Chapter 6

Communities, Formations, and Biomes

Mediterranean Biome• Winter wet, summer dry• Warm summers, mild winters• Found in conjunction with cold ocean currents• Valley forest, open woodlands, shrublands,

grasslands• California – chaparral – oak (Quercus spp)• Chile – matorral – Northfagus obliqua and

Acacia• South Africa – fynbos• Australia - eucalyptus• Europe – maquis – Pines (Pinus spp), Cedars

(Cedrus spp), Fir (Abies spp)

• Vegetation dependent on long summer drought, fire, and low soil nutrients

• Annuals more common than perennials • Drought strategies (avoiders)

– Black sage (Salvia mellifera) loses all but outer leaves in summer

– Shrubs – dimorphism– California valley oak (Quercus lobata) – deep

tap roots– Low soil nutrients makes deciduousness

impractical

Mediterranean Biome

• Fire-tolerant species

• Scarification, serotinous cones, thick bark, resprouting

• Invasives from Australia: melaleuca, eucalyptus

Mediterranean Biome

Temperate Grassland

• North America – prairie

• South America – pampas

• Eurasia – steppe

• South Africa – grassveld

• Variable temperature and rainfall

• Fertile soils

• 20% herbs, 80% grasses on grasslands

• Trees along waterways

• Shortgrass – arid regions– Shallow, extensive root system– 1 foot tall

• Tallgrass – wetter regions– Deep roots to access water table– 6 feet tall– 1% remains

• Fires common• Invasive annual grasses

Temperate Grassland

Shortgrass prairie (below)

Tallgrass prairie (right)

Temperate Forest

• Variable temperatures and rainfall

• In the Southern Hemisphere, evergreens

• In the Northern Hemisphere, deciduous

• General structure: canopy, subcanopy, herb layer

• Biodiversity dependent upon glacial history

• Deciduous forest increasing as farms abandoned – second-growth forest

Temperate Rainforest

• High rainfall, mild temperatures, close to oceans

• Moisture from fog and orographic lifting

• Large, long-lived, evergreen trees

• Redwoods, Douglas fir

• Lower diversity than temperate deciduous forest and tropical rainforest

Coniferous Boreal and Montane Forest

• Northern Hemisphere• Pine, Spruce (Picea spp.), and Fir in North

America and Europe• Bristlecone pine (Pinus aristata)• Larch (Larix spp) in Asia• Krummholtz – high elevation shrublands• Little understory growth• Fire-tolerant plants

Bristlecone pine krummholtz (above)

Boreal forest - Spruce (below)

Geography of Biomes

Tundra Biome

• Found beyond treeline in the Arctic (Arctic Tundra) and in high mountians (alpine tundra)

• Variable temperatures and rainfall

• Lower elevations and latitudes: willow (Salix spp.), shrub birch (Betula nana), alder (Alnus spp.), sedges, grasses, herbs, and mosses – low arctic tundra

Tundra Biome• High arctic tundra (polar desert) – higher

elevations and latitudes – arctic willow (Salix arctica) and heliotropic flowering plants

• Perennials

• Low biodiversity and biomass

• With the exception of crowberry (Empetrum nigrum), arctic and southern hemisphere alpine tundra have no similar species

Tundra Biome

• Threats:– Resource extraction– Mining– Snowmobiles– Global warming

Arctic willow

crowberry