Autor:innen:
Dr. Kenton Stutz | Albert-Ludwigs-Universität Freiburg, Professur für Bodenökologie | Germany
Dr. Klaus Kaiser | Martin-Luther-Universität Halle-Wittenberg, Bodenkunde und Bodenschutz | Germany
Prof. Dr. Bruno Glaser | Martin-Luther-Universität Halle-Wittenberg, Bodenbiogeochemie | Germany
Lilian Benz | Albert-Ludwigs-Universität Freiburg, Professur für Bodenökologie | Germany
Prof. Dr. Friederike Lang | Albert-Ludwigs-Universität Freiburg, Professur für Bodenökologie | Germany
Formation of soil organic matter (SOM) occurs through input of litter that is partially transformed and translocated by soil (micro)organisms and environmental components (e.g., fire and percolating water). However, it is still unclear how more SOM can be sequestered. We hypothesize that SOM forms at ecosystem scales through pulses and patches of disturbance. Namely, disturbance alters SOM stocks when disrupted components of soil-forming factors—e.g., fauna, trees, deadwood, boulders, canopy gaps, gullies—cause change in inputs, transformation, translocation or losses of SOM to differ. For example, when windthrow induces a pulse of deadwood, SOM stocks increase if rates of deadwood transformation and translocation into soil are higher than CO2 losses to the atmosphere. Resulting patches of SOM persist unless heterotrophs adapt to the new conditions or another disturbance occurs. When soil-forming factors and disturbances move within ecosystems, converging patches of SOM may homogenize most of the original patchiness.
Persistent markers sensitive to biological, resource and environmental disturbances would provide evidence of patchy SOM formation. Promising markers are lignin-derived phenolic compounds due to their ubiquity in litter and soil, differences between plant species and litter type, affinity for various minerals and multiple biotic and abiotic transformation pathways. Lignin-derived phenolic compounds indicate that wood-derived organic matter is bioturbated into mineral soil next to woody debris, and distinct lignin-derived phenolic compounds can indicate whether deadwood underwent white or brown rot. Lignin-derived phenolic compounds of other disturbance and degradation pathways are still unknown. For instance, lignin can be degraded by ultraviolet and visible light, a process known as photo-degradation, the products of which may differ from those of biological degradation. As such, lignin-derived markers could serve as means to evaluate the persistence and resilience of SOM to future disturbance and to elucidate what ecological mechanisms sequester more SOM.