Does nitrogen deposition increase forest production? The role of phosphorus.
Effects of elevated N deposition on forest aboveground biomass were evaluated using long-term data from N addition experiments and from forest observation plots in Switzerland. N addition experiments with saplings were established both on calcareous and on acidic soils, in 3 plots with Fagus sylvatica and in 4 plots with Picea abies. The treatments were conducted during 15 years and consisted of additions of dry NH4NO3 at rates of 0, 10, 20, 40, 80, and 160 kg N ha(-1) yr(-1). The same tree species were observed in permanent forest observation plots covering the time span between 1984 and 2007, at modeled N deposition rates of 12-46 kg N ha(-1) yr(-1). Experimental N addition resulted in either no change or in a decreased shoot growth and in a reduced phosphorus concentration in the foliage in all experimental plots. In the forest, a decrease of foliar P concentration was observed between 1984 and 2007, resulting in insufficient concentrations in 71% and 67% of the Fagus and Picea plots, respectively, and in an increasing N:P ratio in Fagus. Stem increment decreased during the observation period even if corrected for age. Forest observations suggest an increasing P limitation in Swiss forests especially in Fagus which is accompanied by a growth decrease whereas the N addition experiments support the hypothesis that elevated N deposition is an important cause for this development.
Braun
Sabine
S
Institute for Applied Plant Biology, CH-4124 Schönenbuch, Switzerland. sabine.braun@iap.ch
Thomas
Vera F D
VF
Quiring
Rebecca
R
Flückiger
Walter
W
D000596:Amino Acids / Q000032:analysis; D018533:Biomass; D029964:Fagus / Q000254:growth & development* / Q000378:metabolism; D016468:Forestry; D019015:Geologic Sediments / Q000032:analysis; D015999:Multivariate Analysis; D009584:Nitrogen / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D028222:Picea / Q000254:growth & development* / Q000378:metabolism; D013557:Switzerland; D014887:Weather
D000596:Amino Acids; D010758:Phosphorus; D009584:Nitrogen