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Abstract: Determining the drivers of shifting forest disturbance rates remains a pressing global change issue. Large‐scale forest dynamics are commonly assumed to be climate driven, but appropriately scaled disturbance histories are rarely available to assess how disturbance legacies alter subsequent disturbance rates and the climate sensitivity of disturbance. We compiled multiple tree ring‐based disturbance histories from primary Picea abies forest fragments distributed throughout five European landscapes spanning the Bohemian Forest and the Carpathian Mountains. The regional chronology includes 11,595 tree cores, with ring dates spanning the years 1750–2000, collected from 560 inventory plots in 37 stands distributed across a 1,000 km geographic gradient, amounting to the largest disturbance chronology yet constructed in Europe. Decadal disturbance rates varied significantly through time and declined after 1920, resulting in widespread increases in canopy tree age. Approximately 75% of current canopy area recruited prior to 1900. Long‐term disturbance patterns were compared to an historical drought reconstruction, and further linked to spatial variation in stand structure and contemporary disturbance patterns derived from LANDSAT imagery. Historically, decadal Palmer drought severity index minima corresponded to higher rates of canopy removal. The severity of contemporary disturbances increased with each stand's estimated time since last major disturbance, increased with mean diameter, and declined with increasing within‐stand structural variability. Reconstructed spatial patterns suggest that high small‐scale structural variability has historically acted to reduce large‐scale susceptibility and climate sensitivity of disturbance. Reduced disturbance rates since 1920, a potential legacy of high 19th century disturbance rates, have contributed to a recent region‐wide increase in disturbance susceptibility. Increasingly common high‐severity disturbances throughout primary Picea forests of Central Europe should be reinterpreted in light of both legacy effects (resulting in increased susceptibility) and climate change (resulting in increased exposure to extreme events). [ABSTRACT FROM AUTHOR]

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 >1.3 m in height and extracted increment cores of all canopy trees >6 m 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 20–50 m 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. [ABSTRACT FROM AUTHOR]