No / Paleoanthropological studies often center on teeth, not only because these elements are commonly preserved in the fossil record, but because they apparently contain a wealth of information with regard to development, phylogeny, and function. However, despite a plethora of studies, somefundamental problems are still unresolved. For example, while it is recognized that the 3-dimensional arrangement of enamel prisms may hold important information with regard to phylogeny (von Koenigswald and Sander, 1997) and function (Rensberger, 2000), many paleoanthropological studies have thus far relied on investigating enamel microanatomy as a 2-dimensional structure (e.g., Dean et al., 2001 C Dean, M.G Leakey, D Reid, F Schrenk, G.T Schwartz, C Stringer and A Walker, Growth processes in teeth distinguish modern humans from Homo erectus an earlier hominins, Nature 414 (2001), pp. 628¿631. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (120)Dean et al., 2001). This is mainly due to difficulties in visualizing and quantifying the 3-D structure of prisms. In order to overcome these limitations a computer model was developed (Jiang et al., 2003) which attempted to simulate the effects of biophysical processes governing enamel formation in modern humans (adapted from Osborn, 1970). Here we extend our model and present preliminary data on inter-specific variation in prism arrangement among primates. Furthermore, during our work torecreate the 3D microstructure of prismatic enamel it became increasingly clear that there are not only limitations with previous dental growth studies, but that these studies are based on fundamentally different concepts regarding evolutionary processes from those assumed in our approach. These limitations and differences will be highlighted also.

The spring bloom of microalgae within the bottom of sea ice provides a significant contribution to primary production in the Arctic Ocean. The aim of this research was to improve observations of the ice algae bloom using a transmitted irradiance technique to remotely estimate biomass, and to examine the influence of physical processes on biomass throughout the sea ice melt season. Results indicate that bottom ice temperature is highly influential in controlling biomass variability and bloom termination. Snow depth is also significant as it buffers ice temperature from the atmosphere and largely controls transmission of photosynthetically active radiation (PAR). The relationship between snow depth and biomass can change over the spring however, limiting biomass accumulation early on while promoting it later. Brine drainage, under-ice current velocity, and surface PAR in the absence of snow cover are also important factors. Overall this research helps to characterize the spring ice algae bloom in the Arctic by improving in situ biomass estimates and identifying primary factors controlling it.

The spring bloom of microalgae within the bottom of sea ice provides a significant contribution to primary production in the Arctic Ocean. The aim of this research was to improve observations of the ice algae bloom using a transmitted irradiance technique to remotely estimate biomass, and to examine the influence of physical processes on biomass throughout the sea ice melt season. Results indicate that bottom ice temperature is highly influential in controlling biomass variability and bloom termination. Snow depth is also significant as it buffers ice temperature from the atmosphere and largely controls transmission of photosynthetically active radiation (PAR). The relationship between snow depth and biomass can change over the spring however, limiting biomass accumulation early on while promoting it later. Brine drainage, under-ice current velocity, and surface PAR in the absence of snow cover are also important factors. Overall this research helps to characterize the spring ice algae bloom in the Arctic by improving in situ biomass estimates and identifying primary factors controlling it.

The study was conducted at the vicinity of the rural town of Doka in an area of about 55 x 40 km2. The aim of the study was to map and model the influences of the introduction of mechanized rain-fed agriculture and its rapid expansion on the natural vegetation in the southern Gadarif Region. To achieve these objectives the study utilized a series of techniques. Beside the intensive use of remote sensing imagery, interviews with key informants and farmers as well as detailed field surveys were carried out. Multi-temporal analyses of remote sensing imagery showed that during the seventies the average natural vegetation clearing rate increased most rapidly and then began to slow down. Farmers are aware that land degradation, in various forms, is taking place on their cultivated agricultural land. This is based on their perception and the interpretation of indicators such as weed infestation, reduced soil fertility and soil compaction. Continuous cropping, mono-cropping, rainfall shortage and the use of inferior seeds were the main reasons of land degradation indicated by the farmers. Abandonment of agricultural land to restore soil fertility is a common practice among farmers in the Gadarif Region. The study proved that the subsequent natural regeneration of plant species and the vegetation development on abandoned agricultural land are subject to the previous cultivation period and the duration of the fallow. The current regeneration capacity of the abandoned land may not be sufficient to reach full restoration of the previous vegetation climax except for some pockets which received more regenerative resources. Field surveys in conjunction with remotely sensed and topographic data have the potential to explain the restoration and rehabilitation patterns of degraded/abandoned agricultural land to a good extent. The findings of the study seem to be representative not only for the whole Gadarif Region or other areas in Sudan, but also for other regions in the Sahel Zone with similar problems and environmental and social conditions. One of the most practical conservation approaches is to let farmers play an active role in managing their abandoned land. Such management aims to allow for a certain level of use and benefits while maintaining the natural vegetation development on theses area in order to achieve maximal restoration. Although the study investigated the vegetation development in abandoned mechanized rainfed agricultural land, a full understanding of the path-way needs surveys that include more types of abandoned land and investigation of the effects of other local environmental factors (e.g. fire, grazing, distance from forests etc.) for more than one season.

The study was conducted at the vicinity of the rural town of Doka in an area of about 55 x 40 km2. The aim of the study was to map and model the influences of the introduction of mechanized rain-fed agriculture and its rapid expansion on the natural vegetation in the southern Gadarif Region. To achieve these objectives the study utilized a series of techniques. Beside the intensive use of remote sensing imagery, interviews with key informants and farmers as well as detailed field surveys were carried out. Multi-temporal analyses of remote sensing imagery showed that during the seventies the average natural vegetation clearing rate increased most rapidly and then began to slow down. Farmers are aware that land degradation, in various forms, is taking place on their cultivated agricultural land. This is based on their perception and the interpretation of indicators such as weed infestation, reduced soil fertility and soil compaction. Continuous cropping, mono-cropping, rainfall shortage and the use of inferior seeds were the main reasons of land degradation indicated by the farmers. Abandonment of agricultural land to restore soil fertility is a common practice among farmers in the Gadarif Region. The study proved that the subsequent natural regeneration of plant species and the vegetation development on abandoned agricultural land are subject to the previous cultivation period and the duration of the fallow. The current regeneration capacity of the abandoned land may not be sufficient to reach full restoration of the previous vegetation climax except for some pockets which received more regenerative resources. Field surveys in conjunction with remotely sensed and topographic data have the potential to explain the restoration and rehabilitation patterns of degraded/abandoned agricultural land to a good extent. The findings of the study seem to be representative not only for the whole Gadarif Region or other areas in Sudan, but also for other regions in the Sahel Zone with similar problems and environmental and social conditions. One of the most practical conservation approaches is to let farmers play an active role in managing their abandoned land. Such management aims to allow for a certain level of use and benefits while maintaining the natural vegetation development on theses area in order to achieve maximal restoration. Although the study investigated the vegetation development in abandoned mechanized rainfed agricultural land, a full understanding of the path-way needs surveys that include more types of abandoned land and investigation of the effects of other local environmental factors (e.g. fire, grazing, distance from forests etc.) for more than one season.