Effect of Tree Shelters and Regeneration Method on Survival and Growth of Cork Oak Plantations in the Maamora Forest, Morocco

Background

Forest managers often favor natural regeneration for its low cost, ecological benefits, and ability to conserve genetic diversity. However, unreliable fruiting patterns, unpredictable climate, and herbivory often hinder its success. Managers address these challenges by incorporating assisted and artificial regeneration, which involves removing growth barriers or actively planting seeds and seedlings. In Morocco, cork oak (Quercus suber) forests, particularly the Maamora forest—the world’s largest continuous lowland cork oak forest—experience significant degradation due to drought and human pressures, prompting the need for strategies that combine assisted and artificial regeneration. One effective measure is using tree shelters to create a favorable microenvironment for seedlings and protect them from herbivory. However, researchers have primarily studied tree shelters' short-term outcomes, leaving their long-term effects unexplored.

Goals and Methods

This study examines the long-term effects of tree shelters on cork oak plantations in Morocco, focusing on seedling survival and growth under different regeneration methods. The goal is to develop effective strategies for restoring cork oak forests in areas with intense human-animal interactions. The researchers used a split-plot design to compare direct seeding and seedling planting in the Maamora Forest. Over eight years (2010–2018), they measured seed germination, plant survival, and growth parameters annually until 2015, when they opened the tree shelters.

Conclusions and Takeaways

The study showed that tree shelters improve cork oak survival, particularly for direct-seeded plants. While tree shelters promote early height growth, their effects diminish in later seasons and have minimal long-term impact on radial growth. The researchers found that direct seeding outperformed seedling planting, yielding higher survival and growth rates. These findings highlight the combined importance of tree shelters and regeneration methods for successful cork oak restoration in the Maamora Forest. The authors recommend conducting longer-term studies to assess the sustained impacts of tree shelters, exploring their influence on above- and belowground processes, and evaluating their scalability for large-scale reforestation. They also suggest comparing tree shelters to alternative protective measures, such as fencing, to optimize regeneration strategies.