A short history of agroforestry in Portugal

Tree protection is referred at least in 13th June 1310, where the King D. Dinis forbids thinning in his land by decree. Wood demand for the naval construction in the XIV and XV centuries led to landscape tree depletion, despite the D. Dinis being the mentor of Leiria National Forest still existing nowadays (11,000 ha of maritime pine). In the XV century “slash and burn” already was referred as an overstressed land use practice method in agricultural fields (Lobo, 1903). At that time the textual explicit recognition of existing soil and wood resources depletion already generated some legislation in the XVI century, for example an “Alvará of 3rd October 1565” stating the need for tree planting in agricultural fields. Restauration war (1640-1668) between Portugal and Spain, led to cultivated land abandonment, promoting shrubland development and tree natural regeneration. In the XVIII century starts the charcoal business and in the XIX century this market reaches the highest prices with Industrial Revolution and consequent depletion of trees in abandoned areas. In the first half of the XX century (1926), the “wheat campaign” orchestrated by the dictatorship Salazar forced an intensive agriculture removing trees form the agricultural fields and, due to the lack of soil fertility high fertilization rates were applied. Currently the main agroforestry tree species in Portugal are cork oak (Quercus suber L.) and holm oak (Quercus rotundifolia L.). Statistics are fuzzy concerning agroforestry. This is related to the nature of the agroforestry systems themselves as the limits of classification between forest and agroforests are fuzzy as the understorey management is a dynamic land use rotating from conventional cropping, pasture, and set-aside sometimes more than a year promoting shrub occurrence being at this stage classified as forest by misinterpretation of the land management context or by aerial-photo/satellite imagery interpretation. According to the 2010 National Forest Inventory (NFI), forests/agroforests cover 716,000 and 413,000 ha respectively for cork oak and holm oak respectively, accounting for 30% of the total carbon (C) present in Portuguese forests, with cork oak storing 64 x 106 Mg CO2eq and holm oak storing 20 x 106 Mg CO2eq. The figures represent a slight increase of cork oak (713 to 716 kha) and a slight decrease in holm oak (462 to 413 kha) since 1998.