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Simpósio 6 - Oportunidades e desafios da expansão florestal e renaturalização da paisagem pós-abandono agrícola Localização: Sala A1.13 Moderação/coordenação de sessão: Lien Imbrechts Moderação/coordenação de sessão: João C. Azevedo | |
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Effects of artificial canopy gaps on holm oak regeneration in dryland afforestations 1: CIBIO, Research Center in Biodiversity and Genetic Resources, InBIO Associated Laboratory, Campus de Vairão, Universidade do Porto, 4485-661 Vairão, Portugal; 2: CIBIO, Research Center in Biodiversity and Genetic Resources, InBIO Associated Laboratory, Instituto Superior de Agronomia, Universidade de Lisboa, Lisboa, Portugal; 3: Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, 4099-002 Porto, Portugal; 4: BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Campus de Vairão, 4485-661 Vairão, Portugal; 5: BOKU, University of Natural Resources and Life Sciences, Gregor-Mendel-Straße 33, 1180 Vienna, Austria; 6: Biological Station of Mértola, Rua Professor Baptista nº 1, 7750-360 Mértola, Portugal; 7: Migratory Bird Center, Smithsonian Conservation Biology Institute, National Zoological Park, 3001 Connecticut Ave NW, Washington, DC 20008, USA Holm oak (Quercus rotundifolia) naturally regenerates in the understory of stone pine (Pinus pinea) and eucalypt (Eucalyptus camaldulensis) plantations in southern Portugal, offering an opportunity to test the creation of canopy gaps as a technique for assisting natural regeneration in degraded forest patches. The responses of holm oak plants have been explored in a manipulative experiment, started in 2023, using a Before-After Control-Impact (BACI) design involving replicates of 20x20m plots for each of two restoration treatments (logging and thinning) and a control implemented in both pine and eucalypt plantations. It is expected that canopy-thinning optimizes light availability for the growth of holm oak recruits, while protecting them from environmental extremes that can risk their development. Over three years, we monitored the survival and growth of holm oak individuals under varying light conditions. Preliminary results show distinct regeneration patterns between the two plantation types. In stone pine stands, moderate thinning yielded the highest survival rate of holm oak individuals (98%), though differences were not statistically significant. However, this treatment showed significantly lower growth rates among seedlings, while saplings exhibited the opposite trend. In eucalypt plantations, the survival and growth of seedlings and saplings showed no significant differences among treatments. In 2024, an additional trial was established in the same experimental areas, where 100 acorns were cached per plot to assess the influence of treatments on germination. In the germination trials, moderate thinning resulted in the highest seedling emergence (50%) in pine areas with high significance. While increased canopy openness also had a positive effect on germination in eucalyptus stands, the differences were not significant. Our results demonstrate how holm oak regeneration responds to the creation of canopy openings in different contexts and how gap size influences its dynamics. These findings inform thinning operations that can optimize light conditions while reducing environmental stress, providing insights into assisted natural regeneration as a viable strategy for restoring afforested landscapes in semi-arid regions. | |