Chapter 6
The Multiple Factors Explaining Decline
in Mountain Forests: Historical Logging
and Warming-Related Drought Stress
is Causing Silver-Fir Dieback
in the Aragón Pyrenees
J. Julio Camarero
Abstract The drivers and patterns of drought-related forest dieback are not as well
understood in mountain conifer forests. Most studies have obviated the role of
historical use as a predisposing factor of forest dieback. Here I focus on the recent
silver-fir (Abies alba) dieback observed since the 1980s in the Aragón Pyrenees
(NE Spain) as study case. I argue that such dieback was predisposed by past
historical logging and incited by warming-induced drought. I analyzed environmental, structural and tree-ring data from 32 sites with contrasting degrees of
dieback at the tree and stand levels. I found that a peak in late-summer water deficit
observed in 1985 caused a severe growth reduction in 1986, resulting in subsequent
crown defoliation, dieback and increased mortality. Dieback was more severe and
widespread in western low-elevation mixed forests dominated by smaller trees with
low growth rates. These marginal sites receive less late-summer rainfall, which is a
key climatic variable controlling silver-fir growth, than eastern sites. Declining sites
showed more frequent growth releases induced by historical logging than
non-declining sites. Silver-fir growth is becoming more dependent on climatic
conditions of previous September, which may be connected with changing modes
of atmospheric variability affecting Iberian climate. Historical logging and
warming-induced drought stress during late summer are the most likely predisposing and inciting factors driving silver-fir dieback, respectively. A sustainable
management of mountain forests shaped by past historical use requires changing
their current structure and composition to make them more resilient to climate
warming.
Keywords Abies alba Á Climate warming Á Dendroecology Á Radial growth Á
Releases
J.J. Camarero (&)
Instituto Pirenaico de Ecología (IPE-CSIC), Avda. Montañana 1005,
50192 Zaragoza, Spain
e-mail: jjcamarero@ipe.csic.es
© The Author(s) 2017
J. Catalan et al. (eds.), High Mountain Conservation in a Changing World,
Advances in Global Change Research 62, DOI 10.1007/978-3-319-55982-7_6
131
The Multiple Factors Explaining Decline
in Mountain Forests: Historical Logging
and Warming-Related Drought Stress
is Causing Silver-Fir Dieback
in the Aragón Pyrenees
J. Julio Camarero
Abstract The drivers and patterns of drought-related forest dieback are not as well
understood in mountain conifer forests. Most studies have obviated the role of
historical use as a predisposing factor of forest dieback. Here I focus on the recent
silver-fir (Abies alba) dieback observed since the 1980s in the Aragón Pyrenees
(NE Spain) as study case. I argue that such dieback was predisposed by past
historical logging and incited by warming-induced drought. I analyzed environmental, structural and tree-ring data from 32 sites with contrasting degrees of
dieback at the tree and stand levels. I found that a peak in late-summer water deficit
observed in 1985 caused a severe growth reduction in 1986, resulting in subsequent
crown defoliation, dieback and increased mortality. Dieback was more severe and
widespread in western low-elevation mixed forests dominated by smaller trees with
low growth rates. These marginal sites receive less late-summer rainfall, which is a
key climatic variable controlling silver-fir growth, than eastern sites. Declining sites
showed more frequent growth releases induced by historical logging than
non-declining sites. Silver-fir growth is becoming more dependent on climatic
conditions of previous September, which may be connected with changing modes
of atmospheric variability affecting Iberian climate. Historical logging and
warming-induced drought stress during late summer are the most likely predisposing and inciting factors driving silver-fir dieback, respectively. A sustainable
management of mountain forests shaped by past historical use requires changing
their current structure and composition to make them more resilient to climate
warming.
Keywords Abies alba Á Climate warming Á Dendroecology Á Radial growth Á
Releases
J.J. Camarero (&)
Instituto Pirenaico de Ecología (IPE-CSIC), Avda. Montañana 1005,
50192 Zaragoza, Spain
e-mail: jjcamarero@ipe.csic.es
© The Author(s) 2017
J. Catalan et al. (eds.), High Mountain Conservation in a Changing World,
Advances in Global Change Research 62, DOI 10.1007/978-3-319-55982-7_6
131