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The Response Potential of Silver Fir Trees to Global Warming
Tinner, W., Colombaroli, D., Heiri, O., Henne, P.D., Steinacher, M., Untenecker, J., Vescovi, E., Allen, J.R.M., Carraro, G., Conedera, M., Joos, F., Lotterr, A.F., Luterbacher, J., Samartrin, S. and Valsecchi, V. 2013. The past ecology of Abies alba provides new perspectives on future responses of silver fir forests to global warming. Ecological Monographs 83: 419-439.

Noting that "paleoecology can provide valuable insights into the ecology of species that complement observation and experiment-based assessments of climate impact dynamics," the authors give as an example the fact that "new paleoecological records (e.g., pollen, macrofossils) from the Italian Peninsula suggest a much wider climatic niche [for] the important European tree species Abies alba (silver fir) than observed in its present spatial range."

What was done
Tinner et al. explore this discrepancy between current and past distributions of A. alba by (1) analyzing "climatic data (temperature, precipitation, frost, humidity, sunshine) and vegetation-independent paleoclimatic reconstructions (e.g., lake levels, chironomids)," and by (2) using "global coupled carbon-cycle climate (NCAR CSM1.4) and dynamic vegetation (LandClim) modeling."

What was learned
The fifteen scientists say their analyses suggest that "during the mid-Holocene (~6000 years ago), prior to humanization of vegetation, A. alba formed forests under conditions that exceeded the modern (1961-1990) upper temperature limit of the species by ~5-7°C (July means)," when "annual precipitation during this natural period was comparable to today (>700-800 mm)," but with "drier summers and wetter winters." And they also report that "in the meso-Mediterranean to sub-Mediterranean forests A. alba co-occurred with thermophilous taxa such as Quercus ilex, Q. pubescens, Olea europaea, Phillyrea, Arbutus, Cistus, Tilia, Ulmus, Acer, Hedera helix, Ilex aquifolium, Taxus and Vitis." And they say that "results from the last interglacial (ca. 130,000-115,000 BP), when human impact was negligible, corroborate the Holocene evidence."

What it means
"On the basis of the reconstructed realized climatic niche of the species," Tinner et al. conclude that "the future geographic range of A. alba may not contract regardless of migration success, even if climate should become significantly warmer than today with summer temperatures increasing by up to 5-7°C, as long as precipitation does not fall below 700-800 mm/year, and anthropogenic disturbance (e.g., fire, browsing) does not become excessive." And they make a point of stating that their work "contradicts recent studies that projected range contractions under global-warming scenarios, but did not factor how millennia of human impacts reduced the realized climatic niche of A. alba."

Reviewed 23 April 2014