Individual-based approach to the detection of disturbance history through spatial scales in a natural beech-dominated forest

QuestionWe connected tree-census and dendrochronological research data (74.2ha) in order to answer the following questions: How do we apply an individual-based approach, which allows us to abandon the traditional patch model, in the research of disturbance history through spatial scales? What is the disturbance history of the natural forest? How do we understand the influence of the Kyrill storm, which affected the reserve on 18 January 2007? How does the disturbance history in dendrochronological records correspond to real disturbances? LocationZofinsky Prales (48 degrees 40N, 14 degrees 42E, 735-830m a.s.l., granite, Czech Republic) MethodsRepeated tree-censuses (>20000 trees) were carried out in 1975, 1997 and 2008. These surveys served as the basis of dendrochronological research, during which 3020 trees were sampled. A boundary line (BL) approach and geostatistical techniques were used to detect disturbance intensity and its spatial pattern. ResultsThe mean disturbance rate was 11.0% canopy loss per decade (maximum 33.7%) in the core zone. Bordering forests were directly affected by humans after 1800. A maximum of nine disturbance events were recorded per tree, but there were also 3% of non-suppressed trees without records of disturbance events. The Kyrill storm represented a singular event in the forest history from the point of view of its exceptional spatial pattern (ranges up to 320.0m), but not from the perspective of disturbance intensity. The relationship between disturbance intensity (y) and the range of spatial autocorrelation (x) can be explained by the equation y=10.6863+0.0783*x (R-2=0.546, P=0.009). The spatial variability of releases 50% of BL corresponds to real disturbance events, while the insertion of weak releases led to the overestimation of range. The frequency of releases was affected by a decrease in air pollution at the beginning of the 1990s. ConclusionsEffects of small-scale disturbances predominate in forest dynamics. Disturbance intensity was often not directly in accordance with the range of spatial autocorrelation. The ecological role of disturbance is therefore biased if disturbance intensity is used as the sole criterion. The results suggest the importance of historical and geographical contingency in ecosystem development.