The effects of anthropogenic impact on plant and soil cover in Mongolia.
Under the prevailing variable natural conditions nomadic pastoralism was the most suitable form of land use in Mongolia and the neighboring countries in the past. Furthermore, small areas were used for agriculture in some regions. Therefore, anthropogenic influence was present throughout history. In the forest steppe zone this led to the disappearance of forest sites which then gave way to meadow steppe. The severe impact on the natural pastures by continuous increase of livestock herding and other human activities was perceptible during the socialist period. But since the 1990s, after the transition to market economy, this impact has increased greatly and a great number of degradation features and irreversible damages in the plant and soil cover can be observed now. Especially in the vicinity of the Mongolian capital Ulaanbaatar, along the north-south road corridor from Russia to the Chinese border, but also in some western regions of the country herders concentrate their livestock in search for better marketing opportunities. Especially there, the vegetation in vast areas is overgrazed by biting and trampling to such an extent that its regeneration is endangered. Degraded and devastated pasture types with a decrease of valuable forage plants and a high increase of ruderal elements can be found in these grasslands. Characteristic sequences of pasture degradation are presented here. The degradation effects steppes and desert steppes as well as reed, mire, and meadow vegetation in the river valleys and lowlands. In the desert regions saxaul vegetation is especially threatened. In some cases after degradation of the plant cover these degradation processes effect soil cover, too. Impacts on soil cover caused by ploughing of virgin land, by ploughing of long term used arable land, and by irrigation are the main reasons for soil degradation. Also recreational activities in the vicinity of settlement centers and traffic along the tracks lead to detrimental vegetation and soil cover changes. Unsystematic forest clearing goes on at a high level and often results in irreversible soil degradation.
Wandel und Kontinuität in der mobilen Tierhaltung der Mongolei
Die Mongolei gehort weltweit zu denjenigen Landern, wo die mobile Tierhaltung eine bedeutende Rolle spielt. Seit dem Ende des Sozialismus hat sich in der mobilen Tierhaltung ein tief greifender Wandel vollzogen. Anfang der 1990er Jahre wurden die kollektiv gehaltenen Tierbestande der viehwirtschaftlichen Vereinigungen (Negdel) privatisiert und an alle Mitglieder verteilt. Viele so genannte ?neue Nomaden? nahmen die mobile Tierhaltung auf. Es werden die Hintergrunde und Kennzeichen des jungen Wandels und die Hauptprobleme in der mobilen Tierhaltung der Mongolei aufgezeigt. Weiterhin werden neue, unter marktwirtschaftlichen Bedingungen entstandene Formen raumlich-sozialer Organisation dargestellt. Die Autoren kommen zu dem Schluss, dass landliche Regionalentwicklung nur durch einen holistischen Ansatz ereicht werden kann. Verringerung der Tierzahlen, Einfuhrung neuer rechtlicher Regelungen zur Erreichung eines okologisch angepassten Weidemanagements, Aufbau von tierische Produkte verarbeitenden Betrieben sowie Ausbau der technischen und sozialen Infrastruktur sind wichtige Ziele, deren Erreichung eine dauerhafte Entwicklung im landlichen Raum und damit die Kontinuitat der mobilen Tierhaltung in der Mongolei auch in Zukunft gewahrleisten konnte.
Frequency distributions of the mixing height over an urban area from SODAR data
The height of the mixing-layer (MLH) is an important parameter in the assessment of the dilution of primarily emitted or secondarily formed air pollutants in the atmospheric boundary-layer. A continuous measurement of MLH is possible only by remote sensing. Here, 17 months of SODAR data have been analysed automatically to derive the MLH over the city of Hannover in Northern Germany. In contrast to earlier studies the MLH has been determined from vertical profiles of the acoustic backscatter intensity and from the variance of the vertical velocity component. The results are presented in form of monthly frequency distributions and mean daily courses of MLH. These statistical evaluations of MLH show a clear annual course and interannual variability. The study shows the possibility to derive meaningful climatological information from long-term SODAR measurements for air quality issues.