The past ecology of Abies alba provides new perspectives on future responses of silver fir forests to global warming

• Published in: Ecological monographs 2013-11, Vol.83 (4), p.419-439
• Main Authors: Tinner, Willy, Colombaroli, Daniele, Heiri, Oliver, Henne, Paul, Steinacher, Marco, Untenecker, Johanna, Vescovi, Elisa, Allen, Judy, Carraro, Gabriele, Conedera, Marco, Joos, Fortunat, Lotter, AndréF, Luterbacher, Jürg, Samartin, Stephanie, Valsecchi, Verushka
• Format: Article
• Language: English
• Subjects: Abies alba; Animal and plant ecology; Animal, plant and microbial ecology; bioclimatic envelope models; Biological and medical sciences; Climate change; Climate models; climatic niche; Climatology. Bioclimatology. Climate change; dynamic vegetation models; Earth, ocean, space; Ecological modeling; Exact sciences and technology; External geophysics; Flowers & plants; Forest ecology; Forestry; Fossils; Fundamental and applied biological sciences. Psychology; General aspects; General aspects. Techniques; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; global change; Global climate models; Global warming; Meteorology; Methods and techniques (sampling, tagging, trapping, modelling...); Paleoclimatology; Paleoecology; Plant ecology; Pollen; realized niche; REVIEWS; Species; Vegetation
• ISSN: 0012-9615; 1557-7015
• DOI: 10.1890/12-2231.1

Paleoecology can provide valuable insights into the ecology of species that complement observation and experiment-based assessments of climate-impact dynamics. New paleoecological records (e.g. pollen, macrofossils) from the Italian Peninsula suggest a much wider climatic niche of the important European tree species Abies alba (silver fir) than observed in its present spatial range. To explore this discrepancy between current and past distribution we analyse climatic data (e.g. temperature, precipitation, frost, humidity, sunshine) and vegetation-independent paleoclimatic reconstructions (e.g. lake levels, chironomids) and use global coupled carbon-cycle climate (NCAR CSM1.4) and dynamic vegetation (LANDCLIM) modelling. The combined evidence suggests that during the mid-Holocene (ca. 6000 years ago), prior to humanization of vegetation, A. alba formed forests under conditions that exceeded modern (1961-1990) upper temperature limit of the species by ca. 5-7 °C (July means). Annual precipitation during this natural period was comparable to today (>700-800 mm), with drier summers and wetter winters. 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 . Results from the last interglacial (ca. 130,000-115,000 BP), when human impact was negligible, corroborate the Holocene evidence. Thermophilous Mediterranean A. alba stands became extinct during the last 5000 years when land-use pressure and specifically excessive anthropogenic fire and browsing disturbance increased. Our results imply that the ecology of this key European tree species is not yet well understood. On the basis of the reconstructed realized climatic niche of the species, we anticipate 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 disturbance (e.g. fire, browsing) does not become excessive. Our finding 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 .