PARENT SESSION
Poster Session 6: Arctic and Alpine Ecology
Tuesday, August 9, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Contemporary rates of treeline shift in the Pyrenees do not support predictions of rapid migration of trees in response to climate warming.
Batllori Presas, Enric1, Camarero Martínez, Jesús Julio2, Gutiérrez Merino, Emilia1, 1 Universitat de Barcelona, Barcelona, Spain2 Centro de Investigación y Tecnología Agroalimentaria, Zaragoza, Spain
ABSTRACT- Recent findings suggest that altitudinal treelines might not necessarily react to climate warming through upslope expansion due to the pronounced spatio-temporal variability in their response to climate at regional and local scales. We evaluate if altitudinal treelines in the Pyrenees respond to the observed temperature increase through an upslope advance and enhanced recruitment. We reconstruct current rates of treeline shift and compare them with estimates of tree migration based on the paleorecord. To study treeline dynamics at regional and local scales, we describe the spatio-temporal dynamics of tree recruitment in six treeline ecotones located in the Pyrenees and dominated by Pinus uncinata. A rectangular plots (0.1-0.4 ha) was placed at each site crossing the treeline ecotone with its longest side parallel to the maximum slope. The position of each tree within each plot was recorded. The age of all living individuals was estimated taking basal cores that were dated using dendrochronological techniques. The rates of treeline shift (m*yr-1) were estimated calculating age differences across the plots for trees whose location was known. We found a lack of synchrony in major recruitment events among treelines, pointing out the importance of local conditions even for nearby sites. However, at the late 19th and early 20th centuries there was an important recruitment event in most plots which caused the main treeline ascent of the past century. The rates of treeline shift ranged from 0.32 to 1.87 m*yr-1, being 2-3 orders of magnitude lower than the estimates of postglacial migration rates based on paleoecological records (100-1000 m*yr-1). According to our estimates, treeline migration might be considerably slower than believed. Treelines do not respond to climate warming in a linear way because additional factors (fecundity, seed dispersal, regeneration niche) influence their response to climate.
Key words: treeline, recruitment, migration rate, Pyrenees