气候变化的响应和反馈的重要指示,已成为区域或全球生态环境领域研究的热点。基于非对称高斯拟合方法重建了2001—2010年MODIS EVI时间序列影像,利用动态阈值法提取藏北高原植被覆盖2001—2010年每年关键物候参数。选取研究区内东部高寒灌丛草甸、中部高寒草甸及西部高寒草原和高寒荒漠4种典型植被类型,并结合附近的4个气象台站气候资料,分析典型植被物候在近10a对关键气候因子的响应特征。研究结果表明:(1)4种不同典型植被的物候特征(EVImax降低、返青期延后和生长季长度缩短)均表现出高寒灌丛草甸→高寒草甸→高寒草原→高寒荒漠草原的过渡;(2)藏北高原近10a的年平均气温及春、夏、冬三个季度的平均气温均呈显著升高的趋势,升温幅度在0.8—3.9℃/10a,降水减少趋势不显著,在这种水热条件下典型植被均表现出返青提前(7.2—15.5d/10a)、生长季延长(8.4—19.2d/10a)的趋势,而枯黄出现时间为年际间自然波动;(3)高寒灌丛草甸EVImax主要受春季降水量和气温影响,且降水的影响程度大于气温;对高寒草甸植被而言,春、夏季的气温和降水均有较大的影响;而高寒草原和高寒荒漠草原主要受夏季平均气温和降水量影响;(4)高寒灌丛草甸的返青时间主要受前一年秋季降水量的影响,相关系数达-0.579;而高寒草甸、高寒草原和高寒荒漠草原主要受春季平均气温影响,高寒荒漠草原的特征最为明显(r=-0.559)。

小花风毛菊的性器官在青藏高原的海拔变异

小花风毛菊（Saussurea paniflora）是菊科风毛菊属的一种多年生草本植物，是该属在青藏高原东缘的一个优势种。该文研究了小花风毛菊11个居群性器官的变异与11个海拔高度（2100～3500m）之间的相关性，以及花丝、花药长和花柱、花柱分枝长与花粉数之间的相关性；探讨了小花风毛菊的性器官是如何随海拔高度发生变异，如何与胁迫环境相适应，实现交配成功，提高繁殖成功率，使其成为该属植物“现代分布中心”的优势种。结果表明：1）花丝、花药长与海拔高度呈极显著的正相关关系（P〈0．01）；2）花粉数与海拔高度呈极显著的负相关关系（P〈0．01）；3）花柱、花柱分枝长及花柱分枝长和雌蕊长的比与海拔高度呈极显著的正相关关系（P〈0．01）；4）花柱、花柱分枝长和花丝长与花粉数呈显著的负相关关系（P〈0．05）；5）种子的成熟率与海拔高度呈显著的正相关关系（P〈0．05）。说明小花风毛菊种内性器官在特定的生存环境下发生了变异，特别是在花粉数随海拔的升高明显减少以及昆虫的多样性、丰富性和活动性明显降低的情况下，它能够通过花柱分枝长度的变异来提高柱头对传粉昆虫的感受性，能通过种子成熟率的提高来保证高海拔数目显著减少的种子的成功发育，进而在一定程度上导致了该物种繁殖成功率的上升，使它成为青藏高原这一胁迫环境中的优势种。