Plant–soil feedbacks mediated by humus forms: A review

The present review was undertaken to add more information on the place taken by humus forms in plant–soil interactions. Three questions were asked: (i) are humus forms under the control of plant–soil relationships, (ii) are humus forms the main seat of these relationships, and (iii) can humus forms explain interactions between aboveground and belowground biodiversity. Some conflicting views about humped-back models of species richness may be resolved by considering a limited number of stable humus forms (here considered as ecosystem strategies) which should be treated separately rather than in a single model. Mull, moder and mor pathways are each characterized by a fine tuning between aboveground and belowground communities, the humus form (including litter) being the place where resonance between these communities takes place, both in functional and evolutionary sense.