Variation in leaf nitrogen and phosphorus stoichiometry in Picea abies across Europe: An analysis based on local observations

Nitrogen (N) and phosphorus (P) and N:P ratio in terrestrial plants and the patterns at a large geographical scale are an important issue in ecological stoichiometry. In particular, it is essential to know that for a single species, how the N:P stoichiometry varies with climatic factors in the context of global warming. Our analysis was based on a data set including 2583 observations at 441 sites on nutritional status of Norway spruce (Picea abies L.) located in European counties (including Austria, Belgium, Bulgaria, Czech Rep., Finland, Germany, Ireland, Italy, Lithuania, Norway, Slovak Rep., Slovenia, United Kingdom). Our objectives are to demonstrate how leaf N and P concentration and N:P ratio in Norway spruce vary with altitude (ALT), latitude (LAT), longitude (LON), mean annual temperature (MAT) and mean annual precipitation (MAP) across Europe. The results showed that for 1-year-old needles of Norway spruce, the N and P concentration were 13.28 mg g⁻¹, 1.41 mg g⁻¹ and the N:P ratio was 9.76. Leaf N displayed a convex curve pattern with increasing MAT and decreasing LAT from the boreal Europe to the Mediterranean area. The N concentration and N:P generally reached peak at about 7 °C in MAT or 53° N in LAT. The N:P ratio varied non-linearly with LAT and MAP, but linearly with MAT. Leaf N concentration and N:P ratio decreased linearly with increasing ALT in temperate European area. Across Europe, that the patterns of leaf N and N:P ratio were mainly driven by climate-related geochemistry and plant physiology, but also greatly impacted by anthropogenic N deposition.