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Advisor(s)
Abstract(s)
This paper reports on results from eddy covariance measurements of carbon uptake and evapotranspiration
in the eucalypt site of Espirra in Southern Portugal (38◦38 N, 8◦36 W). This site was included in
the “Carboeurope” European network and is part of a 300 ha eucalypt forest, with about 1100 trees ha−1,
intensively managed as a coppice for pulp production and characterized by a 12-month annual growing
period. The climate is of Mediterranean type with a long term (1961–1990) annual average precipitation
of 709mm and an annual average air temperature of 15.90 ◦C. During the measurement period
(2002–2009) two main events took place, which changed the annual sink pattern of the forest: a drought
period of two years (2004–2005) and a tree felling (October and November 2006). We analyzed the daily,
seasonal and inter-annual variation of carbon uptake and evapotranspiration, and their relationships
with the events and the variability of the main meteorological variables. Before the felling, annual net
ecosystem exchange (NEE) increased from −865.56gCm−2 in 2002 to −356.64gCm−2 in 2005 together
with a deep decrease in rainfall from 748mm in 2002 to 378.58mm and 396.64mm in 2004 and 2005,
respectively. For the same period, seasonal patterns of carbon uptake showed maximum values in April
and decreased in July–August. The eucalypt stand recovered its carbon sink ability since June 2007 and
had a NEE of −209.01gCm−2 in 2009. After the felling, the carbon uptake occurred from mid-February to
mid-October, following an almost opposite pattern than that of the trees in the term of their productive
cycle. A quantitative approach using generalized estimating equations (GEEs) was made for the period
before the felling to relate monthly NEE and GPP with accumulated photosynthetic active radiation, water
vapour pressure and precipitation. In conclusion, our study showed the relevant effects of water stress
and anthropogenic interventions in the daily, seasonal and annual patterns of carbon uptake, under a
context of good environmental conditions for carbon sequestration.
Description
Available at ScienceDirect
Keywords
Eddy covariance carbon tree felling water stress dought GEEs
Pedagogical Context
Citation
"Agricultural and Forest Meteorology". ISSN 0168-1923. 151 (2011) 493-507