Variation in Scots pine needle longevity and nutrient conservation in different habitats and latitudes

Abstract

Within-species variation in needle traits is an important characteristic of conifers enabling trees to grow in different environments. We compared mean needle age (NA), shoot growth, and nutrient conservation in Scots pine ( Pinus sylvestris L.) populations in different habitats and latitudes (peatlands and Vaccinium -type stands in Estonia (59°N) and Lapland (66°30′N)). In Vaccinium-type stands, trees with higher NA (mostly in Lapland) had lower shoot length increment and lower concentration of nitrogen and phosphorus in current-year needles than trees with low NA (mostly in Estonia). However, in peatlands, variation in NA (which was as high as in the Vaccinium-type stands) was weakly or insignificantly related to shoot growth and needle nutrient concentration. Within latitudes, pines with different shoot length increments and needle nutrient concentrations tend to have similar NAs. Resorption efficiency and concentration of nitrogen and phosphorus in senescent needles decreased with the initial concentrations of these nutrients in green needles. Our results demonstrate that slow growth and low needle nutrient concentration are not necessarily followed by higher NA and greater nutrient conservation in Scots pine. This is the opposite of the results often obtained in among-species comparisons or within species along latitudinal and altitudinal gradients.