Soil and landscapes cyclicities / Deforestation and land degradation
Paepe, R. (1990). Soil and landscapes cyclicities / Deforestation and land degradation, in: UniversiTECH 90: Remote sensing techniques and global change research. Seminar 30-31 March 1990. pp. 5 In: (1990). UniversiTECH 90: Remote sensing techniques and global change research. Seminar 30-31 March 1990. Vrije Universiteit Brussel: Brussel. 6 p. abstracts, 19 p. pp., more |
| Abstract | Soils are an integrated part of a landscape. Fossil soils, or better geosoils(palaeosoils), are part of landscapes of the past. Soils are the interphase between changinglandscapes and climatic (atmospheric) conditions. Hence soils and landscape changes areintimately connected with climatic changes.During the Quaternary a number of climatic changes have occurred, respecting anumber of cyclicities which all are differring in both intensity and frequency. Actually one is tomake a distinction between long term, middle term and short term cycles which respectivelycover the time-span of 2.4 million years (Ma) Le. the whole of the Quaternary Period, the last130 000 years, the Last Interglacial - Glacial cycle, and the last 10 000 years covering thetime-span of approximately the current Interglacial (Holocene). During the long term cycle,Interglacial warm humid climatic conditions prevailed and returned approximately everyhundred thousand years. During these Interglacials the vegetation cover, especiallywoodlands, could reach maximum natural expansion over broad land surfaces. This reads inthe geological sections as a sequence of twenty geosoillevels alternating with unweatheredsediments. The latter mostly represent deposits of the cold climatic stages occurring in betweenthe warm stages. During these cold stages forest vegetation naturally decayed into a steppe oreven polar desert and desert conditions. Natural rejuvenation of the forest occurredautomatically during the next warm Interglacial.The Last Interglacial - Glacial cycle provides an interglacial soil only at the beginning of thecycle some 127 000 years ago. Hereafter, during the next and Last Glacial, under prevailingcold conditions, another series of twelve weaker soil levels (interstadials) developed pointing atcyclicities of forty to twenty thousand years.Finally, during the last 10 000 years, which is considered as the current Interglacial, anothertwenty soil levels are developed pointing at cyclicities of 500 years in average.In conclusion forestation and deforestation are naturally bound to several typesof climatic variation which are difficult to distinguish one for another at a given point of thetime scale. Therefore it is difficult to forecast climatic changes inducing natural deforestationand erosion for the future as well as to determine the amount artificial global heating due tomans impact on the climate. |
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