Influence of canopy position, needle age and season on the foliar gas exchange of Pinus canariensis

Abstract

We investigated the seasonal variation in the gas exchange of current and 1-year-old needles in the upper sun and lower shade crown of adult Pinus canariensis trees. In general, current year needles displayed lower gas exchange rates than the 1-year-old needles. In both needle age classes, gas exchange was signiWcantly lower in the shade than in the sun crown. However irrespective of crown position and needle age, maximum daily net photosynthesis, transpiration, and stomatal conductance for water vapour were generally higher during the wet and cold winter as compared to the dry and hot summer. These higher gas exchange values obtained during the cold and wet season can mainly be explained by higher soil-water availability and lower evaporative demand as compared to the warm and dry seaon. In addition, we also observed a displacement in the temperature optimum of net photosynthesis towards lower temperatures during the cold and wet season as compared to the warm and dry season. The observed gas exchange characteristics indicate a conservative water saving strategy and thus allowing P. canariensis needles to maintain a positive carbon gain even at periods of high evaporative demand and low soil-water availability.

Canopy transpiration of a semi arid Pinus canariensis forest at a treeline ecotone in two hydrologically contrasting years

“…This can be primarily attributed to a decrease in g c with increasing D (Fig.7) as also observed by others (Granier et al, 1996Hogg and Hurdle, 1997;Lopushinsky, 1986;Meinzer et al, 1993;Wieser and Leo, 2012;Zimmermann et al, 2000). Stomatal closure due to increasing D and soil drought has also been found in P. canariensis at the leaf level (Gieger and Leuschner, 2004;Peters et al, 2003Peters et al, , 2008Wieser et al, 2002). Furthermore, daily maximal stomatal conductance of mature P. canariensis trees tends to decline from 1600 m a.s.l.…”

Spatial and seasonal variations in stem CO2 efflux of Pinus canariensis at their upper distribution limit

“…which experiences frequent fog impacts and consequently more humid conditions (Luis et al 2005;Peters et al 2003Peters et al , 2008Wieser et al 2002Wieser et al , 2006Wieser et al , 2009, such measurements at the semi-arid and seasonally drought affected timberline ecotone are rare (Gieger and Leuschner 2004;Köhler et al 2006); especially with respect to ecosystem functioning such as carbon dynamics and respiratory fluxes.…”

Effects of thinning intensity on radial growth patterns and temperature sensitivity in Pinus canariensis afforestations on Tenerife Island, Spain

“…)-a species endemic to the western Canary Islands-can be vulnerable to global warming processes, because water availability is already a key limiting resource in most forests where it occurs. Despite its morphological and physiological adaptations to cope with drought and heat (Jonsson et al 2002;Peters et al 2008), the tree line in the Canary Islands can be modified by the effects of heat and drought on pine establishment (Gieger and Leuschner 2004). On the other hand, the additional stress provided by inter-tree competition should also be considered for Canary pine afforestations established on Tenerife Island during the twentieth century.…”