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1.
Macrophyte communities of European streams with altered physical habitat   总被引:2,自引:2,他引:0  
The impact of altering hydro-morphology on three macrophyte community types was investigated at 107 European stream sites. Sites were surveyed using standard macrophyte and habitat survey techniques (Mean Trophic Rank Methodology and River Habitat Survey respectively). Principal Components Analysis shows the macrophyte community of upland streams live in a more structurally diverse physical habitat than lowland communities. Variables representing the homogeneity and diversity of the physical environment were used to successfully separate un-impacted from impacted sites, e.g. homogeneity of depth and substrate increased with decreasing quality class for lowland sites (ANOVA p < 0.05). Macrophyte attribute groups and structural metrics such as species richness were successfully linked to hydro-morphological variables indicative of impact. Most links were specific to each macrophyte community type, e.g., the attribute group liverworts, mosses and lichens decreased in abundance with increasing homogeneity of depth and decreasing substrate size at lowland sites but not at upland sites. Elodea canadensis, Sparganium emersum and Potamogeton crispus were indicative of impacted lowland sites. Many of the indicator species are also known to be tolerant to other forms of impact. The potential for a macrophyte tool indicative of hydro-morphological impact is discussed. It is concluded one could be constructed by combining indicator species and metrics such as species richness and evenness.  相似文献   

2.
Aim We analysed lake‐sediment pollen records from eight sites in southern New England to address: (1) regional variation in ecological responses to post‐glacial climatic changes, (2) landscape‐scale vegetational heterogeneity at different times in the past, and (3) environmental and ecological controls on spatial patterns of vegetation. Location The eight study sites are located in southern New England in the states of Massachusetts and Connecticut. The sites span a climatic and vegetational gradient from the lowland areas of eastern Massachusetts and Connecticut to the uplands of north‐central and western Massachusetts. Tsuga canadensis and Fagus grandifolia are abundant in the upland area, while Quercus, Carya and Pinus species have higher abundances in the lowlands. Methods We collected sediment cores from three lakes in eastern and north‐central Massachusetts (Berry East, Blood and Little Royalston Ponds). Pollen records from those sites were compared with previously published pollen data from five other sites. Multivariate data analysis (non‐metric multi‐dimensional scaling) was used to compare the pollen spectra of these sites through time. Results Our analyses revealed a sequence of vegetational responses to climate changes occurring across southern New England during the past 14,000 calibrated radiocarbon years before present (cal yr bp ). Pollen assemblages at all sites were dominated by Picea and Pinus banksiana between 14,000 and 11,500 cal yr bp ; by Pinus strobus from 11,500 to 10,500 cal yr bp ; and by P. strobus and Tsuga between 10,500 and 9500 cal yr bp . At 9500–8000 cal yr bp , however, vegetation composition began to differentiate between lowland and upland sites. Lowland sites had higher percentages of Quercus pollen, whereas Tsuga abundance was higher at the upland sites. This spatial heterogeneity strengthened between 8000 and 5500 cal yr bp , when Fagus became abundant in the uplands and Quercus pollen percentages increased further in the lowland records. The differentiation of upland and lowland vegetation zones remained strong during the mid‐Holocene Tsuga decline (5500–3500 cal yr bp ), but the pattern weakened during the late‐Holocene (3500–300 cal yr bp ) and European‐settlement intervals. Within‐group similarity declined in response to the uneven late‐Holocene expansion of Castanea, while between‐group similarity increased due to homogenization of the regional vegetation by forest clearance and ongoing disturbances. Main conclusions The regional gradient of vegetation composition across southern New England was first established between 9500 and 8000 cal yr bp . The spatial heterogeneity of the vegetation may have arisen at that time in response to the development or strengthening of the regional climatic gradient. Alternatively, the differentiation of upland and lowland vegetation types may have occurred as the climate ameliorated and an increasing number of species arrived in the region, arranging themselves in progressively more complex vegetation patterns across relatively stationary environmental gradients. The emergence of a regional vegetational gradient in southern New England may be a manifestation of the increasing number of species and more finely divided resource gradient.  相似文献   

3.
在江西阳际峰自然保护区调查的25个样地中,共采集到地面生苔藓植物34科56属106种(包括1变种)。应用CCA排序法,首次定量分析了该区38种主要地面生苔藓植物与环境因子的关系。结果表明,苔藓植物的分布和生物多样性受环境因子的影响较大,湿度、基质是影响地面生苔藓植物分布的主要环境因子,其他影响因子依次为乔木郁闭度、灌木盖度、海拔高度、人为干扰和坡度。  相似文献   

4.
北京百花山自然保护区地面生苔藓植物与生态环境的关系   总被引:1,自引:0,他引:1  
运用典范对应分析法,定量分析了北京百花山自然保护区37个森林植被样地中33种主要地面生苔藓植物与生态环境之间的关系,结果表明:该区森林植被样地与环境因子的关系呈现多元化特点:相同植被聚为一组、环境因子相似的植被聚为一组、植被相同环境因子不同归为不同组和生境特殊的植被自成一组。得出该区多数地面生苔藓植物的分布与乔木郁闭度的相关性最大且与人为干扰程度密切相关,少数种类与草本层盖度和灌木盖度呈正相关。此外凋落物盖度、海拔、苔藓植物的生长基质也直接影响苔藓植物的分布。  相似文献   

5.
The aims of this study were to explore the environmental factors that determine the distribution of plant communities in temporary rock pools and provide a quantitative analysis of vegetation–environment relationships for five study sites on the island of Gavdos, southwest of Crete, Greece. Data from 99 rock pools were collected and analysed using Two-Way Indicator Species Analysis (TWINSPAN), Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA) to identify the principal communities and environmental gradients that are linked to community distribution. A total of 46 species belonging to 21 families were recorded within the study area. The dominant families were Labiatae, Gramineae and Compositae while therophytes and chamaephytes were the most frequent life forms. The samples were classified into six community types using TWINSPAN, which were also corroborated by CCA analysis. The principal gradients for vegetation distribution, identified by CCA, were associated with water storage and water retention ability, as expressed by pool perimeter and water depth. Generalised Additive Models (GAMs) were employed to identify responses of four dominant rock pool species to water depth. The resulting species response curves showed niche differentiation in the cases of Callitriche pulchra and Tillaea vaillantii and revealed competition between Zannichellia pedunculata and Chara vulgaris. The use of classification in combination with ordination techniques resulted in a good discrimination between plant communities. Generalised Additive Models are a powerful tool in investigating species response curves to environmental gradients. The methodology adopted can be employed for improving baseline information on plant community ecology and distribution in Mediterranean ephemeral pools. Handling editor: S. M. Thomaz  相似文献   

6.
Uplands are expected to provide refuges for species subject to lowland habitat loss and projected climate changes. Here, we argue that upland populations also provide refuges when lowland sites are subject to climatic fluctuations and extreme events and that species with populations dispersed over adjoining uplands and lowlands spread their risk of extinction. A proviso is that development is sufficiently lagged with altitude but that development rates are compatible. Emergence patterns and development of the butterfly Anthocharis cardamines and its larval host plant Cardamine pratensis show these characteristics, and coupled with the butterfly’s capacity to migrate between isolated populations present a case where upland and lowland populations can act as sources when one or the other area is adversely affected by extreme events.  相似文献   

7.
浙江省红楠生境地群落数量分类和环境解析   总被引:1,自引:0,他引:1  
为探讨群落结构与环境因子对红楠Machilus thunbergii在浙江省分布及发展的影响,采用双向指示种分类(TWINSPAN)、典范对应分析(CCA)并结合种间联结分析,对浙江省172个红楠生境地群落进行数量分类排序与环境解析。结果表明:(1)TWINSPAN将172个样地群落分成8个群落类型,红楠在群落中为优势种或主要伴生种。群落类型的不同是影响红楠生长及更新的重要原因。(2)海拔高度及坡度是决定红楠分布及发展的主导环境因子。红楠作为优势种的生境地主要特征为海拔900m以下、坡度35°以下。(3)甜槠(Castanopsis eyrei)、青冈(Cyclobalanopsis glauca)、木荷(Schima superba)为群落中的稳定优势种,种间联结结果显示与红楠均为显著正关联。  相似文献   

8.
The longitudinal distribution of Trichoptera at 37 sampling sites along 800 km of the Loire River (France) was analyzed in order to better understand large-scale changes in community structure occurring on a stream continuum. Different simple ordination methods — centered PCA and Correspondence Analysis — were performed to investigate these changes. Both analyses showed that a major change occurs in the community in the upper reaches of the Loire River between the Serre de la Fare and Vorey sampling sites with the appearance of Hydropsyche contubernalis and H. Exocellata. Even though other changes in community structure could exist, revealed either by Correspondence Analysis at the first sampling sites (crenal), or by PCA at sampling sites influenced by dams, this Trichoptera community appears to be stable enough in the latter part of the Loire River with the addition of a few species, Hydropsyche bulgaromanorum, Ecnomus tenellus and E. deceptor, rather than changes in species. The results are discussed in the light of different concepts in stream ecology, and the validity of such data analyses to describe some community patterns.  相似文献   

9.
1. Previous studies have identified lowland areas as barriers to gene flow (dispersal) between distinct mountain ranges in montane species of aquatic insects. In this study, we investigated the population genetic structure of two closely related Atalophlebia (mayfly) species inhabiting lowland areas of south‐east Queensland, Australia, with the expectation of widespread gene flow throughout the low‐altitude environment and associated homogeneous genetic structure. 2. In particular, we asked whether species with lower‐altitude distributions demonstrate greater spatial distribution of mtDNA (COI) alleles than the upland species studied previously. This pattern would be expected if good dispersal ability is associated with population persistence in these drought‐prone habitats. 3. The two species demonstrated contrasting genetic population structure. Atalophlebia sp. AV13 D revealed strong population structure, with populations on each side of the low‐altitude area isolated from each other for a long time (c.350 kya), and the presence of an isolation‐by‐distance pattern over relatively small geographical distances (<40 km). In contrast, Atalophlebia sp. AV13 A was panmictic at the scale investigated (≤160 km), with no history of past population fragmentation. 4. Examination of sample distribution along the altitudinal gradient reveals that Atalophlebia sp. AV13 D may have a more upland distribution (associated with greater habitat stability) than previously supposed, while Atalophlebia sp. AV13 A inhabits more xeric lowland areas, where freshwater habitats are less stable. We consequently hypothesise that these contrasting genetic population structures result from differences in habitat stability along the altitudinal gradient, only species with good dispersal ability being able to persist in unstable habitats. These findings may be applicable to other regions of the globe where habitat instability is associated with altitudinal gradients.  相似文献   

10.
用聚类分析和主成分分析法对阿尔泰山两河源自然保护区地面生地衣群落进行划分;根据优势地衣种类进行群落命名。应用典范对应分析法探讨了地面生地衣种类分布与环境间的关系。结果表明:阿尔泰山两河源自然保护区地面生地衣可分为以下4个群落:白腹地卷+硫石蕊+喇叭粉石蕊群落;茸珊瑚枝+长根地卷+黑瘿地卷群落;土星猫耳衣+软鹿蕊+膜地卷群落;雪岛衣+北方石蕊+绿皮地卷群落。各群落中的地面生地衣种类与盖度,在一定程度上反映了地面生地衣在阿尔泰山两河源保护区分布格局与环境的关系。典范对应分析结果表明,阿尔泰山地面生地衣群落物种分布受到土壤湿度、土壤pH、海拔高度、林冠层郁闭度和灌木层盖度等环境因素的影响,其中海拔、土壤湿度、林冠层郁闭度等对地衣物种分布的影响最大。  相似文献   

11.
Pattison RR  Mack RN 《Oecologia》2009,158(4):591-602
Identifying the environmental constraints that affect the distribution of an invasive species is fundamental to its effective control. Triadica sebifera (Chinese tallow tree) has invaded the southeastern United States, but its potential for further range and habitat extension has been unresolved. We explored experimentally environmental factors in macro- and microhabitats that affect its persistence at five widely separated sites along the Atlantic seaboard of the United States and at two sites inland; three sites occur well beyond the tree’s current range. At each site, seeds and young vegetative plants (0.5–0.65 m tall) of T. sebifera were placed in four microhabitats (closed-canopy upland, closed-canopy lowland, open-canopy upland, and open-canopy lowland). Plant growth, leaf CO2 assimilation rates, leaf N concentrations and δ13C ratios, and stem water potential were measured for two growing seasons. Percent seed germination was consistently higher in open-canopy microhabitats and lowest at northern and inland sites. T. sebifera grew in all open-canopy microhabitats, even 300–500 km beyond its current distribution. Plant growth in closed-canopy habitats was lower, attributable to lower carbon gain per unit leaf area in shaded compared with open-canopy environments, especially at northern and inland sites. Neither competition, other than canopy shade, nor grazing was a key constraint on distribution at any scale. Our results demonstrate that T. sebifera is dispersal limited at landscape scales but limited locally by dispersal and overstory shade; it has yet to occupy the full extent of its new range in North America. Quantifying environmental factors both within and well beyond a species’ current range can effectively highlight the limits on its distribution.  相似文献   

12.
Models were developed of relationships among water quality, geospatial and species-level diatom data for 465 samples collected from stream sites across south-eastern Australia. Transfer functions were derived from weighted averaging and artificial neural network approaches. Analysis of spatial variations in species assemblages was used to divide the sites into two groups according to site elevation. The strongest predictive models for the upland group associated diatom assemblages with conductivity, longitude, altitude, and to a lesser extent pH, NO x and TKN. The strongest predictors for the lowland group were longitude and conductivity, but artificial neural network models performed well for NO x and temperature. The importance of the geospatial variables suggests that there may be a capacity to develop diatom sub-regions within which robust models for other water quality variables important to management can be generated. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users. Handling editor: R. Norriss  相似文献   

13.
北京市区苔藓植物空间分布与环境关系的研究   总被引:3,自引:0,他引:3  
在2006年10月至2007年10月期间,对北京市五环路内及附近部分区域的苔藓群落进行了调查,共调查了31个地点、164个样地,采集苔藓植物标本327份。经整理鉴定,调查区有苔藓植物12科24属55种,其中阔叶小石藓(Weisia planifolia)和立碗藓(Physcomitrium sphaericum)等种类为调查区的广布种。通过对调查区同类型、不同地点苔藓植物多样性指数分析,发现北京市苔藓植物的分布特点为城西、城北苔藓植物多样性高于城东、城南。用典范对应分析法(CCA)分析27个样地中的20种地面生苔藓植物的盖度与主要环境因子的关系,结果表明,土壤含水量、距主干道距离、人为踩踏、土壤pH值、林木郁闭度等环境因子对北京市苔藓植物的分布有显著影响,其中土壤含水量、土壤pH值对苔藓植物分布的影响最为显著,北京市区大多数常见苔藓种类喜生于土壤含水量较高、偏酸性的环境。  相似文献   

14.
该研究通过采集、鉴定和测量苔藓植物标本并用SPSS软件进行数据分析,对贵州省月亮山自然保护区苔藓植物的垂直分布规律进行了初步分析。结果表明:月亮山自然保护区苔藓植物共有69科147属374种,苔藓植物呈明显的带状分布;不同海拔苔藓植物科属种所占的百分比均呈先升高后降低,优势科灰藓科( Hypnaceae)和细鳞苔科( Lejeuneaceae)和优势属凤尾藓属( Fissidens)、耳叶苔属( Frullania)、真藓属( Bryum)、疣鳞苔属( CoLoLejeunea)和细鳞苔属( Lejeunea)内种数在不同海拔也呈相同趋势;该地区苔藓植物石生群落和土生群落分布最广,木生群落次之,水生群落分布最少;苔藓植物雌雄异株数量在不同海拔均比同株数量多,比例约为7∶3;随着海拔升高,多种不利环境使长柄绢藓( Entodon macropodus)的叶片显著变小、叶长与叶宽的比显著增大,叶片由卵圆形变为卵状披针形,孢蒴极显著缩短、孢子直径显著增大,孢子的产量逐渐减少,不利苔藓植物的繁殖,蒴柄显著增长,有利于孢子的传播,体现了苔藓植物在不同的海拔的适应性。该研究结果为进一步研究苔藓植物的分布及环境适应性提供了基本资料。  相似文献   

15.
Aims To determine the relationship between satellite‐derived land cover data and distribution patterns of water beetle species pools. Location A total of 687 British national grid 10 km squares in Scotland and 588 1 km grid squares in 99 10 km grid squares in northeast England. Methods Multivariate classification and constrained ordination analyses were used with water beetle species and land cover data. Results The major variation in both the Scotland and northeast England 10 km species pools was from squares with upland acid water habitats to squares with lowland fens and ponds whilst for the 1 km northeast England data it was from squares dominated by fast‐flowing streams and rivers to those with fens and ponds. The secondary variations in the 10 and 1 km analyses were the primary ones juxtaposed. Constrained ordination of the Scottish 10 km data showed upland land cover types to be most influential in determining species pool distribution whilst lowland covers were more important with both the 10 and 1 km northeast England pools. The three analyses showed that coastal cover had a relatively high influence on species pool distribution but no species pool group was dominated by coastal species. Main conclusions There were strong relationships between water beetle species pool distributions and the satellite‐derived land cover types dominating upland and lowland areas. The major variation in the northeast England species pool data differed at the two scales analysed. Results indicated that there is considerable potential for the synthesis of water beetle distribution and land cover data for use in environmental and conservation monitoring at both the regional and national scales.  相似文献   

16.
以贵州典型岩溶地区贵阳市云岩区的3座峰丛为研究对象,对苔藓植物的多样性分布及其生态特征进行调查研究。结果表明:(1)该区域内,苔藓植物由13科31属62种组成;其中苔类有1科1属2种,藓类12科30属60种;(2)苔藓植物生活型有3种,主要为交织型(占61.3%)和丛集型(占35.5%);(3)3座峰丛苔藓植物物种丰富度指数排序为仙人洞山>照壁山>东山;3座峰丛苔藓植物的Pielou指数差距不大,表明物种个体分布较为均匀;相似性指数结果表明东山与照壁山、仙人洞山苔藓物种有较大差异性,岩性是影响其差异性的重要原因之一;(4)苔藓物种数在3座峰丛山底、山腰和山顶呈现不同的分布规律,导致此趋势的直接原因可能为人为干扰;(5)CCA排序表明人类活动频繁的东山和照壁山,影响苔藓植物分布的主要环境因子为人为干扰,其次为海拔高度;受人为干扰程度轻的仙人洞山,苔藓植物的分布规律则受自然环境因子(海拔高度、光照、土壤温度)影响。美灰藓(Eurohypnum leptothallum)作为最大优势种,能适应严峻的自然环境和人为干扰,其抗干扰能力对改善恶化环境具有潜在价值。  相似文献   

17.
In order to determine the effect of prior land use on secondary succession, woody plant species abundances were determined on the Lake Erie Islands in 21 sites 20–90 yr post-abandonment: 11 former vineyards, 8 former orchards, and 2 former quarries. Detrended Correspondence Analysis ordination was used to compare the relative abundances of woody plants in the 21 successional sites to each other and to 5 mature upland forests and 3 mature lowland forests. Vineyards 20–45 yr post-abandonment had closed canopies 2–4 m tall and were dominated by the same mix of species dominating mature forests at similar elevations. Abandoned orchards 20–45 yr post-abandonment supported species common in mature forest floras as well as many shade-intolerant, pioneer tree and shrub species not found in mature stands. These differences in successional patterns seem to be related to differences in the suite of colonization sites presented upon abandonment, with orchards being dominated by open, bare ground, and vineyards by shaded ground receiving ca. 20% of full sunlight. Newly abandoned vineyards had appreciable ‘advanced regeneration’ of saplings of shade-tolerant species 3–7 yr old growing among the grapes. While former quarries remained open, marginal habitats with sparse, open canopies dominated by species typical of rocky cliff edges, the community structure of former vineyards and orchards converged toward each other and toward the composition of mature forests at similar elevations. Thus patterns of secondary succession varied with prior land use and were determined by the suite of colonization sites available at the time of abandonment.  相似文献   

18.
黑龙江兴凯湖沼泽地苔藓植物群落初步研究   总被引:1,自引:0,他引:1  
2009年夏在黑龙江兴凯湖沼泽地中随机选取47个1m×1m样方,进行苔藓植物及相应维管植物群落调查,并测量记录环境因子,以分析苔藓植物多样性,探讨影响苔藓植物生长与分布的主要环境因子。结果表明:所调查的沼泽地中共有苔藓植物5科、6属、7种,其中粗叶泥碳藓(Sphagnumsquarrosum)和中位泥碳藓(S.magellanicum)为优势种。CCA分析结果显示,粗叶泥炭藓和中位泥炭藓多分布于水位埋深大的生境中,且前者常出现于以细叶苔草(Carexrigescens)为主的群落中,而后者则主要出现于以芦苇(Phragmitesaustralis)-小叶章(Deyeuxiaangustifolia)为主的群落中;中位泥炭藓能生长于沼泽地pH4·4~6·5的所有生境中,粗叶泥碳藓则局限生长于pH5·3左右的生境中,而大湿原藓(Calliergonellacuspidata)、万年藓(Climaciumdendroides)、地钱(Marchantiapolymorpha)和镰刀藓(Drepanocladusaduncus)等4种苔藓植物生长于水体pH值为6·3左右的生境中。研究认为,沼泽地的水位埋深、水pH值和维管植物群落特征是影响这7种苔藓植物生长和分布的主要因子。  相似文献   

19.
The disappearance of amphibian populations from seemingly pristine upland areas worldwide has become a major focus of conservation efforts in the last two decades, and a parasitic chytrid fungus, Batrachochytrium dendrobatidis, is thought to be the causative agent of the population declines. We examined the altitudinal distribution of chytrid infections in three stream‐dwelling frog species (Litoria wilcoxii, L. pearsoniana and L. chloris) in southeast Queensland, Australia, and hypothesized that if B. dendrobatidis were responsible for the disappearance of high‐altitude frog populations, infection prevalence and intensity would be greatest at higher altitudes. Overall, 37.7% of the 798 adult frogs we sampled were infected with B. dendrobatidis, and infections were found in all the populations we examined. Contrary to our initial hypothesis, we found no consistent evidence that high‐altitude frogs were more likely to be infected than were lowland frogs. Further, the intensity of fungal infections (number of zoospores) on high‐altitude frogs did not differ significantly from that of lowland frogs. Batrachochytrium dendrobatidis appears to be capable of infecting frogs at all altitudes in the subtropics, suggesting that all populations are at risk of decline when conditions favour disease outbreaks. We did find evidence, however, that chytrid infections persist longer into summer in upland as compared with lowland areas, suggesting that montane amphibian populations remain susceptible to disease outbreaks for longer periods than do lowland populations. Further, we found that at high altitudes, temperatures optimal for chytrid growth and reproduction coincide with frog metamorphosis, the life‐stage at which frogs are most susceptible to chytrid infections. While these altitudinal differences may account for the differential population‐level responses to the presence of B. dendrobatidis, the reason why many of southeast Queensland's montane frog populations declined precipitously while lowland populations remained stable has yet to be resolved.  相似文献   

20.
We investigated the hypothesis that maritime climatic factors associated with summer fog and low cloud stratus (summer marine layer) help explain the compositional diversity of chaparral in the coast range of central California. We randomly sampled chaparral species composition in 0.1‐hectare plots along a coast‐to‐interior gradient. For each plot, climatic variables were estimated and soil samples were analyzed. We used Cluster Analysis and Principle Components Analysis to objectively categorize plots into climate zone groups. Climate variables, vegetation composition and various diversity measures were compared across climate zone groups using ANOVA and nonmetric multidimensional scaling. Differences in climatic variables that relate to summer moisture availability and winter freeze events explained the majority of variance in measured conditions and coincided with three chaparral assemblages: maritime (lowland coast where the summer marine layer was strongest), transition (upland coast with mild summer marine layer influence and greater winter precipitation), and interior sites that generally lacked late summer water availability from either source. Species turnover (β‐diversity) was higher among maritime and transition sites than interior sites. Coastal chaparral differs from interior chaparral in having a higher obligate seeder to facultative seeder (resprouter) ratio and by being dominated by various Arctostaphylos species as opposed to the interior dominant, Adenostoma fasciculatum. The maritime climate influence along the California central coast is associated with patterns of woody plant composition and β‐diversity among sites. Summer fog in coastal lowlands and higher winter precipitation in coastal uplands combine to lower late dry season water deficit in coastal chaparral and contribute to longer fire return intervals that are associated with obligate seeders and more local endemism. Soil nutrients are comparatively less important in explaining plant community composition, but heterogeneous azonal soils contribute to local endemism and promote isolated chaparral patches within the dominant forest vegetation along the coast.  相似文献   

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