The structural dynamics of managed uneven-aged conifer stands in the Italian eastern Alps

Abstract

The development of close-to-nature silvicultural systems is a major challenge facing modern silviculture. Despite these systems are partly based on natural “self-regulation”, they are not easy to achieve in practice. In this context, a better understanding of the structural dynamics of stands managed with close-to-nature silvicultural systems is important for their correct application. In uneven-aged coniferous stands of Cadore (in Italy’s eastern Alps), a close-to-nature silvicultural approach, ranging from single-tree selection cutting to irregular shelterwood, has produced irregular structures even at small spatial scales. In a representative selection of these stands we analysed the structural dynamics, both in space and in time, in six different plots (1.5 ha in total, between 1400 and 1450 m a.s.l.), by distinguishing four different developmental phases (innovation, early aggradation, late aggradation and biostatic). Each phase was characterised for: average duration in time, total area, number of trees of different heights and PPFD (photosynthetic photon flux density) in the understorey. Because of the relatively frequent and moderate harvests, the structural dynamics of the examined forest is characterised by an extremely fine-grained shifting mosaic and by a relatively short cycle as compared to natural or near-natural forests. The pattern of seedling recruitment in the different phases follows the pattern of light availability in the understorey, which decreases from the innovation to the late aggradation phase and then slightly increases in the biostatic phase, and suggests an important role of the advance regeneration for the maintenance of the current silvicultural equilibrium. As the area covered by each developmental phase is close to being proportional to its duration in time, the examined forest appears close to a structural steady-state.