Hygrophilous Communities Research Articles

Diversity of insect galls in veredas of the Brazilian Cerrado in Minas Gerais, Brazil

Brazilian veredas are hygrophilous communities with high species diversity, featuring many floristic studies but a still incipient number of faunistic studies. In the present study, we conducted an inventory of insect galls in four different veredas located in the Northern region of Minas Gerais, Brazil. Overall, we found 75 gall morphotypes, distributed across 50 host species representing 37 plant genera and 22 families. Fabaceae was the plant family with the greatest number of insect gall morphotypes (n = 21), followed by Malpighiaceae (n = 10). The plant genera that supported the highest diversity of insect galls were Copaifera (n = 8) and Byrsomima (n = 5). The plant species Copaifera oblongifolia (n = 6) and Anacardium humile (n = 4) exhibited the highest richness of insect galls. The leaves were the most attacked organs (89% of all galls). Most morphotypes are glabrous (83%), green (69%) and lenticular (60%). The taxa of gall-inducing insects were identified for 46 morphotypes (80%), and were recorded inducers from the orders Diptera, Lepidoptera, and Hymenoptera. Cecidomyiidae (Diptera) was the most representative galling group, with 42 morphotypes, making up 93.3% of the recorded inducers. Among the sampled veredas areas, the Vereda do Peruaçu presented the highest richness of insect gall morphotypes and host plant species. The faunistic similarity was higher in the Pedras and Tiririca veredas, followed by Almescla and Peruaçu veredas. This is the first systematic inventory of insect galls and their host plant in Brazilian veredas. The diversity of insect galls in the studied veredas is relatively high when compared to other Brazilian Cerrado vegetation types.

Temporal and spatial variation of floral resources of woody species in a vereda ecosystem: Uniformity and habitat complementarity

Floral resource distribution, pollinator community structure, and flowering season are essential for maintaining and preserving pollination services in ecosystems. In humid Cerrado areas, veredas are considered hygrophilous communities, marked by the presence of the Mauritia flexuosa palm tree emerging in the wetter zones. Waterlogged portions present dense hygrophilous forests, whereas open areas predominant present herbaceous and shrubby components. We identified the pollination syndromes of woody species in a vereda ecosystem and characterized the pollination resource availability between habitats (hygrophilous forest and open area). The study was conducted on a vereda located in the north of Minas Gerais, Brazil. We characterized pollination syndromes using information on floral attributes, pollinator observations, and a literature survey. We performed phenological monitoring for 24 months and examined the occurrence of flowering using circular statistics. The differences in pollination syndrome occurrence among months and habitats were determined using modularity analysis. We found eight pollination syndromes, with melittophily being the most frequent pollination type among the woody species in the studied vereda. Flowering occurs throughout the year in the community and peaks from September to November during the transition from the dry to the wet season. In hygrophilous forest the species flowered preferentially in November, whereas in open area, preferentially between September and October. The syndromes distribution differed between the habitats, as well as resource availability. This difference between habitats can influence pollinator diversity. Modularity showed complementarity among the habitats, with continuous resource availability throughout the entire ecosystem. Species present in the hygrophilous forest provide their resources mainly during the rainy season, whereas species from the open area, during the dry season. Information on these interactions is necessary to understand the functionality of a vereda ecosystem, through the characterization of the resource's availability, and maintenance of pollination services in the ecosystem. In addition, our results demonstrate the importance of the vereda ecosystem as an important area in the availability of resources for the Cerrado formation. This information can strengthen protection laws and contribute to sustainable practices that boost the conservation of pollinators in the biome.

Sexual and reproductive systems of woody species in vereda are distributed according to the life form and habitat occurrence

AbstractIn Cerrado humid areas, veredas are considered as hygrophilous communities, with an herbaceous/shrub stratum in open areas and an arboreal stratum in forest areas. We identified the sexual and reproductive systems of woody species, and the distribution of these systems among the different habitats and plants habits in this ecosystem. We investigated whether the occurrence of sexual and reproductive systems may be related to ecological and/or evolutionary factors and if hermaphroditism predominates in open areas. In this case, we evaluated which reproductive strategies promote cross‐pollination and which species are dependent on pollinating agents to promote the reproductive process. We selected the species according to a phytosociological study, using plots distributed in parallel transects and allocated in the hygrophilous forest and open areas. Floral morphology analyses, self‐pollination treatments, presence of barriers that prevent self‐pollination, phylogenetic signal and literature survey were performed. We did not find phylogenetic signal evidence for the traits evaluated. Most species are trees, followed by shrubs and sub‐shrubs. Dioecy predominated among tree species in the open area, with hermaphroditism more related to shrub species in the open areas. Shrubs and sub‐shrubs were mainly represented by autogamous and apomictic species. Despite autogamy and apomixis were related to the open areas, we found no significant difference between the habitats. In veredas, that are considered a poorly resilient environment that has constant problems with recent anthropogenic activities, we expected a high number of autogamous and apomictic species. However, the results showed that most species have characteristics that promote allogamy and are pollinating agents dependent for reproduction.

Vegetation structure and edaphic factors in veredas reflect different conservation status in these threatened areas

In Cerrado humid areas, veredas are considered as hygrophilous communities, marked by the presence of the Mauritia flexuosa palm tree emerging in the wetter zones. Changes in veredas ecosystems due to drought and changes in the water table, which represent important areas for biodiversity maintenance in the Brazilian cerrado, can lead to the emergence of new landscapes and ecosystems. Assuming that the veredas are changed in species composition due to anthropogenic factors, in this study, we evaluated the flora composition and described the current vegetation profile of two veredas under different disturbances levels that are located in the north of Minas Gerais State, Brazil. Altogether, 2,268 individuals of 91 species belonging to 36 families were recorded. Our results demonstrated that the studied veredas were floristically different in terms of the arboreous-shrubby species composition, richness, and diversity. Despite the hygrophilous forest formations and open areas in the two veredas present typical species from these environments (same species with high importance values), the drought in the water table caused an expansion of Cerrado species in the open areas and in the hygrophilous forest. Furthermore, in the hygrophilous forest there was an increase in the abundance of species that occur in less saturated soils. Our results demonstrate that the studied veredas are changing in species composition due to anthropogenic factors which leads to the drought of these formations (water balance effect). These anthropogenic effects cause a modification with the expansion and increase in the abundance of typical species of other areas of Cerrado and resistant to less saturated soils, leading to the veredas collapse. Finally, future studies should investigate other veredas on a broader scale to detect changes in the water table that lead to a consequent change in vegetation structure. In this way, we will have support for the conscientious management and conservation of these areas that represent equilibrium places for the Cerrado biome.

Paleoenvironmental interpretation of the mid‐late Holocene of Corrientes province, Argentina

The objective of the present paper is to recognize and reconstruct, from the analysis of pollen recovered from sedimentary cores, the predominant plant communities and their variations during the Holocene in Corrientes Argentina, in order to infer changes in climatic conditions, vegetation and paleoenvironmental evolution in the northeast of Argentina. For this study, lakes located in the central region of Corrientes province were selected, comprising part of the western margin of the Iberá Wetland. The palynological analysis of the paleocommunities shows, in a first stage of the mid Holocene, the predominance of marsh grasslands and hygrophilous communities that indicates humid to sub‐humid environmental conditions. In a later stage of the mid Holocene, the paleocommunities show a characteristic association of wetlands, which together with the presence of Typha sp., would indicate sub‐humid to humid conditions and waterlogged or flooded soils with slow‐moving water. For the late Holocene, the paleocommunities show, initially, the presence of a grass‐dominated herbaceous steppe, indicating environmental disturbances, which in the fossil record could reflect the combination of intense wind action under a dry climate. In a later stage, the frequency and variety of species characteristic of humid environments increase, dominated by marshy‐herbaceous species, in addition to the development of the hygrophilous forest. Consequently, since the mid Holocene, the main climate factors responsible for the observed changes in wetland conditions were the location and intensity of the Atlantic and Pacific anticyclones in addition to changes in sea level. These forces mainly affected the distribution of precipitation, causing significant changes in the vegetation communities.

Hydrological Characteristics and Paradoxes of Mediterranean High-Mountain Water-Bodies of the Sierra-Nevada, SE Spain

Each lake complex must be understood before attempting any regional synthesis leading us to view these water-bodies as indicators of regional climate change. Therefore, in order to improve knowledge of these Mediterranean biotopes, we examined the dependence of the fringes of hygrophilous communities surrounding the water-bodies (green fringes) on their hydrological and geomorphological features. The climate of the western sector of this massif is cryo–oromediterranean, where thawing produces 53 hm3 of run-off and 11 hm3 of sub-surface flow. Part of this water is stored in 123 water-bodies located from 2480 to 3200 m a.s.l., 72 of which (58%) are located on the south-facing Mediterranean watershed. The total surface of the water sheet is approximately 170,000 m2, and volume is approximately 215,000 m3, of which 140,000 m3 (65%) are stored in the south-facing water-bodies. Green fringes surrounding 84 water-bodies have a total surface area of approximately 186,000 m2. Surprisingly, the more xeric Mediterranean watershed holds 58 such fringes (149,000 m2, 80%) while 26 are found on the Atlantic watershed (38,000 m2, 20%). Green fringes are mainly associated with small water-bodies (<5000 m3), which occupy 148,000 m2 on the Mediterranean watershed, while on the Atlantic side, green fringes occupy 31,000 m2. Sierra Nevada also has 46 times higher water-efficiency in the smaller water-bodies than in the large ones; 16.4 and 335.8 times higher on the Atlantic and Mediterranean watersheds, respectively. The differences in gradient of the massif hillsides must largely explain this uneven behaviour.

Vegetation and fire dynamics during the last 4000 years in the Cabañeros National Park (central Spain)

The Holocene vegetation dynamics of low- and mid-altitude areas of inland Iberia remain largely unknown, masking possible legacy effects of past land-use on current and future ecosystem trajectories. Here we present a 4000-year long palaeoecological record (pollen, spores, microscopic charcoal) from a mire located in the Cabañeros National Park (Toledo Mountains, central Spain), a region with key conservation challenges due to ongoing land-use changes. We reconstruct late Holocene vegetation history and assess the extent to which climate, land-use and disturbances played a role in the observed changes. Our results show that oak (Quercus) woodlands have been the main forested community of the Toledo Mountains over millennia, with deciduous Quercus pyrenaica and Quercus faginea more abundant than evergreen Quercus ilex and Quercus suber, particularly on the humid soils of the valley bottoms. Deciduous oak woodlands spread during drier periods replacing hygrophilous communities (Betula, Salix, hygrophilous Ericaceae) on the edges of the mire, and could cope with fire disturbance variability under dry conditions (e.g. ca. 3800–3000–1850–1050BC- and 1300–100cal BP–AD 650–1850-) as suggested by regional palaeoclimatic reconstructions. Pollen and coprophilous fungi data suggest that enhanced fire occurrence at ca. 1300–100cal BP (AD 650–1850) was due to deliberate burning by local people to promote pastoral and arable farming at the expense of woodlands/shrublands under dry conditions. While historical archives date the onset of strong human impact on the vegetation of Cabañeros to the period at and after the Ecclesiastical Confiscation (ca. 150–100cal BP, AD 1800–1850), our palaeoecological data reveal that land-use was already intense during the Arab period (ca. 1250–900cal BP, AD 700–1050) and particularly marked during the subsequent City of Toledo's rule (ca. 700–150cal BP, AD 1250–1800). Finally, we hypothesize that persistent groundwater discharge allowed the mires of the Toledo Mountains to act as interglacial hydrologic microrefugia for some hygrophilous woody plants (Betula, Myrica gale, Erica tetralix) during pronounced dry spells over the past millennia.

A review of plant diversity, vegetation, and phytogeography of the Khorassan-Kopet Dagh floristic province in the Irano-Turanian region (northeastern Iran–southern Turkmenistan)

The Khorassan-Kopet Dagh (KK) floristic province is located in the northeastern parts of Iran and partly in southern Turkmenistan. The area is a transition zone and a corridor connecting different provinces of the Irano-Turanian region and also Hyrcanian montane forests of the Euro-Siberian region. The unique combination of Irano-Turanian species and also presence of a local center of endemism are evidence of a separate biogeographic entity. The complicated topography, high habitat heterogeneity and vegetation history are reasons for the development of diverse vegetation types. In order to achieve up-to-date information on the plant diversity and distribution patterns, a database was prepared using all floristic records from the area defined as KK. A total of 2576 species/infraspecific taxa belonging to 702 genera and 112 families of vascular plants have been reported from the area, 2498 of which occur within Iran. Altogether, 28 different distribution patterns are recognized among five major phytogeographical groups, including widespread, tri-regional, bi-regional, Euro-Siberian and Irano-Turanian patterns. Irano-Turanian elements, which make up the core flora of KK, are subdivided further into 14 distribution patterns. A significant number of species, i.e. 356 species (13.8%), are endemic to the area. The flora of KK is highly influenced by central Irano-Turanian elements. The main vegetation types of the area include Juniperus woodlands, Pistacia vera woodlands, some isolated enclaves of Hyrcanian forests and scrub, cliff vegetation, mountain steppe communities, semi-desert steppes, loess and marl vegetation, halophytic vegetation, aquatic and hygrophilous communities, and ruderal/invasive plant communities. There are several major threats to the ecosystems and biodiversity of the area. The areas presently protected do not cover all of the vegetation types, and therefore many threatened species are not safe.

Nomenclature adjustments to neglected syntaxa of the tall-herb hygrophilous communities of the SE-Europe

Background and Purpose: During the preparation of a coenological paper concerning the tall-herb vegetation of the Balkans, it emerged that some syntaxa were invalidly described in their original papers, while some other synataxa had been forgotten or considered invalid according to the current phytosociological literature even if they had been validly published in their original papers. The present study deals with the nomenclatural problems of the Rumicetalia balcanici Lakušić 1973, a neglected order of the montane tall-herb vegetation, and those of all its related lower-rank syntaxa.Materials and Methods: All published papers that treated the nomenclatural issues regarding the tall-herb vegetation in the Balkans were analysed. The nomenclature adjustments were made in accordance with the rules of the Code of Phytosociological Nomenclature (ICPN). The original relevés presented in this paper were carried out using the Braun-Blanquet phytosociological approach.Results and Conclusions: The nomenclature adjustments made in the paper result in the validation of the order Rumicetalia balcanicae and of four alliances: Rumicion balcanici, Ranunculion serbici, Cicerbition pancici and Petasition doerfleri. The validity of the alliance Cirsion appendiculati Horvat, Pawlowski et Walas 1937 was here confirmed while the name citation Geion coccinei Horvat in Quezel 1969 was here given for the first time. Finally several tall-herbs association were here validated and some others were proposed as new.

Nomenclature adjustments to neglected syntaxa of the tall-herb hygrophilous communities of the SE-Europe

Background and Purpose: During the preparation of a coenological paper concerning the tall-herb vegetation of the Balkans, it emerged that some syntaxa were invalidly described in their original papers, while some other synataxa had been forgotten or considered invalid according to the current phytosociological literature even if they had been validly published in their original papers. The present study deals with the nomenclatural problems of the Rumicetalia balcanici Lakusic 1973, a neglected order of the montane tall-herb vegetation, and those of all its related lower-rank syntaxa. Materials and Methods: All published papers that treated the nomenclatural issues regarding the tall-herb vegetation in the Balkans were analysed. The nomenclature adjustments were made in accordance with the rules of the Code of Phytosociological Nomenclature (ICPN). The original releves presented in this paper were carried out using the Braun-Blanquet phytosociological approach. Results and Conclusions: The nomenclature adjustments made in the paper result in the validation of the order Rumicetalia balcanicae and of four alliances: Rumicion balcanici, Ranunculion serbici, Cicerbition pancici and Petasition doerfleri. The validity of the alliance Cirsion appendiculati Horvat, Pawlowski et Walas 1937 was here confirmed while the name citation Geion coccinei Horvat in Quezel 1969 was here given for the first time. Finally several tall-herbs association were here validated and some others were proposed as new.

English

The vegetation composition and landscape analysis of the Taormina region (Messina, Sicily) in relation to anthropogenic influences was investigated. A total of 183 phytosociological relevés were performed in the period 2009-2012. Despite strong human influence, the area studied is characterized by the occurrence of several plant-communities, mainly represented by woods and shrubs vegetation (Quercion ilicis, Oleo sylvestris-Ceratonion siliquae), riparian woods and shrubs (Platanion orientalis, Rhamno-Prunetea), dry grasslands (Lygeo-Stipetea), hygrophilous communities (Molinio-Arrhenatheretea, Nasturtio-Glycerietalia and Isoeto-Nanojuncetea), rupicolous communities (Asplenietea trichomanis, Parietarietea judaicae), rocky coast communities (Crithmo-Limonietea), pasture coenosis (Poetea bulbosae), spring-flowering meadows (Tuberarietea guttatae and Stipo-Trachynietea distachyae) and nitrophilous communities (Onopordetea acanthii). The vegetation analysis allowed the identification of 34 vegetation types, with 8 new associations and 3 new sub-associations, and also allowed the reconstruction of the vegetation series and landscape units (geosynphytosociology). The synphytosociological analysis of the plant communities allowed the identification of the main vegetation series: climatophilous acidophilous series of metamorphic substrates (Erico arboreae-Querco virgilianae sigmetum); climatophilous basophilous series of sedimentary substrates (Oleo-Querco virgilianae sigmetum); edaphomesophilous series of the cliffs (Bupleuro fruticosi-Querco ilicis sigmetum); edapho-xerophilous series of the semirupestrian maquis (Euphorbieto dendroidis sigmetum); edafo-hygrophylous geoseries of the riparian wood (Platano-Salico gussonei sigmetum); and chasmophilous permaseries of the cliffs (Erucastro virgati sigmetum, Limonio ionici sigmetum). Overall, this territory should be considered an area of remarkable geobotanical significance, which still shows interesting vestiges of natural vegetations and deserving of preservation.

Clonal Growth Strategies Along Flooding and Grazing Gradients in Atlantic Coastal Meadows

Specific composition and species clonal traits were characterized along combined flooding and grazing gradients to answer two questions. i) To what extent does the interaction of flooding and grazing influence the clonal characteristics of the vegetation? ii) Are the effects of both environmental factors independent or interactive? This study was carried out in a wet meadow along the Atlantic coast (France). Three plant communities (hygrophilous, meso-hygrophilous and mesophilous) were distinguished along a flooding gradient and five levels of grazing pressure were controlled through an experimental design (from no grazing to heavy grazing). We monitored species composition and retrieved, for each species, the type of clonal growth organs (CGOs) and clonal traits from the CLO-PLA3 database. We identified two syndromes of clonal traits: “above-ground splitters” and “below-ground integrators”. Clonal traits played a key role in plant assembly in the studied meadows. The interaction of both environmental factors selected for particular syndromes of clonal traits; however, flooding had a stronger filtering effect than grazing. The hygrophilous community was dominated by above-ground splitters, whereas the meso-hygrophilous vegetation was dominated by below-ground integrators. In the mesophilous community, clonal composition was the most diverse and shared clonal traits with the vegetation of both the hygrophilous and meso-hygrophilous communities. Grazing impact on CGOs and clonal traits differed between plant communities, i.e., the effect of grazing was modulated by the flooding regime. This study confirmed that vegetation responses to grazing might depend on the pool of traits, primarily filtered by environmental factors such as flooding.

Eco-coenotic conditions and structure of Trollius europaeus L. populations in an extrazonal habitat complex (Transylvanian Carpathian foothills)

To estimate the importance of community structure and environmental factors for maintenance and in situ conservation of populations of European Globeflower ( Trollius europaeus subsp. europaeus) in four sites (one within a natural reserve) in a low elevation but cool valley of the Transylvanian Carpathian foothills, an inventory of all globeflower individuals was performed and floristic relevés were recorded in different community types (meadow, fen and scrub). As a surrogate for habitat conditions, we used plant species indicator values for light, moisture and nitrogen. Globeflower density is highest in mesic habitats, the ecological optimum estimated (about 6 on Ellenberg's scale) being slightly lower than that indicated for Central Europe (7). The juvenile:fertile plants ratio (J:F) declines with increasing soil moisture. Larger flower production in hygrophilous communities does not result in a higher proportion of juveniles or J:F ratio. Despite the presumed strong competition determined by high species richness in some host communities, the most dynamic population (large proportion of juveniles) was found in mesophilous, mown meadows. A clumped distribution of fertile plants under the open scrub canopy seems to be responsible for the significantly larger number of flowers per individual observed, as compared with the relative amount of flowers produced in the adjacent sward. Irrespective of host community, the juveniles display an aggregated distribution with respect to fertile plants, which is probably related to short-distance dispersal of seeds. Our results reveal the importance of host community species richness and soil moisture for the target population stage structure and reproductive investment.

Effects of permafrost degradation on ecosystems

Permafrost, covering approximately 25% of the land area in the Northern Hemisphere, is one of the key components of terrestrial ecosystem in cold regions. As a product of cold climate, permafrost is extremely sensitive to climate change. Climate warming over past decades has caused degradation in permafrost widely and quickly. Permafrost degradation has the potential to significantly change soil moisture content, alter soil nutrients availability and influence on species composition. In lowland ecosystems the loss of ice-rich permafrost has caused the conversion of terrestrial ecosystem to aquatic ecosystem or wetland. In upland ecosystems permafrost thaw has resulted in replacement of hygrophilous community by xeromorphic community or shrub. Permafrost degradation resulting from climate warming may dramatically change the productivity and carbon dynamics of alpine ecosystems. This paper reviewed the effects of permafrost degradation on ecosystem structure and function. At the same time, we put forward critical questions about the effects of permafrost degradation on ecosystems on Qinghai–Tibetan Plateau, included: (1) carry out research about the effects of permafrost degradation on grassland ecosystem and the response of alpine ecosystem to global change; (2) construct long-term and located field observations and research system, based on which predict ecosystem dynamic in permafrost degradation; (3) pay extensive attention to the dynamic of greenhouse gas in permafrost region on Qinghai–Tibetan Plateau and the feedback of greenhouse gas to climate change; (4) quantitative study on the change of water-heat transport in permafrost degradation and the effects of soil moisture and heat change on vegetation growth.

Taxonomic composition of the Holocene forests of the northern coast of Spain, as determined from their macroremains

Eight sites distributed over a distance of some 400 km of the Cantabrian coast (northern Spain) provided 153 wood, 50 fruit and over 350 leaf remains belonging to the area's Holocene forests. The high taxonomic precision with which these macroremains were identified (in many cases at the species level), plus the accurate information available regarding the original growth locations of these plants, provide new geobotanical insights into the history of northern Spain's Atlantic forests. Radiocarbon dating of the wood samples showed the collected material to have lived between 8550 and 800 cal. BP. Analysis of the macroremains showed the deciduous mixed forests of the Holocene to contain a majority of Quercus robur and Corylus avellana, accompanied by Acer pseudoplatanus, Ulmus minor, Castanea sp., and hygro-thermophilous taxa (Arbutus, Laurus and Vitis vinifera). The remains of hygrophilous communities, dominated by Salix atrocinerea, Alnus glutinosa and Fraxinus sp., show these to have expanded during the Holocene. The absence of conifer macroremains is interpreted as reflecting the disappearance of Würmian conifer populations at the beginning of the Holocene. The different taxa (eg, Ilex spp. and V. vinifera) that survived the last glaciation in the refugia offered by Spain's northern coast persisted in the same areas during the Holocene. A leaf sample of Ulmus minor dating to 3950 ±120 cal. BP reveals for the first time the natural occurrence of this species on the northern coast of Spain.

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.

Dynamics and Development of Floristic Richness in the Vegetation of a Large Depressed Area of the Great Chaco

Summary In the present paper the dynamics of the vegetation of the Subermeridional Lowlands of the Great Chaco is discussed. The whole area is in a steady-state defined by edaphic conditions and the disturbance regime. Recurrent floods and fires shape the structure of the communities. The most important communities are ordered along a smooth gradient related to elevation, and they shift along this gradient as a result of irregular cycles of wet and dry years. Strong dominance depresses floristic richness, but a large number of species, most of them rarities, are recorded in each community. These species thrive in microsites created by the interaction between matrix development and disturbance. Ant-hills also provide microsites which increase floristic richness. Hygrophilous communities have a very Gleasonian nature, but around temporary ponds and lakes there seems to be a successional trend.

Floristic groups and plant communities of southeastern Santa Fe, Argentina

This paper is a survey of the vegetation of the southeastern departments in the Province of Santa Fe (Argentina). The vegetation was analyzed following Braun-Blanquet's approach modified by Mueller-Dombois & Ellenberg (1974). The most relevant species of the region were placed in 25 groups according to their requirements or general behaviour. Most of the communities are herbaceous, and apart from the woody and some other miscellaneous ones they were grouped into three ecologically and floristically defined sets. The first set, the Stipa grasslands and related communities, which are characterized by the more or less abundant presence of Stipa hyalina, Stipa neesiana and Stipa papposa, comprises five different communities. The second, the halophilous communities, comprises five communities, the two Spartina ssp. grasslands, the halophilous prairies of Distichlis spicata, the short sedge Scirpus americanus communities and the ‘pela-dales’. The third, the hygrophilous communities, comprises nine communities which are not so well defined as the ones in the other sets. Besides, two further communities have been included, the Paspalum quadrifarium and the Melica macra tall grasslands.