Long-term nutritional trends of conifer stands in Europe: results from the RECOGNITION project

Abstract

Since 1999Since -2002 the European Commission has funded and the European Forest Institute has coordinated the interdisciplinary RECOGNITION project aiming at elucidating the causes of the growth acceleration which has been observed in some forest tree species in several parts of Europe. Within this project, it was our task to identify and quantify long-term changes in the nutritional status of representative forest stands that potentially could explain this growth increase, using available long-term series of foliar analyses. An inquiry among 25 forest research institutions in Europe resulted in 28 Scots pine (Pinus sylvestris L.) and 21 Norway spruce (Picea abies [L.] Karst.) stands for this historical development investigation (HDI). The stands generally are control plots of fertilization experiments and are located mainly in Central Europe and in Scandinavia. The monitoring periods vary from 15-40 years. The foliar data were given to us by our partner organisations, subjected to rigorous tests for plausibility and comprehensively evaluated using mainly single linear regression approaches. Most Scots pine stands under study in Central Europe, which grow predominantly on naturally poor or devastated soils in regions with relatively high atmospheric N deposition, suffered from N deficiency at the start of the monitoring period, but exhibited a considerable improvement in N nutrition over the past decades. The increase in N levels was usually associated with an increase in the ratios of N and P, K, Ca, and Mg, although critical values of these ratios are far from being reached. For the majority of the investigated Scots pine stands in Central Europe, growth acceleration due to a better N supply is highly probable.In contrast, N seems to be far less important as a potential driving factor for long-term growth changes in Scots pine in Scandinavia. Norway spruce stands examined in Central Europe were, in general, initially well supplied with N and characterised by a decreasing trend in foliar N levels although they received considerable N deposition from the atmosphere. This decrease in concentrations of N and other macronutrients is believed to be mainly a dilution effect as indicated by a simultaneous increase in needle weights. Spruce in Finland also turned out to be adequately provided with N at most sample sites, and no general trend of improving N nutrition was detected.

Phosphorus nutrition of beech (Fagus sylvatica L.) is decreasing in Europe

“…Increased N deposition during the last decades (Galloway 2001) balanced out the growth limitation by N in many temperate forests (Nihlgård 1985), which eventually became N saturated (Aber et al 1998). The improved N nutrition initially led to increased forest growth (Braun et al 1999;Högberg et al 2006;Spiecker 1999), but might also have provoked nutrient imbalances (Aber et al 1998) including P deficiency (Flückiger and Braun 1998;Mellert et al 2004;Mohren et al 1986). In N-saturated forests, a shift from N to P limitation of forest growth has already been observed (Braun et al 2010;Gradowski and Thomas 2006;Peñuelas et al 2013) and may be due to several processes.…”

Temporal trends in the foliar nutritional status of the French, Walloon and Luxembourg broad-leaved plots of forest monitoring

“…fuel combustion, intensive agriculture) may induce or aggravate nutritional imbalances in nutrient-poor forest ecosystems. Although tree nutrient demand augments with increased forest productivity resulting from the fertilizer effect of N deposition (Mellert et al, 2004) and from certain changes in sylvicultural practices and in climate conditions (Lebourgeois et al, 2001), the supply of P and base cations remains generally low in forest soils and is likely to decrease with soil acidification (Adams, 1999).…”

“…In the past, such data sets were scarce and were obtained, for example, by using the control plots of fertilization or thinning trials (Mellert et al, 2004). Another option consisted in re-sampling stands after a certain time lag (Alfani et al, 2000;Duquesnay et al, 2000); however, this method did not allow researchers to separate the long-term trends from the inter-annual variability.…”

“…Based on data analyzed at national level, the temporal variation in foliar chemistry has already been described for several regions (Flückiger and Braun, 1998;Thelin et al, 1998;Luyssaert et al, 2004;2005). Generally, the temporal pattern is characterized by an increase in foliar N concentration and a decrease in foliar phosphorus (P), calcium (Ca), magnesium (Mg) and potassium (K) concentrations (Duquesnay et al, 2000;Flückiger and Braun, 1998;Luyssaert et al, 2004;Mellert et al, 2004;Thelin et al, 1998).…”

The application of potato starch effluent causes a reduction in the photosynthetic efficiency and growth of Scots pine (Pinus sylvestris L.)

“…In regularly fertilized forests, under the controlled conditions, the positive influence of fertilization on tree growth was observed (Moller 1992;Fox et al 2007). Mellert et al (2004) observed that improvements in N nutrition were reflected in positive trends in foliar N concentration and constant or increased needle mass (100-needle weight) or a positive trend in the foliar N content (product of foliar N concentration and needle mass). Our study revealed that after the nutrient concentration increased, a growth decline was observed.…”