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Climate variability effects on productivity of a cork oak woodland

Publication . Bicho, Maria Catarina Gomes Pedro; Costa e Silva, Filipe Miguel de Carvalho; Correia, Alexandra Cristina Pires; David, Jorge Soares

Trees, herbs and shrubs are the “engines” of the cork oak ecosystem productivity. Although climate have an impact on each compartment productivity, the system is intrinsically linked with human presence and management practices which interfere with the ecosystem responses to environmental stresses. Herbaceous layer and shrubs are very well adapted and responsive to these variations, but trees productivity is strongly associated with the amount of leaves produced which results from a complex interaction between climate, phenology and accumulated reserves. Long-term monitoring sites located in representative areas allows to consolidate the knowledge on these processes because they offer the opportunity to understand the cycles of decline and recovery after disturbance. This knowledge is essential to support management decisions that must be adaptive under a paradigmatic economic and climate change scenario. This work was carried out in a cork oak forest in the central region, where continuous data was collected over nine years and in two vegetation strata: herbs and trees. Herbaceous production in the monitored improved pasture was 8 times higher than in the natural pasture, due to initial fertilization and legume-rich seed mixtures used. The accumulated rainfall from February to May was determinant in both systems. Drought increased the proportion of grasses and reduced the legumes with the natural pasture showing a higher drought resilient tendency. The pattern of production and fall of leaves, flowers, acorns and radial growth of trees was assessed in contrasting years. Leaf production decreased with reduced accumulated rainfall from autumn/winter prior to budburst but the acorn mast years were determinant in this reduction suggesting a competitive interaction between reproductive and vegetative growth. Dry winters/springs led to an anticipation of the maximum seasonal cork growth rate by approximately 2 months compared to wet years. Dry years strongly reduced phellogen activity and radial growth.

2024-06-05Doctoral thesis

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