Relationships between phenology and the remobilization of nitrogen, phosphorus and potassium in branches of eight Mediterranean evergreens

Abstract

Summary• Few studies have examined the effects of plant growth on nutrient remobilization in phenologically contrasting species. Here we evaluated the consequences of above-ground seasonality of growth and leaf shedding on the remobilization of nutrients from branches in eight evergreen Mediterranean phanaerophytes that differ widely in phenology.• Vegetative growth, flower bud formation, flowering, fruiting, leaf shedding, and the variations in nitrogen (N), phosphorus (P) and potassium (K) pools in branches throughout the year were monitored in each species.• Nitrogen and P remobilization occurred in summer, after vegetative growth and synchronously with leaf shedding. Despite the time-lag between growth and remobilization, the branches that invested more nutrients in vegetative growth also remobilized more nutrients from their old organs. Potassium remobilization peaked in the climatically harshest periods, and appears to be related to osmotic requirements.• We conclude that N and P remobilization occurs mainly associated with leaf senescence, which might be triggered by factors such as the replenishment of nutrient reserves in woody organs, the hormonal relations between new and old leaves, or the constraints that summer drought poses on the amount of leaf area per branch in summer.

Gradients of light availability and leaf traits with leaf age and canopy position in 28 Australian shrubs and trees

“…However, since age-related trends in both leaf N and P have been reported only rarely, it is unclear whether this is a general phenomenon or one peculiar to the species we studied. While similar age-related trends in leaf P and N have been observed in several tree species (Chapin and Kedrowski 1983;Nambiar and Fife 1991;Mediavilla and Escudero 2003a;Niinemets et al 2004;Milla et al 2005), in other species N and P have shown rather different time trends (Hevia et al 1999).…”

Potassium: a neglected nutrient in global change

“…Tomlinson et al (2013), while comparing leaf traits of different plant species growing in wet and arid environments, observed that leaves of species adapted to arid sites are small with high K concentrations. Furthermore, it was observed that tree species at the driest sites, such as in mediterranean evergreen and dry tropical forests, have a higher capacity to change their seasonal internal allocation of K, with a higher allocation of K to leaves during summer (the driest season) than the species at wetter sites (Milla et al, 2005;Rivas-Ubach et al, 2012;Sardans et al, 2012a).…”

The Role of Plants in the Effects of Global Change on Nutrient Availability and Stoichiometry in the Plant-Soil System

“…As observed in plants adapted to severe periods of drought, P tends to remobilize from leaves to roots, whereas K has the opposite movement, as observed in Mediterranean trees during summer drought (Milla et al, 2005;SanzPérez et al, 2009;. Plants with the genotypic capacity to maintain N, P, and K concentrations and contents under drought have a competitive advantage if drought persists or becomes more severe (Ghandilyan et al, 2009).…”

“…In addition to activating mechanisms for improving the capacity to take up water, plants respond to drought by enhancing mechanisms for conserving water and nutrients, such as the retranslocation of nutrients prior to tissue senescence (Heckathorn andDeLucia, 1994, 1996;Correia and Martins-Loução, 1997;Milla et al, 2005) and the internal remobilization of nutrients dependent on the availability of water . As observed in plants adapted to severe periods of drought, P tends to remobilize from leaves to roots, whereas K has the opposite movement, as observed in Mediterranean trees during summer drought (Milla et al, 2005;SanzPérez et al, 2009;.…”