Testing Hypotheses at Scales beyond Micro: Striving for Relevance.

Current research reflects a persistent inadequacy in scaling up successes in the description of soil biological processes at microscopic or soil profile scale to a regional or global – more relevant - scale. Incidentally, research funding seems more likely towards projects that promise the application of a new molecular biology tool in soil biology rather than towards proposals addressing larger scale issues. In this presentation, I will highlight a number of examples, showing a striking discrepancy between our understanding of a process at the micro-scale and the lack thereof at a larger scale.

First I will focus on the actual interest in the dynamics of dissolved organic matter (DOM) and its role on carbon fluxes between the terrestrial and aquatic ecosystems and the atmosphere. At lab and lysimeter scale, significant progress has been made to unravel the relations between origin and quality of the DOM measured in soil solution or in water leaving the vadose zone. Yet, so far we have failed to deliver a good understanding of the dynamics and quality of DOM in surface waters at regional and even less so at global scales.

Similarly, most carbon sequestration studies rarely address issues at scales larger than a field plot. Hence very often misleading conclusions are drawn. Reduced tillage is conventionally considered as benign for organic matter conservation. However, when the relations between erosion and carbon sequestration are analyzed at the scale of a watershed, positive feedback effects on carbon storage rather than carbon losses due to erosion are observed.

Spatial analysis of soil processes and parameters is nevertheless very popular. New methods of soil analysis allow insights in its three-dimensional architecture hitherto never attainable. GIS tools, powerful ecosystem models, terrestrial biomarkers, stable isotope techniques and powerful statistical analysis enable scientists to perform extrapolations for more relevant conclusions.