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The European-Wide and Holocene-Long Growth Rates of Fir Trees
Buntgen, U., Tegel, W., Kaplan, J.O., Schaub, M., Hagedorn, F., Burgi, M., Brazdil, R., Helle, G., Carrer, M., Heussner, K.-U., Hofmann, J., Kontic, R., Kyncl, T., Kyncl, J., Camarero, J.J., Tinner, W., Esper, J. and Liebhold, A. 2014. Placing unprecedented recent fir growth in a European-wide and Holocene-long context. Frontiers in Ecology and the Environment 12: 100-106.

The authors write that about 35 years ago in Europe there was a "widespread public perception that forests were dying as a result of air pollution and related acid deposition," citing Schutt and Cowling (1985), Innes (1987) and Kandler and Innes (1995). And they say that this state of affairs "stimulated new pollution control legislation and promoted environmental awareness." A decade or so later, however, they indicate that interest in the subject had waned considerably "in conjunction with evidence of forest ecosystem recovery," citing Spiecker (1995).

What was done
Dedicated to exploring this subject in greater depth in terms of what had happened and why, as well as positioning it within a much longer temporal context, Buntgen et al. compiled "ring-width measurements from living fir trees and historical construction timbers throughout Europe" and used them "to quantify trends in forest productivity over the past millennium," while they employed "paleobotanical pollen profiles to reconstruct trends in fir land cover over the entire Holocene."

What was learned
Focusing on the last two centuries, the 18 researchers report that the long-term ring-width increase that occurred from ~1840 to 1940 in almost all fir habitats across the continent was "probably stimulated by a combination of land-use practices and warming without drying, as well as through fertilization by nitrogen (N) and carbon dioxide (CO2)," citing Korner (2006) and Thomas et al. (2008). After 1950, however, fir tree growth declined significantly, due to pollution by substances such as SO2, NOX and tropospheric ozone (O3). But following major pollution mitigation initiatives, they found there was "a rapid surge in Central European growth after ~1982, with the effects of forest management, climate warming and atmospheric [CO2] fertilization potentially also amplifying this boost," which propelled fir-tree growth rates to a new modern high.

What it means
When real atmospheric pollutant concentrations were significantly reduced, and when concentrations of the world's most powerful atmospheric fertilizer (CO2) were concomitantly increased, Europe's fir trees experienced their greatest growth rates of the entire past millennium.

Innes, J.L. 1987. Air Pollution and Forestry. Forestry Commission Bulletin 70. HMSO, London, United Kingdom.

Kandler, O. and Innes, J.L. 1995. Air pollution and forest decline in Central Europe. Environmental Pollution 90: 171-180.

Korner, C. 2006. Plant CO2 responses: an issue of definition, time and resource supply. New Phytologist 172: 393-411.

Schutt, P. and Cowling, E.B. 1985. Waldsterben, a general decline of forests in Central Europe: symptoms, development, and possible causes. Plant Disease 69: 548-558.

Spiecker, H. 1995. Growth dynamics in a changing environment - long-term observations. Plant and Soil 168: 555-561.

Thomas, R.Q., Canham, C.D., Weathers, K.C. and Goodale, C.L. 2008. Increased tree carbon storage in response to nitrogen deposition in the U.S. Nature Geoscience 3: 13-17.

Reviewed 23 April 2014