西藏的高山座垫植被

本文根据在西藏高原多年考察所收集到的第一手资料,对西藏高原座垫植被生态环境、分布规律以及植被的基本特征和主要组成群系作了概括性的论述。     

Observations on the Morphology and Ecology of the Cushion Plants in Togme Region of Northern Xizang

The cushion plant is an ecotype adapted to the environment of the alpine cold climate. There are over 15 species in Northern Xizang plateau, among them Thylaco- spermum caespitosum, Arenaria musciformis and Androsace tapete being common. The general morphology of such plants is expressed as a cushion-like body resulted from the shoots piled up together closely. They may be divided into two types, the close cushion plant and the sparse one, based upon the different degree of compactness of the shoot. The cushion plant is distributed from 4500 to 5300 meters. Different species have different environmental requirement and form the specific community of the alpine cushion vegetation. It has formed in course of the natural selection of the surrounding factors such as plateaus' intense solar radiation, cold weather, strong wind, etc. For a long time, they have sufficiently used the favorabe factors and avoided the unfavorable factors under severe conditions.     

祁连山地区植被特征及其分布规律

分析和讨论了祁连山地区主要植被类型及其分布特征。祁连山地区随着青藏高原的强烈隆升表现为整体抬升,植被具有明显的生态地理边缘效应特征和高原地带性规律。该区植被虽然受到四周的较大影响,但各类高寒植被占有绝对优势,表现出与青藏高原植被整体明显的相似性和广泛的一致性。另一方面,本区植被也有其特殊性及与高原面存在一些差异。因此,建议把祁连山地区做为青藏高原植被区的次一级独立单元     

The Cushion Plant in the Hoh Xil Area of Qinghai

During the first scientific expedition to the Hoh Xil area of Qinghai, the author had collected about 210 speceis of seed plant, which belong to 30 families and 102 genera. Among these plants, 48 species are cushion plant included 8 families and 15 genera. They occupy respectively 26.7% of the total number of the family, 14.7% of the total number of the genus and 22.9% of the total number of the species of the seed plant in this area. Therefore, Qinghai Hoh Xil is the most developed area for the growth of the cushion plant. These cushion plants are morpho-structural and roughly divided into four types: Typical (spongy) cushion plant; Dense clumping cushion plant; Brevi-rhizome or collar tillaring cushion plant; and collar radial dense branching cushion plant. These cushion plants are very much adaptable to the special harmful climate and the adverse nature environment on the plateau platform of Hoh Xil. The community or the population of cushion plant occurs extensively of the various of types of vegetation are very luxurient in the Hoh Xil area. They often become the dominant community or together with often vegetation form a huge landscape of cushion vegetation. The cushion plants are the pioneers in the Hoh Xil area. Their growth cycle, from sprouting, growing, multiplying, flourishing until dying, contribute to the accumulation of soil rich in organic nutrients and create a favourable condition for migration, growth and development of the flora and vegetation in the Hoh Xil area.     

青海可可西里地区垫状植物

首次考察青海可可西里地区,共采集到种子植物约２１０ 种,隶属于３０ 科１０２ 属。其中垫状植物有８ 科１５ 属约４８ 种,分别占该地区全部种子植物科的２６．７％ 、属的１４．７％ 、种的２２．９％ 。该区是青藏高原上垫状植物最发达的地区。垫状植物按其形态结构可以划分为４ 种类型：典型（海绵体）垫状植物;密丛垫状植物;短根茎或根蘖型垫状植物;根颈辐状分枝型垫状植物。垫状植物种群或群落广泛存在于该地区各种植被类型中,并且非常发达,甚至可组成优势群落或群丛,形成大面积垫状植被景观。垫状植物是可可西里地区的先锋植物,它们的存在、繁衍、发达和衰退为其它类型植物迁入生长和漫延积累了细土和有机质,改善了生境     

Seasonal comparison of bacterial communities in rhizosphere of alpine cushion plants in the Himalayan Hengduan Mountains

Positive associations between alpine cushion plants and other species have been extensively studied. However, almost all studies have focused on the associations between macrofauna. Studies that have investigated positive associations between alpine cushion plants and rhizospheric microbes have been limited to the vegetation growing season. Here, we asked whether the positive effects that alpine cushion plants confer on rhizospheric microbe communities vary with seasons. We assessed seasonal variations in the bacterial diversity and composition in rhizosphere of two alpine cushion plants and surrounding bare ground by employing a high throughput sequencing method targeting the V3 region of bacterial 16S rRNA genes. Soil properties of the rhizosphere and the bare ground were also examined. We found that cushion rhizospheres harbored significantly more C, N, S, ammonia nitrogen, and soil moisture than the bare ground. Soil properties in cushion rhizospheres were not notably different, except for soil pH. Bacterial diversities within the same microhabitats did not vary significantly with seasons. We concluded that alpine cushion plants had positive effects on the rhizospheric bacterial communities, even though the strength of the effect varied in different cushion species. Cushion species and the soil sulfur content were probably the major factors driving the spatial distribution and structure of soil bacterial communities in the alpine communities dominated by cushion plants.     

青藏高原高山植被的初步研究

青藏高原是我国高山植被类型最丰富、独特和分布最广泛的区域,发育有大面积的高山灌丛、高寒草甸、高寒草原,高寒荒漠、高山流石坡稀疏植被及零散分布的高山垫状植被。它们占据着森林上线至永久雪线之间的高山带和广阔的高原面,从高原东南部至西北部有水平方向的地域分异。联系高山带以下各垂直带的植被特征及各地的气候条件分析,初步认为高原东南部的山地植被垂直带谱属于湿润型山地垂直带结构类型,高原腹地及西北部的山地植被垂直带谱属于干旱型山地垂直带结构类型。此外,还对青藏高原高山植被类型的丰富性及高山垫状植被的生态地理分布特点进行了初步探讨。     

Tempo and mode of vegetation dynamics over 50 years in a New Zealand alpine cushion / tussock community

Abstract. Question: What are the tempo and mode of long‐term succession and of demographic processes in an alpine community, especially: tenacity, transition patterns, predictions, growth of individual cushion plants, cyclic succession, spatial patterns? Location: A low‐alpine mixed cushion /turf /snow‐tussock / shrub community in southeastern New Zealand. Methods: The distribution of seven plant cover‐types was recorded at 1024 fixed points in an 8 m × 8 m plot at approximately decade intervals for 50 years. The diameters of eight Donatia novae‐zelandiae cushions were monitored. Results: The process was essentially first‐order Markovian. There was a change in transition frequencies about 1980. The tenacity of the two major cover types — cushion and turf — was high, but that of cushion decreased about 1980 as some of its area was taken over by turf. The original informal prediction of 1955 that the cushion/turf would increase proved to be correct, probably because of paludification of the site. A prediction of 1987 made from observed transitions that cushion would dominate over turf has proved untrue because of a change in the transition probabilities in the 1980s, of unknown cause. There is a ten‐fold range in diameter growth rates among the eight cushions measured, but the mean rate of 5.3 mm.a^‐1 is similar to that reported from other alpine and arctic sites. As cushions aged, turf colonized their centres, and in two cases new cushions colonized into this turf: consistent with cyclic succession. The pattern of transitions was compatible with a general interpretation of cyclic succession, but not definitive. Conclusions: Change is slow in this alpine community, and tenacity high. The change in transition frequencies about 1980, the invasion of individual cushions, and the decrease in spatial autocorrelation all suggest that cushions established on the site as a result of the clearance of woody vegetation after 1400 AD. Paludification may be causing some loss of tussock grass. A tendency for the cushions to break up, and the shallow peat accumulated below them, may indicate that they are the first generation of cushions on the site. Though these cushions are breaking up, other cushions are establishing, and cushions will continue to be an important part of the vegetation dynamics which may be part of a cyclic succession.     

Fine‐scale vascular plant species richness in different alpine vegetation types: relationships with biomass and cover

Abstract. Vascular plant species richness was related to biomass and vegetation cover in nine different alpine vegetation types on the Hardangervidda mountain plateau, western Norway. Each vegetation type was sampled within an 8m × 6m area, and the species‐richness pattern analysed. Evidence for a unimodal relationship between species richness and both biomass and cover was found at the within‐vegetation type scale. Cover was a better predictor for species richness than biomass, suggesting that light may be an important factor influencing species richness at this scale in alpine vegetation. The possibility that the results are an artefact of small grain size is also discussed, and several arguments for an ecological explanation of the humpback relationship between species richness and cover are discussed.     

Diversity patterns of cushion plants on the Qinghai-Tibet Plateau: A basic study for future conservation efforts on alpine ecosystems

The Qinghai-Tibet Plateau (QTP) is an important cushion plant hotspot. However, the distribution of cushion plants on the QTP is unknown, as are the factors that drive cushion plant distribution, limiting our understanding of the evolution of cushion species in the region. In this study, we assessed spatial patterns of total cushion plant diversity (including taxonomic and phylogenetic) over the entire QTP and compared patterns of diversity of cushion plants with different typologies (i.e., compact vs. loose). We also examined how these patterns were related to climatic features. Our results indicate that the southern QTP hosts the highest total cushion plant richness, especially in the south-central Hengduan Mountains subregion. The total number of cushion species declines from south to north and from southeast to northwest. Compact cushion plants exhibit similar patterns as the total cushion plant richness, whereas loose cushion plants show random distribution. Cushion plant phylogenetic diversity showed a similar pattern as that of the total cushion plant richness. In addition, cushion plant phylogenetic community structure was clustered in the eastern and southwestern QTP, whereas random or overdispersed in other areas. Climatic features represented by annual energy and water trends, seasonality and extreme environmental factors, had significant effects on cushion plant diversity patterns but limited effects on the phylogenetic community structure, suggesting that climatic features indeed promote the formation of cushion plants. Because cushion plants play vital roles in alpine ecosystems, our findings not only promote our understanding of the evolution and formation of alpine cushion plant diversity but also provide an indispensable foundation for future studies on cushion plant functions and thus alpine ecosystem sustainability in the entire QTP region.     

Positive associations between the cushion plant Azorella monantha (Apiaceae) and alpine plant species in the Chilean Patagonian Andes

Low growing, compact cushion plants are a common and often dominant life form in temperate and subpolar alpine habitats. The cushion life-form can modify wind patterns, temperature and water availability and thus cushion species could be expected to act as nurse-plants facilitating the establishment of other alpine plant species on their surfaces. It has been suggested that the nurse effect should be most pronounced under more stressful environmental conditions, as found with increasing elevation in the alpine. One of the approaches used to detect the nurses has been the study of spatial associations among species, in which extreme clumping within or beneath one species has been interpreted as evidence of nursing. We characterized microclimatic conditions (soil and air temperature) within and outside cushions of Azorella monantha at two elevations (700 m a.s.l., corresponding to an elevation just above treeline, and 900 m a.s.l., corresponding to the upper limit of the cushion belt zone) on Cerro Diente in the Patagonian alpine of southern South America (50° S) and recorded all plant species growing upon cushions of various sizes and for paired sampling areas of equivalent sizes outside cushions. At 5 cm depth, soil temperature was slightly higher under cushions than under bare ground, but only significantly so at 900 m. Air temperature at ground level was significantly higher in the cushion microhabitat at both 700 m and 900 m, with the difference being more exaggerated at the highest elevation. At 700 m, a total of 27 species were recorded growing within cushions as compared to 29 outside cushions. At 900 m the corresponding numbers were 34 and 18. At the highest elevation, significantly more species grow within cushions than for equal areas outside cushions. Here moreover, 17 (48.6%) species grew preferentially within cushions, with eight of the latter being limited to the cushion microhabitat at this elevation. However, at 700 m there was no significant difference in species richness in the two microhabitats, and only one species (3.1%) grew preferentially on cushions. Considering individual species, nine occurring at both elevations showed non-preferential recruitment on cushions at 700 m, but significantly higher frequencies on cushions at 900 m. Results suggest striking altitudinal variation in the association with Azorella monantha on Cerro Diente, ranging from a very strong at 900 m to near absence at 700 m. Milder air and soil temperatures, shelter from wind, and greater water availability within cushions as opposed to outside cushions are discussed as possible factors favoring strong plant recruitment on cushions at higher elevations in the harsh Patagonian alpine environment. This revised version was published online in August 2006 with corrections to the Cover Date.     

A Preliminary Study of the Subnival Vegetation in Xizang

An attempt has been made in this paper to describe briefly the characteristics, ecological environments and the origin of the subnival vegetation of Xizang based on the information collected in the field. 1. This snbnival vegetation of Xizang is distributed in the subnival zone between the continual plant cover line and the permanent snow line on the alpine zone. The climate is severe. The vegetation is primitive, being composed mainly of some lower plant com- munities, mosses communities and some mesophytic flowering plant communities in spots. It is lower and sparse and can be classified into three major types, as follows: (1) Type of humid climate in the southern slopes of the eastern ttimalaya and Kangrigarbo rang. (2) Type of subhumid climate in the eastern Xizang. (3) Type of arid and semiarid climate in the central and western Xizang. 2. The mieroclimate plays a decisive role in the existence and development of the subniwfi vegetation. To the severe conditions, plants also wisely adapt, utilizing whatever water and heat available, completing their growth and development stages in a very short period, and resisting to cold and other unfavorable factors. 3. Frmn the analysis of the cmnposition of the flora of subnival vegetation in Xizang, it is shown that the subnival vegetation has evolved from alpine vegetation of Xizang and the neighbour region to eastern Xizang and southern Xizang.     

乌鲁木齐河源区高寒冰缘植被的生态特征研究

对乌鲁木齐河源区高寒冰缘植被进行了调查和生态环境分析。研究了高寒冰缘植物对寒区环境在形态结构和繁殖方式等方面的适应特征及其生态对策,在该区域垂直带谱中,植被包括了两个垂直带;高山草甸和高山垫状植被。主要植物群系有：苔草群系、蒿草群系、早熟禾群系、四蕊山莓草系、高山红景天群系、族生柔籽草群系、珠芽蓼群系等７个,共包括２７类植物群（群丛）此外,在高山流石堆上具有有牌演替早期阶段的高山植物群聚。决定该区     

青海省东部地区的自然植被

青海省东部地区地处青藏高原和黄土高原的交汇地带。该地区受青藏高原和黄土高原的影响,自然植被与青藏高原上的高寒植被和黄土高原上的植被类型均有一定联系,从而形成该区较为复杂的植被类型。据考察,该地区的主要植被类型包括荒漠草原、草原、森林、灌丛、高寒灌丛和高寒草甸,并在该地区形成明显的垂直分布。在海拔较低的河谷低山分布着与黄土高原相连的植被类型;而海拔较高的山地则分布与青藏高原相连的高寒植被,形成有一定过渡性而又独具特色的植被景观。我们认为,该地区是青藏高原和黄土高原的过渡地带。     

Holocene Palynological Records in Lake Selincuo,Northern Xizang

Selincuo (31°34′–31°57′N, 88°31′–89°21′E)is one of the great lakes in northern Xizang surrounded by alpine grassland, composed mainly of Stipa purpurea, S, subssessifolia var. bassipulomosa. A 3.08 m long core has been taken from a water depth of 27 m, 3 km to the north from the lake. Palynological records of the core combined with surface sample results have revealed from the regional as well as local vegetational and environmental history since the last 12 000 a BP, a very low pollen concentration (19–209 grains/g), mainly of airborne pollen, which indicated a treeless alpine sparse vegetation. A great vegetation change took place at Ca. 9 600 a BP when alpine sparse vegetation was replaced by alpine grassland lasting until Ca. 6 000 a BP. Quite a number of tree pollen grains found in this time interval might be explained as a result of expansion of forests somewhere around the Xizang Plateau. These changes must have caused by climatic warming during the Early Holocene. During the last 6 000 years the vegetation had remained as the alpine grassland, although probably more luxurouste than before, but their was an obvious increase of arboreal pollen, such as the increase of Abies during Ca. 6 000–4 000 a BP, Picea 4 000–2 200 a BP, Pinus 2 200–1 000 a BP which indicated continuous expansion of forests growing around the plateaus. During the last 1 000 years both the concentration and proportion of the arboreal pollen decreased and those of Cypraceae pollen increased sharply. This might mean a reduction of the forests around the plateau and an expansion of swamps around the lake.     

The spatial pattern of grassland aboveground biomass on Xizang Plateau and its climatic controls

Aims Grassland is the most widely distributed vegetation type on the Xizang Plateau. Accurate remote sensing estimation of the grassland aboveground biomass (AGB) in this region is influenced by the types of vegetation indexes (VIs) used, the grain size (resolution) of the remote sensing data and the targeted ecosystem features. This study attempts to answer the following questions: (i) Which VI can most accurately reflect the grassland AGB distribution on the Xizang Plateau? (ii) How does the grain size of remote sensing imagery affect AGB reflection? (iii) What is the spatial distribution pattern of the grassland AGB on the plateau and its relationship with the climate?Methods We investigated 90 sample sites and measured site-specific AGBs using the harvest method for three grassland types (alpine meadow, alpine steppe and desert steppe). For each sample site, four VIs, namely, Normalized Difference VI (NDVI), Enhanced VI, Normalized Difference Water Index (NDWI) and Modified Soil-Adjusted VI (MSAVI) were extracted from the Moderate Resolution Imaging Spectroradiometer (MODIS) products with grain sizes of 250 m and 1 km. Linear regression models were employed to identify the best estimator of the AGB for the entire grassland and the three individual grassland types. Paired Wilcoxon tests were applied to assess the grain size effect on the AGB estimation. General linear models were used to quantify the relationships between the spatial distribution of the grassland AGB and climatic factors.Important findings The results showed that the best estimator for the entire grassland AGB on the Xizang Plateau was MSAVI at a 250 m grain size (MSAVI 250 m). For each individual grassland type, the best estimator was MSAVI at a grain size of 250 m for alpine meadow, NDWI at a grain size of 1 km for alpine steppe and NDVI at a grain size of 1 km for desert steppe. The explanation ability of each VI for the grassland AGB did not significantly differ for the two grain sizes. Based on the best fit model (AGB =^-10.80 + 139.13 MSAVI 250 m), the spatial pattern of the grassland AGB on the plateau was characterized. The AGB varied from 1 to 136g m ?2. Approximately 59% of total spatial variation in the AGB for the entire grassland was explained by the combination of the mean annual precipitation (MAP) and mean annual temperature. The explanatory power of MAP was weaker for each individual grassland type than that for the entire grassland. This study illustrated the high efficiency of the VIs derived from MODIS data in the grassland AGB estimation on the Xizang Plateau due to the vegetation homogeneity within a 1×1 km pixel in this region. Furthermore, MAP is a primary driver on the spatial variation of AGB at a regional scale.     

Micro-pattern in an area of New Zealand alpine vegetation

An area of New Zealand alpine herbfield, 22×22 m, was sampled on a 3×3 m grid.Two community types could be distinguished, dominated respectively by the cushion epacrid Dracophyllum muscoides and the subshrub asterad Celmisia viscosa. Each type was subdivided into three communities. The distribution of these communities was correlated with the environmental factors measured, with a predictability of up to 81%. Some of the factors, such as soil organic matter, could have been influenced by the vegetation, but others were microtopographic ones, unlikely to have been so influenced. There was no evidence of cyclic succession. Possibly the distribution of the two major types reflects previous patch burns, but distributions of individual communities are related to the current environment.Association between the more common species revealed two very clear groups, which characterise, but are not exclusive to, the two community types.     

Vegetation Characteristics and Its Distribution of Qilian Mountain Region

The main vegetation types and distributional characteristics in the Qilian Mountain region were studies. It is shown that characteristic of the Vegetation is evidanced by eeo-geography marginal effect and plateau zone law. The vegetation of this region is affected considerably by the vegetation around the Qilian Mountain region, but is advantageous for all kinds of alpine vegetations, and has an evident similarity and an extensive unanimity with those of Qinghai-Xizang Plateau. On the other hand, the vegetation of the area has its specificity difference with the plateau plane. So, the authors consider to classify the Qilian Mountain region as the secondary unit of the Qinghai-Xizang Plateau vegetation region.     

The Fundamental Characteristics of the Steppe Vegetation in Xizang Plateau

The steppe vegetation of the Xizang (Tibet) Plateau is somewhat similar to the temperate steppe of our country, but it possesses its own characteristics: 1. The elements of the Qinghai-Xizang floral region or plant species taking the Qinghai-Xizang Plateau as their chief distribution center play a dominant part in tile constitution of the steppe communities. In these communities, the plants are usually sparse and dwarf, their growth period is shorter and the biological productivity is lower than the steppe in the temperate zone. They possess synusia consisting of herbaceous plants fit for cold climate, synusia consisting of kobresia and synusia consisting of cushion plants. 2. There are 4 types of steppe vegetation in the Xizang Plateau. And the tussock-grass steppe is the most typical. According to their different ecological characteristics, they may be divided into 3 types. Of these, the most widely distributed type is the cold temperate-weak semiarid steppe. And there are many characteristical steppe communities. 3. Distributionally, the steppe in the Xizang Plateau belongs to a special type of vertical distribution in the subtropical latitude zone, it is different from the gene- rally known montane vertical belt, and possesses a vertical-horizontal distributive nature, i.e. "zonation of plateau". Within the Plateau steppe region, steppe eommunities with different ecological characteristics have clearly marked areal differentiaton, and which has determined the nature of the vertical belts in these areas. According to different basal belts of the vertical belt spectrum, such belts may be divided into 3 types. There are no forests in the montane vertical belt spectra in the Plateau steppe region, and the upper distributional limit of the steppe vegetation reaches an altitude of about 5200 (5400) m., which is the highest distributional limit of steppe on the earth.     

山西吕梁地区湿地植被数量分类研究

吕梁地区地处黄土高原东部,湿地植被主要分布于三川河、湫水河和文峪河流域及文峪河水库与吴城水库等。在野外调查的基础上,本文用TWINSPAN对吕梁地区湿地植被进行了分类,结果将吕梁湿地分为芦苇节节草群落、水蓼群落、虎尾草群落、假苇拂子茅群落、猪毛蒿群落、野苜蓿群落、苔草野苜蓿群落、赖草群落、苔草群落、猪毛蒿黄花蒿群落和虎尾草柳叶蒿群落。此外,还讨论了湿地植被的动态以及与水分的关系,提出了对吕梁地区湿地植被的保护利用对策。