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Flore illustrée du Burkina Faso et du Mali. Hrsg. von Jean César, Cyrille Chatelain, Marco Schmidt, Georg Zizka, Blandine Marie Ivette Nacoulma, Mamadou Lamine Diarra, Adjima Thiombiano, Stefan Dressler, Rodolphe Spichiger. Band 1: Ptéridophytes et Monocotylédones Band 2: Dicotylédone Senckenberg 2024, 1062 Seiten, 807 Fotos, 2800 Illustrationen, 3 Grafiken, 1 Tabelle, 16,4 x 24 cm, gebunden, in Französisch

In the autumn of 1955 a research team from Frankfurt University carried out field investigations in the Sierra de los Organos, Cuba. Altogether an area of approximately 400 sq. Km. was mapped and investigated geomorphologically (by H. Lehmann), geologically (by K. Krömmelbein) and botanically (by W. Lötschert). In addition chemical research was pursued on karst corrosion processes under tropical conditions. The main object of the field ,investigations taken altogether was the study of the tropical type of karst and its genesis. The Sierra de los Organos, the Organ Pipe Range, forms a mountain chain in western Cuba stretching from La Palma to Guane. lt is of Laramic folding, and its highest parts, which hardly exceed 500 m., consist of Jurassic to Cretaceous and possibly also Eocene limestones and a series of sandstones and shales, the so-called Pizarras or Cayetano-formation. These latter, which occur on both sides of the limestone sierras, form a maturely dissected area of hills of an average altitude of 300 m., as for instance between the Anc6n and the Vifiales-InfernoChain; in part, however, this hill area is considerably lower. Contrary to Palmer (1945), the Cayetano formation is, because of its pre-Oxfordian age, to be considered older than the limestone in which, for the first time, fossils (Trigonia sp.) were found. Neither can Vermunt's opinion be maintained that the limestone is embedded within the Cayetano formation. Tectonically the mountains show an ordinary imbrication structure in which the succession of strata - Cayetano formation, Jagua-formation (Upper Oxfordian), Vifiales limestone of Upper Jurassic to Cretaceous age - ,is repeated several times. The extent of the thrust faults is far smaller than was thought by Palmer; their dip is mainly northwards. The longitudinal and transversal faults are characterised by the occurrence of serpentinic masses which are frequently joined to and kneaded with layers of the Habana formation. The age of the imbrication is Post-Eocene or Late-Eocene; the Eocene Strata which have been affected tectonically and which superimpose normally the unstratified limestone of Cretaceous age still require a more exact stratigraphical classification. As regards the morphology, the existing relief originated from an arch whose axis nearly coincides with the present watershed. The highest hills, however, the limestone sierr:1s, are located north of this axis in the northern part of the arch. The results of the geomorphological research showed that three different levels were formed in the course of erosion and denudation. The oldest may be consider d comparable to the Upper Miocene peneplain of other parcs of Cuba. lt corresponds with the level of the plateau-like limestone sierras taken as a whole, which are dissected into single limestone cones. A considerably lower level cuts the steeply dipping Pizarras and part of the limestone rocks. A third level is formed by plains and enclosed basins which surround the limestone sierras. Individually the limestone sierras show eh e typical Kegelkarstrelief of rounded cones and chimney like sinkholes or Yamas. Their sur face is completely covered by pointed lapies (Karren). Those beds which consist of other than the Upper Oxfordian pure limescone show no tendency towards formation of Kegelkarst, though they too display karsttopography. lt is a new observation that basins and plains, for which I suggest the name Randpolien (marginal poljes), without surface drainage, have formed around the limestone sierras. They all show the features of a poljie. They are surrounded by higher ground, are without surface drainage, have a fairly flat bottom, but are bordered on one side by insoluble rocks (Pizarras) . As is shown by isolated limestone covers (Mogocen) which rise above the polje bottoms, these marginal poljes (Randpolien) have expanded into the limestone from the boundary between the limestone and the shale. The drainage of these poljes takes place subterraneously through the limestone mountains. Evidently detritus of insoluble matter is also carried away subterraneously since sand and gravel of shale and serpentine occur at the mouths of cavernous rivers. In chose cases where surface drainage is found, I suggest the adoption of the term Karst margin plains (Karstrandebenen) as understood by K. Kayser, since these plains are mostly situated still within the limestone area. Both marginal poljes and karst margin plains always lie deeper than the neighbouring shale area and lie considerably deeper than the limestone sierras which rise out of them with steep cliffs of often more than 100m in height. In addition the genuine poljes completely surrounded by limestone are also found (Jaruko Hoye, Portreico Hoye, etc ). The development of the poljes, marginal poljes and karst margin plains is a result of undermining by karst corrosion as described by H. Lehmann elsewhere. The level of their bottoms depends on the level of the Vorfluter, i.e. the surface stream , into which they are being drained and which form a local base level. The karst formation process advanced under tropical conditions at considerable speed . Although the warm tropical rainwater contains only small quantities of C02 (2.5-3.5 milligrams per litre) a great quantity of C02 is brought into the ooze water and the water running down the lapies (Karren) by the carbon dioxide which becomes available through the respiration of the microorganisms of the endolothic limestone rows (Verrucaria sp.) and the macro vegetation. Our analysis showed that water which had been running down on limestone for only a short distance already contained up to 21mg of free C02 per litre. Consequently the corrosion effect is unusually great; analyses of water trickling down limestone showed up to 157 mg CaCO3 per litre. These quantities are considerably greater than those measured in Europe. As regards the vegetation in the area of the Sierra de los Organos, according to the different ecological conditions three types of woods have developed. The xerophytic vegetation of the limestone is characterised by the joint occurrence of Spathelia brittonii, Bombax emarginata and Carissia princeps. The hilly Pizarras are covered with dry oak woods (with Quercus virginiana) and in the higher parts with woods of Pinus tropicalis and Pinus carribbea. Both oaks and pines form a mesophytic mixed forest.

Highlights • Northern and eastern grassland-savanna boundary defined by minimum temperature. • Dynamics of fire, frost and growing season temperatures combine to produce this limit. • Western limit is related to moisture availability. • Modern, high-resolution climate data enables refinement of bioclimatic limits. • Reparameterisation improves global model performance at regional scale. Abstract Understanding the controls of biome distributions is crucial for assessing terrestrial ecosystem functioning and its response to climate change. We analysed to what extent differences in climate factors (minimum temperatures, water availability, and growing season temperatures (degree days above 5 °C (GDD5)) might explain the poorly understood borders between grasslands, savannas and shrublands in eastern South Africa. The results were used to improve bioclimatic limits in the dynamic global vegetation model (DGVM) LPJ-GUESS. The vegetation model was also used to explore the role of fire in the biome borders. Results show no clear differences between the adjacent biomes in water availability. Treeless grasslands primarily occur in areas with minimum temperatures and GDD5 values below that of savannas. The standard fire module in LPJ-GUESS is not able to reproduce observed burned area patterns in the study region, but simulations with prescribed fire return intervals show that a combination of low temperatures and fire can explain the treeless state of the grassland biome. These results confirm earlier hypotheses that a combination of low winter temperatures, causing frost damage to trees, and low growing season temperatures that impede tree sapling growth and recruitment, particularly under re-occurring fires, drive the grassland-savanna border. With these insights implemented, the LPJ-GUESS simulation results substantially improved grass distribution in the grassland biome, but challenges remain concerning the grassland-shrubland boundary, tree-grass competition and prognostic fire modelling.

Highlights • Floating ability facilitates water dispersal. • Hydrochorous seed dispersal is more effective than wind dispersal. • Storage in water induced germination rate. Abstract In many Central European countries Fraxinus pennsylvanica is an invasive species that spreads rapidly in floodplain forests. The aim of this study was to analyse anemochorous and hydrochorous dispersal distances and to compare the findings with dispersal data for the native Fraxinus excelsior. A simulation revealed that wind dispersal distances are similar for both species, reaching to 120–250 m. By contrast, the mean floating time (50% floating samaras) measured in an experiment was 2 days in the case of F. pennsylvanica and 0.5 days for F. excelsior. This high floating ability facilitates water dispersal over several kilometres in both species, but for the invasive species the modelled mean dispersal distance was 3.7 times higher. A germination test of F. pennsylvanica seeds revealed that the rate, onset and speed of germination increase with the duration of the inundation. After a maximum storage time in water of about 15 days the germination rate amounts to 78%, which was higher than the germination rate of seeds without storage in water (53%). We also found that regeneration was enhanced in flooded areas. Hydrochory, therefore, may be viewed as an important factor explaining the successful invasion of F. pennsylvanica in floodplain forests in Central Europe.