Herdade da Ribeira Abaixo - Portugal

Herdade da Ribeira Abaixo is one of the six research and monitoring stations of LTER-Montado, an umbrella site located in the Alentejo province in south Portugal (southwestern Iberia). The "Montado" represents an unique agro-silvo-pastoral ecosystem (named "dehesa" in Spain) found only in the Mediterranean basin. These savannah-like landscapes are dominated by evergreen cork and/or holm oaks and were shaped over millennia of traditional land use practices. These multi-use forests are two-layered systems that combine, in a single space, forest harvesting, extensive livestock husbandry, pastures and/or cereal cultivation (the most evident economical revenues), with other traditional uses (hunting, beekeeping and mushroom picking). Recently, increasing awareness arose on their benefits as biodiversity reservoirs, recreation grounds, and other ecosystem services providers, but these non-productive functions are not equally perceived and valued by users, as they tend to be conflicting with productive ones. Herdade da Ribeira Abaixo is a state property, located on the left bank of Sado River, in Baixo Alentejo province, 100 km south of Lisbon and 7 km from Grândola (38.06° N – 8.35°W). Cork oak (Quercus suber) is the dominant tree type, with an average of 43 adult trees per hectare. Since 1990, there is a single main economic output - cork, which is harvested in a 9-year cycle, with an average production of 450 kg (dry weight) per hectare per year. Since 1998, cattle herding was abandoned and substituted by sheep, with an average stocking of 0.1 animals per hectare. Recently (2003 and 2004) the property was subject to management actions aiming to foster the natural regeneration of cork oaks; cork oak saplings were also planted in a recently burned area. The shrub layer is cleared heterogeneously across the property every 4-5 years. A serious tree decline is observed, especially in the high plateaus. Natural regeneration is not uniform, being concentrated in north facing slopes with a dense shrub layer. Ovine grazing, though of low intensity, is partly responsible for lack of regeneration. Holm oaks are rare in the property, but are increasing. Parts of the property were burnt repeatedly (the more recent fires happened in 2001 and 2003); however some of the north facing slopes maintain a luxurious mixed oak forest and were not burnt in the last 30 years. In these areas, shrub cover and height are increasing.