The paleobotanical record of Colombia: Implications for biogeography and biodiversity

Plant microfossil and macrofossil associations obtained from six dated sections from the area of the basin of Bogota¿ (2550 m, Eastern Cordillera, Colombia) show the evolution of the late Neogene Andean montane forest, triggered by the Andean orogeny. Progressive adaptation of warm tropical taxa to cool montane conditions, evolution of new neotropical montane taxa, and immigration of temperate Laurasian, Holarctic, and Austral-Antarctic elements gave shape to the present-day montane forest. Vegetational characteristics inferred from fossil plant associations reveal the altitude at the time of deposition. Neogene forests are floristically compared with contemporary forests at comparable altitudinal intervals in the surroundings of the Bogota¿ basin; however, the absence of taxa that had not yet arrived, or evolved, is most salient and shows that non-analogue plant communities are common. The main phases of montane forest development are: (1) pre-uplift phase of the late Miocene with abundant lowland taxa with tropical or neotropical affinities (Mauritia Kunth, Amanoa Aubl., Ceiba Miller, and representatives of Humiriaceae); montane forest rich in Podocarpaceae (potentially including Nageia Gaertn., Podocarpus L'He¿r., Prumnopitys Phil., and Retrophyllum C. N. Page) covered other previously uplifted areas in the region; (2) toward the early Pliocene the area was uplifted to ca. 1000 m; the relative proportion of temperate taxa of North American and southern South American stock increased and occupied the slopes of the low mountains; and (3) by the middle Pliocene uplift had proceeded to ca. 2000-2200 m and tropical lowland taxa, which are now restricted to altitudes below 1000 m, are no longer recorded in the fossil plant associations; the increase in the number of newly appearing montane taxa (Myrica L., Turpinia Vent., Gunnera L., Bocconia L., Gaiadendron G. Don f., Daphnopsis C. Martius, and Monnina Ruiz & Pav.) suggests a significant increase of diversity. Until the late Pliocene there is little to no evidence for the existence of the pa¿ramo; taxa such as Xyris L., Hypericum L., Carex L., Montia L., and Ranunculus L. might have formed swamp or bog vegetation only. It is believed that these taxa colonized mountaintops with half-open vegetation; these areas extended when the mountains reached above upper forest line elevations. The distribution areas of the endemic genera of the Espeletiinae largely coincide with the youngest parts (<5 Ma) of the northern Andes. Changing climatic conditions forced individual plant species to migrate vertically. Composition of plant communities changed continuously and vegetation belts frequently were altitudinally squeezed or offered possibilities for expansion. This long process stimulated speciation and provoked sequential non-analogue vegetation types. Thus, the biodiversity hotspot of the northern Andes has a dynamic histor

Analysis of interference to cable television due to mobile usage in the Digital Dividend

The start of use of mobile applications in the 800 MHz band, which forms part of the ‘Digital Dividend’, will cause interference to TV signals under certain conditions. The new mobile applications (called LTE, Long Term Evolution) use frequencies also used in cable TV networks. This report examines how much interference may occur when providing digital television over cable networks

Onderzoek naar storing op kabeltelevisie door mobiel gebruik in het Digitaal Dividend

De introductie van het gebruik van mobiele toepassingen in de 800 MHz band, die onderdeel vormt van het zogenaamde digitaal dividend, leidt onder bepaalde omstandigheden tot een verstoring van tv-signalen. De nieuwe (LTE) mobiele toepassingen gebruiken frequenties die ook worden toegepast in kabel-tv-netwerken. Dit rapport gaat in op de mate waarin deze storing kan plaatsvinden in het (digitale) televisie aanbod van de kabel.\u

Botanical ecology and conservation of the laguna de la herrera (sabana de bogotá, colombia)

Se estudió la vegetación alrededor de la Laguna de La Herrera, una laguna andina a 2550 m. Se diferenciaron una comunidad de Phytolacca bogotensis (1): comunidades helofíticas dominadas por: Scirpus californicus y Typha angustifolia (2); Scirpus californicus (3); Polygonum punctatum (4); Rumex obtusifolius y Polygonum punctatum (5); Bidens laevis (6); Hydrocotyle ranunculoides (7); comunidades pleustofíticas con: Limnobium laevigatum; (8); Azolla filiculoides y Lemna cf. gibba (9) y Eichhornia crassipes (10). Se registraron la estructura, composición florística, los rasgos ecológicos y la distribución de las comunidades y se comparó con la conductividad eléctrica y la calidad del agua. Finalmente, se hacen recomendaciones para la conservación de la laguna y la vegetación acuática.The acuatic, helophytic and pleustophytic vegetation of the Laguna de La Herrera, on the southwestern border of the high plain of Bogotá at 2550 m was studied following the Zurich- Montpellier approach. The communities recognized were: terrestrial community of Phytolacca bogotensis; helophytic communities of scirpus californicus and Typha angustifolia ; scirpus californicus ; Polygonum punctatum ; Rumex obtusifolius with Polygonum punctatum; Bidens laevis ; Hydrocotyle ranunculoides. Pleustophytic communities of Limnobium laevigatum; Azolla filiculoides with Lemna cf. gibba and Eichornia crassipes. The structure, floristic composition and ecological aspects were also considered. Several recommendations about conservation of the Laguna are given

Middle Miocene Tectonic Boundary Conditions for Use in Climate Models

Utilizing general circulation models (GCMs) for paleoclimate study requires the construction of appropriate model boundary conditions. We present a middle Miocene paleotopographic and paleobathymetric reconstruction geographically constrained at 15 Ma for use in GCMs. Paleotopography and paleogeography are reconstructed using a published global plate rotation model and published geological data. Paleobathymetry is reconstructed through application of an age-depth relationship to a middle Miocene global digital isochron map, followed by the overlay of reconstructed sediment thickness and large igneous provinces. Adjustments are subsequently made to ensure our reconstruction may be utilized in GCMs