Abstract
Aim of the study: The study analyzes the long-term response of Atlas cedar, Cedrus atlantica (Manneti), to climate variability. Area of study: Atlas cedar forest of Guetiane (Batna, Algeria).Material and methods: The dendrochronological approach was adopted. An Atlas cedar tree-ring chronology was established from twenty trees. The response of the species to climate variability was assessed through the pointer years (PYs), the common climate signal among the individual chronologies, expressed by the first component (PC1), the mean sensitivity (msx), and response function and correlations analysis involving the tree-ring index and climate data (monthly mean temperature and total precipitation).Results: The highest growth variability was registered from the second half of the 20th century. The lower than the mean PYs, the PC1, and the msx increased markedly during the studied period. Dramatic increases in the PC1 and msx were detected at the end of the 1970s, reflecting a shift towards drier conditions enhancing an increasing trend towards more synchronous response of trees to climate conditions. The response function and correlations analysis showed that tree growth was mainly influenced by precipitation variability.Research highlights: Our findings provide baseline knowledge concerning the ecological response of Atlas cedar to climate variability in in its southern distribution limit, where a high level of tree mortality has been observed during recent decades, coinciding with the driest period Algeria has ever experienced. This information is vital to support ongoing ecosystem management efforts in the region. Keywords: Atlas cedar; annual growth variability; dieback; dendrochronology.
Highlights
The climate has changed over the past century and it is expected to continue to change in the future (IPCC, 2007), resulting in warmer temperatures and changed precipitation regimes (Chmura et al, 2011)
Research highlights: Our findings provide baseline knowledge concerning the ecological response of Atlas cedar to climate variability in in its southern distribution limit, where a high level of tree mortality has been observed during recent decades, coinciding with the driest period Algeria has ever experienced
In Algeria, Allen et al (2010) reported that the recent C. atlantica mortality began as small patches on drier aspects in the arid near-Sahara mountains, eventually coalescing into large patches affecting all ages on all exposures
Summary
The climate has changed over the past century and it is expected to continue to change in the future (IPCC, 2007), resulting in warmer temperatures and changed precipitation regimes (Chmura et al, 2011). Recent studies in northwestern Africa reported recurrent drought events over the last few decades (Touchan et al, 2008a, 2010; Linares et al, 2011; Kherchouche et al, 2012, 2013), suggesting climate conditions more limiting to tree growth and drought-sensitive species geographical distribution, especially for those at the edge of their range (Fritts, 1976). In Algeria, Allen et al (2010) reported that the recent C. atlantica mortality began as small patches on drier aspects in the arid near-Sahara mountains, eventually coalescing into large patches affecting all ages on all exposures. Benabid (1994) noticed that a steppization process is increasingly affecting C. atlantica forests in the Atlas Mountains, in Morocco, and in the massifs of El Hodna, Belezma and the Aurès, in Algeria. In Morocco, Mokrim (2009) and Linares et al (2011) reported similar results. Linares et al (2011) noticed that C. atlantica forests that have experienced severe drought in combination with grazing and logging may be in the process of shifting dominance toward more drought-tolerant species such as Q. rotundifolia. Benabid (1994) noticed that a steppization process is increasingly affecting C. atlantica forests in the Atlas Mountains, in Morocco, and in the massifs of El Hodna, Belezma and the Aurès, in Algeria. Cheddadi et al (2009) reported that environmental changes in northern Africa since the last glacial period have had an impact on the geographical distribution of C. atlantica and on its modern genetic diversity, and it is possible that by the end of this century C. atlantica may be unable to survive in its present-day locations
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