Terms Of Floristic Composition Research Articles

Vegetation types of the Arid Chaco in Central-Western Argentina

Aims: We address the following questions: 1) Which are the main vegetation types that currently occur in the Arid Chaco? 2) Do those vegetation types differ in terms of floristic composition, endemism, chorotypes and life forms? and 3) Is there any spatial association between the vegetation types and the environmental heterogeneity of the Arid Chaco? Study area: The southwestern extreme of the Gran Chaco, in Central-Western Argentina. Methods: The survey was based on a dataset comprising 654 relevés collected according to the Braun-Blanquet method. Data were classified by the hierarchical ISOmetric feature mapping and Partition Around Medoids (ISOPAM), and ordinated through isometric feature mapping (ISOMAP). Bioclimatic and edaphic variables were related to the ISOMAP ordination. Results: We recorded 439 vascular plant species, 62 endemic at the national level and 22 endemic species restricted to the study and surrounding environments in Central-Western Argentina. A total of nine vegetation types, belonging to four major clusters, were identified. The most prominent chorotypes included species distributed in the Chaco region and in the Arid Chaco/Monte phytogeographic units. The predominant life forms were micro- and nano-phanerophytes, followed by hemicryptophytes, chamaephytes and mesophanerophytes. Conclusions: Major results highlighted that xerophytic shrublands are the most common vegetation types in this area as a result of the historical and present use, while old growth forests were constrained to areas with low anthropogenic disturbance in the last decades or to protected areas. Most vegetation types (with the exception of halophytic environments) are poorly differentiated from a floristic point of view; however, they clearly differ in physiognomy. The floristic composition of the vegetation types described revealed numerous species in common with other sectors of the Chaco of northern Argentina, Bolivia and Paraguay. Although the number of species restricted to the Arid Chaco was quite low, the most relevant chorotype included species with Western and Eastern Chaco distribution, conferring a clear Chaquenian identity to this area and discriminating it from other phytogeographic units. Taxonomic reference: Catálogo de las Plantas Vasculares del Cono Sur (Zuloaga et al. 2008) and its online update (http://www.darwin.edu.ar). Abbreviations: ISOMAP = isometric feature mapping; ISOPAM = isometric partitioning around medoids.

Inselbergs: potential conservation areas for plant diversity in the face of anthropization

Faced with the loss of biodiversity, particularly plant diversity, due to anthropogenic pressure, particular ecosystems such as inselbergs can constitute refuge areas. The objective of this study is to determine the conservation potential of plant biodiversity on inselbergs in Burkina Faso. A comparative study was carried out between inselberg’s vegetation and the surrounding plains vegetation. In each of these vegetation types, stratified and random sampling was adopted and data were collected in plots of 900 m² for the woody stratum and 100 m² for the herbaceous stratum. The specific diversity was evaluated through the effective numbers of Hill of order Q = 0; 1; 2. The Hill index does not vary between inselbergs and plains and thus reflects a strong similarity in floristic diversity between the two ecosystems. Sorensen’s similarity coefficient also shows a similarity in terms of floristic composition between inselbergs and surrounding plains. In inselbergs, relict species that have disappeared from the surrounding plains of some phytogeographic sectors occur. The flora of inselbergs is also characterised by indicative species of anthropized ecosystem absence. However, these species are present on the surrounding plains. Indeed, the flora of inselbergs is characterised by 11 endemic species. Inselberg’s vegetation is characterised by unique plant communities such as rock pools and Afrotrilepis pilosa mats. The exploitation and mortality rates of woody plants are significantly higher on the surrounding plains than on the inselbergs. The flora and vegetation of inselbergs show the absence of indicator species of disturbed ecosystems. They present endemic and relict species and stable woody stands. Due to the steep slope, lack of suitable soil for agriculture and sacred status of someones, the inselbergs constitute a refuge for plant species and thus contribute to the conservation of biodiversity like the protected areas.

The relationships between the physical and chemical properties of an aquatic environment and the floristic specificity of pleustonic communities in northern Poland

A comparative phytosociological and habitat analysis of 84 pleustonic phytocoenoses in northern Poland was carried out in order to determine the scale of their floristic distinctiveness and to obtain an answer to the question whether and to what extent the floristic differentiation of pleustonic communities corresponds to the differentiation of their habitat conditions. Based on phytosociological studies, it was shown that the investigated phytocoenoses are not random groups of species, but well differentiated in terms of floristic composition and phytocoenotic structure by communities. It was shown that the studied phytocoenoses represent the following separate associations in phytosociological terms: Salvinio natantis-Spirodeletum polyrhizae, Lemno-Spirodeletum polyrhizae, Riccietum fluitantis and Ricciocarpetum natantis. Hydrochemical studies showed that the floristic distinctiveness of these communities is largely confirmed by the differentiation of properties of the water habitat. Salvinio natantis-Spirodeletum polyrhizae is characterised by the deepest waters (mainly 0.7–1.2 m), alkaline, of a low colour, rich in ions (Mg2+, Na+, Cl−) and therefore characterised by the highest electrolytic conductivity, poor in dissolved organic matter, NO3− and total iron. Lemno-Spirodeletum polyrhizae is characterised by medium deep waters (mainly 0.3–0.8 m), mostly alkaline, of a low colour, less rich in ions (Ca2+, Na+, Cl−) and relatively low in dissolved organic matter and NO3−. Riccietum fluitantis is characterised by shallow waters (mainly 0.2–0.4 m), most often slightly acidic, of a quite high colour, low in cations and Cl−, and relatively rich in total iron, NO3−, and dissolved organic matter. Ricciocarpetum natantis is characterised by the shallowest waters, (mainly < 0.3 m), most often acidic, of the highest colour, low in ions, and rich in total iron, dissolved silica, NO3− and dissolved organic matter. By demonstrating habitat distinctiveness, the studied pleustonic communities may have significance as indicators of various types of aquatic environment.

Phytocenotic conditions and structure of the local population for Betula humilis Schrank near Zhornyska village (Ukrainian Roztochchia)

hytocoenotic conditions and structure of the local population for Betula humilis in the north-eastern environs of the village Zhornyska, Yavoriv district, Lviv region, on the territory of the Roztochchia International Biosphere Reserve have been studied. Four coenopopulations (CP) of the species are confined to secondary plant communities of sicaciogenic and pyrogenic successions with different sod levels of the peat soil, as well as missing or unequally expressed tree layer. The least transformed communities with the dominance of B. humilis (40-80% p.c.) in the shrub layer and no stands in terms of floristic composition and spatial structure correspond to the derived mesohygrophytic and hygromesophytic variants of the association Betuletum humilis Steffen 1931. The most transformed areas with sparse tree layer are represented by pioneer forest communities - birch woodlands. Seventy-five species of higher plants (seventy vascular plants and five bryophytes) were found in the floristic composition of phytocenoses. The minimal participation of helophytes and the presence of invasive species indicate a high level of mesophytization and synanthropization of modern phytocenoses. Within the locality B. humilis forms different in area and density of formation shoots (turions) of the colony-curtain mainly from semi-autonomous subpartial bushes 0.3-2.2 m tall. The largest curtains (up to 300 m2) with a high density of living formation shoots (up to 293 pcs/m2) are confined to open well-lit areas. The age of old skeletal axis, not exceeding 9 years was determined and the annual growth of shoots has been calculated. The parameters of seed productivity (SP) of the local population of B. humilis vary within: potential SP - 89.48–109.24 seed germs, actual SP - 80.84–100.4 seeds. The coefficient of seed productivity is quite high (86.69-92.16%) for all coenopopulations. Based on the results of research and analysis of the literature the life form of B. humilis, which belongs to vegetatively mobile hypogeogenic-geoxyl deciduous shrubs that form colonies or clones of (semi) autonomous (sub) partial (daughter) shrubs and are characterized by monopodial-sympodial shoots growth has been clarified. The big life cycle of the species characteristic of shrubs consists of development cycles for systems shoots formation (main skeletal axes), which are successively replaced, and lasts for decades. The development cycle of the system formation shoot covers the periods of intensive growth (appearance of formation shoot from an additional or dormant bud in the first year), relative stabilization of growth processes with the formation of first and higher-order branching shoots (from second to tenth years) and ageing and death of shoots (after about ten years of age).

Phytosociology and the timber potential of transitional ecosystems from forested campinarana to dense forest in the south of Roraima, Brazil

Transitional forest ecosystems in the south of the state of Roraima show great heterogeneity of tree species and represent different volumes of timber stock in projects of vegetation suppression requiring Deforestation Licences (DL). The aim of this study was to evaluate the phytosociology and standing timber volume in ecosystems of Submontane Dense Ombrophilous Forest (Ds) and transitional Campinarana/Ombrophilous Forest (LOt1 and LOt2) in the district of Rorainópolis, Roraima. The DL were issued and authorised from 2011 to 2016 by the State Foundation for the Environment and Water Resources of Roraima (FEMARH) and the Brazilian Institute of the Environment and Renewable Natural Resources (IBAMA). A total of 9,391 timber-yielding trees were analysed, with a DBH ≥ 45 cm in 646.5 hectares; these belonged to 21 botanical families, 73 species and 8 taxa identified at the genus level. Diversity and evenness were greater in Ds (H’ = 3.34; J = 0.82) compared to LOt (H’ = 1.92 to 2.20; J = 0.55). The floristic similarity was greater between Ds and LOt2, of different forest typologies, showing that transitional environments can be complex in terms of floristic composition and diversity. However, the larger volumes of timber stock in LOt1 and LOt2 compared to Ds may be related not only to natural processes, but also to the influence of deforestation and illegal selective logging in the surrounding area. There is a strong need for studies on transitional forest ecosystems in the Amazon, due to the complexity of the ecological relationships, the influence of environmental gradients, and anthropogenic factors.

Vegetation–environment relationship and floristic diversity of Wadi Al-Sharaea, Makkah Province, Saudi Arabia

Due to their biological significance, physiographic variation, and environmental gradients, desert wadis are essential habitats for socioeconomic development. The current study aims to enrich the knowledge about the importance of Wadi Al-Sharaea, Makkah as a biodiversity hotspot for desert ecosystems in terms of floristic composition, community structure, potential economic uses of identified plants, and behaviour of the common species along soil physicochemical gradients. To collect the data, 95 stands distributed in 17 sampling sites were selected to represent the vegetation physiognomy along the wadi. During the field survey, 110 species belonging to 77 genera and 33 families were discovered with Poaceae family dominating. Therophytes were the dominant life form, and bioregional elements were the dominant chorotype. The TWINSPAN analysis resulted in nine vegetation groups (VGs), which were distinctly segregated on the two axes of DECORANA. Rhiza stricta dominated three VGs (G, H, and I) with Citrullus colocynthis, Polycarpaea repens, and Aristida funiculata, respectively, were codominant species. The Principal Component Analysis (PCA) ordination clarified that the pH, EC, TDS, Mg, and gravels had the most significant effect on the plant communities. Regarding the Pearson correlations, some plant communities were positively affected by some soil variables (e.g., pH, HCO3, K, and Cl), while others were negatively affected by other variables (e.g., EC, TDS, Ca, SO4, and Cl). The species richness varied from 1.5 species stand−1 in Maerua crassifolia-Cynanchum radians community (VG: A) to 21.0 species stand−1 in Citrullus colocynthis-Hypertelis cerviana (VG: B). The low species diversity in some plant communities indicated that the original vegetation was subjected to destruction, and consequently, habitat rehabilitation is urgently required.

ENVIRONMENTAL CHANGE AND LANDUSE SCENARIOS UNDER CHANGING CLIMATES: THE EXPERIENCE IN THE UPPER CROSS RIVER REGION, NIGERIA

This paper seeks to show that due to changing climates, there are salient marginal Sahelian conditions (conditions of aridity) emerging on the Northern fringes of Cross River State, a state that is geographical positioned in the southern rainforest belt of Nigeria. The paper adopts a simple descriptive approach and shows the distinct characteristics of this zone, in terms of floristic composition and edaphic and geomorphic structures under changing conditions. Some relationships are established between environmental variables like health, water supply and crop-yield on one hand, and climatic variation, floral life-forms and soil conditions on the other. The changing land use patterns relative to environmental changes are also examined. The paper concludes with a look at current and future adaption strategies to these climate-induced conditions.

Floristic diversity of receiving environments polluted by effluent from agri-food industries

Till date, there are few studies on the flora found in receiving environments polluted by effluent from agri-food industries. Floristic inventories of ten receiving environments in Cameroon. were carried out using the line transect method from upstream to downstream discharge areas in the Littoral and Center regions during the dry and rainy season. The abundance/dominance (AD) of each floristic survey was assessed using Braun–Blanquet scale. Species richness of the different receiving environments is marked by higher and lower Shannon Weaver (H′) diversity index values, respectively in the rainy season and dry season from upstream to downstream. Regularity values (R) show that the maximum number of species is involved in the covering of the surface. In terms of floristic composition, the Simpson's diversity index (D) shows similarities between the different receiving environments. The Sorensen index (Q) shows similar number of common species between upstream and downstream zones of the same site. Nitrophilous species are abundant. Some could be organic pollution indicators, namely: Pennisetum purpureum, Cynodon dactylon, Commelina benghalensis, Lemna minor, Acroceras zizanoides, Echinochloa pyramidalis and Panicum maximum. The Poaceae family dominates the ten receiving environments.

Caracterización de la flora epífita vascular del Parque Iberoamérica,Santo Domingo, República Dominicana

Se presentan los resultados del inventario de la flora epífita vascular del Parque Iberoamérica, un área verde de la ciudad de Santo Domingo, República Dominicana. Los muestreos fueron realizados durante un mes, desde el 21 de noviembre hasta el 13 de diciembre del año 2017, utilizando el método de transecto y parcela. El transecto, de 1,200 m de largo x 30 m de ancho, cubrió el área total del parque (1.2 km2). En el caso de la parcela, el área de ocupación fue menor (120m2), esta se delimitó en el sitio de mayor cobertura vegetal dentro del parque. Además, se hicieron recorridos fuera del transecto y la parcela para documentar la mayor diversidad posible. Se identificaron 35 especies, distribuidas en 29 géneros y 23 familias. Las familias más representativas fueron: Moraceae con cuatro especies, seguida de Bromeliaceae y Fabaceae con tres especies cada una. Las especies más abundantes fueron Tillandsia recurvata con 3,531 individuos, seguida de Tillandsia balbisiana con 556 individuos, y Nephrolepis acutifolia con 296. A pesar del reducido tamaño del parque, en términos de composición florística, la comunidad de epífitas es diversa.

Community patterns and environmental drivers in hyper‐diverse kwongan scrub vegetation of Western Australia

AbstractQuestionsThe community patterns in kwongan, a mediterranean‐type scrub on nutrient‐poor soils occurring in Western Australia, are poorly understood due to only few, focused studies using disparate sampling designs. We aimed to determine whether (a) classification of the kwongan vegetation of the Eneabba Sandplains leads to an ecologically informative classification scheme, and (b) we could identify environmental drivers underpinning the plant community patterns.LocationTownship of Eneabba (29°82′S, 115°27′E), approximately 250 km north of Perth, Western Australia, covering 1,210 km2.MethodsWe used a data set consisting of 512 relevés, collected following the standard field methodology of the Braun‐Blanquet approach, and accompanied by an extensive set of environmental data consisting of 94 variables representing climate, fire, soil and terrain properties across 189 relevés. The data were classified and ordinated by a series of multivariate analyses. OptimClass assisted in the selection of the most robust classification procedure. Distance‐based redundancy analysis (db‐RDA) inferred the major ecological drivers of the vegetation patterns.ResultsNumerical classification, nonmetric multidimensional scaling, and syntaxonomic tabular analysis revealed two major community groups (MCG A and B), eight community groups, and 17 communities in the kwongan vegetation of the study area. All vegetation units are characterised in terms of floristic composition and position along major ecological gradients in the studied area. The MCGs separated along a composite gradient of soil‐texture and exchangeable cations. The first two db‐RDA axes explained 21% of the total variance which is very low, considering the high number of environmental variables used.ConclusionsOur study provides a comprehensive insight into the high variability of vegetation types in hyper‐diverse kwongan scrub at a landscape spatial scale; it is the first syntaxonomic account of the Western Australian kwongan vegetation, presenting a complete tabular comparative analysis. The studied major community groups segregate along a soil‐texture and an exchangeable‐cation content gradient. At a community scale, environmental filtering explained a small fraction of the vegetation–environment relationship. We suggest that the unexplained portion of the vegetation‐environment relationship might be a product of slow‐acting neutral processes in this hyper‐diverse system; this assertion is amenable to rigorous future testing.

Diversity of wild yams (Dioscorea spp., Dioscoreaceae) collected in continental Africa

Plant genetic resources, especially crop wild relatives like wild yams, are under high risks of extinction due to habitat loss, climate change, unacceptable collection practices, shifting cultivation practice and over-exploitation. To contribute to their conservation, the diversity of wild yams (Dioscorea spp.) collected in continental Africa was analyzed. Specimens from Herbaria (B, BR, K, P, WAG and YA), databases, literature and actual collection from Cameroon were considered. The collection localities were georeferenced and projected to Lambert azimuthal equal-area projection. Spatial analyses of sampling and diversity were conducted at three different resolutions: 50 × 50-, 100 × 100- and 150 × 150-km sized grid cells. Four thousand and eighty-seven specimens, collected in 2895 localities, were inventoried and grouped into 55 taxa including 43 species, five subspecies, four varieties and seven morpho-species. The genus Dioscorea occurred in fifteen out of the eighteen phytochoria recognized on African mainland. The Guineo–Congolian regional centre of endemism was the most sampled and the richest phytochorion with 28 taxa. In terms of floristic composition, the Sudanian regional centre of endemism and the Guinea–Congolia/Sudania regional transition zone were the most similar (similarity coefficient SCi = 0.84). Globally, the most diversified grid cells were located in Sierra Leone, Liberia, Ivory Coast, Ghana, Togo, Benin, Nigeria, Cameroon, Gabon, Equatorial Guinea, CAR, Congo, DRC, Tanzania and Malawi. In terms of phytogeography, they were found in two regional centres of endemism (Guineo–Congolian and Zambezian), two regional transition zones (Guinea–Congolia/Zambezia and Guinea–Congolia/Sudania) and one regional mosaic (Zanzibar–Inhambane). These areas could therefore be considered as potential sites for in situ conservation of wild yams in continental Africa.

Transférer le sol pour restaurer des communautés végétales: quelles leçons pour mesurer la résilience des pelouses sèches ? (Plaine de La Crau, Sud-Est de la France).

Ecological restoration can accelerate the resilience of degraded dry grasslands. Among the ecological restoration techniques used, soil transfer has already given promising results for restoring species-rich plant communities by providing the ability to recreate rapidly a habitat that corresponds to the reference ecosystem (the non disturbed dry grasslands). However, soil transfer is a destructive method, since it involves the use of non-renewable resources such as grassland soils of the donor sites that are the produce of centuries of interactions between climate, plants and animals. In south-eastern France, the plain of La Crau is an example of Mediterranean dry grasslands where the resilience of the steppe vegetation is extremely slow after land use changes which have impacted soil and vegetation. On 7th August 2009, a major oil leak occurred in the steppe center, destroying more than 13 acres of steppe vegetation. As a consequence, in 2010, the polluted soil was excavated and evacuated in a specialised dump. This operation was, then, combined with various in situ experiments of soil transfer, with exclusion of traditional sheep grazing management, to test (i) the importance of respecting the vertical organization of the main soil horizons and (ii) some opportunities to save this non-renewable resource. In May 2011, just after the soil transfer (72,000 tons) was achieved in April 2011 from a nearby quarry which extension had been authorised prior to the oil leak, different quadrats were materialized in the reference steppe vegetation around and in the restored site, with at the soil surface: the organic layer (top-soil, treatment ABC) with or without compaction (treatment ABCnc), the mineral layer (sub-soil, treatment BC) or the altered bedrock only (treatment C). After three years of vegetation monitoring, all the different treatments of soil transfer resulted in a rapid resilience of steppe vegetation in terms of floristic composition and plant species richness. Indeed, in 2013, the treatment with the transfer of mineral layer only at the soil surface, showed no significant difference in terms of plant species richness with the reference steppe plant community. Furthermore, there was a significant higher species richness for the treatments with the transfer of organic layer, compacted or not, in comparison with the reference steppe plant community. In addition, between 2011 and 2013, the natural colonisation by some ruderal opportunistic species was very low. Nevertheless, the reference steppe plant community organization was not restored for none of the different soil transfer treatments, as revealed by the calculation of the Bray-Curtis index. In addition, species abundances in the uncompacted organic layer, mean vegetation height and plant cover were significantly higher, than in the reference steppe plant community. Our results show that after only 3 years, the results of the different soil transfer treatments seem very promising. It appears from this three year monitoring that soil transfer of a mixture of the organic (top soil) and mineral (sub soil) layers, without final compaction, could be sufficient to boost the natural resilience of the typical plants of the reference steppe plant community. It might also be possible to increase the surface where the soil will be spread according to ratios of 1 to 2 or 1 to 3, instead of 1 to 1. This method will allow the protection of the steppe soil that is still a non-renewable resource. Because none of the different soil transfer treatments has allowed for the restoration of the integral steppe plant community, it seems now necessary to reinstall the traditional sheep grazing system with the aim to increase the restoration of the reference steppe plant community spatial organization.

Ecological consequences of land use change: Forest structure and regeneration across the forest-grassland ecotone in mountain pastures in Nepal

The ecotone; the spatial transition zone between two vegetation communities; is claimed to have more species than the adjoining communities. However; empirical studies do not always confirm higher richness at the ecotone. The ecotone position and structure are dynamic over time and space and it is driven by the changes in climate; land use or their interaction. In this context; we assessed the forest-grassland ecotone of temperate mountains in central Nepal by i) comparing species composition and richness across the ecotone; ii) analyzing if the forest-grassland ecotone is shifting towards the grassland center by colonizing them with trees; and iii) discussing the consequence of changed disturbance regime in the dynamics of this ecotone and the surrounding grasslands. We analyzed vegetation data sampled from belt transects laid across the forest-grassland ecotone in semi-natural grassland patches. Vegetation data consisting of species richness and composition; and size structure and regeneration of the two most dominant tree species; namely Rhododendron arboreum and Abies spectabilis; from the transects; were used to analyze the trend of the forest-grassland ecotone. Forest and grasslands were different in terms of floristic composition and diversity. Vascular plant species richness linearly increased while moving from forest interior to grassland center. Spatial pattern of tree size structure and regeneration infers that forest boundary is advancing towards the grasslands at the expense of the grassland area; and tree establishment in the grasslands is part of a successional process. Temporally; tree establishment in grasslands started following the gradual decline in disturbance. We argue that local processes in terms of changed land use may best explain the phenomenon of ecotone shift and consequent forest expansion in these grasslands. We underpin the need for further research on the mechanism; rate and spatial extent of ecotone shift by using advanced tools to understand the process in-depth.

Habitat preferences of some red‐listed alpine plants in Scandinavia

Scandinavian alpine vascular plants are red‐listed (R‐L) according to criteria defined by IUCN. These are based on an evaluation of their risk for extinction in the future, which for most alpine plants have been related to possible effects of climate change. In the present study, ecological characteristics of R‐L alpine plants are inferred from their occurrence in previously studied alpine plant communities. In total, data on 231 communities were compiled from studies in Norway and Sweden, and a total of 39 red‐listed vascular plants were found in 142 of them. The data were analysed by numerical analyses in order to assess if and how communities with and without R‐L species differ in terms of floristic composition and environmental conditions. The analysies show that most of the R‐L plants are situated at the ends of the main floristic gradients extracted by Detrended Correspondense Analysis (DCA). These extremes are interpreted to represent high‐altitudinal communities with long‐lasting snow cover. In productive communities dominated with herbs and ferns, R‐L plants are few or missing. A Principal Components Analysis (PCA) indicated that the R‐L species form a heterogeneous group both in terms of ecology, abundance, and geographic distribution. Some of the communities were considered to be especially valuable because they included several (up to eight) R‐L plants. Such communities are found in the upper part of the middle alpine or high alpine zone (460–675 m above the forest limit) and on calcareous substrate. It may generally be assumed that alpine plants with optima at the edges of the floristic gradients may be especially vulnerable to climate changes.

Fossil woods from late Pleistocene sediments from El Palmar Formation, Uruguay Basin, Eastern Argentina

The Santa Ana fossiliferous locality (Entre Ríos, Argentina) of the El Palmar Formation is located in the southernmost part of the Uruguay Basin, in eastern Argentina. It contains evidence of a late Pleistocene paleoflora, consisting mainly of fossil woods. These remains were studied and are described based on anatomically preserved secondary xylem. Two new morphospecies of Mimosoxylon Müller-Stoll et Mädel 1967 and Prosopisinoxylon Martínez 2010 are described, as well as two new morphogenera, related to Holocalyx Micheli, 1883 and Amburana Schwacke et Taub. 1894. These two new morphogenera represent the first recorded fossil wood with affinity to Faboideae from the Uruguay Basin. Schinopsixylon heckii Lutz 1979, (Anacardiaceae) was also recognized. These fossil woods are discussed here in terms of floristic composition and palaeoclimatic requirements. The morphotypes described here, as well as previously recorded ones from the Uruguay Basin, increases our understanding of floral diversity during the late Pleistocene in this region.

Testing a sahelian grassland functioning model against herbage mass measurements

A simple grassland process model is tested against ground measurements collected during 15 years in the sahelian zone in Mali. The model uses standard daily meteorological variables and a limited number of site specific parameters to simulate herbage growth and canopy functioning. The model has two calibration parameters. Due probably to the strong interannual variation of both the herbaceous layer in terms of floristic composition and soil nutrient mineralization, the use of default values for the two calibration parameters leads to large errors in the prediction of herbage yields. In contrast, once the parameters have been optimised, a good concordance is found between the model outputs and the seasonal variation of the herbage standing mass in sites on sandy soils located along a north-south bioclimatic gradient.

First record of fossil wood and phytolith assemblages of the Late Pleistocene in El Palmar National Park (Argentina)

Two paleoxylologic assemblages and two phytolith assemblages were recovered from Late Pleistocene sediments of El Palmar Formation. These deposits are found in outcrops along the western margin of the Uruguay River. The spectra of taxa obtained in both sets by different methods is complementary. The fossil remains are characterized in terms of floristic composition and paleoclimate. Seven families are recognized: Podostemaceae, Myrtaceae, Anacardiaceae, Mimosoideae, Arecaceae, Poaceace, and Cyperaceae. Sponge siliceous spicules also have been found in these assemblages. The state of preservation of the phytoliths and their weathering degree is analyzed. These studies can be used as a potential paleoecological tool for alluvial sediments. The comparison of fossil assemblages with modern analogs clarifies the paleoecological requirements and composition of two paleocommunities, one dominated by woody forests and the other by palms. The climatic conditions inferred from the reconstructed vegetation and sedimentary deposits indicate a temperate-warm, humid climate. The results constitute the first evidence of the floral diversity of the vegetation in El Palmar National Park during the Late Pleistocene.

Transitions in Ancient Inland Freshwater Resource Management in Sri Lanka Affect Biota and Human Populations in and around Coastal Lagoons

The increasing anthropogenic pressure on natural environments results in impacts that affect tropical forest areas and their biodiversity. Adverse impacts on terrestrial and oceanic environments often compound in the intertidal area, where mangrove forest ecosystems thrive. In tropical coastal areas of many developing countries where people depend on wood and other mangrove forest products and services, forest degradation leads to socioeconomic problems. At the same time, increasing freshwater needs in these areas are expected to cause additional problems. On the basis of remote sensing and ground truthing complemented by colonial archival material from the Dutch East India Company (1602-1800), we report that changes to the historic system of inland freshwater management have increased dramatically in recent times. Hydrological changes, such as interbasin transfers, have resulted in a qualitative ecological and socioeconomic degradation in three coastal lagoons in southern Sri Lanka. Variations in river hydrology have caused changes in the areas suitable as mangrove habitat and, thus, have resulted in an altered distribution. However, increases in mangrove area can mask the degradation of the site in terms of floristic composition, significance of the species, and biodiversity (this effect is termed "cryptic ecological degradation"). It is important that such changes be carefully monitored to ensure biological and socioeconomic sustainability.

Patterns of long-term woody vegetation change in a sandstone-plateau savanna woodland, Northern Territory, Australia

Aerial photographs were used to assess changes in woody vegetation cover at 122 locations within a sandstone-plateau savanna woodland in the Victoria River region, Northern Territory, Australia. Despite locally variable vegetation responses, there has been little change in total woody vegetation cover since 1948. Thirty-three locations were also surveyed on the ground. It was found that sites for which vegetation cover had changed over the 50-y period were not significantly different from stable sites in terms of floristic composition, recent fire history, demographic stability among the dominant tree species, or edaphic setting. However, two of the dominant overstorey tree species – Eucalyptus tetrodonta and Eucalyptus phoenicea – showed significantly higher mortality on sites that had experienced vegetation cover decline since 1948. We suggest that observed changes in woody vegetation cover are a consequence of natural cycles of die-back and recovery of at least these two species in response to spatially heterogenous variables such as dry-season moisture stress. Although the widespread decline of fire-sensitive Callitris intratropica populations clearly indicates a historical shift from lower- to higher-intensity burning conditions within the study area, we reject the hypothesis of a landscape-wide process such as changing fire regimes or climatic change as the driving factor behind large-scale vegetation changes detected by aerial photographic analysis.

Shrub encroachment in Argentinean savannas

Abstract. In the Wet Chaco region of Argentina, increasing shrub encroachment in savannas over the last few decades has led to important changes in the structure and functioning of the landscape. Some sectors of this territory are characterized by the appearance of circular clusters of woody patches, dispersed throughout the grassland matrix. The increasing size of these patches leads to a gradual change from grassland to dense shrubland. We studied these circular woody patches in the eastern region of the Argentine province of Formosa and characterized the variation in terms of floristic composition, diversity and predominant seed dispersal mode in different size patches. We observed an increase in species richness, diversity and compositional heterogeneity among patches with increasing patch size. Seed dispersal by animals, especially birds, is an important factor in the expansion of these woody vegetation patches within the grassland matrix.