Recovery of GPP monthly pattern in a eucalypt site in Portugal after felling

Abstract. The main objective of this work was to report the recovery of seasonal pattern of GPP obtained by eddy covariance measurements in a eucalypt (Eucalyptus globulus Labill.) site in Pegões (Southern Portugal) after a felling processed in October and November of 2006. This was made in a wider context of a general description of the evolution of carbon sequestration at several timescales in the period 2002–2010. In Portugal eucalypt stands aimed mainly for pulp production occupies an area of about 739 515 ha, (National Forest Inv 2005–2006) corresponding to about 23% of total forest area. The site is part of a 300 ha eucalypt stand, located in Herdade da Espirra, intensively managed as coppice under a twelve year productive cycle with a density of about 1100 trees/ha and characterized by a 12-month growing period. A prolonged drought in 2004 and 2005 and a felling in October–November 2006, followed by the start of a new production cycle, changed the carbon sink ability of eucalypt stand. In the two drought years, rainfall was reduced to values of 50%, relatively to long-term 709 mm average of. In the period prior to cutting NEE of 8.7 g cm⁻² was maximum in 2002 decreasing to a minimum of 3.6 tons/ha in 2005 at the peak of the effect of drought. After the felling the eucalypt stand recovered its carbon sink capacity in June 2007 with an annual GPP of 1621.6 g cm⁻² in 2010. Seasonal patterns of GPP in 2007, 2008 and 2009 were almost opposite to that of the period before the felling, with a tendency to recover to the situation prior the felling in 2010.