Interacting effects of changes in climate and forest cover on mortality and growth of the southernmost European fir forests

Abstract

AimsThe combined effects of changes in climate and land use on tree mortality and growth patterns have rarely been addressed. Relict tree species from the Mediterranean Basin serve as appropriate models to investigate these effects, since they grow in climatically stressed areas which have undergone intense cover changes. The aim is to use climate, aerial photographs, stand structure and radial-growth data to explain the mortality and historical patterns of growth of Abies pinsapo in the area where this relict species was first protected.Location Sierra de las Nieves, West Baetic Range, southern Spain. MethodsWe assessed variations of tree cover in A. pinsapo forests through image analyses of aerial photographs spanning the last 50 years. We sampled 31 stands to assess current altitudinal patterns of forest structure and mortality. We evaluated the relationships between radial growth and regional climate using linear models in three sites at different elevations. ResultsRegional warming and a decrease in precipitation were detected. Forest tree cover increased at all elevations from 1957 until 1991, but it afterwards decreased below 1100 m. Currently, the likelihood of tree mortality increases downwards and is associated with dense, closed stands with a low living basal area. In contrast to previous droughts, a sharp synchronized reduction in tree growth, not fully accounted for in linear climate-growth models, occurred at low elevations in 1994-95, but not upwards. It was preceded by a weakening of the negative association between low-elevation growth and water deficit since the late 1970s. ConclusionsThe intense densification of A. pinsapo forests following strict protection measures in the late 1950s enhanced the vulnerability of climate-sensitive A. pinsapo forests to recent drier conditions. Such abrupt land-use changes help to explain recent patterns of mortality and growth decline in low-elevation A. pinsapo forests.

Consistent limitation of growth by high temperature and low precipitation from range core to southern edge of European beech indicates widespread vulnerability to changing climate

“…One of the fundamental principles of dendroecology and dendroclimatology is that tree populations in marginal regions are more sensitive to climate than those in core regions, with more interannual variability in growth and stronger relationships between growth and limiting climate factors, particularly summer drought (Fritts 1966). This principle has been demonstrated for conifers (Carrer et al 2010;de Luis et al 2013;Linares et al 2009) and also to a more limited extent in broadleaved species such as F. sylvatica, although research has focused on elevation transects or regional networks of sites. For example, studies have shown that F. sylvatica at low elevations is more sensitive to summer drought than at high elevations (Di Filippo et al 2007;Hartl-Meier et al 2014).…”

Comparative Drought Responses of Quercus ilex L. and Pinus sylvestris L. in a Montane Forest Undergoing a Vegetation Shift

“…The impacts of climate change on vegetation are likely to vary regionally and will result from a combination of stress factors, including elevated temperatures [3], reduction of rainfall [4], and shifts in wildfire regimes [5]. Furthermore, the consequences of these new conditions will be modulated by biotic factors and direct human impacts on forests (e.g., management) [6,7].…”

The role of climate change in the widespread mortality of holm oak in open woodlands of Southwestern Spain

“…Research indicates an increase of forest decline in Iberian woodlands (Martínez-Vilalta and Piñol, 2002;Linares et al, 2009;;Hereş et al 2012;Carnicer et al, 2011;. Nevertheless, the increase in oak mortality occurring in our study region is, to our knowledge, the first case in the Iberian Peninsula of massive population-level die-off threatening the sustainability of a forest ecosystem.…”