Transactions of the Botanical Society of Edinburgh

Background: Due to the dry continental climate, the mountains of eastern Ladakh are unglaciated up to 6200–6400 m, with relatively large areas of developed soils between 5600 and 6000 m covered by sparse subnival vegetation. However, there are no studies on the composition of plant assemblages from such extreme elevations, their microclimates, vertical distributions and adaptive strategies.

Aims: The subnival vegetation was described and the relationship between microclimate, species distribution and species functional traits was analysed.

Methods: In total, 481 vegetation samples from 91 permanent plots, a floristic database of Ladakh and extensive microclimate measurements were used. Measurements of 15 functional traits were made and their relationship with species distribution between 4600 and 6150 m was tested.

Results: The subnival zone was characterised by extreme diurnal temperature fluctuations, a short growing season (between 88 and 153 days) and low soil temperature during the growing season (between 2.9 °C and 5.9 °C). It hosted 67 species, mainly hemicryptophytes, and ranged from ca. 5600 m to the highest known occurrence of vascular plants in the region (6150 m). The most common plant families were Brassicaceae, Asteraceae, Poaceae, Fabaceae and Cyperaceae. Subnival specialists with narrow elevational ranges represented 42% of the flora; these species were shorter, had relatively higher water content and water-use efficiency and contained more nutrients and soluble carbohydrates than species with a wider elevational range.

Conclusions: The subnival vegetation of eastern Ladakh is dominated by generalist species with wide vertical ranges and not by high-elevation specialists. These findings, in view of the vast unglaciated areas available for range extension, suggest a relatively high resilience of the subnival flora to climate change in this region.     

广西蕨类植物区系的基本特征

对广西蕨类植物区系的组成、特征、区系地理成分作了详细阐述。该蕨类区系十分丰富 ,现已发现 5 6科、1 5 8属、85 4种 (变种、变型 )。区系地理成分复杂 ,属划分为 1 4种类型 (变型 ) ,种划分为 1 8种类型 (变型 )。文中对该区系的性质进行了探讨 ,认为该区系是热带向亚热带过渡的植物区系 ,南部具有热带性质 ,北部具有亚热带性质 ,中部是过渡区     

Vegetation history from archaeological charcoals in central Australia: The late Quaternary record from Puritjarra rock shelter

Archaeological charcoals from Puritjarra rock shelter provide the first direct information about the vegetation of central Australia during the late Pleistocene and early Holocene. During the late Pleistocene there appears to have been a more open vegetation than today with fewer trees and shrubs, though with many of the taxa that are important in the modern central Australian flora. The persistence of species such as Acacia macdonnelliensis, Callitris glaucophylla and Eucalyptus opaca throughout the time of the last glacial maximum and the presence of appreciable quantities of wood charcoal in the archaeological deposits at this time indicate that the region was not a tree-less steppe even during full glacial aridity. From 13,000 B.P. onwards, acacias are strongly represented in the charcoal assemblage both quantitatively and in terms of the number of species present. Acacia aneura is for the first time a major component of the assemblage indicating that it had by this time become a significant element of the local vegetation. These changes coincide with evidence elsewhere in the Australian arid zone for the onset of wetter conditions in the early Holocene.     

Validating the use of woodrat (Neotoma) middens for documenting natural invasions

Aim Plant macrofossils in fossil woodrat (Neotoma) middens are the primary source of information on late Quaternary biogeographical history of plants in arid and semi‐arid regions of North America. Macrofossil records from middens are playing particularly important roles in documenting spatial and temporal patterns of plant migrations and invasions since the last glacial maximum 21,000 years ago. However, relatively few actualistic studies comparing contents of modern middens with surrounding flora and vegetation have been carried out. The primary aim of this study is to assess the reliability of midden assemblages in detecting the presence of tree, shrub and several other plant species growing on the surrounding landscape. The secondary aims are to determine whether probability of occurrence of species in middens is related to abundance in vegetation, and whether representation of individual species in middens is contingent on presence/absence or abundance of other species. Location Our five study sites were bedrock escarpments or canyons in the central Rocky Mountains (north‐eastern Utah, central Wyoming and south‐central Montana). All sites were in conifer woodland or forest/woodland variously dominated by Juniperus osteosperma, J. scopulorum, Pinus edulis, P. flexilis and Pseudotsuga menziesii. Neotoma cinerea is the only woodrat species in the region. Methods Macrofossil assemblages from 59 modern middens (all showing clear signs of recent or ongoing woodrat activity) were compared with floristic composition of vegetation within 50 m of the middens, and with percent cover of vegetation within 30 m of the middens. Results Coniferous trees and shrubs were well‐represented in middens, occurring consistently even when abundance in the local vegetation was very low. Juniperus osteosperma and J. scopulorum were particularly well‐represented, occurring in middens regardless of local abundance. Other conifers (P. edulis, P. flexilis, P. ponderosa, Pseudotsuga menziesii) were occasionally absent from middens when abundance in vegetation was low (< 20% canopy cover). Occurrence of dicot shrubs and graminoids was less consistent. Main conclusions Middens constructed by N. cinerea are highly reliable sensors of presence/absence of J. osteosperma and J. scopulorum, and hence can be used to infer invasions and past biogeographical distributions of these species. The middens are also reliable in registering populations of other conifers, although presence in middens may be contingent on local abundance. Additional comparative studies are needed to develop a sound empirical basis for using middens of N. cinerea and other species to infer past presence/absence of plant species on the landscape, and to explore the vegetation‐sensing properties of midden assemblages.     

Composition and seasonal flux of the soil seed bank of species-rich Themeda triandra grasslands in relation to burning history

Abstract. Most species-rich grasslands dominated by Themeda triandra in southeastern Australia have been ungrazed and frequently burnt for decades. The seedling emergence technique was used to determine the size and taxonomic composition of the soil seed bank of five grasslands that had different fire histories (i.e. burnt at 1 yr, 3 yr and > 10 yr intervals) and this was compared to the standing vegetation at each site. A nested sampling design (subplot, plot, site) was used to determine the effect of spatial scale on the patterns observed in both the vegetation and the seed bank. Temporal variation in the seed bank was assessed by repeated soil sampling over a two year period. 61 native and 30 exotic species were recorded in the vegetation. Richness varied more between sites than within sites. Sites were therefore internally homogeneous for species richness. However, no correlation between burning frequency and richness was found. DCA ordination separated the sites into distinct groups, but sites with similar fire history did not necessarily group closely. 60 taxa germinated from the soil seed bank, comprising 32 native and 28 exotic species; 11 species, mostly therophytes, were restricted to the seed bank. The richness of the seed bank was significantly lower than the vegetation at all spatial scales. No correlation between seed bank richness and fire history was found. The seed bank of species-rich grasslands is dominated by a limited number of widespread, highly clumped, annual, native and exotic monocots. Most native hemicryptophytes, and perennials in general, were represented in the soil by a transient seed bank. Only 12 % of study species, all therophytes, were considered to form large, persistent seed banks, the size of which was greater in unburnt grasslands at all times of the year. The distinct floristic patterns observed in the vegetation are less clearly represented in the seed bank. The seed bank represents a floristically distinct (and less variable) component of the vegetation when compared to the standing flora. The size of the long-term soil seed bank suggests that it has little functional importance for many native species and probably contributes little to seedling regeneration processes following disturbance. Altering established fire regimes is likely to only change the composition and small-scale richness of the existing site vegetation and will not re-integrate species previously lost from the vegetation due to past management. It is suggested that the maintenance of vegetation remnants and processes that encompass a range of long-term burning histories will be necessary if the flora is to be conserved in situ. Restoration of degraded grasslands cannot rely on the soil seed bank but rather, will be dependent on the reintroduction of propagules.     

THE ROLE OF SEED BANKS IN THE PERSISTENCE OF ONTARIO'S COASTAL PLAIN FLORA

Seed banks are important in wetland vegetation, but their role on lakeshores has received little attention. The influence of seed banks on lakeshore vegetation was investigated near eastern Georgian Bay in Ontario, where there is a rich shoreline and aquatic flora. Some lakeshore species found there can be considered “coastal plain disjuncts” similar to those of southwestern Michigan and adjacent Indiana, and central Wisconsin. Matchedash Lake in Simcoe Co., Ontario, has a particularly rich assemblage of these shoreline species. Based on short-term records, and aging of drowned stumps, we demonstrated that yearly mean water levels can and have changed by more than a meter. Such water-level fluctuations partly result from beaver dams on the single outlet stream. Vegetation data collected in a low-water phase (1976) document a rich shoreline flora, largely absent in the present (1979) high-water phase. During this latter high-water phase, we collected 15 sediment sample units from each of six water depths (0–1.5 m). The sample, representing 0.32 m² of lake bottom, was planted out in a greenhouse; 3,149 seedlings representing 41 species of vascular plants emerged. Six (Rhexia virginica, Rhynchospora capitellata, Panicum spretum, Xyris difformis, Polygonum cureyi, Linum striatum) are rare in Ontario. Estimated seed banks for individual species were as high as 6,500 seeds m“². If another low-water phase occurs, a rich shoreline flora should again develop. We hypothesize that water-level fluctuations are essential to the long-term survival of these species.     

Plant Invasions on an Oceanic Archipelago

Plant invasions are particularly noticeable on oceanic islands. For many ecological or evolutionary phenomena, oceanic islands offer advantages in comparison to continental regions, because they are often simpler systems. The Juan Fernández (Robinson Crusoe) Islands, located 667 km west of continental Chile, provide an especially favorable case study of plant invasions on an oceanic archipelago. They have little flora, no influence from aboriginal peoples, and good historical and recent documentation of flora, vegetation and human impacts. The total flora of the archipelago consists of 441 vascular plants, of which 209 are native (125 of them endemic) and 232 are aliens. Many alien species exist on the Juan Fernández Archipelago, but three shrubs are particularly invasive: Aristotelia chilensis, Rubus ulmifolius, and Ugni molinae. About 15% of the total area of the island has been impacted by at least one of these shrubs. In addition, the herbaceous Acaena argentea, now occurs at high abundance in 12% of the total area of the island. Comparisons of earlier and recent surveys of vegetation reveal that the area impacted by Aristotelia, Rubus, and Ugni molinae has increased tremendously. Among the most frequent aliens are Euro-Mediterranean taxa, also present on other archipelagos. A few aliens that are serious invasives on other archipelagos have been recently observed near San Juan Bautisata, the only village on the island. Effective measures involving stronger monitoring and sanitation of incoming materials (foodstuffs, building materials, etc.), cutting or poisoning of invasives, and reseeding with native species, are necessary to help preserve the native and endemic flora (and biota) of these islands.     

Flora e Vegetazione Dell'Isola Di Pianosa (Isole Tremiti)

Abstract

Flora and vegetation of the Isle of Pianosa (Isles Tremiti). – The flora and vegetation of the Isle of Pianosa are here described. The flora is composed of common mediterranean species with some adriatic endemics. The vegetation has a halophilous-nitrophilous character. The plant formations identified on this isle are shown in the map (fig. 1).     

Seed dispersal in the dung of large herbivores: implications for restoration of Renosterveld shrubland old fields

Species-rich, winter-rainfall, microphyllous Renosterveld vegetation in the Western Cape Province of South Africa has largely been transformed for production of wheat and wine. Remaining fragments thus have high conservation value. Abandoned old fields adjacent to natural vegetation fragments could potentially be restored as corridors and habitat for indigenous flora and fauna. We hypothesised that indigenous antelope maintained in a matrix of natural vegetation and abandoned field could play a role in restoration of Renoserveld via seed dispersal.We collected dung of indigenous ungulates in an abandoned field at various distances from natural Renosterveld vegetation, in order to assess the potential of large herbivores to contribute to restoration of plant diversity through seed dispersal. Emerged seedlings from the collected dung represented 29 forb, 13 grass, four sedge, four geophyte and one shrub species. The most abundant emerging seedlings were lawn grass Cynodon dactylon (38%), alien pasture grasses (31%) and indigenous geophyte Romulea rosea (12%). Whereas seeds of annual forbs and grasses were dispersed, only one shrub species was dispersed at very low density. We concluded that large herbivores could retard the rate of recovery of Renosterveld vegetation because viable seeds of herbaceous plants, particularly alien annual grasses and lawn-grasses were more abundant in the dung than the shrub, geophyte or perennial tussock grass species that characterise this vegetation type.     

Persistent soil seed banks in old-growth Hyrcanian Box tree (Buxus hyrcana) stands in northern Iran

Little is known about the soil seed bank and the influence of plant communities on the interaction between the seed bank and aboveground vegetation in the Hyrcanian temperate deciduous forest. We surveyed species composition and diversity of the persistent soil seed bank and the aboveground vegetation in six community types in old-growth Hyrcanian Box tree (Buxus hyrcana) stands in northern Iran. Fifty-two species with an average of 3,808 seeds/spores m⁻² germinated; forbs accounted for 64% of the seed bank flora. Thirty-four species in the aboveground vegetation were not presented in the seed bank, 32 species in the seed bank were not found in the vegetation, and 20 species were in both. The dominant tree species were Diospyros lotus and Alnus subcordata with an average of 17 and 4.6 seeds m⁻², respectively. Our results suggest that (1) vernal geophytes and shade-tolerant perennials are not incorporated in the seed bank, (2) early successional species are well represented in the seed bank, (3) plant community type has significant impacts on seed bank densities, and seed bank richness and diversity were significantly related to presence/absence of Box tree in the aboveground vegetation. The persistent seed bank contained species that potentially have a negative impact on the regeneration of forests, thus forest managers should retain old-growth Hyrcanian Box tree stands to conserve disturbance-sensitive indicator forest species.     

Long‐term effects of drainage and initial effects of hydrological restoration on rich fen vegetation

Questions: What vegetational changes does a boreal rich fen (alkaline fen) undergo during a time period of 24 years after drainage? How is plant species richness affected, and what are the changes in composition of ecological groups of species? Is it possible to recover parts of the original flora by rewetting the rich fen? Which are the initial vegetation changes in the flora after rewetting? What are the major challenges for restoration of rich fen flora after rewetting? Location: Eastern central Sweden, southern boreal vegetational zone. Previously rich fen site, drained for forestry purposes during 1978–1979. The site was hydrologically restored (rewetted) in 2002. Method: Annual vegetation survey in permanent plots during a period of 28 years. Results: There were three successional stages in the vegetational changes. In the first stage there was a rapid (< 5 years) loss of rich fen bryophytes. The second step was an increase of sedges and early successional bryophytes, which was followed by an increase of a few emerging dominants, such as Molinia caerulea, Betula pubescens and Sphagnum spp. After rewetting, there are indications of vegetation recovery, albeit at slow rates. Depending on, for instance, initial species composition different routes of vegetation change were observed in the flora after drainage, although after 24 years, species composition became more homogenous and dominated by a few species with high cover. Conclusion: Major changes have occurred after changes in the hydrology (drainage and rewetting) with a severe impact on the biodiversity among vascular plants and bryophytes. Several rich fen bryophytes respond quickly to the changes in water level (in contrast to vascular plants). The recovery after rewetting towards the original rich fen vegetation is slow, as delayed by substrate degradation, dispersal limitation and presence of dominant species.     

Observations on the Varanasi wall flora

Summary This study deals with the ecology of a man-made habitat, i.e., old walls and buildings of Varanasi, India. The wall flora of Varanasi includes 135 species of angiosperms, 1 species of pteridophyte, 4 species of bryophytes and one lichen. Abundant wall plants likeArthraxon lancifolius, Lindenbergia polyantha, Aristida funiculata and lichens are never seen off the walls. The vegetation of the three types of walls, viz., brick mortar, brick mud and mud walls, classified according to the materials of construction, show sharp differences, despite many common features. Analysis of the wall flora, according to Raunkiaer's life-form system, revealed a marked contrast from the adjoining ground flora in having a very high percentage of therophytes.It is concluded, that the distinctiveness of the wall flora is due to the unique topography, microclimate and xeric nature of the wall habitat. Differences in the physico-chemical nature of the three types of walls are responsible for the variation in their vegetation.     

广西岩溶植被植物区系

通过对数十年来广西植物研究所对广西岩溶植被全面调查积累的资料进行分析研究 ,结果表明 :( 1 )广西岩溶植被的植物区系成分有 1 75科 662属 1 5 0 0种 ,其中 6科 1 71属 83 4种为岩溶植被专有 ;( 2 )广西岩溶植被的区系成分以番荔枝科、椴树科、大戟科、苏木科、榆科、鼠李科、楝科、无患子科、漆树科等为主 ,与岩溶植被区系关系密切的科或乔木层优势科一般是落叶种类多或藤本种类多的科 ,如果优势科多数种类或优势种类是常绿的 ,这些种类不是热带植物区系成分 ,就是一类硬叶阔叶或针叶的亚热带种类 ;( 3 )岩溶植被植物区系组成为地域性但带有明显的地带性烙印 ;( 4 )广西岩溶植被区系成分以热带成分为主 ,温带成分为辅 ,62 2属种子植物 ,热带分布占 76.2 1 % ,温带分布占 2 1 .1 3 % ,中国特有占 2 .66% ;( 5 )组成山顶矮林的区系成分比较固定 ,乔木种类主要有 :乌冈栎、铁屎米、山胶木 (假水石梓 )、圆叶乌桕、铜钱树、化香树、广东松、翠柏等 ;( 6)与广西酸性土植被比较 ,岩溶植被植物区系中蕨类植物、裸子植物、双子叶植物以及单子叶植物 ,无论是科属组成 ,还是种的组成 ,均没有酸性土植被植物区系占的比例高 ,另外 ,与组成酸性土植被乔木层优势科的关系也很疏远     

The spontaneous flora around street trees in cities—A striking example for the worldwide homogenization of the flora of urban habitats

Cities are well known as rich in vascular plant species. To evaluate the importance of this richness for global biodiversity it is necessary to know the degree of homogenization of the city flora at a continental or even worldwide scale. Therefore, we looked for a habitat type that is typical urban and which is represented in nearly all cities of the world: the area around street trees (“Baumscheiben”). The spontaneous flora of this habitat was recorded in seven West and Central European metropolises situated in six countries and in Baltimore (USA). To test for floristic homogenization, the dissimilarity among the Baumscheiben Flora in the European cities was compared with dissimilarity among relevés of the potential natural vegetation in the cities. On average 81 species were found growing on Baumscheiben in each of the European cities. 29 species (i.e. more than one third of the total) were found in every city, 59 species (i.e. 74%) were represented in at least four of the seven cities. The obvious homogenization of the flora of this habitat is confirmed by low total variation among European Baumscheiben. Furthermore, the dissimilarity among Baumscheiben was much lower than among the potential natural vegetation (forests) around these cities. There is not only low variation between the Baumscheiben flora of the seven European metropolises analyzed, but also great similarity to the Baumscheiben flora of Baltimore: 80% of the species found on Baumscheiben in Baltimore also belong to the spontaneous flora of most European cities and 26% even belong to the group of the most common species of West and Central European tree bases.     

Taphonomy of the early Miocene flora, Hiwegi Formation, Rusinga Island, Kenya

A fossil flora was collected in situ from early Miocene deposits at site R117 in the Hiwegi Formation of Rusinga Island contemporaneous with and in close proximity to the sites from where the anthropoid primates were recovered. The flora exhibits a spatially and temporally patchy distribution of fruits and seeds, mixed with twigs of various sizes, fragments of wood, bark, and leaves, all with random orientations and very low depositional dips. There has been minimal transport and the flora evidently accumulated as in situ litter beneath local vegetation. Based on Nearest Living Relatives (NLR) of fruits and seeds, the vegetation represented is a deciduous broad-leaved woodland with continuous canopy, with trees, shrubs, lianas, and climbers, reminiscent of the structure of the modern vegetation in the steep-sided protected valleys in the Laetoli-Endulen area. The interpretation of the vegetation is supported by the presence of twigs, wood, and bark fragments from larger diameter axes. Climbers are represented by twining stem fragments as well as by a wide variety of distinctive fruits and seeds. The proportion of fossilised thorny twigs represents only 3% of the twig collections, and there are no unequivocal forest trees amongst the NLR. No grasses were present; monocotyledons are only represented by a single date palm stone. No conifer seeds or cones have been recovered, and there are no coniferous leafy shoots.     

Seed bank composition and above-ground vegetation in response to grazing in sub-Mediterranean oak forests (NW Greece)

We investigate the persistent soil seed bank composition and its relation to the above-ground flora of grazed and non-grazed sub-Mediterranean deciduous oak forests of NW Greece. Twenty-eight taxa were recorded in the soil seed bank and 83 taxa (70 taxa in plots of seed bank sampling) in the above-ground vegetation. The dominant tree species and many woodland species found in the above-ground vegetation were absent from the soil seed bank. Similarity between the soil seed bank and the above-ground vegetation decreased with grazing, and grazing led to a decrease of species richness in above-ground vegetation and soil seed bank. Beta diversity of vegetation among grazed and among non-grazed plots did not differ, but was significantly higher between grazed and non-grazed areas. Beta diversity of the soil seed bank declined with grazing. When applying classification tree and logistic regression analyses, non-grazed forest sites are clearly differentiated by the presence of Phillyrea latifolia, Euphorbia amygdaloides and Brachypodium sylvaticum. PCA ordination of above-ground species composition reflected a gradient from sites grazed by ruminants to non-grazed sites, but no clear structure was detected in the seed bank.     

Isolated Pasture Trees and the Vegetation under their Canopies in the Chiapas Coastal Plain,Mexico1

The Coastal Plain of Chiapas (southern Mexico) was formerly covered by large tracts of subhumid tropical forests but is heavily deforested at present. In this region, 15 pastures were selected to characterize species composition of isolated trees, as well as to describe species composition, growth form patterns, and patterns of dispersal units in the vegetation growing under their canopies. The 65 recorded pasture trees belonged to 20 species and 11 families, of which Fabaceae and Moraceae were the most species-rich. Coccoloba barbadensis (Polygonaceae) and Enterolobium cyclocarpum (Fabaceae) were the most abundant and frequent trees in the studied pastures. More than half (55%) of isolated tree species were fleshy-fruited. In the vegetation sampled under pasture trees, 134 species and 45 families were found. Fabaceae and Poaceae had the largest numbers of species. Herbs were the predominant growth form (46.3%), followed by shrubs (23.9%), trees (23.1%), and lianas (2.2%); 6 species could nor be placed in any growth form category. Most species of this flora were fleshy-fruited (43.3%), followed by heavy, gravity-dispersed fruits (17.9%). The analysis of dispersal units by growth form category confirmed the prevalence of fleshy fruits, although their predominance was not so obvious among herb species. Almost half (49.2%) of the flora under pasture trees was typical of secondary vegetation; this pattern was true for herbs but not for most woody species, which were typical of primary vegetation. A numeric classification of the vegetation samples taken under pasture trees produced eight floristic groups, all of which were independent of the specific identity of pasture trees. No significant effect of dispersal unit type of pasture tree on the characteristics of the vegetation growing under them was found. Future attempts to re-create the original forest cover using isolated trees in pastures as regeneration foci should pay more attention to the maintenance of a large specific diversity independently of the dispersal types among these components of tropical landscapes.     

青藏高原东南部察隅河流域种子植物区系研究

在野外植被调查、标本采集和资料查询整理的基础上,汇总了察隅河流域种子植物名录,并对流域内植物物种的组成、优势科属、区系地理成分及性质进行分析。运用R语言在属水平上与其周边16个地区的植物区系进行聚类及主成分分析,探讨察隅河流域种子植物区系与其他区系之间的关系。结果表明：(1)察隅河流域共含种子植物138科、689属、2 771种(含变种),其中裸植子物4科12属56种,被子植物134科677属2 715种,被子植物中双子叶植物112科531属2 270种占绝对优势。(2)区内地理成分联系广泛,科的区系划分除世界分布类型外,热带分布型53科(55.21%),温带分布型43科(44.79%);属的区系划分中所有类型均有分布,温带分布型396属(62.07%),热带分布型230属(36.05%);属的分布型与科相比具有更明显的温带性质;植物种类丰富度高但特有成分低,无特有科,仅含12特有属。(3)流域内植被垂直地带性分布较为明显,保留了较多古老孑遗植物,如裸子植物的西藏红豆杉(Taxus wallichiana)、察隅冷杉(Abies chayuensis)和云南松(Pinus yunnanensis)等;由于青藏高原的上升运动,成为杜鹃花属(Rhododendron)、虎耳草属(Saxifraga)、龙胆属(Gentiana)和报春花属(Primula)等新生高山植物区系成分分化繁衍的摇篮。(4)察隅河植物区系属喜马拉雅山南侧热带成分向温带成分过渡的区系性质,与珠峰自然保护区植物区系更为相似。     

四川九顶山东坡植物群落的区系研究

对九顶山东坡植物群落野外调查 ,得到种子植物 10 4科 345属 4 85种。通过植物区系成分分析可知 ,该区区系比较复杂 ,15种分布类型在该区均有分布。其区系特征具有明显的温带性质 ,温带成分 2 0 1属 ,占总属的 5 8 2 6 % ,而且以北温带分布 (96属 )为主 ;与热带有一定的亲缘关系 ,热带成分 10 5属 ,占 30 4 3% ;中国特有植物多 ,17属 18种 ;区系起源古老。