Multispectral remote sensing data and digital elevation models were used to examine the spatial and temporal evolution of the New Lakes of Sahara in southern Egypt. These lakes appeared in September 1998, when water spilled northwestward toward the Tushka depression due to an unusual water rise in Lake Nasser induced by high precipitation in the Ethiopian Highlands. Five lakes were formed in local depressions underlain by an impermeable Paleocene shale and chalk formation. The lakes developed through three stages. (1) A rise stage occurred from September 1998 to August 2001; the area covered by the lakes reached ~1586 km 2 . In this stage the rate of water supply far exceeded the rate of water loss through evaporation. This stage was characterized by an early phase (August 1998-August 1999) when the area covered by the lakes increased by ~75 km 2 /month. This was followed by a late phase (August 1999-August 2001), in which area increase averaged ~28 km 2 /month. (2) A steady-state stage occurred from August 2001 to August 2003, during which the area covered by the lakes remained relatively unchanged and water lost through evaporation was continuously replaced by water supply from Lake Nasser. (3) A demise stage occurred from August 2003 to April 2007, during which water supply from Lake Nasser stopped completely and water was continuously evaporating. The area covered by the lakes decreased to ~800 km 2 with an average loss of ~17 km 2 /month. If this trend continues, the New Lakes of Sahara will disappear completely by March 2011. The spatial distribution of the New Lakes of Sahara is strongly controlled by morphologically defi ned east-, north-, northeast-, and northwest-trending faults. The water recharge of the Nubian aquifer by the New Lakes of Sahara is insignifi cant; much of the lakes' area is above an impermeable formation.

No abstract

The mapping of geology is conventionally done visually in a hands-on fashion, and the data are recorded in a fi eld book or with photography. An alternative technique that combines refl ectorless laser rangefi nders or high-speed terrestrial laser scanners, global positioning system, and the Environmental Systems Research Institute (ESRI) ArcGIS software platform has been developed that is effective for mapping geology at a distance and in three dimensions. Portable handheld refl ectorless lasers are used to capture geologic features such as contacts and terrain and can be combined with digital elevation models in ArcGIS software. Fast terrestrial laser scanners capture an entire exposure at the detail and accuracy of (3D) photorealistic (virtual) models with the additional color information from image pixels. This latter method is expensive and complicated and requires signifi cant amounts of fi eld and processing effort. The laser gun approach is simple, portable, and cost effective. When integrated with ESRI ArcGIS software and a module, such as our recently developed ArcGIS extension 3DLT (laser tool), a simple yet sophisticated platform exists for mapping, visualizing, and analyzing outcrops in real time in the fi eld. The potential of laser mapping is demonstrated in the Paleozoic outcrops of a structural geology teaching site in the Slick Hills, Oklahoma. Fast laser scanning and digital photography are used to build a 3D photorealistic model of an area of the anticline. The 3DLT is used for mapping specifi c detailed features such as contacts and faults. Three-dimensional quantitative information can be extracted from the geology with these methods. A laser rangefi nder combined with 3DLT can image and display terrain and outcrop features in the fi eld, in real time. Mapping with fast scanners requires several steps in processing of the point cloud data utilizing a variety of sophisticated and expensive software, but can capture an entire outcrop, such as a mountainside. The resulting model then can be analyzed in the lab. When combined with digital photography, virtual photorealistic models derived from point clouds can be even more effectively analyzed. The most appropriate method for digitally mapping geology depends on a variety of issues, such as cost, time, complexity, portability, and the project goals.

Sustainable agriculture management typically requires detailed characterization of physical, chemical, and biological aspects of soil properties. These properties are essential for agriculture and should be determined before any decision for crop type selection and cultivation practices. Moreover, the implementation of soil characterization at the beginning could avoid unsustainable soil management that might lead to gradual soil degradation. This is the only way to develop appropriate agricultural practices that will ensure the necessary soil treatment in an accurate and targeted way. Remote sensing and geophysical surveys have great opportunities to characterize agronomic soil attributes non-invasively and efficiently from point to field scale. Remote sensing can provide information about the soil surface (or even a few centimeters below), while near-surface geophysics can characterize the subsoil. Results from the methods mentioned above can be used as an input model for soil and/or soil/water interaction modeling. The soil modeling can offer a better explanation of complex physicochemical processes in the vadose zone. Considering their potential to support sustainable agriculture in the future, this paper aims to explore different methods and approaches, such as the applications of remote sensing, geophysics, and modeling in soil studies.

Spatial simulation models of seed dispersal have been constructed at the landscape level under the assumption of ubiquitous or uniform dispersibility. The anisotropic nature of vegetation distribution caused by different dispersal agents such as wind, gravity, water and animals were ignored. We propose a prototype of a GIS-based spatially explicit model of dispersal agent behavior (SEMODAR) to simulate the seed dispersal process by considering the unique behavioral characteristics of each seed dispersal agent. As a result, the influence of dispersal agent behavior on the species coexistence in competitive communities with and without habitat destruction could be explored. The model consists of four module components: dispersal rules, species competition, species colonization, and habitat destruction. An experimental simulation was conducted using three hypothetical species with differing competitive and migration abilities in both intact and disturbed conditions for 250 years. The findings of this study support the theoretical expectation that inferior competitors can coexist with superior competitors given that the inferior competitors have efficient colonization ability. The simulation also reveals the important role of agent behavior in the seed dispersal process and the biased impact of environment fragmentation on superior competitors that are not superior dispersers. #