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41.
The indigenous soil knowledge among the Fulani subsistence farmers in two villages of northern Burkina Faso is examined, analysed and assessed with the aim of evaluating its adequacy for sustaining soil fertility and for the appropriateness of tapping indigenous knowledge in development programmes. The analytical framework is a multidisciplinary approach combining soil science and anthropology. The results show a high degree of consistency between the science-based western soil classification and the Fulani soil classification although the routes of generation are different. The farmers are aware of and active in management of soil fertility based on their experience, but express no thorough understanding of the mechanisms of plant growth. The soil knowledge is applied in the farming strategies which, as a primary aim, seek to minimize the risk of harvest failure. However, the analysis also suggests that the knowledge is no part of a free-standing knowledge body which can be separated from the actual agricultural performance. The farmers express a general concern about the present state of the environment and degradation processes; however, there is no motivation to take active control of and manage the bush area. This is in contrast with the way millet cultivators actively manage their fields. An explanation of this is suggested by the division between the two Fulani ethnic subgroups, the FulBe who are the former masters and the RimayBe, the former slaves. 相似文献
42.
Lars Olov Andersson 《Physics and Chemistry of Minerals》2010,37(7):435-451
A number of different impurities are located in the open channels of natural beryl crystals. The rare Maxixe beryl contains
an unusual amount of NO2. The isoelectronic CO2
− radical is found in the irradiated Maxixe-type beryl. The NO2 radicals are distributed in the Be–Al plane of the crystal, with the nitrogen atom close to the oxygens of the beryl cavity
wall. These oxygens repel the negative CO2
− radical, which is located at the center of the beryl cavity and rotates around its O–O axis, which is parallel to the crystal
c-axis. When there is a nearby alkali ion at the center of the beryl channel, it reorients the CO2
− radical so that its bisector is parallel to the c-axis and points toward the positive ion. Different signals are analyzed for Li+, Na+, and another counter-ion, which probably is Cs+. The related NO3 and CO3
− radicals are the color centers in the investigated deep blue beryls. The slow decay of the color, which makes these beryls
useless as gem stones, is related to the decay of the hydrogen atoms which are present in these crystals. Evidence is given
that NO3 is created in Maxixe beryl by a natural process, while CO3
− in Maxixe-type beryl has been created by irradiation. The temperature dependence of the EPR signals of these two radicals
was investigated, but a definitive proof that they rotate at the center of the beryl cavity could not be given. EPR signals
from some other radicals in beryl have been observed and described. 相似文献
43.
44.
Nico-Alexander Urbanski Malte Vöge Ralf Seyfried Lars Rüpke Tanja Petersen Till Hanebuth Matthias Hort 《International Journal of Earth Sciences》2002,91(4):712-722
The intention of our study was to gain new insight into the complex interplay between different types of eruption of the Stromboli volcano by combining detailed field observation with different geophysical methods. We recorded more than 600 eruptions by use of continuous Doppler radar measurements. We detected the onset of the seismic precursor and the beginning of the visible eruption by use of seismic and infrared data. Two soil samples per day were used to monitor the effect of humidity on the eruptive style. We mapped the crater region as a reference base for the long-term morphological changes of the active region and for the exact positions of our measurement systems. Two distinct types of eruption were distinguished from each other on the basis of seismic and radar data - short, wide-angle Strombolian explosions and pulsating, sharp angle fountain-like eruptions. Data and visual observations imply that weather conditions significantly effect volcanic activity. We also interpret the intensification of eruptive activity during our field study as replenishment of the reservoir with a new batch of magma in late September 2000. 相似文献
45.
Barbara Wohlfarth Ludmila Filimonova Ole Bennike Leif Bjrkman Lars Brunnberg Nadja Lavrova Igor Demidov Gran Possnert 《Quaternary Research》2002,58(3):261
High-resolution lithostratigraphy, mineral magnetic, carbon, pollen, and macrofossil analyses, and accelerator mass spectrometry 14C measurements were performed in the study of a sediment sequence from Lake Tambichozero, southeastern Russian Karelia, to reconstruct late-glacial and early Holocene aquatic and terrestrial environmental changes. The lake formed ca. 14,000 cal yr B.P. and the area around the lake was subsequently colonized by arctic plants, forming patches of pioneer communities surrounded by areas of exposed soil. A minor rise in lake productivity and the immigration of Betula pubescens occurred ca. 11,500 cal yr B.P. The rise in summer temperatures probably led to increased melting of remnant ice and enhanced erosion. The distinct increase in lake productivity and the development of open Betula-Populus forests, which are reconstructed based on plant macrofossil remains, indicate stable soils from 10,600 cal yr B.P. onward. Pinus and Picea probably became established ca. 9900 cal yr B.P. 相似文献
46.
47.
Anders Elverhi Willy Fjeldskaar Anders Solheim Mona Nyland-Berg Lars Russwurm 《Quaternary Science Reviews》1993,12(10)
On the basis of geomorphological and sedimentological data, we believe that the entire Barents Sea was covered by grounded ice during the last glacial maximum. 14C dates on shells embedded in tills suggest marine conditions in the Barents Sea as late as 22 ka BP; and models of the deglaciation history based on uplift data from the northern Norwegian coast suggest that significant parts of the Barents Sea Ice Sheet calved off as early as 15 ka BP. The growth of the ice sheet is related to glacioeustatic fall and the exposure of shallow banks in the central Barents Sea, where ice caps may develop and expand to finally coalesce with the expanding ice masses from Svalbard and Fennoscandia.The outlined model for growth and decay of the Barents Sea Ice Sheet suggests a system which developed and existed under periods of maximum climatic deterioration, and where its growth and decay were strongly related to the fall and rise of sea level. 相似文献
48.
Lars?JacobssonEmail author Karin?Appelquist Jan?Erik?Lindkvist 《Rock Mechanics and Rock Engineering》2015,48(4):1485-1503
Specimens of coarse-grained Äspö diorite were axially compressed to observe stress-induced spalling. The specimens had a novel design characterized by two manufactured large radius notches on opposite sides. The tangential stress occurring in the notches aimed to represent the tangential loading around a circular opening. Fracture stages were monitored by acoustic emission measurements. Rock chips were formed similar to those found in situ, which indicates a similar fracture process. Slabs were cut out from the specimens and impregnated using a fluorescent material to visualize the cracks. The cracks were subsequently examined by the naked eye and by means of microscopy images, from which fracture paths could be identified and related to different minerals and their crystallographic orientations. The microscopy analyses showed how the stress field and the microstructure interact. Parallel cracks were formed 2–4 mm below the surface, sub-parallel to the direction of the maximum principal stress. The crack initiation, the roles of minerals such as feldspar, biotite and quartz and their grain boundaries and crystallographic directions are thoroughly studied and discussed in this paper. Scale effects, which relate to the stress gradient and microstructure, are discussed. 相似文献
49.
Mangrove ecosystems play an important, but understudied, role in the cycling of carbon in tropical and subtropical coastal
ocean environments. In the present study, we examined the diel dynamics of seawater carbon dioxide (CO2) and dissolved oxygen (DO) for a mangrove-dominated marine ecosystem (Mangrove Bay) and an adjacent intracoastal waterway
(Ferry Reach) on the island of Bermuda. Spatial and temporal trends in seawater carbonate chemistry and associated variables
were assessed from direct measurements of dissolved inorganic carbon, total alkalinity, dissolved oxygen (DO), temperature,
and salinity. Diel pCO2 variability was interpolated across hourly wind speed measurements to determine variability in daily CO2 fluxes for the month of October 2007 in Bermuda. From these observations, we estimated rates of net sea to air CO2 exchange for these two coastal ecosystems at 59.8 ± 17.3 in Mangrove Bay and 5.5 ± 1.3 mmol m−2 d−1 in Ferry Reach. These results highlight the potential for large differences in carbonate system functioning and sea-air CO2 flux in adjacent coastal environments. In addition, observation of large diel variability in CO2 system parameters (e.g., mean pCO2: 390–2,841 μatm; mean pHT: 8.05–7.34) underscores the need for careful consideration of diel cycles in long-term sampling regimes and flux estimates. 相似文献
50.
Ghislain Dubois Benjamin Sovacool Carlo Aall Maria Nilsson Carine Barbier Alina Herrmann Sébastien Bruyère Camilla Andersson Bore Skold Franck Nadaud Florian Dorner Karen Richardsen Moberg Jean Paul Ceron Helen Fischer Dorothee Amelung Marta Baltruszewicz Jeremy Fischer Françoise Benevise Valérie R. Louis Rainer Sauerborn 《Chemie der Erde / Geochemistry》2012
Through their consumption behavior, households are responsible for 72% of global greenhouse gas emissions. Thus, they are key actors in reaching the 1.5 °C goal under the Paris Agreement. However, the possible contribution and position of households in climate policies is neither well understood, nor do households receive sufficiently high priority in current climate policy strategies. This paper investigates how behavioral change can achieve a substantial reduction in greenhouse gas emissions in European high-income countries. It uses theoretical thinking and some core results from the HOPE research project, which investigated household preferences for reducing emissions in four European cities in France, Germany, Norway and Sweden. The paper makes five major points: First, car and plane mobility, meat and dairy consumption, as well as heating are the most dominant components of household footprints. Second, household living situations (demographics, size of home) greatly influence the household potential to reduce their footprint, even more than country or city location. Third, household decisions can be sequential and temporally dynamic, shifting through different phases such as childhood, adulthood, and illness. Fourth, short term voluntary efforts will not be sufficient by themselves to reach the drastic reductions needed to achieve the 1.5 °C goal; instead, households need a regulatory framework supporting their behavioral changes. Fifth, there is a mismatch between the roles and responsibilities conveyed by current climate policies and household perceptions of responsibility. We then conclude with further recommendations for research and policy. 相似文献