A tree-ring reconstruction of wind disturbances in a forest of the Slovakian Tatra Mountains, Western Carpathians

Question: Have past windstorm events influenced the structure and composition of mountain forests in the Tatra Mountains? Can severe and infrequent wind disturbances lead to dynamic coexistence of two tree species with different ecological requirements? Location: Subalpine mixed spruce-larch forest at 1200-1300 m a.s.l. in the Slovakian Tatra Mountains. A forested site affected by catastrophic large-scale windthrow on 19 November 2004. Methods: Sixty-seven spruce and 30 larch cross-sections from the oldest cohorts were collected in a regular pattern in a 100-ha plot. Tree-ring series were analysed to reconstruct growth releases associated with past windthrows. A boundary-line release criterion was applied to detect disturbance year. Spatial patterns of release signals were statistically detected with Mantel's test. We compared reconstructed years of disturbance events with historical records. Results: Releases in both species showed three main pulses. More than 85% showed major or moderate releases in 1865-1879, 48% in 1915-1924, and 25% in 1940-1949. All of these disturbance events affected the whole 100-ha area. Releases were spatially patterned in the first disturbances, but distributed randomly in the last. Releases co-occurred in time with enhanced production of compression wood, suggesting disturbances were of wind origin. Reconstructed dates of windthrows were confirmed using historical data on storms. Conclusions: At least three windthrows of major and moderate severity took place in the last 150 years on southern slopes of the Tatra Mountains. This disturbance regime may contribute to coexistence of spruce and larch through differences in vulnerability and response to heavy windstorms.