Three hundred years of spatio-temporal development in a primary mountain Norway spruce stand in the Bohemian Forest, central Europe

Abstract

The model of developmental dynamics has grown in recent years to include the role of disturbances, but few studies have examined fine-scale spatio-temporal dynamics. We present a unique study from mountain Norway spruce (Picea abies (L.) Karst.) forests in central Europe to evaluate the role of disturbances in spatio-temporal tree distribution patterns.We established three one-hectare permanent study plots (PSP) in an old-growth mountain Norway spruce forest in a strictly protected nature reserve in central Europe. We mapped the spatial positions of all trees >1.3m in height and extracted increment cores of all canopy trees >6m in height. Disturbance chronologies were reconstructed based on dendroecological approaches indicating disturbance events from: (1) abrupt increases in radial growth (release) and (2) intensive juvenile growth (open canopy recruitment). Spatio-temporal patterns were detected using Moran’s I.Recruitment and canopy accession were discontinuous over time. Synchronous radial growth release events were observed during 1750–1770 and 1810–1830 and synchronous new recruitment was observed in 1770–1800. Most of the detected disturbances could be associated with historical records of strong winds or bark beetle outbreaks of moderate severity. Most trees ascended into the canopy via open canopy recruitment and many formed distinct patches (about 20–50m in diameter) with a similar date of canopy accession.Our study provides evidence of a mixed historical disturbance regime including large-scale infrequent moderate intensity disturbance combined with frequent low severity events. These disturbances created large-scale synchronous periods of recruitment and canopy accession. The resulting developmental model indicates a complex spatio-temporal pattern of tree death and establishment across a large range of patch sizes. For ecologically based management systems we suggest the application of mixed harvest intensities at different spatial and temporal scales to better replicate natural disturbance patterns and associated legacies.