Campbell, Jennifer F. E.
[Author];
Fletcher, William J.
[Author];
Joannin, Sebastien
[Author];
Hughes, Philip D.
[Author];
Rhanem, Mustapha
[Author];
Zielhofer, Christoph
[Author]
Environmental Drivers of Holocene Forest Development in the Middle Atlas, Morocco
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Media type:
E-Article
Title:
Environmental Drivers of Holocene Forest Development in the Middle Atlas, Morocco
Contributor:
Campbell, Jennifer F. E.
[Author];
Fletcher, William J.
[Author];
Joannin, Sebastien
[Author];
Hughes, Philip D.
[Author];
Rhanem, Mustapha
[Author];
Zielhofer, Christoph
[Author]
imprint:
Lausanne: Frontiers Research Foundation, [2023]
Published in:Frontiers in Ecology and Evolution ; 5, (2017)
Description:
In semi-arid regions subject to rising temperatures and drought, palaeoecological insightsinto past vegetation dynamics under a range of boundary conditions are needed todevelop our understanding of environmental responses to climatic changes. Here, wepresent a new high-resolution record of vegetation history and fire activity spanning thelast 12,000 years from Lake Sidi Ali in the southern Middle Atlas Mountains, Morocco.The record is underpinned by a robust AMS radiocarbon and 210Pb/137Cs chronologyand multi-proxy approach allowing direct comparison of vegetation, hydroclimate, andcatchment tracers. The record reveals the persistence of steppic landscapes until10,340 cal yr BP, prevailing sclerophyll woodland with evergreen Quercus until 6,300cal yr BP, predominance of montane conifers (Cedrus and Cupressaceae) until 1,300cal yr BP with matorralization and increased fire activity from 4,320 cal yr BP, andmajor reduction of forest cover after 1,300 cal yr BP. Detailed comparisons betweenthe pollen record of Lake Sidi Ali (2,080m a.s.l.) and previously published data fromnearby Tigalmamine (1,626m a.s.l.) highlight common patterns of vegetation change inresponse to Holocene climatic and anthropogenic drivers, as well as local differencesrelating to elevation and bioclimate contrasts between the sites. Variability in evergreenQuercus and Cedrus at both sites supports a Holocene summer temperature maximumbetween 9,000 and 7,000 cal yr BP in contrast with previous large-scale pollen-basedclimate reconstructions, and furthermore indicates pervasive millennial temperaturevariability. Millennial-scale cooling episodes are inferred from Cedrus expansion around10,200, 8,200, 6,100, 4,500, 3,000, and 1,700 cal yr BP, and during the Little Ice Age(400 cal yr BP). A two-part trajectory of Late Holocene forest decline is evident, withgradual decline from 4,320 cal yr BP linked to synergism between pastoralism, increasedfire and low winter rainfall, and a marked reduction from 1,300 cal yr BP, attributed tointensification of human activity around the Early Muslim conquest of Morocco. Thistrajectory, however, does not mask vegetation responses to millennial climate variability.The findings reveal the sensitive response ofMiddle Atlas forests to rapid climate changesand underscore the exposure of the montane forest ecosystems to future warming.