Floristic composition and diversity of mixed primary and secondary forests in northwest Guyana

The adequate protection and sustainable management of a tropical rain forest requires a good knowledge of its biodiversity. Although considerable parts of Guyana's North-West District have been allocated as logging concessions, little has been published on the forest types present in this region. The present paper reviews the floristic composition, vegetation structure, and diversity of well-drained mixed and secondary forests in northwest Guyana. Trees, shrubs, lianas, herbs and hemi-epiphytes were inventoried in four hectare plots: two in primary forests, one in a 20-year-old secondary forest and one in a 60-year-old secondary forest. The primary forests largely corresponded with the Eschweilera–Licania association described by Fanshawe, although there were substantial variations in the floristic composition and densities of dominant species. The late-succession forest contained the highest number species and was not yet dominated by Lecythidaceae and Chrysobalanaceae. There is a need for updating the existing vegetation maps of northwest Guyana, as they were based on limited information. Large-scale forest inventories may provide a fair indication of species dominance and forest composition, but do not give a reliable insight in floristic diversity. Although previous reports predicted a general low diversity for the North-West District, the forests plots of this research were among the most diverse studied in Guyana so far. These results will hopefully influence the planning of protected areas in Guyana.     

A multivariate approach to identify vegetation belts: Gallery forest and its surrounding savanna along the river Kota in north Benin

Abstract

The floristic composition and spatial structure of a West African riverine forest in north-western Benin were studied in order to identify vegetation zones and their arrangement and composition. Data were collected on five continuous belt transects and were analysed using multivariate methods. A total of 133 tree taxa from 34 plant families were identified, with Rubiaceae and Leguminosae-Papilionoideae as the most frequent families. Fifteen homogeneous transect sections were documented. Near-river sections were dominated by water-demanding species (Syzygium guineense, Garcinia ovalifolia, Berlinia grandiflora, Breonardia salicina) (=gallery forest), whereas uphill sections were characterised by savanna species (Terminalia laxiflora, Hymenocardia acida, Detarium microcarpum, Burkea africana) (= savanna). The shift from gallery forest to savanna was reflected by a floristic turnover and the different physiognomy of the vegetation, although diversity values for gallery forest and savanna were very similar. In the Principal Co-ordinates Analysis (PCoA), gallery forest and savanna sections did not overlap. Parallel sections at both sides of the river could be linked by isolines following the topography parallel to the river, resulting in a continuous gallery forest belt (width between 10 and 30 m) flanked by savanna. Tree species typical for gallery forests have wider areas of distribution than savanna species.     

Vegetation patterns,regeneration rates and divergence in an old-field succession of the high tropical Andes

Vegetation restoration during old-field succession was studied in an alpine Andean ecosystem (paramo). 123 plots with different fallow times (1 to 12 years) and 8 plots under natural vegetation were sampled. The results indicate that secondary succession in the paramo, like in other extreme environments, can be interpreted as an autosuccession: there are mainly changes in species relative abundance and little floristic relay (i.e. species turnover). Only a few herbaceous species, mostly introduced (e.g. Rumex acetosella), act as strict pioneers and strongly dominate the early stages. Then, they undergo a progressive decline, while native forbs (e.g. Lupinus meridanus) and grasses (e.g. Vulpia myuros) have their peak abundance in intermediate stages. The characteristic paramo life forms, sclerophilous shrubs (e.g. Baccharis prunifolia, Hypericum laricifolium) and giant rosettes (e.g. Espeletia schultzii), appear very early and gradually increase in abundance during succession, becoming dominant in the late stages and showing a dual behaviour, both as ruderal and stress tolerant species. The 1st axis of a Detrended Correspondence Analysis arranges the sites according to their fallow time. The 2nd and 3rd axes, associated with diverging pathways of regeneration, are correlated with topographic factors and physio-chemical soil characteristics. Hence, structural divergence between plots increases along succession as community composition starts to reflect the conditions of each site. We found evidence of a constant rate of succession during the first 12 years, contradicting the generally accepted hypothesis in the succession literature of a continous slow down up to the climax. Regeneration of vegetation physiognomy is relatively fast, questioning the prevailing idea of slow restoration in alpine ecosystems. However, 12 years of fallow are insufficient to attain the species richness of the natural paramo. Under the current trend of fallow length reduction observed in traditional potato cultivation in the Andes, our results raise doubts about the conservationist value of this management strategy.     

Does understory vegetation reflect the history of fluvial disturbance in a riparian forest?

We have examined the relationship between the history of fluvial disturbance and understory vegetation in a riparian forest. The study site was divided into three sites, by use of aerial photographs and topographical maps, with different histories of fluvial disturbance: (1) Fagus-type on land that has not been flooded for the last 39 years, at least; (2) Populus-type on land that has not been flooded since debris flow occurred 34 years ago; and (3) Salix-type on land that has been flooded periodically from an abandoned channel since debris flow occurred 34 years ago. Species richness in the Salix-type was significantly higher than in the other types. Detrended correspondence analysis revealed obvious floristic differences among the three canopy types. Canonical correspondence analysis showed that herbaceous species were mainly found on lower plots with high moss cover, implying that moss layers may capture seeds transported by the stream. Tall herbs occurred in less shaded plots and on higher plots, suggesting that their rapid growth prevented the occurrence of other species. Fagus-type was dominated by species with ingested fruits which depended on animals for their dispersal. Populus and Salix-types were dominated by species with wind dispersal or no dispersal mechanism, which depended on physical phenomena for dispersal. Attributes of current understory vegetation were connected with historical events, suggesting that riparian vegetation reflects the history of fluvial disturbance.     

Effect of Low Vegetation on the Recruitment of Plants in Successional Habitat Types1

I assessed the role of low vegetation (plants ca 1 yr old and ≤50 cm tall) as a biotic facilitator or barrier in the recruitment of different growth forms and species in primary forests, secondary forests, and old‐fields (abandoned pastures) in southeastern Mexico. I removed by hand all plants (≤100 cm tall, including roots) and litter from 20, 0.25 m² plots in each habitat. For 1 yr, I counted the number of plant species (5–50 cm tall) recruited, grouped them into different growth forms, and compared them to undisturbed control plots. Prior to manipulation, the standing density of trees and lianas was highest in primary and secondary forests. Shrubs were more abundant in secondary forests, whereas herbs, epiphytes, and hemi‐epiphytes were more abundant in old‐fields. Herbaceous plants appeared as important components of the community in all habitats. The removal of low vegetation increased total plant recruitment in all habitats. Considering each growth form, the absence of vegetation increased recruitment in primary forests for herbs, in secondary forests for epiphytes and hemi‐epiphytes, in old‐fields for trees, and for lianas in primary forests and old‐fields. In vegetation removal plots, recruitment of species was greater in pastures, lower in secondary forest, and similar in primary forest with respect to control plots. Depending on habitat type, species, and growth form, the presence of low vegetation may act as a recruitment barrier or facilitator for different species, affecting plant community structure, diversity, and composition in different habitats.     

Cryptogams on decaying wood in old-growth forests of southern coastal British Columbia

Abstract. We studied the floristic composition of lignicolous cryptogams (i.e. bryophytes and lichens inhabiting decaying wood) in the old-growth coniferous forests of southern coastal British Columbia. The composition of the cryptogams was related to forest communities (described by vegetation units using forest floor cryptogams and vascular plants) and regional climates (described by biogeoclimatic zones). The study is based on a total of 247 sample plots, each of 0.04 ha in size. The plots were located in three different biogeoclimatic zones and were classified into 12 alliances and four orders in a previous study. We used indicator species analysis to determine cryptogam indicator species for each vegetation unit and biogeoclimatic zone, and used similarity analysis and multi-variate analyses (discriminant analysis and detrended correspondence analysis) to detect differences in the floristic composition of the cryptogams among sample plots, vegetation units, and biogeoclimatic zones. Most of the cryptogams in this study had a narrow distribution, and only < 5% of the species were present across all the vegetation units and biogeoclimatic zones. The overall means of Jaccard coefficients between two sample plots from the same vegetation unit (alliance or order) or biogeoclimatic zone were significantly higher (P < 0.05) than those from different vegetation units or biogeoclimatic zones. The difference in the mean Jaccard coefficients within- and between-units was highest for zones. The results of detrended correspondence analysis and discriminant analysis suggest that the composition of lignicolous cryptogams changes with the change in the floristic composition of forest floor vegetation. When the first axes of detrended correspondence analysis were compared, the Pearson's correlation coefficients between the first axes of lignicolous cryptogams and forest floor vascular plants and between the first axes of lignicolous cryptogams and forest floor cryptogams were 0.78 and 0.87, respectively. The degree of correspondence in the composition of lignicolous cryptogams and forest floor vegetation increased from alliance to order to biogeoclimatic zone. This trend suggests that the floristic composition of lignicolous cryptogams is influenced at the community level mainly by edaphic conditions and at the regional level by climatic conditions.     

A phytosociological survey of some serpentine plant communities in the Dominican Republic

This paper presents a floristic and vegetation study of the serpentinised territories of the Dominican Republic, corresponding to the Yamasá and Prieta mountains, Dajabón, Puerto Plata and Gaspar Henández. These sites are very important at a local level as they act as speciation centres and have a specific ultramafic flora with a high endemicity rate. The floristic analysis revealed the existence of 219 species, of which 54 (24.7%) are endemic. Twenty-one plots of vegetation distributed in five areas dominated by serpentines have been analysed in this study. The phytosociological approach is based on the Braun-Blanquet method. The study was combined with statistical techniques such as multivariate analyses. The results revealed three different kinds of forests, one dominated by the endemic Bignoniaceae, Tabebuia berterii (CC.) Britton, which is peculiar to the subhumid–humid environments of the Caribbean-Cibensean territory. The second type of forest is dominated by the serpentinophyte Polygonaceae, Leptogonum buchii Urb. which thrives in the humid ombrotype of the north territory. Finally, the third one adopts the form of the pine forest of Dajabón, dominated by Pinus occidentalis Sw. Four associations and three alliances are proposed as new syntaxa based on statistical and phytosociological analyses.     

Vegetation dynamics in central european forest ecosystems (near-natural as well as managed) after storm events

All over the world forests and woodlands are damaged or reset to initial stages by fire, insect outbreaks or storms. In Central Europe storm events are the most important natural disturbances affecting stand structures of both natural and managed forests and yet only a few studies exist on long-term forest development following the destruction of the tree layer by a storm. This paper presents a permanent plot study established in 1988 in the Bavarian Forest National Park (SE Germany) on areas, where the tree layer had been destructed by a storm on August 1, 1983. The records concerning (1) floristic composition (spermatophytes, pteridophytes, bryophytes, lichens) and cover degree, (2) location and shape of each tree higher than 1 meter (height, diameter at breast height) including position of fallen trees and (3) number of seedlings and saplings were taken in 1988, 1993 and 1998. Two windfall areas, situated next to each other in the same broad and flat valley bottom on wet soils under local cold climate conditions (potential as well as recent vegetation:Calamagrostio villosae-Piceetum bazzanietosum) were analyzed, one of them with completely free development after the storm event (“untouched”), the other with dead wood cleared off after the event, but thereafter with free development (“cleared”). The vegetation analysis separated two major trends in vegetation dynamics: (1) On the cleared plots with intensive soil-surface disturbance (removal of the damaged wood) the species composition changed towards pioneer herb vegetation (Rubus sp.), and pioneer forest species (here: birch,Betula pendula and/orB. pubescens) established. Subsequently, vegetation dynamics leading towards clusters of forest ground-layer species composition took place. (2) In untouched stands, where soil-surface disturbances were restricted to pit-and-mound-system created by uprooted trees, the patchiness of forest vegetation increased and a regeneration of mainly terminal tree species (here: Norway spruce,Picea abies) started. Stand development for the next 100 years was simulated using the model FORSKA-M. The model is individual-based and includes competition for light, soil water, and nutrients. The simulations suggest that floristic structures of cleared and untouched plots, respectively, will remain different for several decades, but within one century, the floristic structure becomes rather similar. Major processes in forest ecosystems which can be used to improve forest management and nature conservation practices have been identified based on the results of the case study.     

Tree species composition and diversity gradients in white-water forests across the Amazon Basin

Aim Attention has increasingly been focused on the floristic variation within forests of the Amazon Basin. Variations in species composition and diversity are poorly understood, especially in Amazonian floodplain forests. We investigated tree species composition, richness and α diversity in the Amazonian white‐water (várzea) forest, looking particularly at: (1) the flood‐level gradient, (2) the successional stage (stand age), and (3) the geographical location of the forests. Location Eastern Amazonia, central Amazonia, equatorial western Amazonia and the southern part of western Amazonia. Methods The data originate from 16 permanent várzea forest plots in the central and western Brazilian Amazon and in the northern Bolivian Amazon. In addition, revised species lists of 28 várzea forest inventories from across the Amazon Basin were used. Most important families and species were determined using importance values. Floristic similarity between plots was calculated to detect similarity variations between forest types and over geographical distances. To check for spatial diversity gradients, α diversity (Fisher) of the plots was correlated with stand age, longitudinal and latitudinal plot location, and flood‐level gradient. Results More than 900 flood‐tolerant tree species were recorded, which indicates that Amazonian várzea forests are the most species‐rich floodplain forests worldwide. The most important plant families recorded also dominate most Neotropical upland forests, and c. 31% of the tree species listed also occur in the uplands. Species distribution and diversity varied: (1) on the flood‐level gradient, with a distinct separation between low‐várzea forests and high‐várzea forests, (2) in relation to natural forest succession, with species‐poor forests in early stages of succession and species‐rich forests in later stages, and (3) as a function of geographical distance between sites, indicating an increasing α diversity from eastern to western Amazonia, and simultaneously from the southern part of western Amazonia to equatorial western Amazonia. Main conclusions The east‐to‐west gradient of increasing species diversity in várzea forests reflects the diversity patterns also described for Amazonian terra firme. Despite the fine‐scale geomorphological heterogeneity of the floodplains, and despite high disturbance of the different forest types by sedimentation and erosion, várzea forests are dominated by a high proportion of generalistic, widely distributed tree species. In contrast to high‐várzea forests, where floristic dissimilarity increases significantly with increasing distance between the sites, low‐várzea forests can exhibit high floristic similarity over large geographical distances. The high várzea may be an important transitional zone for lateral immigration of terra firme species to the floodplains, thus contributing to comparatively high species richness. However, long‐distance dispersal of many low‐várzea trees contributes to comparatively low species richness in highly flooded low várzea.     

The botanical diversity in the Ayawasi area, Irian Jaya, Indonesia

In the karst-dominated Ayawasi area (Bird's Head peninsula), the botanical diversity and its relation to soil and geological substratum were studied. An inventory in 22 plots of 0.1 ha was made of all plants (1945) with a dbh 10 cm (mainly trees). Myrtaceae, Burseraceae, and Euphorbiaceae were the most frequent families (considering relative number of individuals), whereas Myrtaceae, Lauraceae, and Meliaceae were most species-rich. The most frequent genera were Syzygium, Haplolobus, and Lithocarpus, and most species-rich were Syzygium, Garcinia, Elaeocarpus, and Pouteria. The most frequent species were Anisoptera thurifera, Tristaniopsis ferruginea, and Gymnacranthera farquhariana var. zippeliana. Species richness was greater in plots in mixed forest (38–57 species, average 48) than in limestone forest (26–42 species, average 33) and secondary forest (21–46 species, average 34). Some very common species, such as Xanthophyllum novoguineense (Polygalaceae) and Macaranga suwo (Euphorbiaceae), were hitherto herbarium rarities, known from very few collections only. Species dominating earlier investigated forests elsewhere in the Bird's Head Peninsula range from being less important to absent in the presently investigated forest. Explanatory factors for this phenomenon are variation due to the geographical distance, the high beta-diversity of tropical forests in general, habitat differences, and differences in research methods, in particular in their scale.     

西南喀斯特峰丛洼地木本植物群落结构与多样性变化

为了阐明喀斯特峰丛洼地植物群落结构和物种多样性特征及其变化规律,选择西南喀斯特具有代表性的灌木林、次生林和原生林3种植被类型,基于2007年、2012年、2017年3次植被的系统调查,研究了木本植物群落物种组成、群落结构和物种多样性的动态变化。研究结果表明,灌木林2007—2012年减少1个种,2012—2017年减少7属5种;次生林2007—2012年减少1科1属,2012—2017年增加4科7属6种;原生林2007—2012年减少1科4属6种;2012—2017年增加1科3属3种。增加和减少的物种为偶见种或稀有种,引起群落中物种数量的波动。灌木林中黄荆(Vitex negundo)、八角枫(Alangium chinense)重要值均大于10,黄荆占绝对优势;次生林中菜豆树(Radermachera sinica)、灰毛浆果楝(Cipadessa cinerascens)、香椿(Toona sinensis)等物种重要值大于10,占主要优势;原生林的优势种不突出,为多优势种群落。3种植被类型群落的胸径各年份差异显著,平均树高在5年间的差异不显著,10年间达到了显著差异;群落总径级结...     

Secondary succession and effects of clear-logging on diversity in the subtropical forests on Okinawa Island,southern Japan

In order to clarify the recovery process of the subtropical forest on Okinawa Island, southern Japan, biomass accumulation and the successional trend of species diversity with time were investigated by comparing plots of old-growth and clear logged secondary forests. Self-thinning was an important factor in the development of young secondary forests, and the small variance in tree size within a stand was related to the stand not being fully stratified after clear-cutting. A large variance of size structure in old secondary and old-growth forests implies re-initiation of the understorey. Additionally, the trajectory of stand development indicated that the subtropical forest quickly recovered aboveground biomass, which reached its upper limit at about 50 years after disturbance. However, there was a large distinction in species diversity between the secondary forests and old-growth forests. The diversity of forest floor plants did not recover well after being clear-cut. This indicates that management of the subtropical forest should not only take timber-oriented tree species into account, but also the biodiversity in ground flora. The secondary forests were characterized by Castanopsis sieboldii and Schima wallichii, and the monopolization of C. sieboldii through secondary succession had a negative influence on species diversity. Distylium racemosum dominated at the late development stage and was considered a long-lived competing species that reduced the dominance of C. sieboldii and facilitated the co-occurrence of understorey species. Light-demanding pioneer tree species such as S. wallichii that regenerated after logging should be replaced by competitive effects of climax species, and thus relayed floristic change might increase species diversity along secondary succession.Nomenclature: Hatushima and Amano (1994).     

Traditional land use associated with swidden agriculture changes encounter rates of the top predator, the army ant, in Southeast Asian tropical rain forests

We examined the effect of traditional swidden agriculture on biodiversity using the litter arthropod top predator, the army ant Aenictus (Hymenoptera: Formicidae) as an indicator species in and around an intact tropical rain forest in Sarawak, Borneo, Malaysia. We compared the encounter rates with Aenictus colonies among five forest types: continuous primary forest, isolated primary forest, old secondary forest (>20 years elapsed after abandonment of the fields), young secondary forest (5 years after abandonment), and new fallow (2 years after abandonment) by intensive area searching in 2003 and 2005. In total, seven Aenictus species (15 colonies) and six Aenictus species (11 colonies) were encountered in 2003 and 2005, respectively. The encounter rates were the highest in continuous and isolated primary forests, intermediate in old and young secondary forests, and the lowest in new fallow. Year and the interaction between year and forest type were not significant. That is, abundance of top predators, which is rare and likely to be vulnerable to disturbance, has never fully recovered even 20 years after the termination of cultivation. We discuss forest management strategies to sustain biological diversity.     

Plant Recruitment in Early Development Stages on Rehabilitated Quarries in Hong Kong

To understand vegetation development during the ecological succession of rehabilitated quarries, floristic composition and structure were evaluated at different restoration phases on three quarries in Hong Kong that were planted with exotic woody species over the course of 2–14 years. A total of 113 species, of which 82 were woody species, were recorded. Exotic species dominated the overstory, and species number, richness, and diversity increased with age. Some light‐demanding early successional species were becoming dominant in the overstory vegetation at the older phases of revegetation. These species could be potential candidates for early enrichment planting with Acacia spp. Common secondary forest species occurred naturally in the understory vegetation, and were more abundant and dominant after 10 years of ecological development. The most successful restorations were on scree slopes using leguminous Acacia spp. as nurse species.     

The impact of land conversion on plant biodiversity in the forest zone of Cameroon

Floristic surveys were carried out in different land use systems(primary and secondary forest, fallows of different ages, cocoa plantations,crop fields) within the forest zone of Cameroon, to assess the impact of landconversion on above-ground plant biodiversity. Beside various diversity studies,plant density was measured and diameter at breast height was estimated.The results showed that the forest areas, which represent thehistoric biodiversity of the region, preserve the greatest number of species(160 species in primary forest and 171 in secondary forest). Our resultsindicate the relatively great importance of secondary forests as refuge areasfor primary forest plant species that may function as a starting point forpossible regeneration of original biodiversity. Species richness is reducedprogressively from the original forest (160 spp.) and secondary forests (171spp.), to Chromolaena odorata (Asteraceae) fallow fields(149 spp.), to an old fallow field (139 spp.), to a cocoa plantation (116 spp.)and to the farmland (64 spp.), where only weeds and crops contribute essentiallyto plant biodiversity. Also the number of species that are used for non-timberproducts (construction, food and medicines) decreased with increased landconversion.     

Long‐term changes in the vegetation after the cessation of livestock grazing in Eucalyptus marginata (jarrah) woodland remnants

This paper documents changes in the floristic composition of Eucalyptus marginata Donn (jarrah) woodlands over 7 years of recovery from continual, intensive livestock grazing. In remnants of native woodland left after agricultural clearing, which have been subjected to livestock grazing, comparisons were made between the floristics of fenced exclosure plots and open plots that continued to be grazed. The vegetation in nearby remnants, which had not been subjected to livestock grazing, was also surveyed. An initial increase in annual exotic pasture species after grazing relief was only temporary and highly influenced by fluctuations in annual climatic patterns, particularly rainfall distribution and abundance. Subsequent years saw a decrease in exotic annuals in exclosure plots and an increase in native perennials, in a trend towards becoming more floristically similar to the ungrazed sites. Germination of overstorey species was observed in the exclosure plots, however, development of seedlings and saplings was sparse. Results indicate that for jarrah woodland in southwestern Australia, natural regeneration is possible after the removal of livestock, with the return (within 6 years) of native species richness to levels similar to those found in ungrazed vegetation. Re‐establishment of cover, however, appears to take longer. The floristic dynamics are described in terms of a nonequilibrium model. Two vegetation states exist, degraded remnants with an understorey dominated by annual species, and ungrazed vegetation with an understorey dominated by perennial shrubs and herbs. The former state is maintained by continual heavy grazing by livestock. Upon relief from grazing, the vegetation undergoes a transition towards floristic similarity to ungrazed vegetation. After 6 years, vegetation change in the exclosure plots appears to be continuing and therefore it is still in transition.     

青藏高原植物群落样方数据集

为便于了解青藏高原植被特殊物种组成、群落特征及分布格局, 该文利用2018-2021年在青藏高原不同区域内调查的338个样地、共758个样方的数据, 分析了高原植物群落的物种组成、区系特征和植被分类, 整合形成青藏高原植物群落样方数据集。结果表明: 青藏高原高寒和温性植物群落758个样方中, 共有植物65科279属837种; 其中, 物种数最多的5个科依次是菊科(134种)、禾本科(88种)、豆科(75种)、蔷薇科(43种)和莎草科(40种), 物种数最多的5个属依次是蒿属(Artemisia, 29种)、马先蒿属(Pedicularis, 27种)、风毛菊属(Saussurea, 25种)、黄耆属(Astragalus, 23种)和早熟禾属(Poa, 23种)。植物区系主要由温带(145属)和世界广布(36属)的成分所组成。物种的生长型以草本(83.51%)和灌木(10.87%)为主, 草本和木本的生活型分别以多年生草本(88.23%)和落叶灌木(83.67%)为主。338个样地可以划分为4个植被型组, 10个植被型, 20个植被亚型, 78个群系组和117个群系, 其中草原群系34个, 草甸群系33个, 荒漠群系33个, 灌丛群系14个和针叶林群系3个。该数据集覆盖青藏高原绝大部分高寒灌丛、高寒草原、高寒草甸、高寒荒漠、温性草原和温性荒漠植被区域, 可为研究高原植被特征和地带性分异规律, 气候变化和人类活动对高原植被的影响及其生态恢复提供坚实的数据基础, 同时为下一代中国植被图的更新提供参考。     

Does the invasive species Ailanthus altissima threaten floristic diversity of temperate peri-urban forests?

We examined the influence of the invasive species Ailanthus altissima (Mill.) Swingle on the understory of the Fontainebleau forest, a peri-urban forest of Paris (France), by comparing invaded versus control plots. We performed floristic inventories in fixed plots around the base of A. altissima vs native trees in different habitat types of the forest. Our findings suggest that the understory vegetation is significantly poorer and more common under A. altissima than under the other tree species and that the floristic composition is significantly different. Furthermore, the number of A. altissima root suckers growing in the plots was significantly negatively correlated with floristic richness. This effect can be attributed to both interspecific competition and allelopathic properties of A. altissima. These results give an estimate of the threat to biodiversity ascribed to A. altissima in the Fontainebleau forest.     

Potential Effects of Ateline Extinction and Forest Fragmentation on Plant Diversity and Composition in the Western Orinoco Basin,Colombia

Cattle and agricultural farming in the western Orinoco Basin began in 1555, and since then fragmentation of continuous forest has occurred. We evaluated the effects of the disturbances and the absence of large primates on plant community composition, diversity, and regeneration patterns. Atelines (Lagothrix and Ateles) inhabited the lowlands close to the Andean mountains, but no longer live in fragmented habitats. Their absence may have negative effects on plant populations because atelines play important roles as seed dispersers in neotropical forests, especially for large-seeded plants, which are rarely swallowed by other seed dispersers. We compared 2 1-ha vegetation plots in forest fragments north of the La Macarena Mountains with 7 plots in continuous forest in Tinigua National Park. Both sites share the same climatic conditions and have similar geological origins. There is floristic affinity between forests with similar ecological characteristics; the fragmented forests are also less diverse than the continuous forests. As predicted, the forest fragments have fewer individuals with large seeds. The results suggest that forest fragmentation and local ateline extinctions affect plant communities, reducing diversity and affecting large-seeded plants.