Rapid climate change‐related growth decline at the southern range edge of Fagus sylvatica

Abstract

Studies on Fagus sylvatica show that growth in populations toward the southern limit of this species' distribution is limited strongly by drought. Warming temperatures in the Mediterranean region are expected to exacerbate drought where they are not accompanied by increases in precipitation. We studied levels of annual growth in mature F. sylvatica trees over the last half-century in the Montseny Mountains in Catalonia (northeast Spain). Our results show significantly lower growth of mature trees at the lower limit of this species' distribution when compared with trees at higher altitudes. Growth at the lower Fagus limit is characterized by a rapid recent decline starting in approximately 1975. By 2003, growth of mature trees had fallen by 49% when compared with predecline levels. This is not an age-related phenomenon, nor is it seen in comparable populations at higher altitudes. Analysis of climate-growth relationships suggests that the observed decline in growth is a result of warming temperatures and that, as precipitation in the region has not increased, precipitation is now insufficient to ameliorate the negative effects of increased temperatures on tree growth. As the climateresponse of the studied forest is comparable with that of F. sylvatica forests in other southern European regions, it is possible that this growth decline is a more widespread phenomenon. Warming temperatures may lead to a rapid decline in the growth of rangeedge populations and a consequent retreat of the species distribution in southern Europe. Assessment of long-term growth trends across the southern range edge of F. sylvatica therefore merits further attention.

The altitude-for-latitude disparity in the range retractions of woody species

“…The processes and rates of carbon sequestration are expected to vary as a consequence of the onset and duration of such forest dieback [21,24,78], with the effect of reduced uptake potentially being magnified by increases in carbon released from tree decomposition [31]. Carbon sequestration can be reduced even in the absence of mass mortality events via tree growth decline and elevated mortality rates, as reported recently at the southernmost range edge of beech distribution in Europe [65,66], and in temperate trees across the western USA [31]. Furthermore, such alterations to carbon economy are occurring despite the predicted enhancement of water-use efficiency by increasing CO 2 and its expected fertilization effect (higher atmospheric CO 2 concentrations leading to higher plant productivity) [79].…”

“…Regeneration thus becomes sparse, whereas a more resilient old generation persists [64]. These impacts are evident in the European beech, where trailing range-edge populations are threatened by increasingly rare recruitment and declining growth of remaining adult trees as temperatures increase [12,51,65,66].…”

“…Monitoring data should be provided by remote sensing techniques, such as the NDVI [4,5], in combination with a network of local monitoring plots to ensure changes in NDVI can be correctly interpreted [74]. At the local level, tree establishment and vitality should be assessed using ecophysiological [24] and dendroecological methods [12,31,65,66], in addition to current monitoring of forest condition conducted by international programmes such as the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests, www.icp-forests.org). Trailing range-edge populations represent a potentially valuable resource for the future conservation and management of the species range-wide [25,55] (Box 1) and therefore strategies must be developed to conserve the genetic diversity they contain.…”

Species composition and forest structure explain the temperature sensitivity patterns of productivity in temperate forests

“…Bontemps et al, 2010;Delpierre et al, 2009;Pan et al, 2013;McMahon et al, 2010) as well as negative ones have been found (e.g. Barber et al, 2000;Jump et al, 2006;Charru et al, 2010). However, it remains unclear why forests react differently to temperature change.…”

Extending a physiological forest growth model by an observation-based tree competition module improves spatial representation of diameter growth

“…As comprehensively explained by Brumme and Khanna (2009), its increased cultivation in central Europe is heavily advocated to preserve and enhance biodiversity in a changing climate and to provide long-term sustainability of forests and the productivity of forest stands. In this situation, some concern has been expressed about the relatively small knowledge base about the response of European beech to drought conditions (Jump et al 2006;Geßler et al 2007;Friedrichs et al 2009). Our model evaluation takes advantage of extensive data from two areas in south-west Germany that have repeatedly been investigated for forestry and ecophysiological purposes (e.g.…”