PLEISTOCENE REFUGIA AND THE DISTRIBUTION OF TREE SPECIES IN

THE ALPS

Mauro Lanfranchi

Pleistocene

Cycles of climatic cooling and warming: expansion - contraction of the Arctic and Alpine ice caps

- 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

Ice age: Biodiversity affected in Palaearctic regions

Subdivisions of the Quaternary System

Period Epoch Age (Ma)

Quaternary Holocene 0 – 11,700

Pleistocene 11,700 – 2,588,000

Neogene Pliogene older

Four main Pleistocene cold stages in the Northern Hemisphere

Günz (600-500 kyr BP)Mindel (450-350 kyr BP) Riss (200-135 kyr BP)Würm (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

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)

NVNP - Northern Velebit National Park

- 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

Schönswetter, P.,Tribsch, A., 2003. Patterns of endemism

REFUGIA

Climatic snowline during LGM: 1000–1500 m below the present level (today from 2600 m to 3100 m):

- Surface of ice in the Central Alps was at 2300–2700 m altitude. - Nunataks were present in the Alps.

Habitats available for plant life above the ice sheet (Potentilla frigida, Androsace alpina...)

Tribsch, A., 2004. Areas of endemism

Significant correlation between high endemism and low glacial ice cover

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

Downward displacement of vegetation belts during LGM equivalent to the depression of snowline

Refugia for upper montane conifer forest

Refugia for sub-Alpine / Lower Alpine conifer forest

Schönswetter, P.,Tribsch, A., 2003. Patterns of endemism

2500m

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.

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

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.

FOREST LANDSCAPES IN THE ALPS: Pavari Phytoclimatic classification

Phytoclimatic zones: analogy between similar plant associations in different geographic areas (altitude and latitude) but similar in thermal conditions and rainfall.

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.

Castanetum (from Castanea sativa - Chestnut): - Wide belt -

Colder and more humid than LauretumAv 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

Fagetum (from Fagus sylvatica – Beech):

Av temperature: 6 -7°CAv 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.

Picetum (from Picea spp. – Norway spruce)

From 1000 to 2000 m

Average temperature: 3 to 6°CAv 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.

Alpinetum

From 2000 to 2500 m

Average temperature < 2°Cminimum temperature: - 40°C

It comprises the brush at the upper limit of the beltThe wood is sparse: enhance insolation

Thank you

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-sjeverni-velebit.hr/park/zivapriroda/biljke/?lang=en.