首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Abstract Understanding the factors that affect plant species distribution and coexistence in areas with high plant species diversity is a challenge for ecologists. According to some authors, species occupy specific niches, but for others, species coexistence and geographical distribution patterns are random. Floristic composition of the family Leguminosae was studied on moist and dry slopes of the Baturité mountains in semi‐arid northeastern Brazil and was compared with findings for other plant formations elsewhere in Brazil. Substantial floristic differences were found between the moist windward and dry leeward slopes of the Baturité mountains despite their close geographical proximity. The leeward slope was slightly more diverse than the windward slope. Similarity analyses showed that the windward face is floristically allied to the Amazon forest, whereas the leeward slope is similar to other dry‐area formations of northeastern Brazil, such as thorny woodland (caatinga) and seasonal forests. The strong floristic differences that were observed between the windward and leeward slopes corroborate the theory of ecological niche conservatism, which holds that species occurrence is closely linked to environmental factors, such as temperature and precipitation.  相似文献   

2.
地衣是亚热带山地森林系统附生生物类群的重要组成部分之一,对环境变化极其敏感。为了更好地了解附生地衣对森林边缘效应的响应,我们在云南哀牢山地区原生山地常绿阔叶林中,分别在距林缘5m、25m、50m和 100m处设立样地,收集附生大型地衣的凋落物1年;分析附生地衣凋落物的物种多样性和生物量、功能群特征和组成结构对林缘深度变化的响应特征。研究结果显示,边缘效应能够显著提高林缘附生地衣群落的物种多样性和生物量;其发生的距离最深不超过25m。林缘-林内梯度上,不同地衣功能群的响应模式具有各自的特征。排序分析表明仅在5m样地与其他样地之间存在显著差异,指示种分析则发现仅5m样地具有指示种。哀牢山原生林中边缘效应促进林缘附生地衣生长和分布的现象,可能与当地高湿环境削减了地衣的高光损伤以及以叶状和灌状类群为主的地衣个体受到风力破坏的程度相对较低有关。  相似文献   

3.
Larison, B., Smith, T.B., Fotso, R. & McNiven, D. 2000. Comparative avian biodiversity of five mountains in northem Cameroon and Bioko. Ostrich 71 (1 & 2): 269–276.

Endemism among birds is widespread in the montane forests of western Cameroon and the Gulf of Guinea. The region includes some of the rarest and most threatened species in Africa. We conducted avian surveys of four previously unsurveyed montane sites in northern Cameroon, including Mt. Ngang-Ha, Hoséré Vokré, Tchabal Gandaba, and Tchabal Mbabo, as well as the northern slope of Caldera de Luba on the island of Bioko, Equatorial Guinea. We report here on avian species richness and relative abundance, and evaluate the conservation potential of each site based on avifaunal richness. The montane forest on both Tchabal Mbabo and Caldera de Luba is extensive, while on the other mountains, the vegetation is not characteristic of montane forest, and consists primarily of small gallery forests embedded in savanna. Tchabal Mbabo and Caldera de Luba had the greatest species richness and abundance of montane birds, while Tchabal Gandaba had the greatest overall avian species richness and abundance. Few montane species were noted on Mt. Ngang-Ha and Hosere Vokre, and avian abundance was quite low on both mountains. Of the mountains surveyed, Tchabal Mbabo and Caldera de Luba exhibit the greatest potential for conservation based on extent of montane forest, and montane species richness and abundance.  相似文献   

4.
Habitat preferences of the Andean bear Tremarctos ornatus were studied within two adjacent protected areas in the north-western Bolivian Andes. Standard transects measuring habitat variables and bear sign frequency were used spanning seven different vegetation types. Andean bears were present at 28 of 33 sampled sites and actively preferred high-elevation elfin forest and upper montane humid forests, and used high-elevation humid 'páramo' grasslands and middle montane humid forests according to their availability. Bears were absent from dry montane and Andean foothill forests and relative abundance was low in lower montane humid forests. Elevation and basal area of food items were the variables most closely related to the relative abundance.  相似文献   

5.
The soils are seasonally or permanently saturated in the moist grassland savanna, locally known as Campo Limpo Umido. Soil moisture variation seems to determine spatial distribution of communities. The objective of this study is to analyse the relationship between environmental variables and the patterns of spatial distribution of species in the herbaceous-subshrub layer of an area of moist grassland at the Agua Limpa Farm, Brasília, DF (15 degrees 56' to 15 degrees 59' S and 47 degrees 55' to 47 degrees 58' W Gr.). An area of 400 x 400 m was divided into four sections of 200 x 200 m where four transects were randomly sampled. A line intercept method was adopted for the phytossociological study. Superficial soils samples (0-20 cm) were collected for chemical and textural analyses. Gravimetric soil moisture was measured quarterly during the study-year. A total of 85 species in 67 genera and 24 families were found. The diversity was high, Shannon's index, H', was 2.60 nats.cover(-1). Floristic composition of the transects in soils with a high gravimetric soil moisture and high content of organic matter and sand differed from those transects in soils with a lower gravimetric soil moisture indicating seasonal variation. A Canonical Correspondence Analysis (CCA) showed significant correlations between soil texture and soil moisture features and species distribution. Gravimetric soil moisture, organic matter, clay, silt and sand were significantly correlated to species distribution in the moist grassland determining mosaics in the vegetation.  相似文献   

6.
论滇南西双版纳的森林植被分类   总被引:3,自引:0,他引:3  
朱华 《云南植物研究》2007,29(4):377-387
本文基于多年研究成果的总结,对西双版纳森林植被的分类、主要植被类型及其特征进行了系统归纳,并讨论了它们与世界类似热带森林植被的关系。以群落的生态外貌与结构、种类组成和生境特征相结合作为植被分类的原则和依据,可以将西双版纳的热带森林植被分类为热带雨林、热带季节性湿润林、热带季雨林和热带山地常绿阔叶林四个主要的植被型,包括有至少二十个群系。热带雨林包括热带季节雨林和热带山地(低山)雨林二个植被亚型。热带季节雨林具有与赤道低地热带雨林几乎一样的群落结构和生态外貌特征,是亚洲热带雨林的一个类型,但由于发生在季风热带北缘纬度和海拔的极限条件下,受到季节性干旱和热量不足的影响,在其林冠层中有一定比例的落叶树种存在,大高位芽植物和附生植物较逊色而藤本植物和在叶级谱上的小叶型植物更丰富,这些特征又有别于赤道低地的热带雨林。热带山地雨林是热带雨林的山地亚型,是该地区热带山地较湿润生境的一种森林类型,它在植物区系组成和生态外貌特征上类似于热带亚洲的低山雨林,隶属于广义热带雨林植被型下的低山雨林亚型。热带季节性湿润林分布在石灰岩山坡中、上部,在群落外貌上类似热带山地常绿阔叶林但在植物区系组成上与后者不同,它是石灰岩山地垂直带上的一种植被类型。热带季雨林是分布在该地区开阔河谷盆地及河岸受季风影响强烈的生境的一种热带落叶森林,是介于热带雨林与萨王纳之间的植被类型。热带山地常绿阔叶林(季风常绿阔叶林)是西双版纳的主要山地植被类型,它分布在热带季节雨林带之上偏干的山地生境。它在植物区系组成上不同于该地区的热带季节雨林,在生态外貌特征上亦不同于热带山地雨林,是发育在受地区性季风气候强烈影响的热带山地的一种森林植被类型。  相似文献   

7.
ZHU Hua 《Plant Diversity》2007,29(4):377-387
Xishuangbanna of southern Yunnan is a region of extremely interest to biologists and also a hotspot for biodiversity conservation . It is located in a transitional zone from tropical Southeast Asia to temperate East Asia biogeographically. The present paper reviewed vegetation types of Xishuangbanna and suggested a revised classification system based on theupdated study results over the last two decades . By combining physiognomic and floristic characteristics with ecological performances and habitats , the primary forest vegetation in Xishuangbanna can be organized into four main vegetation types: tropical rain forest, tropical seasonal moist forest, tropical montane evergreen broad-leaved forest and tropical monsoon forest. The tropical rain forest can be classified into two subtypes , i. e. tropical seasonal rain forest in the lowlands and tropical montane rain forest on higher elevations. The tropical seasonal rain forest in this region shows similar forest profile and physiognomic characteristics to those of equatorial lowland rain forests and is a type of world tropical rain forest. Because of conspicuous similarity on floristic composition , the tropical seasonal rain forest in Xishuangbanna is a type of tropical Asian rain forest . However , since the tropical seasonal rain forest occurs at the northern edge of tropical SE Asia, it differs from typical lowland rain forests in equatorial areas in maintaining some deciduous trees in the canopy layer , fewer megaphanerophytes and epiphytes but more abundant lianas and more plants with microphyll . It is a type of semi-evergreen rain forest at the northern edge of the tropical zone . The tropical montane rain forest occurs in wet montane habitats and is similar to the lower montane rain forests in equatorial Asia in floristic composition and physiognomy . It is a variety of lower montane rain forests at the northern tropical edges of tropical rain forests . The tropical seasonal moist forest occurs on middle and upper limestone mountains and is similar to the tropical montane evergreen broad-leaved forest of the region in physiognomy, but it differs from the latter in floristic composition. The monsoon forest in Xishuangbanna is a tropical deciduous forest under the influence of a strong monsoon climate and is considered to be a transitional vegetation type between tropical rain forest and savanna in physiognomy and distribution. The tropical montane evergreen broad- leaved forest is the main vegetation type in mountain areas . It is dominated by the tree species of Fagaceae , Euphorbiaceae , Theaceae and Lauraceae in majority. It differs from the tropical montane rain forests in lack of epiphytes and having more abundant lianas and plants with compound leaves . It is considered to be a distinct vegetation type in the northern margin of mainland southeastern Asia controlling by a strong monsoon climate, based on its floristic and physiognomic characteristics.  相似文献   

8.
Eriocnema fulva Naudin is a perennial herb, endemic to Minas Gerais state, SE Brazil, found on humid, shaded rocky riverbanks in montane semideciduous seasonal forests. The species is threatened, but information regarding its biology is still lacking, although such information is fundamental to any management plan. We aimed to evaluate the reproductive system of Eriocnema fulva in the Jambreiro Forest (19 degrees 58'-59' S and 43 degrees 55'-52' W, 800-1100 m altitude), municipality of Nova Lima, by experiments carried out in 1997 and 1998. The flowers are white, and flowering is of the steady state type, occurring once a year from November to December. Anthers are poricidal, and pollen is the only resource for visitors. The chromosome number is n = 17 during meiosis. The species is self-compatible, but does not produce fruits by spontaneous self-pollination or agamospermy; it requires pollen vectors and buzz pollination in order to produce fruits. Cross-pollination is the main reproductive strategy of E. fulva, and is accentuated by the small number of flowers (one or two in each plant) opened per day. Although the population studied was shaded by forest canopy, the seeds needed light to germinate. Germination ratio was lower in germination cabinet on filter paper (14% after 30 days) than in greenhouse on soil brought from the forest (47% after 25 days). Although the fruit is a capsule and the seeds are small, dispersion (anemochory or hydrochory) does not seem to occur at long distance, as it is the case for other Melastomataceae species with similar syndrome.  相似文献   

9.
Richness and abundance of birds in riparian forest belts of varied breadths at the Sesesmiles river microwatershed, Copan, Honduras. Riparian forests protect many species of plants and animals. We studied bird communities in riparian forest belts of the Sesesmiles river microwatershed, Copan, Honduras (140 degrees 43' 12" - 140 degrees 58' 35" N, 88 degrees 53' 23" - 89 degrees 14' 17" W). The main goal was to explore the effects of belt breadth on the richness and abundance of avian species visiting these forests. We selected 20 belts, and randomly established 30 observation points to monitor bird presence in the dry (March-April 2005) and rainy (June-July 2005) season (N= 60 observations). A total of 1,294 birds belonging to 145 species were recorded. Bird diversity was significantly correlated to the breadth of the riparian belts, with a greater number of species and individuals in belts 50 m wide or wider. Insectivorous and nectarivorous birds were the most abundant guilds. All bird species identified depend to some degree on riparian forests and are affected by belt breadth. Riparian belts over 50 m should be kept or established in order to conserve bird populations within agricultural and fragmented landscapes in similar tropical areas.  相似文献   

10.
Transplant studies can provide valuable information on the growth responses of epiphytic bryophytes and lichens to environmental factors. We studied the growth of six epiphyte species at three sites in moist Afromontane forests of Taita Hills, Kenya. With 558 pendant transplants, we documented the growth of four bryophytes and two lichens over 1 yr. The transplants were placed into the lower canopy of one forest site in an upper montane zone, and two forest sites in a lower montane zone. Several pendant moss species grew very well in the cool and humid environment of the upper montane forest, with some transplants more than doubling their biomass during the year. Conversely, all transplanted taxa performed poorly in the lower montane zone, presumably because of the unfavorable combination of ample moisture with excessive warmth and insufficient light which characterizes the lower canopy in dense lower montane forests. The results demonstrate that pendant transplants can be used for monitoring growth of non‐vascular epiphytes in tropical forests. The starting weight of 0.25 g for pendant transplants worked well and can be recommended for future studies.  相似文献   

11.
12.
The montane forests of northern Mozambique’s isolated massifs are inhabited by numerous range-restricted and threatened bird species, but until recently were extremely little-known. We report on a first avifaunal survey of the isolated montane habitats of Mt Mecula (1 442 m), Niassa National Reserve, notable as the only currently protected montane area in northern Mozambique. Mount Mecula’s moist forest is small (approximately 136 ha in total) and patchy, and although known botanically to have some montane affinities, was found to support an avifauna more typical of riparian forests of medium to low altitude. The only montane forest species recorded was Lemon Dove Aplopelia larvata. Other montane elements included Vincent’s Bunting Emberiza (capensis) vincenti, one of six species recorded new to the Niassa National Reserve list. Overall, it appears that despite its intermediate location, Mt Mecula does not represent a biogeographical ‘stepping stone’ for montane forest bird species. This probably owes to its remoteness from the Eastern Arc Mountains of Tanzania to the north and the massifs of other parts of northern Mozambique, to the south and west.  相似文献   

13.
Abstract. Two 10-metre cores were analysed and a 37,500 year pollen stratigraphy was established for Lake Mala?i. A lowstand from 37,500 to 35,900 BP indicates extremely dry conditions. From 35,900 to 34,000 BP montane forests were widespread indicating cold, moist climate. Between 34,000 and 26,400 BP warm and dry conditions prevailed and forest area decreased. During the Last Glacial Maximum montane forest was widespread in the catchment, although woodlands apparently persisted at low altitudes: the expansion of the montane forest indicates that the aridity that affected equatorial Africa during this time period did not affect the Lake Mala?i Catchment. The cold and relatively moist conditions during the Late Pleistocene probably allowed biotic interchange between the highlands of East and West Africa via the highlands along the Zaire—Zambezi watershed and among now-isolated islands of Afromontane vegetation in the Lake Mala?i catchment. The Holocene is characterized by climate and vegetation quite similar to today, with indications of slightly wetter conditions between 6150 and 3000 bp and slightly drier conditions between 8000 and 6150 bp . The low percentages of montane forest pollen throughout the Holocene support the hypothesis that the montane grasslands of Mala?i are not recently anthropogenic.  相似文献   

14.
Aim To use parsimony analysis of endemicity and cladistic analysis of distributions and endemism to evaluate two hypotheses addressing biogeographical relationships among Amazonia, the Caatinga forest enclaves, Pernambuco Centre and the southern Atlantic Forest. Location North‐eastern Brazil, South America. Methods To find the most parsimonious areagram we analysed a matrix composed of the presence (1) or absence (0) of 745 taxa (i.e. 293 genera and 452 species of woody plants) within 16 localities belonging to the four large regions addressed in this study. Results One most parsimonious areagram was found and it shows a basal separation between the southern Atlantic Forest and all other regions. This break is followed by a separation between all Caatinga forest enclaves (except Baturité) from a cluster composed of Baturité, the Pernambuco Centre and Amazonia. In this cluster, the most basal separation isolates Baturité from the cluster formed by localities from Amazonia and the Pernambuco Centre. The biogeographical relationships among sites could not be explained by either a random distribution of species among sites or by the geographical distance between sites. Main conclusions We found strong cladistic signal within the raw distribution and phylogenetic data used in our analysis, indicating structured species assemblages in the surveyed localities. They have resulted from the fragmentation of an ancestral biota that was once widely distributed in the region. Our results also support the hypothesis that Atlantic Forest is not a biogeographically natural area, because the Pernambuco Centre is more closely related to Amazonia than to the southern Atlantic Forest. Finally, our data do not support the notion that Caatinga forest enclaves comprise a single biogeographical region, because one Caatinga forest enclave (Baturité) is much more closely related to the cluster formed by Amazonia and the Pernambuco Centre than to other sites. These relationships suggest the occurrence of forest connections between Amazonia and the Atlantic Forests across Caatinga during several periods of the Tertiary and Quaternary. However, palaeoecological data currently available for the Caatinga region are still scarce and do not have either the spatial or temporal resolution required to reconstruct the history of connections among the forests in north‐eastern Brazil.  相似文献   

15.
Climate change and its cascading impacts are being increasingly recognized as a major challenge across the globe. Climate is one of the most critical factors affecting biomes and their distribution. The present study assessed shifts in biome types of India using the conceptual framework of Holdridge life zone (HLZ) model, minimum distance classifier and climatic datasets to assess the distribution pattern of potential biomes under climate change scenarios in India. Modelling was conducted on the entire region of India using various combinations; (i) current climate scenario, and, (ii) increased temperature and precipitation scenario. The geographical analysis identifies nineteen (19) HLZs in the Indian sub-continent; seven (7) biomes and nineteen (19) sub-biomes. The overall accuracy and kappa coefficient of the biome map prepared for current climate scenario was 82.73% and 0.75, respectively. With the changes in increasing temperature and precipitation scenario, the modelling results predict significant decrease in the area cover for tropical deserts (plains), tropical desert scrubs (lower montane), tropical moist forests (lower montane) and tropical wet forests (lower montane). Along with these changes, there have been substantial increases in the area cover for tropical dry forests (plains) and tropical very dry forests (plains), especially in central and southern India. The results show shifts from very dry tundra (alvar) to dry tundra (alpine) and moist tundra (alpine) and in some places tropical moist forests (sub-alpine) as well. In central India, decrease in tropical moist forests (lower montane) has been observed, while an increase in the area cover of tropical rain forests (plains) in northeastern India has been observed. It is important to understand the impacts and vulnerabilities of projected climate change on forest ecosystems so that better management and conservation strategies can be adopted for biodiversity and forest dependent communities. The knowledge of impact mechanisms will identify adaptation strategies for some conditions which will help in decreasing the susceptibility to anticipated climate change in the forest sector.  相似文献   

16.
Abiotic and vegetation data were collected along two altitudinal transects through mature montane Quercus forests on the Pacific and Atlantic slopes of Costa Rica's Chirripó Massif. Between 2000 and 3200 m asl twenty-four 0.05 ha forest plots were selected at altitudinal intervals of 100 m, and eight soil profiles were described at intervals of 200 m. A TWINSPAN classification aided in the determination of eight zonal forest communities on the basis of their floristic composition. They are grouped in two sets of four: (i) the palm-rich lauraceous-fagaceous Lower Montane Mollinedia-Quercus Forests (2000–2600 m asl) and (ii) the bamboo-rich myrsinaceous-fagaceous Upper Montane Schefflera-Quercus Forests (2500–3200 m asl), respectively. Vegetation changes seem correlated with two major climatic gradients: (i) a temperature gradient (altitude), and (ii) a moisture gradient (wet Atlantic vs. moist Pacific slope). Most soils are Andepts, and residual, colluvial or derived from volcanic material. Humus layers are thicker on the wetter Atlantic slope. A total of 431 vascular plant species consisted of 86 pteridophytes, 1 gymnosperm, 296 dicots and 48 monocots. Species richness, canopy height and stem diameter decrease with increasing altitude, while the canopy surface becomes more flattend. A comparison with other studies shows that Chirripó's montane Quercus forests fit within the environmental ranges known from altitudinal zonations elsewhere in the Tropics.Abbreviations asl above sea level - dbh diameter at breast height - LM Lower Montane - Mt. Mountain - TWINSPAN two way indicator species analysis - UM Upper Montane - VU code referring to soil profiles as presented in Van Uffelen (1991) This paper is dedicated to the memory of Alwyn H. Gentry, an outstanding and inspiring tropical botanist who tragically died in a plane crash in the mountains of Ecuador on August 3 1993, when surveying possible boundaries for a new tropical cloud forest reserve.  相似文献   

17.
王高升  刘文耀  付昀  杨国平 《生态学报》2008,28(3):1328-1336
在热带、亚热带和温带高海拔潮湿生境的山地森林林冠层中,积累有较为丰富的林冠腐殖质(Canopy humus),是构成山地森林生态系统景观结构的重要组分,为丰富的附生植物提供了重要的生长基质和营养物质.通过对云南哀牢山山地湿性常绿阔叶林林冠腐殖质和其相应林下地表腐殖质的分析测定结果表明,由于林冠和林下地表腐殖质的来源、组成和空间分布的不同,它们之间的理化特性存在较大的差异,其中林冠腐殖质中有机C、全N及全Ca的含量、C/N以及阳离子交换量显著高于林下地表腐殖质,而全K和全Mg的含量则显著低于后者,全P含量差异不明显;林冠腐殖质的微生物量C、N和呼吸强度,以及蔗糖酶、脲酶和蛋白酶的活性均显著高于林下地表腐殖质,说明林冠腐殖质是一种具有较高生物活性的有机土类物质,在山地森林生态系统养分循环、林冠附生植物多样性格局形成及其维持方面具有重要的作用.  相似文献   

18.
Moist lower montane vegetation has rarely been classified beyond broad zonational belts over large altitudinal ranges due to highly diverse species composition and structure. This study shows it is possible to further classify such forest types within Bwindi‐Impenetrable National Park (BINP), and that these assemblages can be explained by a combination of environmental conditions and past management. Botanical and environmental data were collected along some 4000 m of linear transects from the area surrounding Mubwindi Swamp, BINP. Ordination using Nonmetric Multidimensional Scaling (NMDS) and classification using Two‐way Indicator Species Analysis (TWINSPAN) successfully identified four different species assemblages. These forest types were then named on the basis of the ecological characteristics of the species within the group, and the environmental conditions influencing the distribution and past disturbance of the forest. The techniques used were in agreement for three out of the four forest types identified. Analysis using an environmental overlay showed a significant association between forest type and altitude. The results of this study indicate that a regional classification of forest types within moist lower montane forest belt using only tree species is possible, and that the forest types identified can be explained by environmental conditions and past management.  相似文献   

19.
Three species are described here that occur in montane and high-montane forests in Southeastern Brazil.Miconia shepherdii belongs to sectionGlossocentrum and occurs on the Serra da Mantiqueira, on the border between the states of São Paulo, Minas Gerais, and Rio de Janeiro.Miconia kollmannii belongs to sectionHypoxanthus (formerChaenanthera) and occurs in the state of Espírito Santo.Ossaea suprabasalis was also collected in the state of Espírito Santo.  相似文献   

20.
Ants were extracted in Winkler bags from sifted leaf litter sampled in arange of forest and woodland types in and around Mkomazi Game Reserve innorth-eastern Tanzania, including the Eastern Arc Mountains of South Pare andWest Usambara. A total of 87 ant species were recorded, of which 32.2% were onlyrecorded from montane forests (1400–1850 m altitude), 6.9%only from lowland forest (540–810 m), 19.5% only fromwoodland (300–1080 m), and 16.1% in all three forest types.Of the 28 species recorded only from montane forests, 12 species were only foundin the Mkomazi forests, four only in the Pares and seven species only in theUsambaras. Sites of similar altitude grouped together in a cluster analysis, andspecies richness decreased with an increase in altitude. The lowland forest andclosed woodland sites did not form distinct communities. To ensure preservationof ant species, forests from a full range of altitudes need to be conserved.This study confirms the status of the West Usambara forests as having a highlyendemic biota, and the critical need to adequately conserve the remainingvestiges of montane forest within Mkomazi Game Reserve.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号