Is long-lived foliage in Picea mariana an adaptation to nutrient-poor conditions?

Abstract

This study evaluated the contribution of different ages of foliage to the nutrient and carbon balance of black spruce (Picea mariana (Mill.) B.S.P.) from a nutrient-poor peatland in Alberta. Seasonal patterns of foliar nitrogen and phosphorus concentration and content were examined in six needle cohorts up to 10 years old. Trees were treated to simulate excess nutrient deficiency (removal of all one-year-old foliage), nutrient excess (fertilized with 250, 50, 100 kg ha NPK split application in June and July), or left as controls. Gas exchange (net assimilation-Na, stomatal conductance-g, mesophyll conductance-g, water-use efficiency-WUE, dark respiration-RS) was measured on six different needle cohorts in several control trees in 1989 and 1990. Nitrogen and phosphorus concentration decreased with needle age. Foliar nutrient concentration fell from April to June and then was stable until September except for the fertilized trees where it increased. There was no evidence of greater than normal retranslocation of nutrients from older needles for defoliated trees or greater than normal nutrient loading in older needles of fertilized trees. NA, g, g, WUE, and RS were similar for all needles up to six or eight years old, these older needles having NA of 65% of current needles and similar RS. The results do not support to conclusion that older needles of black spruce are retained as an adaptation to nutrient stress. It does not appear that older needles serve as a nutrient storage site in conditions of excess nutrient availability or a greater than normal nutrient source during times of excess nutrient deficiency. It appears that the maintenance of long-livedfoliage in black spruce does not provide for greater flexibility in tree nutrient allocation. Their contribution to the carbon balance of the tree seems to be sufficient to explain their retention.

Needle longevity, shoot growth and branching frequency in relation to site fertility and within-canopy light conditions in Pinus sylvestris

“…An increase in needle dry mass per unit area (table I, figure 8A, B) was the primary age-caused change in needle morphology. Similar changes in M A with age have also been observed previously [27,48,82]. As the former [48] and current work demonstrate, changes in M A primarily result from modifications in needle density (table I).…”

“…Given that low needle growth rates were accompanied by increased average needle age in P. sylvestris, our results also agree with the model. Although nitrogen and other limiting elements are retranslocated from senescing conifer foliage [17,27,31,52], large quantities of nitrogen are necessary to increase the efficiency of light harvesting in shaded needles [9,10]. Given that needles in most shaded shoot positions are the first to abscise [48], keeping high N contents in older, but functionally active needles may be an important acclimation response to increase the light interception efficiency in the low light environments [48].…”

Growth of aspen and white spruce on naturally saline sites in northern Alberta: Implications for development of boreal forest vegetation on reclaimed saline soils

“…Characteristics like long leaf lifespan (Greenway et al 1992;Munson et al 1995;Claveau et al 2002), high leaf mass per leaf area (Claveau et al 2005), and high plasticity in crown morphology (Messier et al 1999) that help white spruce survive in low resource availability conditions in the forest understory could also help it survive in unfavorable soils. Khasa et al (2002) also found that white spruce was slow growing, yet had high survivorship in a comparative salinity experiment.…”

“…They may have been excluding both chloride and sodium by selective membrane permeability or by active ion pumping (Allen et al 1994). Root tissues could have compartmentalized ions in vacuoles (Jacoby 1999) to protect the foliage, the tissues with the highest photosynthetic capacity (Greenway et al 1992;Brooks et al 1996). In laboratory experiments, jack pine (Pinus Banksiana Lamb.)…”

Dynamique d'installation du système racinaire de la régénération pré-établie de l'épinette noire (Picea mariana B.S.P.) après coupe /

“…Cette diminution de la croissance de la tige est attribuable à l'épidémie durant certaines de ces années. Tandis que la croissance racinaire n'est pas nécessairement réduite, probablement parce que l'allocation des produits photosynthétiques aux racines est maintenue, le vieux feuillage contribuant de façon importante dans la balance du carbone chez l'Épinette noire (Greenway et al 1992). Mais le comportement des ratios durant l'épidémie qui a eu lieu après 1970 est contraire à celui des tiges du site Lau.…”