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Climate‐dependent variations in leaf respiration in a dry‐land, low productivity Mediterranean forest: the importance of acclimation in both high‐light and shaded habitats
Author(s) -
ZaragozaCastells Joana,
SánchezGómez David,
Hartley Iain P.,
Matesanz Silvia,
Valladares Fernando,
Lloyd Jon,
Atkin Owen K.
Publication year - 2008
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1111/j.1365-2435.2007.01355.x
Subject(s) - biology , acclimatization , irradiance , photosynthesis , seasonality , phenology , productivity , q10 , mediterranean climate , ecosystem , respiration , botany , atmospheric sciences , horticulture , ecology , physics , macroeconomics , quantum mechanics , economics , geology
Summary1 Climate‐driven changes in leaf respiration ( R ) in darkness have the potential to determine whether low productivity ecosystems exhibit positive or negative carbon balances. 2 We investigated whether sustained exposure to full sunlight, shade and seasonal drought alters the temperature response of leaf R of field‐grown Quercus ilex subsp. ballota in a dry‐land continental Mediterranean ecosystem. The plants studied, experience large diurnal and seasonal variations in temperature. 3 Whilst growth irradiance impacted on photosynthesis, it had little effect on the short‐term temperature dependence of leaf R . Moreover, although basal rates of leaf R (i.e. rates of R at a common measuring temperature) were higher in sun‐exposed than shade‐exposed leaves, growth irradiance had little impact on the degree of acclimation to seasonal changes in temperature and/or moisture. Basal rates of leaf R were higher in winter than summer in both sun‐exposed and shaded plants. Estimated Q 10 values (i.e. proportional increase in R per 10 °C rise in temperature) for leaf R were greater in winter than summer; however, no seasonal variation was found in the apparent activation energy ( E 0 ) of leaf R . These observations were used to construct a simple Arrhenius model that fully accounted for both daily and seasonal variations in the temperature dependence of R in both sun‐exposed and shaded plants. Crucial to the model was accounting for the seasonal and irradiance‐dependent shifts in the basal rate of leaf R . 4 Although the balance between daily R and photosynthesis increased markedly in summer (particularly under full sun), the increase in this ratio was markedly less than would have been the case if leaf R had not acclimated to the high average day time temperatures in summer. 5 It is concluded that seasonal acclimation of leaf R plays a crucial role in determining the viability of tree growth in dry‐land, low productivity forest ecosystems.