Breaking the Barrier: Application of Weeding, Exclosure Fencing and Ditching to Overcome Regeneration Failure in a Cutover Pinus densiflora Forest in South Korea.

Achieving sustainable forest management requires addressing regeneration failures that hinder the continuity of many forest functions and services. However, there remains a need to broaden the range of tools available to improve regeneration outcomes in cutover forests facing simultaneous challenges from weed competition, browsing, and excess soil moisture. We herein designed a full factorial experiment involving 2240 directly sown seeds to explore the impacts of weeding, exclosure fencing, and ditching on the near-term (2013-2017) survival and growth, as well as the long-term (2013-2022) structural traits of Pinus densiflora, an evergreen conifer with significant ecological and economic utility in South Korean forests. Our findings demonstrated that combining biannual weeding (2 times year-1 in July and August) with exclosure fencing enhanced near-term seedling survival by over threefold in drained regeneration plots (p < 0.001) and root collar diameter growth by twofold (p < 0.05). Seedlings within exclosures exhibited at least thrice as much height growth as unfenced seedlings by the end of the near-term observation period, regardless of weed management and drainage conditions (p < 0.001). Areas without fences had no surviving seedlings by 2022 and were overrun by weeds from the ground to the midstory. Long-term stem density benefited substantially from biannual weeding and fencing, exceeding that of unweeded controls by more than threefold on average (p < 0.05). Our findings underscore the merits of integrating active restoration strategies, particularly biannual weeding, exclusion fencing, and ditching, to reduce the risk of unsuccessful regeneration in cutover forests exposed to multiple biotic and abiotic stressors.