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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   
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Characteristics of Danish estuaries   总被引:2,自引:0,他引:2  
We review various aspects of the structure and functioning of Danish estuaries from data collected by the National Monitoring Program and from information in published sources. We present data on the physical, chemical, and biological characteristics of estuaries in Denmark, we evaluate the functioning of these systems as filters and transformers of nutrients and we evaluate the outlook for Danish estuaries in the future. Danish estuarine systems are for the most part shallow (<3 m deep), have short residence times, and tend to be heavily loaded with nutrients primarily from agricultural sources. Total average loads from land per unit watershed area are 112 kg P km?2 yr?1 and 2,400 kg N km?2 yr?1 during the period 1989–1995. The total phosphorus (TP) load in estuaries has been significantly reduced over the last decade, following implementation of the 1987 Action Plan for the Aquatic Environment (Vandmiljøplan in Danish) that prescribed that nitrogen loads to the total aquatic environment should be reduced by 50% and phosphorus loads by 80%. Reductions in the total nitrogen (TN) load have been more modest. Nutrient loading is one of the primary determinants of estuarine nutrient concentration with 70% of the annual variation in TN concentration and 55% of the annual variation in TP concentration explained by variation in the load. Many Danish estuaries have rich communities of macrophytes and benthic filter feeders, such asMytlis edulis andCiona intestinalis, that can control water column chlorophyll concentrations by their filter feeding activities. Many of the estuaries experience hypoxia and anoxia, especially during warm and calm summer months. Further reductions in nutrient loading are expected following implementation of the Action Plan for the Aquatic Environment II, with predicted improvements in oxygen concentrations and in the functioning of these shallow, dynamic estuarine systems.  相似文献   
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Seasonal water storage in high-elevation alpine catchments are critical sources of water for mountainous regions like the western U.S. The spatial distribution of snow in these topographically complex catchments is primarily governed by orography, solar radiation, and wind redistribution. While the effect of solar shading is relatively consistent from year-to-year, the redistribution of snow due to wind is more variable – capable of producing snowpacks that have varying degrees of uniformity across these hydrologically-important catchments. A reasonable hypothesis is that a warmer climate will cause snowfall to become more dense (i.e. wetter and heavier), possibly leading to less wind redistribution and thus produce a more uniformly distributed snowpack across the landscape. In this study, we investigate the role of increasingly uniform spatial snowpack distributions on streamflow generation in the Green Lakes Valley Niwot Ridge Long Term Ecological Research station, within the headwaters of the Boulder Creek watershed in Colorado. A set of idealized hydrologic simulation experiments driven by reconstructed snowpacks spanning 2001–2014 show that more a more uniform spatial snowpack distribution leads to an earlier melt-out of 31 days on average and tends to produce less total streamflow, with maximum decreases as large as 7.5%. Isolating the role of snowpack heterogeneity from melt-season precipitation, we find that snowpack uniformity reduces total streamflow by as much as 13.2%. Reductions in streamflow are largely explained by greater exposure to solar radiation in the uniformly distributed case relative to a more heterogeneous snowpack, with this exposure driving shifts towards earlier snowmelt and changes in soil water storage. Overall, we find that the runoff efficiency from shallower snowpacks is more sensitive to the effects of uniformity than deeper snowpacks, which has potential implications for a warming climate where shallower snowpacks and enhanced sensitivities may be present.  相似文献   
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Geografisk Tidsskrift—Danish Journal of Geography 110(2):143–154, 2010

Inuit have travelled to and settled in the coastal landscapes of Northeast Greenland for several longer periods during the latest ca. 4500 years. Most recently the Thule culture Inuit lived in the region from around 1400 until 1850 AD. The access to partly and periodically ice covered near coastal waters has been crucial to the primarily marine based subsistence strategy of the Thule Inuit culture, and their settlements are therefore found immediately at the coast. Changing geological and geomorphologic settings strongly influence the coastal morphodynamics, and only specific locations offer stable and protected conditions needed for proper winter settlements. The comprehensive study of coastal environments and Thule culture winter settlements in the Young Sound region show an accumulation of winter settlements, nearly all located either in protected pocket beaches or on stable basalt capes. The Thule culture abandoned Northeast Greenland about 1850 AD, and apart from settlements on basalt capes, most of the winter settlement sites in pocket beach areas have been affected by erosion of local character and in some cases also affected by increasing wave erosion during recent periods of less ice in near coastal waters.  相似文献   
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The Niwot Ridge and Green Lakes Valley (NWT) long-term ecological research (LTER) site collects environmental observations spanning both alpine and subalpine regimes. The first observations began in 1952 and have since expanded to nearly 300 available datasets over an area of 99 km2 within the north-central Colorado Rocky Mountains that include hydrological (n = 101), biological (n = 79), biogeochemical (n = 62), and geographical (n = 56) observations. The NWT LTER database is well suited to support hydrologic investigations that require long-term and interdisciplinary data sets. Experimentation and data collection at the NWT LTER are designed to characterize ecological responses of high-mountain environments to changes in climate, nutrients, and water availability. In addition to the continuation of the many legacy NWT datasets, expansion of the breadth and utility of the NWT LTER database is driven by new initiatives including (a) a catchment-scale sensor network of soil moisture, temperature, humidity, and snow-depth observations to understand hydrologic connectivity and (b) snow-albedo alteration experiments using black sand to evaluate the effects of snow-disappearance on ecosystems. Together, these observational and experimental datasets provide a substantial foundation for hydrologic studies seeking to understand and predict changes to catchment and local-scale process interactions.  相似文献   
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In arid and semi-arid regions, many rivers experience extremely low flow conditions during seasonal dry periods. During these times, effluent from wastewater treatment plants can make up the majority of flow in the river. However, water quality in urban systems can also be strongly influenced by the natural or human-influenced flow regime and discharge from other anthropogenic sources such as industrial operations and runoff from impervious surfaces. In this study, we aimed to determine whether water quality was controlled primarily by wastewater discharge in an effluent-dominated river. Between May 2016–May 2019, we systematically measured water temperature, pH, dissolved oxygen, biochemical oxygen demand, and the concentrations of nitrate-N, ammonia-N, and orthophosphate in the South Platte River in the Denver metropolitan area, Colorado, USA. We found that, despite being an effluent-dominated river, wastewater treatment plant discharge was not the principal factor controlling water quality in many of the sampled areas. Non-point source pollution from impervious surfaces, delivered to the river through storm drains and minor tributary streams, also contributed to the high nutrient conditions in several locations. We also noted a strong seasonality in water quality, with higher concentrations of nutrients and higher biochemical oxygen demand in the winter months when wastewater effluent can make up more than 90% of the flow in the river. Thus, the interaction of discharge location and reduced seasonal flow produced spatio-temporal hot spots of diminished water quality. More stringent enforcement of water quality regulations may improve water quality in this system. However, a large portion of the pollution seems to be from non-point sources, which are very difficult to control.  相似文献   
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A relative sea‐level curve over the Holocene is constructed for the Young Sound region in northeastern Greenland. The reconstruction is derived by dating the heights of raised beach ridges in coastal plains using optically stimulated luminiscence (OSL), and by dating palaeoterrestrial surface levels now buried beneath the intertidal frame using the 14C technique. The relative sea‐level curve reveals a rapid fall of at least 10 mm a?1 from ca. 9500 to 7500 a ago, which slowed to 2 mm a?1 until it reached the present sea level ca. 3000 a ago. This part of the curve is based on the raised beach ridge data. Thereafter, relative sea level continued to fall, to reach a minimum level at about 0.5 m below the present sea level ca. 2300 a ago. Since then, relative sea level has experienced a slow rise of about 0.2 mm a?1. This part of the curve uses the data from the palaeoterrestrial surfaces. The study supplements other estimates of Holocene relative sea‐level changes and supports the observations of a decreasing trend in the timing of the cross point and in minimum relative sea level from South to North Greenland. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
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