Open Access

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.

We report on the synthesis of a new praseodymium molybdenum borate under high-pressure/high-temperature conditions. The new compound with the sum formula Pr3Mo4B6O24(OH)3 crystallizes acentrically in the monoclinic space group Cm displaying a new structure type. The structure was solved via single-crystal structure determination. Additionally, the proposed structural model was confirmed by powder X-ray diffraction, second harmonic generation measurement, and single-crystal infrared and Raman spectroscopic investigation.

Non-forest ecosystems, dominated by shrubs, grasses and herbaceous plants, provide ecosystem services including carbon sequestration and forage for grazing, yet are highly sensitive to climatic changes. Yet these ecosystems are poorly represented in remotely-sensed biomass products and are undersampled by in-situ monitoring. Current global change threats emphasise the need for new tools to capture biomass change in non-forest ecosystems at appropriate scales. Here we assess whether canopy height inferred from drone photogrammetry allows the estimation of aboveground biomass (AGB) across low-stature plant species sampled through a global site network. We found mean canopy height is strongly predictive of AGB across species, demonstrating standardised photogrammetric approaches are generalisable across growth forms and environmental settings. Biomass per-unit-of-height was similar within, but different among, plant functional types. We find drone-based photogrammetry allows for monitoring of AGB across large spatial extents and can advance understanding of understudied and vulnerable non-forested ecosystems across the globe.

Measurements of vertical velocity from vertically pointing Doppler lidars are used to derive the profiles of vertical velocity variance. Observations were taken during the FESSTVaL (Field Experiment on Submesoscale Spatio-Temporal Variability in Lindenberg) campaign during the warm seasons of 2020 and 2021. Normalized by the square of convective velocity scale, the average vertical velocity variance profile follows the universal profile of Lenschow et al. (1980), however, daily profiles still show a high day-to-day variability. We found that moisture transport and the content of moisture in the boundary layer could explain the remaining variability of the normalized vertical velocity variance. The magnitude of the normalized vertical velocity variance is highest on clear-sky days, and decreases as the relative humidity increase and surface latent heat flux decrease in cloud-topped and rainy days. This suggests that moisture content and moisture transport are limiting factors for the intensity of turbulence in the convective boundary layer. We also found that the intensity of turbulence decreases with an increase in boundary layer cloud fraction during FESSTVaL, while the latent heating in the cloud layer was not a relevant source of turbulence in this case. We conclude that a new vertical velocity scale has to be defined that would take into account the moist processes in the convective boundary layer.

A comprehensive study of sillenite Bi12SiO20 single-crystal properties, including elastic stiffness and piezoelectric coefficients, dielectric permittivity, thermal expansion and molar heat capacity, is presented. Brillouin-interferometry measurements (up to 27 GPa), which were performed at high pressures for the first time, and ab initio calculations based on density functional theory (up to 50 GPa) show the stability of the sillenite structure in the investigated pressure range, in agreement with previous studies. Elastic stiffness coefficients c11 and c12 are found to increase continuously with pressure while c44 increases slightly for lower pressures and remains nearly constant above 15 GPa. Heat-capacity measurements were performed with a quasi-adiabatic calorimeter employing the relaxation method between 2 K and 395 K. No phase transition could be observed in this temperature interval. Standard molar entropy, enthalpy change and Debye temperature are extracted from the data. The results are found to be roughly half of the previous values reported in the literature. The discrepancy is attributed to the overestimation of the Debye temperature which was extracted from high-temperature data. Additionally, Debye temperatures obtained from mean sound velocities derived by Voigt-Reuss averaging are in agreement with our heat-capacity results. Finally, a complete set of electromechanical coefficients was deduced from the application of resonant ultrasound spectroscopy between 103 K and 733 K. No discontinuities in the temperature dependence of the coefficients are observed. High-temperature (up to 1100 K) resonant ultrasound spectra recorded for Bi12MO20 crystals revealed strong and reversible acoustic dissipation effects at 870 K, 960 K and 550 K for M = Si, Ge and Ti, respectively. Resonances with small contributions from the elastic shear stiffness c44 and the piezoelectric stress coefficient e123 are almost unaffected by this dissipation.