A vegetation map of The Netherlands,based on the relationship between ecotopes and types of potential natural vegetation

Summary The method of mapping the vegetation on scale 1: 200,000 and the starting points in relation to the potential natural vegetation and ecotopes, are discussed.In view of the planological background of this study, some restrictions have been added to the concept of potential natural vegetation, concerning the period of development and the human influence.The relationship between soil, ground water and vegetation was studied, which resulted in the map of the potential natural vegetation.Each type of potential natural vegetation stands for a series of vegetation types on the same site. Seven main series, with a number of sub-series are distinguished. Within each vegetation series the plant communities have been spread over five groups, according to their structure and naturalness.Ecotopes and ecotope complexes are considered as landscape ecological units. A list of ecotopes was obtained by interpreting topographical maps and by inventory data.The actual vegetation was mapped by estimating the size of the ecotopes within the separate areas. It was expressed in a five figure code for the five groups from the vegetation and ecotopes is combined into the vegetation map of The Netherlands.Interpretation problems, some of them specific for The Netherlands, are discussed and some remarks are made on the necessity of further research.Contribution to the Symposium on Plant Species and Plant Communities, held at Nijmegen, 11–12 November 1976, on the occasion of the 60th birthday of Professor Victor Westhoff.Nomenclature follows Heukels-van Ooststroom, Flora van Nederland, 18e druk, 1975, Wolters-Noordhoff, Groningen; nomenclature of syntaxa follows Westhoff & den Held (1969)     

Changes in a salt-marsh vegetation as a result of grazing and mowing — A five-year study of permanent plots

Summary Part of a salt-marsh (32 ha), ungrazed from 1958 until 1971, was grazed again from 1972 onwards with young cattle (1.3–1.7 per ha, May–October). In five vegetation types management experiments, including doing nothing (control). June mowing, August mowing, June and August mowing, all in combination or not in combination with grazing have been started with the objective to compare annually their effects on the vegetational structure and composition by means of permanent plots (2×2 m).Thirteen years (1958–1971) after the grazing had ceased the vegetation types of Festuca rubra/Armeria maritima, Artemisia maritima, Juncus maritimus and Elytrigia pungens hardly changed anymore. The vegetation type of Festuca rubra/Limonium vulgare, changed considerably. The experiments showed rather specific effects during the period 1971–1975 for each type of vegetation. Changes in the Festuca rubra/Armeria maritima vegetation were small and gradually under all treatments. Changes in The Artemisia maritima, Festuca rubra/Limonium vulgare and Juncus maritimus vegetation types were rather great under the different grazing treatments, the changes being abrupt and especially taking place in the third and fourth year of the experiments. The Elytrigia pungens vegetation showed large changes under all treatments, except the control plot, whereas these changes were abrupt, particularly occurring in the first and second year of the experiments. The study is continued.Nomenclature of taxa follows Heukels & van Ooststroom (1970), that of syntaxa Westhoff & den Held (1969).Contribution to the Symposium of the Working Group for Succession research on permanent plots of the International Society for Vegetation Science, held at Yerseke, the Netherlands, October 1975.Thanks are due to Prof. Dr. D. Bakker for his interest in the present study and his critical reading of the text, and to Drs D.C.P. Thalen for critical reading and correction of the English text. Thanks are also due to the students who analyzed the permanent plots: M. van der Duim and F. Prins (1971), M. van der Duim (1972), R. Schwab and T. Schwab-Vos (1973), and G. Allersma (1974, 1975).     

A study of pattern and process in coastal vegetation using principal components analysis

A study is made of the dune system at Tentsmuir Point National Nature Reserve, Scotland, using transects crossing the vegetation zonation. Principal Components Analysis and tabular ordination are used to analyse the data, and an attempt is made to relate the results obtained to the dynamics of the system. The effects of different management regimes are considered, and it is concluded that the establishment of pine on the area has the largest effect on the development of the vegetation. Reduction in grazing pressure by rabbits is found to increase species diversity slightly, but has no major influence as yet on vegetation development. While some information on the dynamics of the vegetation can be inferred, the problems involved in this are considered to be large, and the study raises a number of questions to be studied in greater detail. It is concluded that permanent plots would be the most effective method to employ.Nomenclature follows Clapham, Tutin & Warburg (1962) for vascular plants, Watson (1968) for bryophytes, and Duncan (1970) for lichens.We should like to thank Dr. R. A. H. Smith of the Nature Conservancy Council for her assistance and permission to work on Tentsmuir Point N. N. R., and Mr. J. G. Young, then warden at Tentsmuir for his help at the start of the project. We are grateful to Dr. R. Meutzelfeldt for computational advice. In addition, one of us (R.J.H.) would like to thank Dr. E. van der Maarel and Dr. R. S. Clymo for their tuition during the Nordic Council for Ecology course Numerical Methods in Vegetation Analysis' in Lund, September, 1979.     

From intensively agricultural practices to hay-making without fertilization

In the valley of the Dutch brook Drentsche A formerly fertilized lots came under hay-making without fertilization practices. The vegetation at the beginning of the experiments varied depending on the intensity of former agricultural practices.Clustering revealed unidirectional successional lines in all lots with relatively large changes in the first four years. Changes still occur after 30 years of unfertilized hay-making. Changes concerning vegetation types as well as increasing or appearing and decreasing or disappearing species suggest a diminishing availability of nutrients as the main environmental process. Therefore it is concluded that after a period of fertilizing some restoration of plant communities associated with former agricultural practices is possible.Variation already present within lots nearly always remained and in one lot a divarication of successional lines could be recorded, probably correlated with hydrological differences.The nomenclature of taxa is according to Heukels & van Ooststroom (1977), that of syntaxa according to Westhoff & den Held (1969), Ellenberg (1978) and Everts et al. (1980).The authors would like to thank Drs. N. Schotsman, Drs. A. Zeevalking-van Yperen, Drs. L. Rohof, Drs. P. Struyk, Drs. G. Boedeltje, Mrs. E. Hermans and Mr. W. van der Lans for recording the permanent plots, to Mr. E. Leeuwinga for drawing the figures and to Dr. S. Daan for correcting the English text.     

Evidence for corticotropin releasing factor (CRF) synthesis in the preoptic nucleus of Xenopus laevis tadpoles

Summary For the study of the hypothalamo-hypophysial system of Xenopus laevis tadpoles, hypothalamic lesions were made by means of the electrocoagulation technique. Lesioning of the ventral region of the preoptic nucleus resulted in a decrease of the number of ACTH cells in the pars distalis of the pituitary gland and in a diminution of the PAS-positive reaction of these cells. In addition, regeneration of the neurosecretory cells of the ventral region of the preoptic nucleus observed 6 weeks after lesioning was accompanied by the reappearance of normal PAS-positive ACTH cells in the pars distalis. It is suggested that the neurosecretory cells of the ventral region of the preoptic nucleus of Xenopus laevis tadpoles are related to the ACTH synthesizing cells, probably by producing CRF.Dedicated to Prof. Dr. med. W. Bargmann on the occasion of his 70th birthdayThe authors thank Prof. Dr. J.C. van de Kamer for his interest, Prof. Dr. P.G.W.J. van Oordt for his many helpful comments, and Messrs. H. van Kooten, E. van der Vlist, J.J. van der Vlis and M.C.A. van Pinxteren for preparing the illustrations     

Hydro-ecological analysis of the fen system Lieper Posse,eastern Germany

The Lieper Posse is a calcareous, ground water-fed fen system, situated in the end-moraine area of northeastern Germany. Nowadays the fen is partly drained and the vegetation adversely affected; hence regeneration measures are considered. Here we report a pilot survey of the actual vegetation cover in relation to the hydrological conditions of the system. The vegetation in the central part of the fen system can be assigned to the Caricetum lasiocarpae, with small areas of Eleocharitetum quinqueflorae. The southern part of the system includes a Ledo-Pinetum sylvestris bog. Along the edges eutrophic forest types are present. Peat analysis revealed that the system started as an open lake and subsequently changed into a rheophilous mire, ‘percolating mire’. The southern bog has only recently come into being. Hydrological investigations showed that the original mineral-rich ground water had to a large extent been replaced by acid rainwater; this is likely due to the construction of a ditch before 1850. The effects of this drainage on hydrological conditions and some aspects of soil fertility are discussed. Possible consequences for the restoration of calciphilous vegetation types are being considered. It is concluded that the vegetation development is predictable only to a limited extent, which is mainly due to a lack of knowledge on hysteresis effects in both vegetation and soil.     

The identification of the thyrotropic cells in the adenohypophysis of the cichlid fish Cichlasoma biocellatum and the role of these cells and of the thyroid in osmoregulation

Summary In order to identify the thyrotropic cells in the pituitary gland of Cichlasoma biocellatum, adult animals were treated with thyroxine. Periodic acid Schiff (PAS)- and aldehyde fuchsin (AF)-positive, and Alcian blue (AB)-negative basophils in the meso-adenohypophysis as well as the thyroid were strongly inactivated by such treatment. Since other cell types in the adenohypophysis were not affected, it is concluded that the PAS-positive and AB-negative basophils in the meso-adenohypophysis are the thyrotrops. In normal animals the thyrotrops and the thyroid are very active. Propylthiouracil did not cause a further activation of TSH cells. Keeping the animals in 25% sea-water caused a strong inactivation of the prolactin cells, the thyrotrops and the thyroid. In deionized water the prolactin cells were stimulated, but the thyroid was less active than in controls. Injections of ovine prolactin did not enhance the activity of the thyroid in salt water animals. It is suggested that in Cichlasoma biocellatum prolactin does not have a direct stimulatory effect on the thyroid.Thanks are due to Prof. Dr. P. G. W. J. van Oordt for his continual interest and valuable suggestions, and to Dr. L. Boomgaart for correcting the english. We are indebted also to Messrs. H. van Kooten and E. van der Vlist for making the photographs. The National Institutes of Health, Bethesda, Maryland (U.S.A.) kindly presented the ovine prolactin.     

Spatial and temporal variation in the vegetation of dune slacks in relation to the ground water régime

Summary The aim of the study presented here is to determine the relation between the vegetation and the ground water régime in the dune slacks on the island of Voorne. A distinction is made between the spatial and the temporal variation in the vegetation. On the basis of data from a transect the relation between the spatial variation and the water-table is determined. With respect to the temporal variation data recorded on permanent plots were used. Both the variation in space and that in time proved to be related to differences in the ground water régime. The supposition is put forward that the amount of variation in time depends on the height of site relative to the water-table.Contribution to the Symposium of the Working Group on Succession Research on Permanent Plots held at Yerseke, the Netherlands, October 1975.Nomenclature of phanerogams follows Heukels & van Ooststroom 1975, Flora van Nederland, 18e druk Wolters-Noordhoff, Groningen; that of bryophytes Margadant 1959, Mossentabel, 3e druk, Amsterdam.The author is very much indebted to Mr. P.A. Bakker, Society for the Preservation of Nature reserves in the Netherlands, for the use of the 1966 relevé of site 46, and to Mr. W. Smant for his assistance in field work and the preparation of the data.     

Changes in the flora and vegetation of the coastal dunes of Voorne (The Netherlands) in relation to environmental changes

Ecologically the former isle of Voorne is very varied. This is reflected by an exceptionally high number of plant species and vegetation types. Many data regarding flora and vegetation have been collected during more than 25 years. A comparison of the early and the later data show that in this period many changes have taken place in flora and vegetation. The changes are partly the result of a natural development of the vegetation, but to a considerable extent they are due to human activities in the coastal area itself and in its surroundings. Examples of changes produced by natural developments and by human activities are given. The effects on flora and vegetation of the area are illustrated by comparing flora inventories, vegetation maps and permanent plot studies. In addition, the future development in the region which will strongly affect its natural value, is discussed.I would like to thank Michiel Boeken, Joke van der Linden and Elly van Oosterhoud who carried out the second flora inventory and Jeanette van Beuzekom and Inge Boelens who mapped parts of the Voorne dune area. I am particularly indebted to Wiecher Smant who offered assistance in many ways.     

A model on the competition between two macrophyte species in acidifying shallow soft-water lakes in the Netherlands

To predict changes in vegetation as a result of acidification in shallow Dutch lakes a mathematical model was formulated which describes the growth ofLittorella uniflora andJuncus bulbosus, species characteristic for non-acidified and acidified situations, respectively. The two species compete for light, CO₂ and nutrients. The model integrates current knowledge about the ecophysiology of the species. The results generated by the model are similair to field data concerning dominance of the species in different habitats.L. uniflora is able to grow well under environmental conditions associated with acidification, as long as it is not outcompeted byJ. bulbosus. The competitive advantage of morphological adaptions of the macrophyte species are discussed in relation to the model results.     

A numerical-syntaxonomical study of the Calthion palustris Tx. 37 in the Netherlands

Summary After some remarks on ambiguities in the conventions of the Braun-Blanquet approach of phytosociology, a syntaxonomical study is presented of theCalthion palustris (wet grassland vegetation) of the Netherlands and surroundings. A numerical analysis of the non-optimal vegetation yielded a classification well comparable with the one established before. One new association is described. The pattern of variation in this dataset is compared in several ways with the one described elsewhere. Synoptic tables of different associations from several authors were compared by numerical analyses. The results suggested a large geographical variation within theCalthion of Western Europe.The authors wish to thank Mr H.M. van der Steeg (Nijmegen) and Mr J.C. Smittenberg (Assen) for kindly placing some unpublished relevés at their disposal, as well as several members of the plant sociology working group of the Nederlandse Jeugdbond voor Natuurstudie.     

May seed banks contribute to vegetation restoration on paths in temperate deciduous forest?

Forest paths are characterised by a zonation in vegetation composition as a result of gradients in abiotical conditions and continued recreational impact. Little is known about how much seed bank composition is affected by recreation and the existing path structure. As it is difficult to assess the contribution of seed banks to vegetation restoration, this study imparts relevant knowledge to restore vegetation on paths which are closed for recreational use. We surveyed seed bank and field layer vegetation composition in transects across path ecotones in deciduous forest. Analysis concentrated on seed bank characteristics and similarities of the seed bank and field layer vegetation in terms of ecological and seed size groups. A total of 74 species and 9,815 seedlings germinated out of the seed bank samples. The total seed density does not differ between path zones, but significant differences exist in the depth distribution and composition of the seed bank throughout transects. There is a large discrepancy between the composition of the seed bank and the vegetation. Small seeded species of disturbed environments dominate in each path zone. Typical forest species dominate in the vegetation while their contribution to the seed bank is low. Only with reference to the proportion of species of forest edges and clearings, the seed bank and vegetation do not differ significantly. Similarity between the seed bank on the path centre and the vegetation in the respective path zones decreases towards the undisturbed forest vegetation. Some competitive species like Urtica dioica and Lythrum salicaria are excessively represented in the seed bank and efficiently may obstruct further visitor use. However, these early successional species may not contribute to the conservation values of forests. Therefore management should carefully consider alternative amendments (e.g. soil scarification and seeding) to stimulate vegetation restoration.     

The independent detection of drought stress and leaf density using hyperspectral resolution data

Measurement of vegetation drought stress or leaf density is essential in ecosystem and agronomic studies. The normalized differential vegetation index (NDVI), a widely used vegetation index in remote sensing, seems to have some limitations as it is known to be affected by both drought stress and leaf density. A field experiment was conducted, using two-year-old potted Quercus serrata (a deciduous tree) and Q. glauca (an evergreen tree), to determine the optimal indices of vegetation drought stress or leaf density that have the least a simultaneous effect, and to test if the existing vegetation indices are useful for independently detecting drought stress or leaf density. The results showed that NDVI and similar indices, which utilize the difference or ratio between the reflectance of red and near infrared bands, such as the ratio vegetation index (RVI), the difference vegetation index (DVI), the atmospherically resistant vegetation index (ARVI), the renormalized difference vegetation index (RDVI), the enhanced vegetation index (EVI), the perpendicular vegetation index (PVI), soil-adjusted vegetation index (SAVI) and the improved variants of SAVI, were effective for the independent detection of leaf density but relatively ineffective for drought stress because they were significantly affected by leaf area index (LAI). Similarly, vegetation indices developed as detectors of vegetation stress, such as the water index (WI), the stress index (SI) and the derivative chlorophyll index (DCI), showed weak correlation (r) and partial correlation (r _p) with leaf water content (LWC). The optimal hyperspectral indices were proposed as (F _502.8 − F _852.0)/(F _502.8 + F _852.0) for LWC (r = 0.847, r _p = 0.849) and R ₇₅₀/R ₅₅₀ (R750R550; Lichtenthaler et al. in J Plant Physiol 148:483–493, 1996) for LAI (r = 0.926, r _p = 0.940) where R _λ and F _λ represent reflectance and first derivatives at wavelength λ nm, respectively. A simulation of lower spectral sampling intervals (ca. 3-nm intervals of original to 10-nm intervals) indicated that it will be necessary to check the appropriateness of the derivative indices approximate to the proposed indices before application because derivative spectra are less smooth as a function of wavelength than reflectance spectra.     

Fluctuations in a coastal dune grassland due to fluctuations in rainfall: Experimental evidence

Experiments with rainfall on a dune grassland near Oostvoorne, the Netherlands with Festuco-Galietum as the main syntaxon are described. Both increase in rain through additional watering and decrease in rain through catchment are presented to plots belonging to the xerosere and the mesosere. Clear changes in the floristic composition are the result, even after only two years. Typical Festuco-Galietum species are promoted by high rainfall, species of open habitat such as Corynephorus canescens are promoted by drought. The results are discussed against the background of long term permanent plot observations in the area and a relation with rabbit grazing intensity is supposed.Nomenclature of vascular plants follows Heukels-van Ooststroom (1975) Flora van Nederland 18 ed., Woiters-Noordhoff, Groningen; Nomenclature of syntaxa follows Westhoff & den Held (1969). Plantengemeenschappen in Nederland, Thieme, Zutphen.Field work in 1978 was carried out with Frans Bongers and Marc de Lyon, in 1979 with Marc de Lyon, Picter Meeuwissen and Guiljo van Nuland, all then MSc. students at the Division of Geobotany. Their help and the advice of Dr. Peter van der Aart, Institute of Ecological Research, Oostvoorne, are acknowledged.     

Features and conservation of the Brazilian Pantanal wetland

The Pantanal is a 140,000 km² sedimentary floodplain in western Brazil and one of the largest wetlands in the world. The main landscapes and phytophysiognomies, according to flood origin, are briefly described and some of the characteristic plant species are mentioned: (a) river flood (1–5 m) on clayey eutrophic soils with gallery forests, pioneer forests and scrub, Tabebuia and Copernicia parks, seasonal swamps, grasslands and oxbow lakes; and (b) rain flood (10–80 cm) mainly on dystrophic sandy soils (72% of the total area) with savanna (cerrado) grasslands and woodlands, with or without ponds. Regulating factors of the vegetation such as wet-and-dry cycle and management are considered. Dynamics of the vegetation, in particular the aquatic types, are shortly depicted. The role of grazing for conservation is discussed, and we suggest that 200 years of cattle ranching apparently did not cause major changes in the vegetation, except turning tall grass into short swards, as the domestic herd found a nearly empty niche. However, severe threats to the flora and fauna of the Pantanal originate outside the floodplain. Siltation of the Taquari river is pointed out as the worst environmental problem, changing the hydrology (wet-and-dry to wet), fauna and flora, e.g. eliminating riparian forest.This revised version was published online in March 2005 with corrections to the issue cover date.     

Plant communities and phytogeographical position of a large depression in the Great Chaco,Argentina

A survey is presented of the vegetation of the central region of the Santafesinian Chaco (Argentina), a scarcely populated flat area of 20 000 km², with seasonal flooding. Soils have a strong halo-hydromorphic character and vegetation is basically halophilous. Trees are scarce and most communities are savannas, grasslands or swampy vegetation. Twenty-three communities are described, some of them with several variants. The most widespread communities areSpartina argentinensis grasslands,Elyonurus muticus savannas and a complex of hygrophilous communities. The most important communities are distributed in relation to a topographical gradient, and their structure is shaped by recurrent flooding and fire disturbance. Most of the area is virgin land with very little human interference. The phytogeographical position of the area is discussed. Nomenclature: Burkart, A. 1969, 1974, 1979. Flora ilustrada de Entre Rios, INTA, Buenos Aires, and Cabrera, 1963, 1965a, b, 1967, 1968, 1970. Flora de la Provincia de Buenos Aires, INTA, Buenos Aires.     

Classification of vegetation: Past,present and future

Abstract. This paper is a report on the past, status-quo and perspectives of vegetation classification, still a major occupation of many vegetation scientists. The history of vegetation classification is discussed against a background of several controversial issues such as the problem of continuum vs. discontinuum, naturalness vs. arbitrariness of the nature of plant communities, universality vs. ad hoc character of syntaxonomic schemes, as well as classical versus numerical approaches to data analysis for classification purposes. The development of the methodology of vegetation science and the present image of vegetation classification is documented by a bibliometric analysis of the publication record of four majorjournals: Journal of Vegetation Science, Vegetatio, Phytocoenologia and Tuexenia. This analysis revealed a persisting controversy between traditional and numerical approaches to vegetation classification. A series of important changes in vegetation science (foundation of new journals, change of editorial policy by the established, important meetings) punctuate a period called the ‘Innovation period’. Several trends in the development of methods of vegetation systematics are summarized under the headings formalism, pluralism, functionalism, pragmatism and indeterminism. Some new features, such as the development and improvement of numerical tools, use of large data banks and attempts to summarize the theory of vegetation classification are discussed. The new growth-form system of Barkman initiated a revival of physiognomy-based vegetation classification. Within this framework the use of the character-type concept and the development of new numerical methods for studying the hierarchical structure of character-set types seems to be a promising approach. The achievements of population biology and ecophysiology have affected vegetation science by emphasizing the functionality of species within plant communities. The use of guilds and other functional groups has experienced an increasing interest from vegetation scientists. Applied in vegetation science, fuzzy-set theory has bridged the techniques of classification and ordination of plant communities.     

Vegetation und ökologie eines Sphagnum-Moores in Südbrasilien

In the mountainous rainy climate of the Serra Geral in Southern Brazil, peat bogs have developed, characterized by a cover of Sphagnum pulchricoma over peat layers, about 2 meters thick. In one of these bogs, located in the National Park Aparados da Serra, 950 meters above sea-level, vegetation, stratigraphy and chemistry of the peats were examined. The physiognomy and floristic composition of the vegetation show clear relationships with the andine and subantarctic region. Grasses, often growing as tussocks, (Agrostis, Calamagrostis, Briza) on peats, rich of minerals (Table 1) alternate with types of vegetation, poor of species and characterized by wideleaved tall herbs and ferns (Table 2). On sites with up-welling groundwater a vegetation is growing which resembles that of the hollows in raised bogs of Central Europe. It consists of Mayaca sellowiana, Eryngium floribundum and Plantago gigantea (Table 3). The rosette plants Eryngium pandanifolium and Eriocaulon ligulatum as well as the low-growing tree fern Blechnum imperiale are striking in their appearance. The abundant growth of the species, the concentration of their roots in the upper 20 cm of the soil as well as the very close C/N relation and the high conductivity values of the amorphous and well decomposed peats (Table 5) allow the conclusion that there is a great micro-biological activity in spite of the permanently high ground water level, thereby mobilizing the high N-reserves of the upper peat layer. An accumulation of peat similar to that of the raised bogs, does not exist. Finally the close relationship between the bog genesis and the questions about vegetation history of this region (grass land-Araucaria-forest distribution in Southern Brazil) is discussed.

Wir danken dem Deutschen Akademischen Austauschdienst und der Deutschen Forschungsgemeinschaft, Bonn, sowie dem Núcleo Interpartamental de Estudos Ecológicos, UFRGS, Porto Alegre für die Finanzierung, Prof. N. Matzenbacher, Prof. Dr. Valls, Prof. B. Irgang, Dep. de Botânica, UFRGS, Porto Alegre, und Padre A. Sehnem, São Leopoldo für die Bestimmung eines Großteils der Pflanzenarten, dem regionalen Büro des Instituto Brasileiro de Desenvolvimento Florestal, Porto Alegre für die Gewährung der Arbeitserlaubnis im Nationalpark Aparados da Serra, sowie Ing. (grad.) R. Smetana und Frau A. Garriss, Hohenheim für die Laboranalysen.     

Shrub vegetation on tropical granitic inselbergs in French Guiana

Abstract. In French Guiana, inselbergs in the form of granite outcrops rise abruptly from the surrounding rain forest. They constitute isolated islands of a special type of vegetation restricted to this peculiar substrate. Shrub granitic vegetation, organized in thickets on open exposed rocks of inselbergs, are described using the Braun‐Blanquet method combined with Correspondence Analysis. This phytosociological study revealed only one particular shrub community on each inselberg, including predominantly evergreen and sclerophyllous shrubs, especially microphanerophytes, belonging to the Clusiaceae, Myrtaceae and Bombacaceae. These outcrop communities exhibit species endemic to the Guianas region and also species rare in French Guiana. Affinities with flora of other inselbergs and vegetation types in South America are examined and discussed. Reasons for observed floristic and structural changes in each community are also discussed.