LOESS DEPOSITS AS CARBON SINKS: SEQUESTRATION OF CARBON VIA THE CHERNOZEMISATION PROCESS

Chernozem soils appear to favour loess ground as a preferred medium for development. There seems to be a close link between loess and chernozems. The growth of a chernozem in a fresh loess deposit provides an observable and comprehensible method for observing the sequestration of carbon in a soil system. The chernozem (the classic black earth; subsumed into the USDA Soil Taxonomy Mollisol Soil Order) was believed by its first definers to be essentially climate controlled. We believe that, on the analysis of soil forming factors, parent material is more likely to be the defining factor. Loess first, then chernozem (not the other way round as Pyaskovskii suggested). So, ten thousand years ago a loess deposit forms, in a medium latitude location. It has soil qualities as soon as it is formed and the chernozem development process develops immediately. It is essentially a top-down process; rainfall slightly exceeds evapotranspiration, and carbonaceous material builds up steadily; sequestration begins. Eventually small carbonate is deposited at greater depths but the basic sequestration mechanism is the chernozemisation process; the least well defined of the soil science processes. In fact, although chernozemisation falls within the purview of soil science the key control is geological- the delivery of the loess. Nothing really significant is seen through the soil science window- except the build-up of carbon. The arrival of the loess gives a zero point, carbon content per soil unit is measureable, as is depth of deposit. The transition from geology to soil science can be dated- and we have an ideal measure of sequestration rate, in the perfect soil. At this point we have to divide the incoming rate into all factors- and learn to recogise the atmospheric CO2 contribution.