Aller au contenu principal

page search

Displaying 829 - 840 of 2218

importance of wetlands in the energy balance of an agricultural landscape

Journal Articles & Books
Décembre, 2014

Energy fluxes, including net radiation, latent heat flux and sensible heat flux were determined on clear days during the vegetative period in four types of land cover: wet meadow, pasture, arable field, and an artificial concrete surface. The average net radiation ranged between 123� W� m⁻² at the concrete surface and 164� W� m⁻² at the wet meadow. The mean maximum daytime latent heat ranged between 500 and 600� W� m⁻², which corresponds to an evapotranspiration rate of about 0.2� g� m⁻²� s⁻¹ under the prevailing conditions of the wet meadow.

Sampling for landscape elements—a case study from Lower Saxony, Germany

Journal Articles & Books
Décembre, 2014
Allemagne

The estimation of coverage, i.e., the proportion of the total area in a study region covered by a given target class, is essential to many aspects of environmental monitoring. We analyze and compare the efficiency of different sample-based approaches for the estimation of coverage of different land cover classes from aerial imagery in a case study in Lower Saxony, Germany on the basis of the estimated standard errors.

Invasive grasses change landscape structure and fire behaviour in Hawaii

Journal Articles & Books
Décembre, 2014
États-Unis d'Amérique

QUESTIONS: How does potential fire behaviour differ in grass‐invaded non‐native forests vs open grasslands? How has land cover changed from 1950–2011 along two grassland/forest ecotones in Hawaii with repeated fires? LOCATION: Non‐native forest with invasive grass understory and invasive grassland (Megathyrsus maximus) ecosystems on Oahu, Hawaii, USA.

Multi-temporal landsat images based on eco-environmental change analysis in and around Chah Nimeh reservoir, Balochestan (Iran)

Journal Articles & Books
Décembre, 2014
Iran

Chah Nimeh reservoirs have served as a water storage facility, especially during droughts over the last three decades. It is also an important wintering site for migratory birds. In this study, thematic mapper time-series data were derived from Landsat images for prolonged droughts that occurred in two satellite images (2002 and 2011). The data derived from these images were used for the detection of changes in land cover and water storage in the reservoirs. First, a vegetation cover map was produced using soil-adjusted vegetation index and field sampling.

Assessing the influence of afforestation with Eucalyptus globulus on hydrological response from a small catchment in northwestern Spain using the HBV hydrological model

Journal Articles & Books
Décembre, 2014
Espagne

Land use change as conversion pasture to forest produces several changes on hydrological cycle. In this paper, we analyse the effects on stream discharge of afforestation of a small watershed devoted to pasture using the HBV hydrological model. Streamflow data obtained over the first 10 years after planting were employed to evaluate the capacity of HBV model to simulate hydrological behaviour of catchment after afforestation. Obtained results indicate that the estimation of streamflow was accurate as reflected by statistics (R² = 0.90, NSC = 0.89 and PBIAS = 0.34).

Mercury proxies and mercury dynamics in a forested watershed of the US Northeast

Journal Articles & Books
Décembre, 2014

Although many studies focus on mercury (Hg) and methylmercury (MeHg) dynamics in streams, challenges remain in identifying the relative importance of land cover and seasonality at regulating Hg and MeHg dynamics at the watershed scale. Developing robust proxies for Hg and/or MeHg determination also remains a challenge. Our study used Hg, MeHg, and dissolved organic carbon (DOC) concentration measurements and various DOC fluorescence indices to characterize Hg and DOC dynamics in a forested watershed of the US Northeast.

Land Cover Mapping for Namdapha National Park (Arunachal Pradesh), India Using Harmonized Land Cover Legends

Journal Articles & Books
Décembre, 2014
Inde

Since last few decades RS-GIS is playing vital role in studying and mapping spatiotemporal responses of land cover, however, as a matter of fact, the mapping outputs largely depend on the expert's/user's preferences because location specific and people specific land cover classification systems are adopted autonomously for image classification in GIS. This may actually lead to an ambiguous definition of a particular land cover type when such different maps are compared at global level.

Evaluating common drivers for color, iron and organic carbon in Swedish watercourses

Journal Articles & Books
Décembre, 2014

The recent browning (increase in color) of surface waters across much of the northern hemisphere has important implications for light climate, ecosystem functioning, and drinking water treatability. Using log-linear regressions and long-term (6–21 years) data from 112 Swedish watercourses, we identified temporal and spatial patterns in browning-related parameters [iron, absorbance, and total organic carbon (TOC)]. Flow variability and lakes in the catchment were major influences on all parameters.

Detection of land cover changes around Lake Mutirikwi, Zimbabwe, based on traditional remote sensing image classification techniques

Journal Articles & Books
Décembre, 2014
Zimbabwe

Land cover changes around Lake Mutirikwi in 1984–2011 were mapped from Landsat images using traditional image classification methods including the maximum likelihood classifier algorithm. The possibility of mapping the coverage and abundance of surface floating aquatic weeds was also tested. Landsat images from 1984, 1995, 2001 and 2011 were used to compute a normalised difference vegetation index (NDVI), which was then used as a proxy for indicating areas infested by surface floating aquatic weeds.

Method for Spatially Explicit Representation of Sub-watershed Sediment Yield, Southern California, USA

Journal Articles & Books
Décembre, 2014
États-Unis d'Amérique

We present here a method to integrate geologic, topographic, and land-cover data in a geographic information system to provide a fine-scale, spatially explicit prediction of sediment yield to support management applications. The method is fundamentally qualitative but can be quantified using preexisting sediment-yield data, where available, to verify predictions using other independent data sets.

Exploring the geophysical and socio-economic determinants of land cover changes in Eastern Mau forest reserve and Lake Nakuru drainage basin, Kenya

Journal Articles & Books
Décembre, 2014
Kenya

Understanding the linkages between the biogeophysical and socio-economic processes that operate at different spatial and temporal scales is important for land cover change mitigation. This study analysed several factors that explained the forest-shrubland conversions, grassland conversions and cropland expansions in Lake Nakuru drainage basin and Eastern Mau forest reserve in Kenya from 1985 to 2011.