Résumé - CAFD


Gap dynamics of late successional sugarmaple–yellow birch forests at their northern range limit.

Tiphaine Després, Hugo Asselin, Frédérick Doyon, Igor Drobyshev, Yves Bergeron.

Questions

We investigated whether the gap disturbance rate (percentage area disturbed by canopy gaps per year) differed at the northern range limit of sugar maple (Acer saccharum)–yellow birch (Betula alleghaniensis) forests compared to broad-leaf temperate deciduous forests located more to the south. As an ancillary question, we assessed the relationship between species composition and gap disturbance rate at the stand scale.

Location

Late successional sugar maple–yellow birch forests at their northern range limit in western Quebec, Canada.

Methods

To reconstruct past gap disturbances, we identified growth releases using the boundary line method applied to tree-ring chronologies obtained from 0.25-ha plots sampled within 11 late successional forest stands. We reconstructed past canopy gaps using release events, calculated historical gap disturbance rates and used redundancy analysis to evaluate the relationship between gap disturbance rate and species composition at the stand scale.

Results

The mean gap disturbance rate across the 11 late successional stands was 0.96 ± 0.51%·yr−1. Mean gap size was 39 ± 44 m2 and almost 85% of the gaps were <50 m2. Stands with smaller gaps and lower gap disturbance rates had high importance values for balsam fir (Abies balsamea) and/or yellow birch.

Conclusions

The gap disturbance rate at the northern limit of sugar maple–yellow birch forest was similar to that reported in broad-leaf temperate deciduous forests located ca. 575–1300 km to the south. However, gaps were more numerous and smaller, which could be related to latitudinal differences in allometric traits of the dominant tree species and climate.