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Journal Articles Forest Ecology and Management Year : 2020

Combining partial cutting and direct seeding to overcome regeneration failures in dune forests

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Abstract

Stand regeneration is a crucial step in the management of many forests and its failure can jeopardize future forest growth and production. Thus, adapting forestry practices to improve seedling establishment is of prime importance to maintain sustainable forest management. In the coastal dune forests of maritime pine in SW France, regeneration failure after clear-cutting has greatly increased in the last decades. The aim of this study was to quantify the different stages involved in the regeneration process (seed rain, germination, survival), and to assess the impact of harvesting methods (partial cutting vs. clear-cutting) and of the use of direct seeding (seeding vs. no seeding) on these stages. We established five trials located in areas with contrasting regeneration statuses (of which two sites were in an area characterized by chronic regeneration failure), and we investigated the effect of the harvesting method and the use of direct seeding in a factorial design. We monitored the seed rain, germination and first-year survival for three years. Due to the transient nature of the seed bank, we found that the seed rain of the previous year was the only possible seed source for tree regeneration, and it increased with the proximity and size of surrounding mature trees. Nonetheless, seed rain did not limit regeneration in these stands. In fact, germination was the bottleneck stage of the regeneration process in all sites because it was short-lived and consequently exposed to failure in case of unfavourable conditions. Once established, seedling death was mainly due to summer drought. Clear-cutting without seeding resulted in severe regeneration failures in 4 out of 5 sites, with the most severe in the failure area. Direct seeding increased seedling emergence only in the first year, while partial cutting had a longer-lasting effect by providing a regular seed supply over several years. Partial cutting also decreased biotic and abiotic stresses through microhabitat modification under the tree canopy, resulting in a higher number of germinations and greater seedling survival. This positive effect was more pronounced in the two sites within the failure area, suggesting that conditions were more stressful in this part of the forests. Consequently, we recommend avoiding clear-cutting in favour of partial cutting in all parts of these forests, and ensuring the maintenance of sufficient forest cover to promote regeneration. Direct seeding could be used in addition to partial cutting to maximize the chances of success, but only in areas where natural regeneration is low.
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Dates and versions

hal-02915058 , version 1 (22-08-2022)

Licence

Attribution - NonCommercial - CC BY 4.0

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Arthur Guignabert, Laurent Augusto, Florian Delerue, Francis Maugard, Céline Gire, et al.. Combining partial cutting and direct seeding to overcome regeneration failures in dune forests. Forest Ecology and Management, 2020, 476, ⟨10.1016/j.foreco.2020.118466⟩. ⟨hal-02915058⟩
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