The document discusses how tree species in the Alps survived glacial periods and their current distribution. During the Pleistocene ice ages, the expansion of Arctic ice caps forced tree species southward. Plants survived in refugia above the ice sheets, such as in nunataks and between 2000-2500m altitude. As the ice retreated, species recolonized from these refugia. The cycles of contraction and expansion during the Pleistocene led to genetic signatures in plant genomes and structured biodiversity across Europe. The document also outlines the major Pleistocene glacial periods and how vegetation zones shifted with changing climates.

1. PLEISTOCENE REFUGIA AND THE
DISTRIBUTION OF TREE SPECIES IN
THE ALPS
Mauro Lanfranchi

2. Pleistocene
Ice age: Biodiversity affected in Palaearctic regions
Cycles of climatic cooling and warming:
expansion - contraction of the Arctic and Alpine ice caps
Subdivisions of the Quaternary System
Period
Quaternary
Epoch
Age (Ma)
0 – 11,700
Pleistocene
Neogene
Holocene
11,700 –
2,588,000
Pliogene
older
- LGM (20 -14 ky): Soil temperatures 10 - 20°C lower than present
- By 6 kyr BP (early holocene) the vegetation across most of Europe was similar to the present

3. Four main Pleistocene cold stages in the Northern Hemisphere
Günz
Mindel
Riss
Würm
(600-500 kyr BP)
(450-350 kyr BP)
(200-135 kyr BP)
(120-18 kyr BP)
> 20 interstadials during Würm , (Average temperatures changed by 10- 12°C in 5-10 years).
Younger Dryas (Big Freeze ca. 10.5 kyr BP)
- Southward spread of tundra
- Retreat of temperate forests
Weiss, S., Franzens, K., Nuni, F., 2007. Phylogeography of South European Refugia

4. Cycles of population contraction and expansion left :
- Genetic signals in the genomes of plants and in the genetic structure of populations
- structured (non-random) distribution of genetic diversity across the European continent.
Postglacial demographic expansions resulted in parapatric distributions (vicariance)
- Palaearctic regions covered in ice
- Migration southwards
- Ice started to melt
- Only plants growing on mountain tops (climate similar to northern or
polar regions) were able to survive.
- Harsh climate was easily buffered by elevation (long-term ecological stability).
- Plants became isolated (surrounded by unfavourable warm habitats)
- Adaptation (provenance) and endemics
HOW DID PLANTS SURVIVE THE GLACIATION ?
Weiss, S., Franzens, K., Nuni, F., 2007
NVNP - Northern Velebit National Park

5. REFUGIA
- Surface of ice in the Central Alps was at 2300–2700 m altitude.
- Nunataks were present in the Alps.
Climatic snowline during LGM: 1000–1500 m below the
present level (today from 2600 m to 3100 m):
Habitats available for plant life above the ice
sheet (Potentilla frigida, Androsace alpina...)
Significant correlation between high endemism and low glacial ice cover
Tribsch, A., 2004. Areas of endemism
Schönswetter, P.,Tribsch, A., 2003. Patterns of endemism

6. LGM tree line in the Alps:
Downward displacement of vegetation belts during LGM was equivalent to the depression
of the snowline
Tree line:
- 450 m (± 150 m) in the northeast
- Between 200 m and 800 m in the East
- Tree growth was possible at the southern and eastern borders of the region

7. Downward displacement of vegetation belts during LGM equivalent to the depression of snowline
Refugia for sub-Alpine /
Lower Alpine conifer forest
2500m
Refugia for upper montane conifer forest
Schönswetter, P.,Tribsch, A., 2003. Patterns of endemism

8. The diversity (ecosystems and communities) of the Alps is the related to the
variability of soil and climate (pedoclimate) which is in turn related to the
orography.
Three aspects characterize the Alps:
- Altitude
- Acclivity
- Exposure
Altitude
vertical stratification of flora:
Climate is affected by the altitude not by the latitude.
100 m elevation:
- 120 - 200 km in the latitudinal direction
- 0.6 ° C
- 1 week change in length of growing season
Gusmeroli, F., 2012. Prati,pascoli e paesaggio alpino.

9. Relationship between altitude and latitude (Floristic Regions):
Altitude
Latitude
Nival / Snow Belt
Arctic zone
Alpine Belt
Alpic / upper Boreal zone
Sub-Alpine Belt
Upper Boreal zone
Montane Belt
Lower Boreal / sub-Atlantic zone
Sub-montane Belt
Central European zone
Planar Belt
Sub-Mediterranean zone

10. FOREST LANDSCAPES IN THE ALPS: Pavari Phytoclimatic classification
Phytoclimatic areas are used in :
- Silviculture
- Forest ecology
- Botany
Define the area of distribution of vegetation in plant species regardless the relationship
between altitude and latitude.
Phytoclimatic zones: analogy between similar plant associations in different geographic
areas (altitude and latitude) but similar in thermal conditions and rainfall.

11. Lauretum (from Genus Laurus - Laurel):
Warm limit: Genus Citrus, cold up to the limit of Olea europaea.
Also: Pinus pinaster, Quercus ilex, Quercus suber , Acacia spp...)
Very small timber production (firewood / timber)
Baccolo, P., 2010.

12. Castanetum (from Castanea sativa - Chestnut):
- Wide belt -
Colder and more humid than Lauretum
Av temperature: 10 to 15°C
Av minimum Temperature: - 15°C
Also: Quercus spp, Acer spp., Populus, Fraxinus, Pinus nigra, Pinus pinaster.
Upper limit of Castanetum marked by the grapevine

13. Fagetum (from Fagus sylvatica – Beech):
Av temperature: 6 -7°C
Av minimum temperature: never lower than -25°C
Belt is not as wide as Castanetum, but higher Woodiness index
Also: Quercus robur, Quercus petraea, Tilia spp., Salix spp., Populus, Ulmus, Alnus incana,
Carpinus spp., Sorbus, Pinus nigra.

14. Picetum (from Picea spp. – Norway spruce)
From 1000 to 2000 m
Average temperature: 3 to 6°C
Av minimum temperature: lower than -30°C
Other: Picea spp., Pinus sylvestris, Pinus cembra, Pinus mugo, Larix decidua, Juniperus,
Betula, Alnus viridis, Tilia, Fraxinus, Populus, Salix.

15. Alpinetum
From 2000 to 2500 m
Average temperature < 2°C
minimum temperature: - 40°C
It comprises the brush at the upper limit of the belt
The wood is sparse: enhance insolation

16. Thank you

17. References
Baccolo, P., 2010. Notes from lectures - Held by Prof. Paolo Baccolo, Università degli Studi
di Milano, module Silviculture.
Gusmeroli, F., 2012. Prati,pascoli e paesaggio alpino. (grassland, grazing land and Alpine
landscapes), Fondazione Fojanini, Università degli studi di Milano. ed.
Tribsch, A., 2004. Areas of endemism of vascular plants in the Eastern Alps in relation to
Pleistocene glaciation. J. Biogeogr. 31, 747–760.
Tribsch, A., Schönswetter, P., 2003. Patterns of endemism and comparative phylogeography
confirm palaeoenvironmental evidence for Pleistocene refugia in the Eastern Alps. Taxon
52, 477–497.
Weiss, S., Franzens, K., Nuni, F., 2007. Phylogeography of South European Refugia Phylogeography of South European Mammals - (Evolutionary perspectives on the origins
and conservation of European biodiversity). Springer.
Websites
Alpine convention map http://www.alpenallianz.org/de/die-alpen/karte/image1
NVNP, n.d. NVNP - Northern Velebit National Park - http://www.np-sjevernivelebit.hr/park/zivapriroda/biljke/?lang=en.