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1.
Mass elevation effect(MEE) refers to the thermal effect of huge mountains or plateaus, which causes the tendency for temperature-related montane landscape limits to occur at higher elevations in the inner massifs than on their outer margins. MEE has been widely identified in all large mountains, but how it could be measured and what its main forming-factors are still remain open. This paper, supposing that the local mountain base elevation(MBE) is the main factor of MEE, takes the Qinghai-Tibet Plateau(QTP) as the study area, defines MEE as the temperature difference(ΔT) between the inner and outer parts of mountain massifs, identifies the main forming factors, and analyzes their contributions to MEE. A total of 73 mountain bases were identified, ranging from 708 m to 5081 m and increasing from the edges to the central parts of the plateau. Climate data(1981–2010) from 134 meteorological stations were used to acquire ΔT by comparing near-surface air temperature on the main plateau with the free-air temperature at the same altitude and similar latitude outside of the plateau. The ΔT for the warmest month is averagely 6.15℃, over 12℃ at Lhatse and Baxoi. A multivariate linear regression model was developed to simulate MEE based on three variables(latitude, annual mean precipitation and MBE), which are all significantly correlated to ΔT. The model could explain 67.3% of MEE variation, and the contribution rates of three independent variables to MEE are 35.29%, 22.69% and 42.02%, respectively. This confirms that MBE is the main factor of MEE. The intensive MEE of the QTP pushes the 10℃ isotherm of the warmest month mean temperature 1300–2000 m higher in the main plateau than in the outer regions, leading the occurrence of the highest timberline(4900 m) and the highest snowline(6200 m) of the Northern Hemisphere in the southeast and southwest of the plateau, respectively.  相似文献   

2.
Numerous studies have reported that treelines are moving to higher elevations and higher latitudes.Most treelines are temperature limited and warmer climate expands the area in which trees are capable of growing.Hence,climate change has been assumed to be the main driver behind this treeline movement.The latest review of treeline studies was published in 2009 by Harsch et al.Since then,a plethora of papers have been published studying local treeline migration.Here we bring together this knowledge through a review of 142 treeline related publications,including 477 study locations.We summarize the information known about factors limiting tree-growth at and near treelines.Treeline migration is not only dependent on favorable growing conditions but also requires seedling establishment and survival above the current treeline.These conditions appear to have become favorable at many locations,particularly so in recent years.The review revealed that at 66%of these treeline sites forest cover had increased in elevational or latitudinal extent.The physical form of treelines influences how likely they are to migrate and can be used as an indicator when predicting future treeline movements.Our analysis also revealed that while a greater percentage of elevational treelines are moving,the latitudinal treelines are capable of moving at greater horizontal speed.This can potentially have substantial impacts on ecosystem carbon storage.To conclude the review,we present the three main hypotheses as to whether ecosystem carbon budgets will be reduced,increased or remain the same due to treeline migration.While the answer still remains under debate,we believe that all three hypotheses are likely to apply depending on the encroached ecosystem.Concerningly,evidence is emerging on how treeline migration may turn tundra landscapes from net sinks to net sources of carbon dioxide in the future.  相似文献   

3.
This study proposes an equivalent-elevation method to evaluate the integrated effects of latitude and elevation on regional and local-scale permafrost distribution in the Qinghai-Tibet Plateau,and to model the general permafrost-distribution patterns in regional and local-scale area.It is found that the Gaussian curve―an empirical model describing the relation between variations of altitudinal permafrost lower limit (PLL) and latitude in the Northern Hemisphere―could be applied in regional-and local-scale areas in the Qinghai-Tibet Plateau in a latitude-sensitive interval of 30°-50°N.The curve was then used to evaluate the latitudinal effect on permafrost distribution through transforming the latitudinal effect into a kind of altitudinal difference of PLL.This study then calculated the local equivalent-elevation value by overlaying the altitudinal difference of PLL onto real elevation at a certain location.The equivalent-elevation method was verified in an experimental subwatershed of the Qinghai-Tibet Plateau.However,feasibility of the method should be further tested in order to extend for future studies.The use of equivalent-elevation values can build a platform for comparing the regional general permafrost distribution in the plateau,and for basing further evaluations of local factors’ effects on regional permafrost distribution.  相似文献   

4.
Under conditions of a warmer climate, the advance of the alpine treeline into alpine tundra has implications for carbon dynamics in mountain ecosystems. However, the above- and below-ground live biomass allocations among different vegetation types within the treeline ecotones are not well investigated. To determine the altitudinal patterns of above-/below-ground carbon allocation, we measured the root biomass and estimated the above-ground biomass (AGB) in a subalpine forest, treeline forest, alpine shrub, and alpine grassland along two elevational transects towards the alpine tundra in southeast Tibet. The AGB strongly declined with increasing elevation, which was associated with a decrease in the leaf area index and a consequent reduction in carbon gain. The fine root biomass (FRB) increased significantly more in the alpine shrub and grassland than in the treeline forest, whereas the coarse root biomass changed little with increasing altitudes, which led to a stable below-ground biomass (BGB) value across altitudes. Warm and infertile soil conditions might explain the large amount of FRB in alpine shrub and grassland. Consequently, the root to shoot biomass ratio increased sharply with altitude, which suggested a remarkable shift of biomass allocation to root systems near the alpine tundra. Our findings demonstrate contrasting changes in AGB and BGB allocations across treeline ecotones, which should be considered when estimating carbon dynamics with shifting treelines.  相似文献   

5.
秦巴山地是中国的南北分界线,也是黄河和长江的分水岭,其山体效应的定量化影响秦巴山地山体垂直带的分布格局、非地带性因素的作用强度和机理,以及中国暖温带和北亚热带的具体位置的确定。山体基面高度是影响山体效应最重要和关键的地形因子,其定量化和数字化提取是秦巴山地山体效应定量化研究的重要内容。本研究针对秦巴山地山体效应的定量化研究,使用30 m分辨率的STRM-1数据,分别基于山体特征线和流域分区2种方法提取了秦巴山地的山体基面高度分区,并根据地形起伏度和坡度,确定基面范围,计算了山体基面高度值。结果表明：① 基于山体特征线的方法将秦巴山地分为93个基面高度分区,基于流域分区的方法将秦巴山地分为209个基面高度分区,根据2种分区结果提取的基面高度值相差不大且均体现了秦巴山地地势的特点;② 秦巴山地山体基面高度从东向西呈阶梯状递增的趋势;③ 从南到北,秦巴山地的东段和中段均呈先增高后降低的趋势,即从大巴山向北至汉江谷地降低,再向北至秦岭升高;④ 山地的不同侧翼的山体基面高度不同,秦岭南坡的基面高度（1000~1809 m）明显高于北坡（850~1300 m）。秦巴山地山体基面高度与其植被带分布上限联系密切,实现山体基面高度的数字化提取,为山体效应的定量化研究提供了重要的技术支持。  相似文献   

6.
Climate warming is expected to advance treelines to higher elevations. However, empirical studies in diverse mountain ranges give evidence of both advancing alpine treelines as well as rather insignificant responses. In this context, we aim at investigating the sensitivity and responsiveness of the near-natural treeline ecotone in Rolwaling Himal, Nepal, to climate warming. We analysed population densities of tree species along the treeline ecotone from closed forest stands via the krummholz belt to alpine dwarf shrub heaths (3700-4200 m) at 50 plots in 2013 and 2014. We quantified species - environment relationships, i.e. the change of environmental conditions (e.g., nutrient and thermal deficits, plant interactions) across the ecotone by means of redundancy analyses, variation partitioning and distance-based Moran's eigenvector maps. In particular, we focus on explaining the high competitiveness of Rhododendron campanulatum forming a dense krummholz belt and on the implications for the responsiveness of Himalayan krummholz treelines to climate change. Results indicate that treeline trees in the ecotone show species-specific responses to the influence of environmental parameters, and that juvenile and adult tree responses are modulated by environmental constraints in differing intensity. Moreover, the species - environment relationships suggest that the investigated krummholz belt will largely prevent the upward migration of other tree species and thus constrain the future response of Himalayan krummholz treelines to climate warming.  相似文献   

7.
Alpine treeline ecotones are harsh environment for tree establishment due to low temperature.Tree establishment at treelines requires favorable climate,suitable microsites,and viable seeds.But most researches have been addressed treeline microclimate and its effects on tree regeneration,the knowledge of seed quantity and quality and its controls on seedling recruitment were limited.We measured seed rain,soil seed bank,seed germination rate and seedling recruitment in natural forests in combination with seed transplanting manipulation to evaluate the controls of seed quantity and quality on seedling recruitment of Abies georgei var.smithii(smith fir) along altitudinal gradient,withfocus on treeline ecotone in the Sygera Mountains,southeastern Tibetan Plateau.Both seed quantity and seed quality of smith fir decreased with increasing altitude and was thereby associated with decline in seed germination rate.Seed quantity and seedling recruitment were better in north-facing slope than in south slope.The treeline ecotone above 4200 m appeared as the threshold altitude to sharply decrease seed quality and seedling recruitment.The emergence and overwintering rates of transplanting seeds from 3600-3800 m also went down remarkably above 4200 m at north-facing slope.It also underpins the fact that treeline ecotone is the bottleneck of seedling recruitment.Our results suggest that seed quantity and quality are the principal limitation of treeline upward advance.This study also provides evidence tosupport stable treeline position in southeastern Tibetan Plateau.  相似文献   

8.
It is over 110 years since the term Mass Elevation Effect(MEE) was proposed by A. D. Quervain in 1904. The quantitative study of MEE has been explored in the Tibetan Plateau in recent years; however, the spatial distribution of MEE and its impact on the ecological pattern of the plateau are seldom known. In this study, we used a new method to estimate MEE in different regions of the plateau, and, then analyzed the distribution pattern of MEE, and the relationships among MEE, climate, and the altitudinal distribution of timberlines and snowlines in the Plateau. The main results are as follows:(1) The spatial distribution of MEE in the Tibetan Plateau roughly takes on an eccentric ellipse in northwestsoutheast trend. The Chang Tang Plateau and the middle part of the Kunlun Mountains are the core area of MEE, where occurs the highest MEE of above 11℃; and MEE tends to decreases from this core area northwestward, northeastward and southward;(2) The distance away from the core zone of the plateau is also a very important factor for MEE magnitude, because MEE is obviously higher in the interior than in the exterior of the plateau even with similar mountain base elevation(MBE).(3) The impacts of MEE on the altitudinal distribution of timberlines and snowlines are similar, i.e., the higher the MEE, the higher timberlines and snowlines. The highest timberline(4600–4800 m) appears in the lakes and basins north of the Himalayas and in the upper and middle reach valleys of the Yarlung Zangbo River, where the estimated MEE is 10.2822℃–10.6904℃. The highest snowline(6000–6200 m) occurs in the southwest of the Chang Tang Plateau, where the estimated MEE is 11.2059°C–11.5488℃.  相似文献   

9.
全球海域大风频率精细化统计分析   总被引：1，自引：0，他引：1  
利用1999年8月-2009年7月高精度、高分辨率的QN（QuikSCAT／NCEP）混合风场,对全球海域6级以上的大风频率进行统计分析,为航海、防灾减灾、海洋能开发等提供科学依据。结果表明,全球海域6级以上大风频率具有很大的区域性、季节性差异：1）南北半球西风带海域的大风频率明显高于其余海域,尤其是南印度洋“咆哮西风带”海域出现频率最高,高值中心在60％以上。30°N以内低纬度大范围海域的大风频率整体较低,基本在10％以内,仅在阿拉伯海、琉球群岛——台湾岛——南海大风区一带、南印度洋的马达加斯加——澳大利亚一带存在以东西向椭圆状海域,在20％-40％;2）冬半球的大风频率远大于夏半球,1、4、10月南北半球西风带海域的大风频率明显强于其余海域,7月南半球西风带海域的大风频率较高,北半球大部分海域在10％以内,阿拉伯海、孟加拉湾、南中国海,由于受到强劲西南季风的影响,为北半球的大风频率相对大值区,尤其是阿拉伯海大部分海域在50％以上,大值中心甚至高达90％以上。  相似文献   

10.
At a global scale, tree growth in alpine treeline ecotones is limited by low temperatures. At a local scale, however, tree growth at its upper limit depends on multiple interactions of influencing factors and mechanisms. The aim of our research was to understand local scale effects of soil properties and nutrient cycling on tree growth limitation, and their interactions with other abiotic and biotic factors in a near-natural Himalayan treeline ecotone. Soil samples of different soil horizons, litter, decomposition layers, and foliage samples of standing biomass were collected in four altitudinal zones along three slopes, and were analysed for exchangeable cations and nutrient concentrations, respectively. Additionally, soil and air temperature, soil moisture, precipitation, and tree physiognomy patterns were evaluated. Both soil nutrients and foliar macronutrient concentrations of nitrogen (N), magnesium (Mg), potassium (K), and foliar phosphorus (P) decrease significantly with elevation. Foliar manganese (Mn) concentrations, by contrast, are extraordinarily high at high elevation sites. Potential constraining factors on tree growth were identified using multivariate statistical approaches. We propose that tree growth, treeline position and vegetation composition are affected by nutrient limitation, which in turn, is governed by low soil temperatures and influenced by soil moisture conditions.  相似文献   

11.
The control mechanisms of topography on alpine treeline pattern are critical to understanding treeline dynamics and future changes. These mechanisms have not been understood quite well enough because of increasing human disturbance and low data resolution. In this study, the relationship between the treeline pattern and topography was analyzed based on high spatial resolution remote sensing data and a digital elevation model in an area in Changbai Mountain with little human disturbance. Future treeline patterns were also predicted. The results showed that(a) aspects with high solar radiation and low snow cover have a high coverage rate of trees,(b) the peak coverage rate of trees switches from low slopes(5°) to medium slopes(5°~25°) as the elevation rises because of the extreme environment,(c) the coverage rate of trees is a function that depends on environmental factors controlled by topography,(d) the future treeline pattern is controlled by new temperature mechanisms, new environmental factors and the reallocation effect of topography. Our research implies that topography controls the treeline pattern and changes in the treeline pattern associated with global warming, due to the effect of global warming on environmental factors. This study may well explain the causes of heterogeneous changes in the treeline pattern in the horizontal direction as well as differences in treeline response to climate warming.  相似文献   

12.
The sea level derived from TOPEX/Poseidon(T/P) altimetry data shows prominent long term trend and inter-annual variability.The global mean sea level rising rate during 1993-2003 was 2.9 mm a-1.The T/P sea level trend maps the geographical variability.In the Northern Hemisphere(15°-64°N),the sea level rise is very fast at the mid-latitude(20°-40°N) but much slower at the high-latitude,for example,only 0.5 mm a-1 in the latitude band 40°-50°N.In the Southern Hemisphere,the sea level shows high rising rate both in mid-latitude and high-latitude areas,for example,5.1 mm a-1 in the band 40°-50°S.The global thermosteric sea level(TSL) derived from Ishii temperature data was rising during 1993-2003 at a rate of 1.2 mm a-1 and accounted for more than 40% of the global T/P sea level rise.The contributions of the TSL distribution are not spatially uniform;for instance,the percentage is 67% for the Northern Hemisphere and only 29% for the Southern Hemisphere(15°-64°S) and the maximum thermosteric contribution appears in the Pacific Ocean,which contributes more than 60% of the global TSL.The sea level change trend in tropical ocean is mainly caused by the thermosteric effect,which is different from the case of seasonal variability in this area.The TSL variability dominates the T/P sea level rise in the North Atlantic,but it is small in other areas,and shows negative trend at the high-latitude area(40°-60°N,and 50°-60°S).The global TSL during 1945-2003 showed obvious rising trend with the rate of about 0.3 mm a-1 and striking inter-annual and decadal variability with period of 20 years.In the past 60 years,the Atlantic TSL was rising continuously and remarkably,contributing 38% to the global TSL rising.The TSL in the Pacific and Indian Ocean rose with significant inter-annual and decadal variability.The first EOF mode of the global TSL from Ishii temperature data was the ENSO mode in which the time series of the first mode showed steady rising trend.Among the three oceans,the first mode of the Pacific TSL presented the ENSO mode;there was relatively steady rising trend in the Atlantic Ocean,and no dominant mode in the Indian Ocean.  相似文献   

13.
《山地科学学报》2020,17(10):2405-2417
Ohud mountain is one of the main important historic sites in the Arab Peninsula, and it is distinguishable over the rest of the mountains in the region. No extensive floristic survey has been carried out on Ohud mountain because of the rugged topography of this mountain. The current study investigates the floristic diversity and the correspondence of environmental factors of the phytogeographical distribution of plants, based on the floristic analysis of the present region. The research question is about the relationships between the species diversity and the human impacts of populated area at lowlands around Ohud mountain. A total of 59 species belonging to 56 genera and 28 families were recorded. Asteraceae had the highest contribution, about 12% of the total plant species. The analysis of the life forms demonstrated the prevalence of therophytes(68%) followed by chamaephytes(24%), indicating the adaptation of these life forms to hyperarid conditions. The chorological analysis indicated the predominance of the bi-regional taxa over the other phytochoria. Most of the recorded plant species belong to Saharo-Arabian and Sudano-Zambezian(24%) phytochoria. TWINSPAN analysis was performed to detect the indicator species of different vegetation groups and confirmed by detrended correspondence analysis(DCA or DECORANA). It is concluded that species richness and diversity revealed clear variation along the mountain and among the studied sites. Plant species diversity and richness were more pronounced in the intermediate portion of the elevation gradients across the mountain, with a decrease in the high altitudinal belts. The decrease was also recorded at the lower altitudes, where human impacts clearly affected vegetation; leading to a decrease in alpha diversity. In addition, the beta diversity among moderately highlands and lowlands was considerably high indicating the heterogeneous species composition among the studied sites along mountain elevations. The general pattern of vegetation groups distribution is controlled by a number of environmental factors; such as latitude, longitude, elevation, organic matter and some anions and cations. A Canonical Correspondence Analysis(CCA) ordination revealed that the vegetation structure has a strong association with the latitude of the mountain followed by organic matter and Magnesium. It is recommended that the populated area should be subjected to restoration of mountain ecosystem that might be degraded by human activities.  相似文献   

14.
The altitudinal pattern of vegetation is usually identified by field surveys,however,these can only provide discrete data on a local mountain.Few studies identifying and analyzing the altitudinal vegetation pattern on a regional scale are available.This study selected central Inner Mongolia as the study area,presented a method for extracting vegetation patterns in altitudinal and horizontal directions.The data included a vegetation map at a 1∶1 000 000 scale and a digital elevation model at a 1∶250 000 scale.The three-dimensional vegetation pattern indicated the distribution probability for each vegetation type and the transition zones between different vegetation landscapes.From low to high elevations,there were five vegetation types in the southern mountain flanks,including the montane steppe,broad-leaved forest,coniferous mixed forest,montane dwarf-scrub and sub-alpine shrub-meadow.Correspondingly,only four vegetation types were found in the northern flanks,except for the montane steppe.This study could provide a general model for understanding the complexity and diversity of mountain environment and landscape.  相似文献   

15.
The lofty and extensive Tibetan Plateau has significant mass elevation effect(MEE). In recent years, a great effort has been made to quantify MEE, with the recognition of intra-mountain basal elevation(MBE) as the main determinant of MEE. In this study, we improved the method of estimating MEE with MODIS and NECP data, by refining temperature laps rate, and dividing MBE plots, and then analyzed the spatio-temporal variation of MEE in the Plateau. The main conclusions include: 1) the highest average annual MEE of the plateau is as high as 11.5488°C in the southwest of the plateau, where exists a high-MEE core and MEE takes on a trend of decreasing from the core to the surrounding areas; 2) in the interior of the plateau, the maximum monthly MEE is 14.1108°C in the highest MBE plot(4934 m) in August; while the minimum monthly MEE appeared primarily in January and February; 3) in the peripheral areas of the plateau, annual mean MEE is relatively low, mostly between 3.0068°C–5.1972°C, where monthly MEE is high in January and December and low in June and July, completely different from the MEE time-series variation in the internal parts of the plateau.  相似文献   

16.
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17.
欧亚大陆山地垂直带数字集成系统的设计与应用   总被引：1，自引：0，他引：1  
在欧亚大陆山地垂直带880个带谱点数据采集的基础上,设计和开发了山地垂直带数字集成系统。其功能：(1)垂直带谱可视化显示功能：实时生成垂直带地理分布图、垂直带堆积柱状图、上下限高度随经纬度变化曲线;(2)垂直带上下限提取和绝对高度和相对高度转化功能：提取山地垂直自然带分布上限和下限高度,进行垂直带的宽度和垂直带上限海拔...  相似文献   

18.
A calculation formula on spherical pattern of Qinghai-Tibet plateau moving model is established, Tibet massif moves norward by east in speed of 28 mm/a, Ganshu-Qinghai massif moves to northeast in speed of 15 mm/a, Qomolangma Feng moves northward by a few east in speed of 35 -42 mm/a. The low latitude perimeter is longer than the high latitude perimeter. When the Tibet massif moves northward, its latitude perimeter must be contracted and the Tibet massif must move eastward by Coriolis. Coriolis force is inertial in earth rotation. It makes the fall body turning to east and the rising block turning westward. In the Northern Hemisphere, it makes the northward body turning to east and the southward block turning to west. This is the reason why the tectonic zones of western Pacific are different from those of eastern Pacific.  相似文献   

19.
A calculation formula on spherical pattern of Qinghai-Tibet plateau moving model is established. Tibet massif moves norward by east in speed of 28 mm/a, Ganshu-Qinghai massif moves to northeast in speed of 15 mm/a, Qomolangma Feng moves northward by a few east in speed of 35 ～42 mm/a. The low latitude perimeter is longer than the nigh latitude perimeter. When the Tibet massif moves northward, its latitude perimeter must be contracted and the Tibet massif must move eastward by Coriolis. Coriolis force is inertial in earth rotation. It makes the fall body turning to east and the rising block turning westward. In the Northern Hemisphere, it makes the northward body turning to east and the southward block turning to west.This is the reason why the tectonic zones of western Pacific are different from those of eastern Pacific.  相似文献   

20.
A calculation formula on spherical pattern of Qinghai-Tibet plateau moving model is established. Tibet massif moves norward by east in speed of 28 mm/a, Ganshu-Qinghai massif moves to northeast in speed of 15 mm/a, Qomolangma Feng moves northward by a few east in speed of 35 -42 mm/a. The low latitude perimeter is longer than the high latitude perimeter. When the Tibet massif moves northward, its latitude perimeter must be contracted and the Tibet massif must move eastward by Cofiolis. Cofiolis force is inertial in earth rotation. It makes the fall body turning to east and the rising block turning westward. In the Northern Hemisphere, it makes the northward body turning to east and the southward block turning to west. This is the reason why the tectonic zones of western Pacific are different from those of eastern Pacific.  相似文献   

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